Chapter 12 Web Topics

Chapter 12 Web Topics

12.1 Quantitative Genetic Models of Sexual Selection

Introduction

Models of sexual selection focus primarily on intersexual selection and assume traditional sex roles. They aim to understand the processes by which male sexually selected traits and female preferences for those traits coevolve. The male traits are therefore cues and signals for mate attraction and courtship. Female mating preferences are behavioral, structural, or physiological traits that bias conspecific mating or fertilization success toward males with certain trait values. The myriad models make different assumptions about the nature of the male and female traits, the costs and benefits of these traits with respect to different components of fitness, and the genetic underpinnings of the coevolutionary process. Some models assume there is direct selection on female preference for certain male traits that improve female reproductive success or survival, while other models explore indirect selection on female preference caused by a genetic correlation with another trait under selection. One hypothesis for intersexual selection, the sensory bias model, was initially introduced in verbal form. In order to compare and test this model in relation to the other models (e.g., Fisherian, good genes, direct benefits, and sexual conflict models), Fuller et al. (2005) parameterized this hypothesis in the quantitative genetics framework. In the process, they clearly laid out the key similarities and differences among all five types of models. This Web Topics unit explains the multivariate quantitative genetic approach to sexual selection and summarizes their article.

Multivariate quantitative genetics framework

Quantitative traits are phenotypes determined by a large number of genes with small additive effects. Evolutionary change in the mean population value of such a trait therefore occurs gradually as selection acts on genetic mutations with small overall effects on the trait. As explained in Chapter 9 and Web Topic 9.1, the response to selection, Δz (measured as the change in the mean phenotypic value of a trait between the parental and the offspring generation) is equal to the product of the trait heritability, h2 (measured as the ratio of the trait’s additive genetic variance to its phenotypic variance in the population) and the selection differential on the trait in the parental generation, S (measured as the difference between the mean value of the trait for those that breed and the overall average in the parental population):

When there are multiple traits evolving in tandem, the equation must be expanded to take into account the genetic linkages between the traits. This is accomplished by combining the additive genetic covariances (C) and the additive variances (V) into a G-matrix. The selection differentials on the traits are combined with the overall phenotypic variation in the traits to produce a selection gradient for each trait, called β. Adding in the vector of mutational effects, u, the shorthand matrix formula for this expression becomes:

To investigate sexual selection, we need to consider the simultaneous coevolution of at least three phenotypic traits: a male display trait (t), a female preference for the male display trait (p), and a viability or residual fitness trait (v). The residual viability applies to both sexes and includes the fitness components of fecundity and survivability left over after excluding the sexually selected fitness components of mate number and mate quality. Finally, the selection gradient can be separated into two additive components: the part due to natural selection βN, and the part due to sexual selection βS. The full quantitative genetics equation for the change in each trait’s mean value in one generation is given by:

Below, we show the values these components must have to initiate each sexual selection process, as well as the values that are likely to exist at the equilibrium point. All of the tables use the following notations. Traits that have a significant amount of additive genetic variation will be indicated with V > 0; likewise, if they have a significant genetic covariance with another trait, this will be indicated with C > 0. When a trait is undergoing significant positive or negative selection, the relevant selection gradient β will be shown as either greater or less than zero, respectively. When the gradient is zero, either a selection peak or trough has been reached and there is no net natural or sexual selection; β ≡ 0 indicates that there must be no selection on the trait. All models require some heritable genetic variation in female preference behavior (Vp > 0), and at equilibrium all models predict a balance between positive sexual selection and negative natural selection on the male trait. These conditions will be indicated in the figures by green text; variable states that are essential for the particular selection model are shown in red. The response and mutation vectors will not be shown in the summaries below, as they are the same in each case.

Fisherian runaway model

For the Fisherian model, required initial conditions are positive additive genetic variance for both the male trait and female preference. The non-random mating that results from this female preference for the male trait leads to a genetic covariance between these two traits (Ctp > 0). This happens because choosier females produce offspring that inherit the alleles for stronger female preference and the alleles for greater male trait values, resulting in gametic disequilibrium and coupling of the two traits. A change in female preference p may thus bring about a change in the male trait t. If the covariance term is large, the female preference and male trait will rapidly increase in the runaway process, but if (Ctp < Vt), the population will return to an equilibrium point where selection on p and t are balanced (see main text Figure 12.6). At the equilibrium, there is no natural or sexual selection pressure on the female preference trait, and positive sexual selection for the male trait is balanced by negative natural selection on the male. These initial and equilibrium conditions are shown in Figure 1.

Figure 1. Initial and equilibrium conditions for the Fisherian model. Critical parameters required to initiate an increase in female preference are indicated in colored text. (After Fuller et al. 2005.)

Good genes model

The good genes model requires a positive covariance between the male display trait and genetic variation for residual fitness (Ctv > 0). This essentially means that the trait is condition-dependent, such that males with greater values of the trait have higher survival. Given that female preference also has some positive genetic variance, a positive covariance between p and v can be generated (Cpv > 0). Even though there is no direct selection on p, the preference trait can be indirectly selected for because of this covariance driven by direct selection for high viability v. If the male display trait is also genetically variable (Vt > 0), covariance between p and t is generated (Cpt > 0), which is not essential but can accelerate the good genes process. Figure 2 shows initial and equilibrium stages for the good genes model. In this example, the initial genetic variation in v is generated by biased mutation (uv) but other mechanisms could result in a positive Vv. At the equilibrium, there is direct natural selection against the female mating preference because of costs female incur to search for high quality males, but this is counterbalanced by indirect viability gains through the preference–viability covariance term.

Figure 2. Initial and equilibrium conditions for the good genes model. (After Fuller et al. 2005.)

Direct benefits model

The direct fitness model is the most straightforward of the five models because no genetic correlations are required. By choosing males that provide some type of benefit that improves their fecundity or survival, or the survival of their offspring, females gain directly (βSp > 0). At the equilibrium, females will experience some natural selection cost for being choosy (Figure 3). Genetic variance for the male trait is not required, but the female preference is likely to select for such variance, and then the male trait will also undergo positive sexual selection and negative natural selection, as in the good genes model.

Figure 3. Initial and equilibrium conditions for the direct benefits model. (After Fuller et al. 2005.)

Sensory bias model

In the sensory bias model, females initially evolve a naturally selected preference for some type of environmental feature, such as a food characteristic. This preference is indicated in the first stage of the model by a positive βNp. In the second stage, males evolve a trait that mimics this feature, and if there is genetic heritability for the male trait (Vt > 0), it will respond to sexual selection via the female preference for it (βSt > 0). In one possible type of equilibrium scenario, female preference settles at a local naturally selected stable point and is no longer under selection. As in all of the models, the male display trait reaches a stable balance between sexually selected benefits and naturally selected costs (βSt = – βNt) (Figure 4).

Figure 4. Initial, exaggeration, and equilibrium stages for the sensory bias model. (After Fuller et al. 2005.)

