Animal courtship

Courtship is the ritualistic behavior animals carry out preceding mating. The courtship process allows the male and the female of the species to attract each other and choose a mate for reproduction. This behavior varies greatly among the species. Courtship rituals for mating can be as simple as sign stimuli, such as the emission of pheromones by certain female moths, to the complex dance of the stickleback or the bowerbird.

In nature, most animals are solitary except when courting and rearing their young. For each animal, the signals used to communicate with and attract a mate must be clear and unambiguous. This is to avoid any confusion in identifying the sex and species of an animal’s potential mate, as the ultimate goal of nature is to encourage the reproduction and survival of all species.

The procreation process in most multicellular plants and animals involves a complex form of sexual reproduction. The unique and differentiated male and female reproductive cells, called gametes, unite to form a single cell known as the zygote. The zygote undergoes successive divisions to form a new multicellular organism where half the genes in the zygote come from one parent and half from the other, creating a singularly different living creature.

The sexual reproduction process requires a pair of distinct partners of opposite sexes to mate, hence the need for courtship so that animals can find and attract prospective mates for producing offspring. It is the sexual interest of the opposite sexes that leads to mating; therefore, copulation in most animals is preceded by a period of courtship. The mating of most lower animals is governed by endocrine secretions specific to certain seasons. In female mammals, receptivity to mating is called estrus, which is operative only for short periods during the year. Cows have several such periods of estrus during the year; dogs have one or two.

As courtship is always a precursor to mating, which leads to the proliferation of the species, it is often intermixed with both greeting and aggression. Often, the aggression is directed toward a rival that might wander into marked territory. What is fascinating is that quite often, it is difficult to distinguish between greeting and aggression. There are many different types of courtship behavior, including shoaling, nest building, mouth or pouch brooding, parasitic mates, carnivorous mates, marking territory, pair bonding, domination, female dominance, bower building and gift offerings, communal display, exotic pirouettes, group breeding, monotremes, odor marking, color signals, sounds, and migration.

Fish Courtship

The male stickleback, a fish similar to the minnow, orchestrates its mating by changing its color. During the breeding season, the male's underside turns bright red which attracts females but also instigates attacks from other males. Studies have shown that during this time, nearly any red object can provoke male stickleback aggression. The female’s response to the red signal of the male stickleback is to advance in a posture that clearly exhibits her swollen, egg-filled underbelly. This stimulates the male to carry out a zigzag dance that, in turn, seduces the female into following him to the tunnel-like nest he has built. The male waits until the female struggles into the nest and immediately touches her tail with his nose and starts quivering. The vibration causes the female to release her eggs so that the male stickleback can externally fertilize them. If, for some reason, the male is unsuccessful in executing the last part of this intricately choreographed dance, the female will not lay her eggs. However, it is extremely interesting to note that vibrating the female with some arbitrary object, which she may even realize is not a male stickleback, works just as well to induce the release of the eggs, although, as the male did not complete the last step of the courtship ritual, he does not fertilize the eggs, but rather eats them.

Another fish's courtship habits caused years of confusion among scientists. Divers off the coast of Japan found round, geometric shapes on the ocean floor measuring about 2 meters (6 feet) across. The scientific community was uncertain what could create such patterns until years later when they discovered it was a small male pufferfish 12 centimeters (4 inches) long. This pufferfish's mating habits require about one week of work, including creating a circle in the sand and adding ridges, decorative lines, and pieces of shells or coral. If a passing female likes the male's work, she will lay eggs in the middle of the circle.

Amphibian and Reptile Courtship

Amphibians have varied and interesting courtship rituals. Generally, the tailless amphibians breed communally. Amphibians such as frogs or toads will use sound to attract their mates, whereas male newts use odor to attract the females. The American tree frog (Hyla crucifer) sings in trios. Only the males have vocal sacs that can make sounds; the females are silent. The sounds of the males among the different species are distinctly different and versatile. The notes are delivered at different speeds and frequencies. The female has her own features of recognition. The way a female frog advertises her sex and readiness for mating is that she develops a series of granulations on her thighs, which is clearly visible to a male frog. During courtship, many amphibians use their heads in different ways to rub their partners. For most frogs, the male climbing onto the female’s back and aiding in the discharge of her eggs accomplishes mating. The male, in turn, releases his sperm after being excited by the female’s movements.