Sexual conflict model

Sexual conflict models rely on the prior existence of a female mating preference for a male trait via one of the above models. The first stage thus reflects this initial sexually-selected benefit to females, which creates an opportunity for males to take advantage of this preference. For the scenario shown in Figure 5, a female preference is assumed to have arisen by way of the direct benefits model (βSp > 0). Males then evolve traits or mating tactics that benefit them while reducing the fitness of females. The example discussed in the main text is the transfer of manipulative chemicals in the semen that causes females to mate again more rapidly, or lay more eggs than is optimal for them. This sets up a cycle of conflict in which females try to resist male manipulation, while males counter with more forceful tactics. In one equilibrium scenario shown here, both sexes experience positive sexually selected benefits and negative natural selection via the costs incurred by the conflict.

Figure 5. Initial and equilibrium conditions for the sexual conflict model.

By placing all of the sexual selection models within this single quantitative genetics framework, strategies for distinguishing among them become obvious (Mead & Arnold 2004; Kokko et al. 2006). Clearly, looking for heritability of female mating preferences will not help distinguish the models, as they all require this component. Similarly, looking for evidence of a natural selection cost for males with larger trait values also will not be helpful, as they all predict this relationship. The sensory bias model can be distinguished from the others by looking for evidence of a natural selection benefit for female preference independent of the identity and attributes of the male, since all other models predict that the benefit to females arises from the benefits to selecting particular males (Fuller et al. 2005). The Fisherian and good genes models have many components in common, and in fact the Fisherian conditions will be met whenever the good genes model conditions are met (Kokko et al. 2002, 2003). In particular, looking for a covariance between male trait and female preference will not distinguish these two models. However, if viability benefits to males and possibly females can be demonstrated, a case can be made for the good genes model (Kokko 2001). The sexual conflict model should be distinguishable from the others by finding positive sexual selection and negative natural selection gradients for both sexes.

Literature cited

Fuller, R.C., D. Houle & J. Travis. 2005. Sensory bias as an explanation for the evolution of mate preferences. American Naturalist 166: 437–446.

Kokko, H. 2001. Fisherian and “good genes” benefits of mate choice: how (not) to distinguish between them. Ecology Letters 4: 322–326.

Kokko, H., R. Brooks, M.D. Jennions & J. Morley. 2003. The evolution of mate choice and mating biases. Proceedings of the Royal Society of London Series B-Biological Sciences 270: 653–664.

Kokko, H., R. Brooks, J.M. McNamara & A.I. Houston. 2002. The sexual selection continuum. Proceedings of the Royal Society of London Series B-Biological Sciences 269: 1331–1340.

Kokko, H., M.D. Jennions & R. Brooks. 2006. Unifying and testing models of sexual selection. Annual Review of Ecology Evolution and Systematics 37: 43–66.

Mead, L.S. & S.J. Arnold. 2004. Quantitative genetic models of sexual selection. Trends in Ecology & Evolution 19: 264–271.

12.2 More Examples and Multimedia Clips of Courtship Sequences

Introduction

Nearly all animals engage in some form of courtship before mating, and when they do, they invariably use signals to mediate the process. As discussed in Chapter 1, signal diversity stems from a combination of factors: use of different media in which the signals are generated, transmitted, and received and thus different physical constraints; different phylogenetic histories and thus precursors; different types of information being exchanged; and different pressures and criteria for honesty guarantees. Given broad taxonomic variation in all of these factors, courtship represents the most diverse category of animal communication signals. In this module, we provide links to videos that illustrate both the scope and complexity of animal courtship displays. One cost of the emphasis on video recordings is an under-representation of courtship that is mediated by olfaction. However, this modality is relatively well covered in the text and Web Topic 6.3, and unless senders perform some overt behavior to dispense pheromones, there would be little to see in a video anyway. In addition to the examples in this module, additional courtship signals are included in Web Topics 10.3 and 13.2. Because it is instructive to see how different species in the same taxon have exploited a common ancestral repertoire and faced similar constraints, several taxa receive fairly detailed treatment below. We have tried here to select taxa for this module that have not been covered in other Web Topics.

Spiders

For a taxon of largely solitary species, spiders can have surprisingly elaborate courtship signals. In part, this may be due to the risk that females may attack and eat approaching males. Courtship is initiated when males are attracted to females that have released airborne pheromones or marked pheromones on their webs. Males then approach warily while producing seismic stridulations or drumming signals that are transmitted through the ground or along web threads. Making physical contact is extremely tricky for male spiders and usually involves repeated visual and seismic displays at a safe distance, pheromone release, and eventually quick leg touches. The final stages of courtship are even trickier for males: unlike insects where mating involves contact of the very tips of their abdomens, male spiders must gain access to a central region of the female spider’s ventral side. The genital openings of both spider sexes are located on the anterior ventral side of the rear body segment (called the opisthosoma). If spiders had to oppose their genital openings to copulate, males would be extremely vulnerable. However, before courting, males collect sperm packages from their genital pores into special storage organs on their pedipalps (the pair of small appendages protruding forward from the head). To mate, males then position themselves so that they can insert species-specific tubular structures on their pedipalps into the female’s genital pores. This gives males a bit of flexibility, and spider species differ in the relative orientations of the two sexes during copulation. Still, the risks to males remain high and in many species, females kill and eat the male after copulation if they can. Below, we examine several types of courtship in spiders:

Jumping spiders (Salticidae): This is one of the largest and most diverse families of spiders. They do not build webs but instead stalk invertebrate prey using their excellent vision and highly agile mobility. Males in particular tend to be brightly colored, with different species having quite distinct color patterning (see Figure 1.2, Chapter 1). Males court females with highly stereotyped movements of the pedipalps and first pair of legs accompanied by seismically transmitted striduation and drumming sounds:

Other spiders:

Other invertebrates

  • Leopard slug (Limax maximus): Individuals find each other using olfactory signals in slime trails. One then leads the other up a tree using a comination of tactile and olfactory signals where they jointly hang from a branch by a thick mucous thread and twine around each other. Since these are hermaphrodites, each extrudes its giant penis and these also twine into a spiral with a bell-shaped inflation at the tip. Sperm are transferred and the slugs either drop or break the mucous thread in this amazing sequence. (https://vimeo.com/16731697)
  • Emperor scorpion (Pandinus imperator): Like spiders, both sexes of scorpions have genital pores on the ventral side of their bodies, in this case between the bases of the rear legs. Unlike spiders, males do not load sperm into their pedipalps, which in scorpions form the large anterior “claws.” Instead, a male and female will face each other and, grabbing each other’s pedipalps, move back and forth as courtship proceeds. Eventually, the male will deposit a threadlike white spermatophore on the ground which he then pulls the female over so that it touches her genital pore. The spermatophore has a special trigger on its tip that ejects the sperm into the female’s pore given the right pressure and orientation of the female’s body.
    (http://www.arkive.org/emperor-scorpion/pandinus-imperator/video-09a.html)
  • Fruit fly (Drosophila melanogaster): This well-studied species has a fairly elaborate courtship sequence involving pheromones, production of male near-field sounds, and tactile stimuli. An annotated overview and sound production are shown in these two clips:
  • Stag beetle (Lucanus cervus): Both sexes of stag beetles secrete pheromones from glands on their front legs. Males attracted to females expose the female to their own pheromone and circle the female with their large mandibles expanded. Males are very competitive and multiple males attracted to the same female will fight vigorously for access to a mating. Males will even fight over dead females. This clip shows a male circling a female and then mounting her for copulation.
    (http://www.arkive.org/stag-beetle/lucanus-cervus/video-09b.html)
  • Seed Beetles (Callosobruchus chinensis): This clip is from the research described in Figure 12.11, and shows the female (left) resisting the male’s attempts to mount by kicking with her rear legs.
    (http://www.cell.com/current-biology/supplemental/S0960-9822%2809%2901703-5)

Fish

Fish exhibit a wide diversity of courtship signals. Pelagic and some reef fishes perform group spawning in which multiple members of both sexes simultaneously eject large numbers of gametes into the water column, usually around sunset. While one might assume that these species do not need courtship displays, they often show a variety of stereotyped movements, color changes, and chasing prior to a group spawn (e.g., tuna). Another common mating system in fish involves male defense of a patch of substrate and even the building of a nest. Males fertilize the eggs and guard them until they hatch (sticklebacks, damselfish). In nocturnal forms, such as toadfishes, males produce loud “songs” to attract females. Male pipefish and sea horses collect females’ eggs in a pouch on their body rather than in a substrate-bound nest. Other species such as guppies have internal fertilization and the typical competition between males to be selected by a receptive female has led to male courtship displays. In cichlids, pairs may form longer-term pair bonds and share in parental care; some species even have helpers at the nest. Finally, some species (again cichlids) exhibit lek behavior in which clusters of males display competitively to visiting females. In short, courtship behavior is widespread in fishes and as diverse as their mating systems.

Fish have a wide variety of modalities to incorporate into their courtship signals. Visual components include rapidly changed color patterns and movements, and many species add sounds to their courtship displays. Olfactory signals are likely ubiquitous in fish, both via secretions in their skins and via the passing of urine. One modality that is limited to fish is electrical signaling; although largely limited to freshwater species, the taxa that use electrical signals are highly diverse taxonomically and in signal patterning. Some examples:

  • Brown surgeonfish (Acanthurus nigrofuscus): These common reef dwellers have aggregated into a school near the surface in late afternoon. Subsets of the school rush upwards, release gametes in a group spawn, and dive back into the school. (http://www.arkive.org/brown-surgeonfish/acanthurus-nigrofuscus/video-11a.html)
  • Three-spined stickleback (Gasterorostreus aculeatus): This is a well-studied species in which males build and guard a nest. The clip begins with a male preparing the nest. He then encounters a very gravid female and performs displays including leading her to the nest, which she then enters to lay the eggs. The male then enters the nest to fertilize the eggs. The details of this display are outlined in Figure 12.28. (http://www.arkive.org/three-spined-stickleback/gasterosteus-aculeatus-aculeatus/video-ac09b.html)
  • Damselfish (Pomacentridae): Males of most species of damselfishes defend nesting territories on coral reefs. They are extremely aggressive and try to chase much larger fish away from their territories. Males can change body colors rapidly and markedly. In the bicolor damselfish (Stegastes partitus), males leave their territories shortly after dawn, exchange their usual territorial defense coloration for a different courting pattern, and patrol for possibly receptive females. When they find one, they perform a series of stereotyped dipping and tilting motions accompanied by chirping sounds in attempts to lead her back to their nest. Once at the nest, a female indicates her receptivity by changing her color pattern and the male points at the nest and quivers. The two then take turns laying eggs and fertilizing them until the female leaves. Other species of damselfish show similar combinations of movement, color pattern, and sound production during courtship. See Deloach and Humann (1999) for more details. Examples:
    • Bicolor damselfish (Stegastes partitus): This clip shows adult males in their usual territorial coloration of 2/3 of the anterior dark coloration and the posterior third light. Then it shifts to males defending artificial nest sites (plastic tubes) and one male that is courting a nearby female with the courtship color pattern of the anterior and posterior thirds dark, and a light middle third. This sequence is followed by a short shot of the nest and eggs of a dusky damselfish (Stegastes adustus). (Video clip courtesy of Dr. Kenneth Clifton.)
    • White-spotted damselfish (Dascyllus albisella): Pair spawning in Hawaii:  (http://www.youtube.com/watch?v=vjTj33DHDxE&feature=related)
    • Sergeant major (Abudefduf saxatilis): Territorial males usually exhibit a color pattern of black stripes against a yellow and white background. Here a territorial male tries to keep a school of wrasses from eating its egg clutch. (http://www.youtube.com/watch?v=mNWY7b6rBsg)
    • Sergeant major (Abudefduf bengalensis): In contrast to the territorial coloration above, courting male sergeant majors shift to a much darker background between the stripes especially in the head region. In the following example, a male and a female alternate between laying and fertilizing eggs in the male's nest. http://www.shutterstock.com/video/clip-2523395-stock-footage-indo-pacific-sergeant-abudefduf-vaigiensis-tending-eggs-underwater-in-indonesia.html)
    • Garibaldi (Hypsypops rubicundus): Males of this spectacular damselfish from the kelp forests of the US West coast also defend nest sites. Their bright orange color makes male advertisement of its nesting site very conspicuous to distant females. This clip shows some courtship and other behaviors. (http://www.youtube.com/watch?v=k_JVQGBAdNY)
  • Blue-head wrasse (Thalassoma bifasciatum): This is one of the most common wrasses on Caribbean coral reefs where they are one of the major predators on the eggs in male damselfish nests. During spawning, eggs and sperm are broadcast into down-currents that flow off of the reef and into the plankton. Initial phase fish of both sexes are small and slim with yellow bodies and a dark central stripe. Large females are capable of changing sex into bright blue, black, and white terminal males. Terminal males attempt to defend optimal spawning sites where they chase off other males and advertise themselves by performing a series of short vertical dashes (signal jumps). When a female approaches, the male starts swimming in tight circles and may perform some spiraling dashes upwards. Eventually, both parties dash up into the down-current, release their gametes in a burst, and dash back down to the reef. On small reefs, terminal males can often control optimal spawning sites. As reef size increases, this becomes increasingly difficult and schools of initial phase males either occupy spawning sites up current from a terminal male’s site, or by sheer force of numbers, displace the terminal male. The result is a group spawn of many initial phase males and the female. Several of these activities are visible in this clip provided by Dr. Ken Clifton.
  • Spotted handfish (Brachionichthys hirsutus): Mobility is limited for both sexes in handfish. In this species, males court females by spreading their fins and tails (as shown here), fertilization is external, and females guard the eggs for the 7–8 week incubation period. (http://www.arkive.org/spotted-handfish/brachionichthys-hirsutus/video09a.html)
  • Multiple fish species: This site has collected a number of stills, text, and video on the behavior of different fish taxa. Most are freshwater, but a few marine clips are included. To use the following site, select the preferred language, then click “Courtship display” in the panel on the left. (http://www.fischverhalten.de/)
  • African electric fish (Brienomyrus brachystius): This well annotated video shows a male and female courting and then spawning. The video was taken in the dark using infrared light (in which the fish cannot see), and the electrical discharge patterns produced by each individual are shown graphically and after conversion from electrical to audible sounds as a sound track. (http://www.nbb.cornell.edu/neurobio/Hopkins/media/Courtship Clip/2006_07_06_2-4_courtship.swf)
  • Neotropical electric fish (Sternopygus macrurus): A recording of courtship electrical signals by a male. The pattern is shown as a spectrogram of the discharge frequencies and converted into sounds so that we can monitor the pattern. (http://www.nbb.cornell.edu/neurobio/Hopkins/sternopygus/sternopygus_singing.htm)

Amphibians and reptiles

  • Great crested newt (Triturus cristatus): This clip shows a male with raised crest and tail performing highly conspicuous motion displays to a female. As noted in Figure 12.33, pheromones and tactile signals also play major roles in newt courtship. After a bout of displaying, the male moves ahead of the female and deposits a white spermatophore (circled in the clip); the female then follows and picks up the spermatophore with her cloaca. She then lays fertilized eggs on the vegetation. (http://www.arkive.org/great-crested-newt/triturus-cristatus/video-09.html)
  • Smooth newt (Triturus vulgaris): This clip shows a similar but shorter sequence in a congener. Again, note the deposition of the spermatophore and its retrieval by the female’s cloaca.
    (http://www.arkive.org/smooth-newt/triturus-vulgaris/video-09a.html)
  • Forsten’s tortoise (Indotestudo forstenii): Turtles and tortoises face special challenges during mating. Nearly all species release sex-attractant pheromones from their cloacas, and desert tortoises have additional glands on their heads that are wiped on the forelegs to disperse pheromones. The vomeronasal organ is well developed in turtles and tortoises (Mason and Parker 2010). In this clip, a male tortoise approaches the female and clearly sniffs at her cloacal region before butting her until she stops moving and lets him mount.
    (http://www.arkive.org/forstens-tortoise/indotestudo-forstenii/video-09.html)
  • Banded iguana (Brachylophus fasciatus): These lizards combine erection or sleeking of crests and throat dewlaps, different sequences of head-bobbing and head-shivering movements, and striking changes in coloration during courtship. All of those components can be seen in this clip of a courtship and copulation.
    (http://www.arkive.org/fiji-banded-iguana/brachylophus-fasciatus/video-09a.html)
  • Nile crocodile (Crocodylus niloticus): Crocodiles and alligators do not have a functional vomeronasal organ, but they do respond to cloacal scents and pheromones from glands on the throats of males. Males rub their throat glands on the snouts of females during courtship. In this clip, a male crocodile performs a surprisingly low-key courtship of a female before beginning mating. Note that he rubs his throat on her snout and back early in the process.
    (http://www.arkive.org/nile-crocodile/crocodylus-niloticus/video-09a.html)

Birds with predominantly male courtship displays

We now turn to examples of courtship displays in birds. In this section, we focus on species where courtship is relatively asymmetric: males perform elaborate displays to females who compare males in an ostensibly impassive manner but then pick one for mating by soliciting to him. Where possible, we show equivalent displays in related species to show how species differences are both limited by conserved antecedents and fostered by differences in ecology, mating system, and genetic drift. Readers may also want to review the section on displays of birds of paradise in Web Topic 4.4 and ducks in Web Topic 10.2.

Grouse (Tetraoninae). The 17 species of grouse are typical heavy-bodied and largely terrestrial Galliformes. They are unusual in that adults of many species feed on plant materials that are relatively indigestible or toxic to other animals (e.g., conifer needles, sage brush, catkins, etc.); their precocial chicks are largely insectivorous. Clutches are large and in most species, females perform incubation and offspring care without help from males. There are three types of mating systems in grouse that tend to grade into each other given variation within types. Males of smaller species tend to defend large breeding territories in which one (hazel grouse) or up to three (ptarmigan) females mate with the male and nest in his territory. At the other extreme, males defend small and contiguous display territories on leks to which females come to compare males and select one for mating (sharp-tailed grouse, two species each of black grouse, prairie chickens, and sage grouse). An intermediate type of system also occurs in which each male defends a display territory to which females come to mate, but males are out of earshot or at most, clustered slightly into exploded leks (spruce grouse, blue grouse, ruffed grouse, and capercaillie). Sexual dimorphism in body size, coloration, and elaboration of plumage and eye combs increases as displaying males become increasingly clustered in space. For more details see Hjorth (1970) or Johnsgard (1983).

Male grouse court females by spreading strikingly patterned tail feathers, drooping their folded or slightly open wings, strutting in jerky or rapid running movements around the female, and emitting stereotyped sounds. Most have a fleshy vascularized comb above each eye that can be engorged to make it stand up and be colored red (similar to chickens); some species have other tints on their combs. Many species perform a flutter-jump display in which they leap to varying heights above the ground and flap their wings as they settle back. Most also have some form of strut display performed to nearby females. The typical strut posture involves leaning forwards, fanning the tail (usually exposing brightly patterned feathers), and slightly drooping the wings. Many species have air sacs on the throat or breast that are inflated statically or dynamically during the strut to make them visible while species-specific sounds are emitted. Struts usually involve short runs, stiff-legged stamping, and stereotyped movements of the whole body or the head. Females are usually relatively passive during courtship: they watch and listen, and if multiple males are present, visit a series of males before mating. Females indicate readiness to mate by adopting a typical avian squatting posture. Mate choice on grouse leks can be highly skewed: in species like sage grouse as few as 10% of the males are chosen by females for most of the matings. These basic components are conserved throughout most of the group, with various species-specific embellishments:

  • Red grouse (Lagopus lagopus): Red grouse are one of many sub-species of the pan-northern hemisphere willow ptarmigan. They exhibit the first of the types of mating system listed above. Each fall, males establish a breeding territory of one to two hectares which they then roam in winter and spring with combs erected while giving several different types of territorial calls. Males court females attracted into their territories by fanning their tail, drooping their wings, and making stereotyped circling movements around the female while wagging their heads. Both sexes make soft calls shortly before copulation. The female then nests in the male’s territory.
  • Ruffed grouse (Bonasa umbellus): This forest species of grouse is found throughout Alaska, Canada, and the northern United States. It has the intermediate type of mating system described earlier. Males exhibit small red eye combs during the breeding season. Displaying males are dispersed but often within ear-shot of each other. Each has one or more favored display logs from which it emits a stereotyped drumming: this consists of an accelerating series of low frequency booms (see Chapter 2 for mechanism). These sounds carry long distances and attract females to their display sites. Once a female is present, the male adopts a typical grouse strutting posture with the body leaning forward, the tail fanned, and the wings slightly drooped. Male ruffed grouse also erect a collar of nape feathers that form a crescent around the head. Males then move slowly towards the female while making hissing sounds and rotational movements of the head. The final approach is made in a swifter “rush” with the wings dragging on the ground.
  • Blue grouse (Dendragapus obscurus): Blue, sooty, and dusky grouse are different subspecies, or races of a species inhabiting the conifer forests of the US Pacific north-west, northern Sierra mountains, and Rocky mountains. Like ruffed grouse, they exhibit an intermediate mating system of dispersed and promiscuous displaying males. Males exhibit low frequency hoots to attract females: coastal populations (Pacific northwest and California Sierras) tend to make loud hoots that can be heard at long distances; inland populations (Rocky Mountains) perform the behavior but can barely be heard unless very close to the bird. When other males or females are in sight, a male may perform several different patterns of flutter-jump with accompanying sound emission. Once a female is close, the male fans its tail, engorges its eye combs, droops its wings slightly, and inflating underlying air sacs, exposes two bare patches of throat skin each of which is surrounded by a rosette of white feathers. He then performs a circling rush towards the female ending with a loud hooting call. This may be repeated over smaller distances until the female solicits mating or leaves.
  • Spruce grouse (Falcipennis canadensis): Spruce grouse occur throughout the northern conifer forests of Canada and Alaska. They have the same intermediate mating system of dispersed displaying males seen in ruffed and blue grouse. Males have the usual colored eye combs, but lack the bare skin patches seen in blue grouse. Males can produce a very low frequency hooting to attract females. They also perform a number of variations on flutter-jumps: a typical one is to fly in a conspicuous way to a low branch where it sits with combs erect and tail partially cocked while making a few wing flicks. The courtship posture is typical of most grouse. When courting a female, the male walks towards her opening and folding alternate side of its tail with successive steps to produce a swishing sound. Males may also fan and collapse the tail to produce sounds, bob the head from side to side, or perform ritual pecking at the ground. Like ruffed and blue grouse, spruce grouse will perform a stereotyped rush at a female while hissing and swishing the tail feathers; in spruce grouse, this ends with the male squatting in a position similar to that of soliciting females. Some examples:
  • Capercaillie (Tetrao urogallus): This Eurasian boreal forest species is the largest of the grouse. As with other species, territorial and courting males fan their tails, engorge their eye combs with blood, and droop their wings. However, in this species, the head and neck are stretched up vertically while the bill is snapped accompanied by a variety of swishing sounds. This is one of the species in which males form exploded leks, but they do often position their favored display sites near to each other. In this clip, a male performs the standard display both to the camera and to another male.
    (http://www.arkive.org/capercaillie/tetrao-urogallus/video-13.html)
  • Black grouse (Lyrurus tetrix): Males of this species display on small leks (5–10 males). Interference between males is common and fighting is frequent. Major courtship displays include: (a) short flutter- jumps into the air followed by a fluttering descent and a hissing sound; (b) the roo-coo in which the male tips its body forwards, spreads the tail, lowers the folded wings, and dances in circles around a female while rapidly emitting a roo-coo sound. Females on leks walk around sampling males but perform no courtship signals of their own except to crouch into a solicitation posture when ready to mate. Both displays and males fighting are shown in this clip.
    (http://www.arkive.org/black-grouse/tetrao-tetrix/video-09a.html)
  • Greater prairie chicken (Tympanuchus cupido): Males of this North American species displays on leks of 5–20 males (leks may have been larger before habitat loss and hunting lowered populations). Eye combs in this species are yellow–orange, and both sexes have 8–10 elongated nape feathers called pinnae. Males provide long-range advertisement with flutter-jump displays and loud cackling squeals. In the main courtship strut to a nearby female, a male erects his nape pinnae straight up, stamps his feet as he moves past or around her a short distance, stops and crouches, and finally fans his tail open and closed while emitting a low frequency multiple-syllable coo and inflating and deflating the paired orange throat sacs. He then repeats this sequence. Unlike sharp-tailed grouse (see below), male conflicts usually involve different postures and displays than are used to court females.
  • Sharp-tailed grouse (Tympanuchus phasianellus): The sharp-tailed grouse is a close relative of prairie chickens, and their ranges often overlap in North American prairie areas. It is a lek species with 2–30 males/lek. Males advertise their presence on the lek with loud cackling calls and flutter-jump displays. Females often announce their arrival at the lek with their own cackling. As with the congener, courting males assume a bent-over posture and erect their yellow eye combs. Unlike most other grouse, the wings during strutting are not drooped but held extended laterally from the body, and unlike prairie chickens, the vertically oriented tail is a fluffy oval instead of a fan of stiff feathers. The paired throat sacs are purplish unlike the orange of the prairie chickens. Males court females by circling them with stiff-legged steps like prairie chickens, but the sounds produced are a mix of low amplitude foot-drumming and loud cackling. Intermale aggression is common on sharp-tailed grouse leks and many of the same displays directed at females when courting are also directed at neighboring males. In addition to cackling and drumming, males produce a cooing sound that is similar to the courtship booming of prairie chickens, but is here often directed at other males.
  • Greater sage grouse (Centrocercus urophasianus): This is the largest North American grouse species and is an inhabitant of the sagebrush deserts of the far west. Males display on very small territories within leks that can host over 150 males. Unlike lek species with smaller numbers of males, interference between males when females are present is rare. This genus appears to have lost the flutter-jump display of ancestral grouse. Males perform a single courtship display that is highly stereotyped: the body posture is more erect than in other lek species, although the tail is fanned in typical grouse fashion. The wings are slightly drooped but held against the sides of the body. The male takes several steps forwards and then heaves the heavily muscled and air-filled breast forward twice. Each time, it rebounds and rubs stiff breast feathers against the wings producing two swishes. These are accompanied by low frequency coos and spreading and contracting of the bare green skin over the two chest sacs. The strut ends with two rapid inflations and deflations of the chest sacs, each of which produces a popping sound, and a high frequency whistle emitted between the two pops. The overall body movement flips the male’s nape plumes upwards after which they fall back. The male then stands still for a few seconds and repeats the display. Male sage grouse usually do not herd females (e.g., move in decreasing circles around them), and often face away from them when doing their strut. This appears to be less threatening to females who often approach displaying males closely. This excellent clip with synchronized sound provides close-up views of males strutting including a final slow motion section.
    (http://www.youtube.com/watch?v=m0M8pZnNlnI)
  • Gunnison sage grouse (Centrocercus minimus): The small relic population of this second sage grouse species is currently threatened with extinction. Males are slightly smaller than greater sage grouse males, and their nape plumes are much longer and fuller. Leks have a similar structure and overall behaviors are similar to those of the greater sage grouse. The pattern of the strut however contains more chest-sac popping, louder wing swishes, and multiple quivering of the tail feathers. The nape plumes usually flip both upwards and forwards in contrast to the lesser motion in the other species. In the clip provided, the different emphasis on the head plumes is obvious and the accompanying sounds are clearly more “bubbly” than those of the greater sage grouse. Note that the sound track in this clip is for illustration only and is not a synchronized with the video.
    (http://www.youtube.com/watch?v=I1DI_C7uTDw)

Pheasants (Phasianinae): Pheasants constitute another large group (50–60 species depending on the taxonomist) of Galliform birds with striking courtship displays. Like grouse, adults tend to be mostly vegetarians but are much less specialized and their diets may also include berries, fruits, tubers, fungi, and some insects. Whereas male grouse fight by battering each other with their wings, pheasants have sharp spurs on their lower legs and fight by leaping into the air and trying to stab their opponents with their spurs. Pheasants live throughout south-east Asia in habitats ranging from thick lowland forest to barren montane scrub. Mating systems include monogamous pairs that remain together all year (monals), serially polygyny in which males remain with a female up to or through incubation and then move on to find another mate (tragopans), harem polygyny in which a male guards a group of females (common pheasant and junglefowl), and various types of promiscuity including dispersed displaying males (argus pheasant) and leks (some populations of peafowl). Although there is a tendency for greater sexual dimorphism as one goes from monogamous to promiscuous mating systems, many monogamous pheasants, like monogamous pairs in many other avian taxa, are strikingly dimorphic in plumage coloration. For more details, see Beebe (1936), Delacour (1977), Savage and Ridley (1987), Johnsgard (1999), and Madge and McGowan (2002).

As with the grouse, a common ancestral set of courtship displays has been modified and elaborated, dropped, or augmented depending upon the habitat, mating system, and simple drift. The shared repertoire includes loud crowing calls by males to defend territories, challenge other males, or attract females. As with grouse and their flutter-jumps, many male pheasants perform conspicuous wing flapping and short stylized flights to advertise their presence at intermediate distances. When females are nearby, males of many species perform ritualized tidbitting. This behavior is widespread in Galliformes and consists of a hen pointing or pecking at a food item to instruct chicks on suitable foods. Males have co-opted this behavior to get the attention of females and in some species, such as jungle fowl, they actually point at or peck at food finds to the benefit of females. In other species, male tidbitting is more of a stereotyped movement with no food present. Nearly all species have bare skin around the eyes and cheeks, and in some this may extend under the bill. This skin is usually colored red or blue, although a few exceptional species have white or black skin. The skin in some species is elaborated into fleshy horns, wattles, or bibs that can be engorged with blood or otherwise expanded. Perhaps the most widespread pheasant courtship display is waltzing. This is a lateral display in which males fan the tail, expand the wings, and then tip their body to one side so that one wing touches the ground while the other points nearly straight up. The result is an elliptical sheet of feathers oriented almost vertically with the male’s head on the side nearest the female. Males may remain static or circle the female while waltzing. In many species, the plumage exposed during waltzing is strikingly patterned and colored. Different species of pheasants have different enlarged muscles under the skin that are used to erect and hold their wing, tail, or covert feathers in position during displays (Osborne 1968). Some species also have wiry feathers ending in knobs on their heads that amplify their display movements. As with non-lek grouse, many pheasants make a short rush at the female at the end of a display.

Because pheasants are highly fancied by aviculturists, and much easier to keep in captivity than grouse with their specialized diets, most of the clips below were made in captivity:

  • Koklass Pheasant (Pucrasia macrolopha): The two sexes in this seasonal montane forest species are somewhat dimorphic. Pairs remain together all year (social monogamy). The male remains with the female through incubation and the family moves off together after hatching. Males are highly territorial and crow to defend territories. During the waltz, the male erects the paired pinnae on its head, rears up, lowers the wing on the side of his body away from the female, and exposes the white throat patches. He may also vocalize.
  • Monals (Lophophorus): These pheasants live in seasonal alpine meadows. They often go around in small unisexual parties and males do not appear to be territorial. Both sexes call and this may facilitate getting together during the breeding season. Although originally thought to be monogamous, they are now thought to be serially polygynous.
    • Himalayan monal (L. impejanus):
      • Closeups of male and female plumages:
        http://www.arkive.org/himalayan-monal/lophophorus-impejanus/video-00.html
      • Note that the sound on this clip is dubbed and not the natural sounds of the birds. First sequence shows male crowing (no sound). Males can perform a standard waltz (not shown here) in which they stand laterally to the female, raise the chest, drop the near wing and raise the far one. In this clip, they perform a frontal courtship display which is likely a re-ritualized waltz. The male lowers its head, spreads its wings and tail, and slowly fans the tail forward and backward (shown several times here). The display is symmetrical when the female is in front of the male, but tipped in the usual waltz-manner when she is to one side.
        (http://www.arkive.org/himalayan-monal/lophophorus-impejanus/video-09.html)
    • Chinese monal (L. lhuysii):
  • Tragopans (Tragopan): The five species in this genus are all residents of semi-montane forests where they are one of the few pheasants to nest in trees instead of on the ground. The mating systems are poorly known, but serial or simultaneous polygyny best fits the available evidence. Sexual dimorphism is strong: in addition to a distinctively colored plumage of bright white spots on a red or gray-brown background, males have brightly colored fleshy horns and a large bib that can be inflated during courtship displays. Males have very loud calls that carry long distances and suggest defense of large territories. When they encounter females, they may perform a stiff-legged clucking and/or tidbit. If the female remains, the male inflates its horns and bib and begins a jerky vertical bobbing that waggles the horns and ripples the colored bib. Usually, he then moves behind a rock or fallen log so that the female can just see the waggling horns, the bobbing head, and a tiny top part of the bib. The male then adds shaking of the partially opened wings to the repetitive movements. The male may accompany this with synchronized clicks or clucks. Suddenly, the male rears up from behind the barrier as high as it can extend its body, displaying the bib and horns in full expansion. Then it rushes at the female with the body erect and the wings drooping in a waltz-like fashion, or alternatively collapses back behind its barrier for a repeat performance. If you have never seen these displays, you must look at the following clips!
  • Peacock pheasants (Polyplectron): The 8 species of peacock pheasant inhabit either lowland or montane tropical forests. Most appear to be solitary much of the time. They are relatively monomorphic in plumage coloration with large “ocelli” designs on the wing and tail feathers. Mating systems remain unclear, but serial polygyny seems most likely. Species in this genus appear to exhibit nearly all of the common repertoire for pheasants. Males have favored display areas that they clear and use for calling. Males are often within earshot and respond to each other with counter-calling. Males approach visiting females with stiff-legged gaits, tidbitting sounds, and may even offer females food morsels in their bills. The main courtship displays are frontal and lateral waltzes with asymmetric tilting of the body. These are positioned so as to accentuate the eye-spot patterns of the plumage. Waltzing may be performed statically or while circling around the female. In this genus, females appear less passive during courtship than other taxa, and exhibit a number of head shaking, preening, and circling motions of their own prior to copulation.
  • Junglefowl (Gallus spp.): The habitats for the four junglefowl species range from lowland forest edge to subalpine seasonal zones. The red jungle fowl is the ancestor of domestic chickens. Sexual dimorphism is strong: in addition to colored bare skin around the eyes and face, males have colored fleshy combs on the head and fleshy lappets below the bill. Male plumage is iridescent and brightly colored. In wild populations, jungle fowl live in small flocks that roost together at night and forage over the same home range all year (Beebe 1936; Collias and Collias 1967). Flocks tend to be relatively small (two to six individuals) in the wild, but can be considerably larger in feral and domesticated populations (Beebe 1936; Collias and Collias 1967, 1996; Collias et al. 1996). Each flock hosts one dominant male, multiple females, and varying numbers of subordinate males. At dawn, the dominant male crows and leads the group off to forage, the subordinate males usually trailing along at the end. The dominant male defends the females with crowing and attacks when intruder males come too close during the day’s excursions. In the breeding season, males may court females with tidbitting, food provisioning, wing flapping, neck feather fluffing, headshaking, crouch-scratching, and waltzing displays (Johnsgard 1999). Because dominant males and flock females are already well acquainted, they may dispense with elaborate courtship: the female simply presents, and the male mounts. This is often the case in domestic chickens as well. However, wild females do not always mate with their dominant male, and this provides an opportunity for other males to court them which they do vigorously. When given a choice experimentally, females base their mate choice on both male display performance, particularly waltzing, and on the state and size of male secondary traits such as combs, wattles, and spurs (Zuk et al. 1995). After mating, females leave the flock to nest solitarily, and perform all parental care. Later, they rejoin the flock.
  • Peafowl (Pavo spp.): The two species in this genus, the largest of the pheasants, inhabit forest edge and broken woodland habitats. Both are highly sexually dimorphic in coloration and plumage structure: males have extremely elaborated tail coverts which host broad plumes with multiple ocellus patterns in iridescent colors. The smaller stiff tail feathers are used to help hold up the giant covert plumes. Both sexes have a tuft of feathers on their crown. Although a harem mating system was originally suggested for both species (Beebe 1936; Delacour 1977; Johnsgard 1999), an exploded lek system has been shown in natural populations of Indian peafowl (Harikrishnan et al. 2010), and even more clustered leks near villages or in introduced feral populations (Dakin 2011; Petrie et al. 1991;Yasmin and Yahya 1996). Like junglefowl, peafowl often have communal night roosts in a high tree but then break up each dawn into males that head to display areas and females that form small foraging groups. Males advertise their presence at display sites with loud calls. When females are near, males erect the enormous train into a vertically positioned fan, softly beat the partially opened wings, and periodically quiver the array making a rattling sound. Males often aim themselves away from females forcing females to move to a new position in front of the male to observe the display. When females are ready to mate, they squat and the male rushes over, lowering the train, to copulate.
  • Great argus pheasant (Argusianus argus): This species is an inhabitant of lowland tropical forests where they tend to live relatively solitary lives. Males and females are similarly colored and both have small crests and bare skin around the eyes. Males however have enormously elongated tail feathers (not coverts as in peafowl) and iridescent ocelli that are exposed when displaying. Males call to attract females to widely dispersed courtship sites. Calls can be heard up to 100 hectares around the male. Each male clears a small arena in which it performs displays to visiting females. Once a female enters the arena, the male may perform tidbitting or circle the female with a stamping gait. It then performs a classic pheasant waltz display in which one only marginally open wing is raised and the other lowered with the head facing the female. After several repetitions, the male faces the female and spreads his wing feathers into a giant fan revealing the iridescent ocelli on the plumes. He tucks his head behind one wing and begins a forward and backward pumping of the wing fan which also causes the long tail to wave forwards and backwards overhead. Females invite copulation by squatting, and the male then rushes to her to mate as in many other species.

Some other birds with predominantly male courtship displays

Below is a sampling of a few other interesting courtship displays:

Birds with mutual courtship displays

Courtship displays using objects

As we have seen, males of some species of fish, and some birds (not shown here), build nests in which they entice females to lay eggs after mating with the male. There are some other taxa, however, that build structures solely to attract females for mating; the females will then leave to lay the eggs or raise the offspring elsewhere. Since males that build such display structures are competing for matings, sexual selection has led to their building very elaborate display structures. Perhaps the most amazing examples are bower birds. These construct various alleys and tents and decorate them with brightly colored or rare items. Females visit the males who show off their decorations. Studies using robotic females have shown that, in these species, the courtship between the sexes is very complicated: males cannot move on to more advanced stages unless and until females give them appropriate signals to go ahead (Patricelli et al. 2006). Males are very competitive and often steal from or even destroy a neighboring male’s bower. Interestingly, species with the dullest male plumage tend to construct the most elaborate bowers and the most diverse decorations.

  • Flame bowerbird (Sericulus aureus): Male displaying to female at alley-bower:
    (https://www.youtube.com/watch?v=1XkPeN3AWIE&t=2m22s)
  • Satin bowerbird (Ptilonorhynchus violaceus): In addition to its decorated alley bower, males of this species are superb mimics of the calls of other species.
    • Gerald Borgia web page: Dr. Borgia is a world expert on bowerbirds. This web page provides an introduction to the group, and links to an excellent set of video clips of males displaying successfully and unsuccessfully to females, engaging in destruction of neighbors’ bowers, etc.
      (http://www.life.umd.edu/biology/borgialab/)
  • Vogelkopf bowerbird (Amblyornis inornatus): These drab males build elaborate display huts and decorate them with a wide variety of colorful or shiny objects.

Mammals

Mammal mating systems include relatively solitary species (usually with large male territories containing separate home ranges of multiple females), harems in which a given male oversees the same females for an extended period, monogamous pairs that remain together all year, mixed sex groups with established dominance hierarchies, and various promiscuous systems ranging from well-defined leks to chaotic mating swarms. Males and females that do not live together often require several stages of courtship before either male or female will allow the other to get close enough to mate. Members of stable groups often know each other and require only simple coordination behaviors before copulation; females in harems may have no choice of mate, and as soon as receptive will be approached by the harem male. Females in lek species visit multiple males before attempting to select one based on competitive displays; as with grouse, mammalian lek species differ depending on whether females are relatively free to choose (e.g., hammerheaded bats) or subject to frequent male interference (e.g., ungulate leks). Below, we provide a small sampling of the courtship behaviors associated with different mammalian mating systems:

  • North American otter (Lontra canadensis): North American otters are relatively solitary much of the time but have sufficiently overlapping home ranges that olfactory cues left by oestrus females attract neighboring males. Not surprisingly, both parties are fairly aggressive and wary during pre-copulatory interactions. (http://www.arkive.org/north-american-otter/lontra-canadensis/video-09.html)
  • Ring-tailed lemur (Lemur catta): Ring-tailed lemurs live in stable mixed-sex groups. Because females are dominant to males, they have a fair amount of freedom to choose a mate. Oestrus females are detectable through olfactory cues: this clips shows examples of females actively soliciting a particular mate and one case of a female rejecting one. (http://www.arkive.org/ring-tailed-lemur/lemur-catta/video-09a.html)
  • Flying foxes (Pteropus spp.): Both sexes of these large fruit bats live in communal roosts during the day. In the breeding season, males establish and defend territories on a few branches within the colony roosting tree. They mark the surface of the branches with secretions from shoulder glands. Females initiate mating by entering a male’s territory, and can halt mating by flying off to another site. However, central males in the colony tend to accumulate multiple females who remain within their territories throughout the breeding season. Males are very solicitous and perform extended genital licking on females prior to mating. Eventually, receptive females assume a suitable posture and the male mounts from the rear, using an exceptionally long penis to get past the female’s inter-femoral tail membrane. Several examples:
  • Mandrill (Mandrillus sphinx): Mandrills are another primate that lives in stable mixed-sex groups. However, the dominant male in a mandrill group rules overall and a female in oestrus has no opportunity to exercise choice or engage in preparatory courtship.
    (http://www.arkive.org/mandrill/mandrillus-sphinx/video-09a.html)
  • Northern elephant seal (Mirounga angustirostris): Males arrive at breeding beaches first, spread out and establish dominance hierarchies. Females arrive, give birth, and come into oestrus shortly before or at weaning of the current young. Males are much larger than females making it difficult for females to reject an interested male. However, they are able to incite new fighting among nearby males by moving to certain locations, and then mate with the winner of that outcome. This clip shows a typical copulation in this species. Note marked sexual dimorphism in size.
    (http://www.arkive.org/northern-elephant-seal/mirounga-angustirostris/video-09b.html)
  • Impala (Aepyceros melampus): Impala live in fairly stable harem herds. The harem male and females are well acquainted and courtship is often fairly minimal. (http://www.arkive.org/impala/aepyceros-melampus/video-09a.html)
  • Topi (Damaliscus korrigum): Topi males either defend foraging territories within which they have mating access to oestrus females currently feeding there, or (even in the same population) males display on a lek. In the latter case, each male defends a small display territory by marking it with urine and feces, standing tall in a conspicuous site, walking stiffly with the ears cocked and tail straight out, or actively chasing out intruders. Both sexes get down on their front knees and rub their horns, orbital glands, and foreheads in the ground, preferably muddy ground. This apparently mixes glandular secretion with mud on the horns to facilitate enhanced pheromone dispersion. Males will also meet at a common boundary and perform ritual fights in which they fall on their front knees and clash horns. When females enter a male’s display territory, he lowers his ears, and approaches her with a high stepping courtship walk, usually followed by lifting the ears and sniffing of the female’s genitalia. Females have some choice of mates (by entering a particular territory), but topi, like other lekking ungulates, do show high levels of male interference. This video was taken by Jack Bradbury with input and guidance from Mike Rainy in Kenya.
  • Whales and dolphins (Cetacea): One might think that being relatively weightless in water makes mammalian mating easier. However, there is a significant challenge to establishing suitable alignments between male and female without the earth’s surface as a substrate and given surging seas. In addition, competing males can appear from any direction in water resulting in high levels of interference in many cetaceans. In most species, the male swims upside down under the female, both keep moving, and the male stabs upwards with his long penis until he finds the female’s genital opening. Sexual play is common in both sexes, particularly younger dolphins, although adult male dolphins continue to poke and prod others with their penises in many different contexts. This may provide the dexterity needed for actual mating, but also seems to have other signal functions. Acoustic signals and touch clearly play significant roles during courtship. Males of some species also perform leaps and other gymnastics when courting females, and in a few species, males mate-guard females after copulation. Some cetacean mating examples:

References

Beebe, W. 1936. Pheasants: Their Lives and Homes. Garden City NY: New York Zoological Society and Doubleday, Doran, and Company.

Collias, N.E. and E.C. Collias. 1967. A field study of the red jungle fowl in north-central India. The Condor 69: 360–386.

Collias, N.E. and E.C. Collias. 1996. Social organization of a red junglefowl, Gallus gallus, population related to evolutionary theory. Animal Behaviour 51: 1337–1354.

Collias, N.E., E.C. Collias, D. Hunsaker, and L. Minning. 1966. Locality fixation, mobility, and social organization within an unconfined population of red jungle fowl. Animal Behaviour 14: 550–559.

Dakin, R. and R. Montgomerie. 2011. Peahens prefer peacocks displaying more eyespots, but rarely. Animal Behaviour 82: 21–28.

Delacour, J. 1977. The Pheasants of the World, 2nd Edition. Lamarsh UK: World Pheasant Association.

Deloach, N. and P. Humann. 1999. Reef Fish Behavior: Florida, Caribbean, Bahamas. Jacksonville FL: New World Publications.

Harikrishnan, S., K. Vasudevan, and K. Sivakumar. 2010. Behaviour of Indian peawfowl Pavo cristatus Linn. 1758 during the mating period in a natural population. The Open Ornithology Journal 3: 13–19.

Hjorth, I. 1970. Reproductive behaviour in Tetraonidae. Viltrevy 7:183–596.

Johnsgard, P.A. 1983. The Grouse of the World. Lincoln NE: University of Nebraska Press.

Johnsgard, P.A. 1999. The Pheasants of the World: Biology and Natural History, 2nd Edition. Washington DC: Smithsonian Institution Press.

Madge, S. and P. McGowan. 2002. Pheasants, Partidges, and Grouse: A Guide to the Pheasants, Partridges, Quails, Grouse, Guineafowl, Buttonquails, and Sandgrouse of the World. Princeton NJ: Princeton University Press.

Mason, R.T. and M. R. Parker. 2010. Social behavior and pheromonal communication in reptiles. Journal of Comparative Physiology A 196: 729–749.

Osborne, David R. 1968. The functional anatomy of the skin muscles in Phasianinae. Ph.D. Thesis. East Lansing MI: Michigan State University.

Patricelli, G.L., S. W. Coleman and G. Borgia. 2006. Male satin bowerbirds (Ptilonorhynchus violaceus) adjust their display intensity in response to female startling: an experiment with robotic females. Animal Behaviour. 71:49–59.

Petrie, M., T. Halliday, and C. Sanders. 1991. Peahens prefer peacocks with elaborate trains. Animal Behaviour 41: 323–331.

Savage, C. and M.W. Ridley. 1987. Pheasants in Asia: Proceedings of the 2nd International Symposium on Pheasants in Asia. Reading UK: World Pheasant Association.

Takahashi, M., H. Arita, M. Hiraiwa-Hasegawa, and T. Hasegawa. 2008. Peahens do not prefer peacocks with more elaborate trains. Animal Behaviour 75: 1209–1219.

Yasmin, S. and H.S.A. Yahya. 1996. Correlates of mating success in Indian peafowl. The Auk 113: 490–492.

Zuk, M., S.L. Popma, and T.S. Johnsen. 1995. Male courtship displays, ornaments, and female choice in captive red jungle fowl. Behaviour 13: 821–836.

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