In reptiles, even though the courtship behavior is not very complex, bobbing, circling, and marking of territory are noticed. Snakes such as the crotalids, including vipers and rattlesnakes, have a mutual dancelike ritual for courtship. As the snakes circle each other, they rear up, facing one another, and intertwine for copulation. Most snakes of the Crotalidea family give birth to living young from eggs that hatched inside the mother’s body. The colubrids, such as the boomslangs and kingsnakes, and elapids, such as the cobras, have a nuptial procedure where the male rubs his lower jaw along the back of the female in an attempt to stimulate her. It is conjectured that perhaps this behavior also stimulates him and all the other males in the matrix group. A male snake copulates by throwing coils around the female and bringing their cloacas into juxtaposition. However, sometimes they simply lie close without the retaining coils. They may use a branch or similar object to maintain a grip to hold them close together. Even though most snakes are more aggressive during mating season, few males fight among themselves. Other than among the elapids, there does not seem to be much competition among the males.

This is contrary to what is noticed in crocodiles and alligators. In these reptiles, the breeding season for the males is a loud and contentious time. They will battle and resist any potential competitor with ritual gaping, lunging, and hissing. Yet the courtship behavior is serene. The male marks his territory using a secretion from his musk glands. This not only warns off unwelcome male rivals, but it also attracts females. Male crocodiles and alligators confidently bellow their love calls to make their presence and location known to the females. Once a female gets paired with a male, they swim together. They progressively increase their speed, and the male rubs his throat against the female’s snout to mark her with his odor and vocalizes without encumbrance before he copulates with her. The male leaves to find his own area after mating. The female goes on to build a nest above flood level using mud and vegetational debris. She covers her eggs with mud and decaying vegetation so that the sun’s heat will incubate her eggs. She guards her eggs until they are hatched. She may aid the young ones to get to the water’s edge by carrying them in her mouth. It has been observed that some female alligators may even stay with their young for a year or more. A female alligator is quite protective of her young and responds quickly to the sharp croaks of a young one in distress.

Bird Courtship

Birds, in general, have engaging and quite elaborate courtship rituals. Usually, birds do not stay with the same mate all year round or from year to year. Sometimes, the same pair may be together for several years, but nonetheless, the pair bond, that is, the couple's relationship, must be renewed or reinforced at the onset of each breeding season. Birds use auditory, visual, or both kinds of display to conclude their courtship ritual. Peacocks use intricate visual displays that involve specialized plumes. In the barbets and wrens, duetting is used for courtship and attracting the mate. The male and female alternate their calls in such exact synchronization that it seems as though the sound is coming from one bird. This is an example of an auditory display. Using both auditory and visual displays, blue-capped cordon-bleu songbirds bob their heads, sing, and tap their toes for one another during mating season. Some birds, such as ducks, follow an extremely stereotyped movement pattern. However, both birds must respond with the correct display, or the sequence is broken. There are certain birds where a pair bond does not exist at all. The male birds gather and display against each other, contending for the right to mate with the maximum number of females possible. This type of gathering of males is called a lek. The bird of paradise is well known for this type of courtship behavior. Other examples would be manakins, sandpipers, and grouse.

The different types of bowerbirds are renowned for their extraordinary courtship behavior. These birds are commonly found in New Guinea and Australia. It is believed that the bowerbirds are close relatives of the birds of paradise of this area. For the most part, the males and females live apart from each other during the year. Only during mating season do the males gather and compete for females. Each male bird creates a clearing on the forest floor that becomes his “playing field.” This is where he tries to entice and lure the females. The bird will arrange rocks, shells, colorful fruits and berries, flowers, and inanimate articles such as pieces of glass or other interesting human manufacturing items. In some species, the males will construct different types of forms and structures. Some of these birds erect what look like upright poles of sticks around a tree trunk that are embellished with colorful flowers, mushrooms, lichens, and other objects.

The Australian male satin bowerbird is a silky blue-black bird that is approximately 20 centimeters (about 7.8 inches) long, with bright blue eyes. The male bird builds a stick mat. He then places two walls of vertical sticks down the middle. These walls may reach a height of thirty-eight centimeters (sixteen inches). The bird then mixes his own saliva with a blue or green fruit juice to form a “paint.” He uses a tree bark to paint the bower and tries to attract the grayish-green female into the bedecked bower to mate. This is one of the few known instances of birds using tools.

Another species known as the gardener or Vogelkop bowerbird makes a tentlike structure that resembles a teepee. The bird is only about 25 centimeters (10 inches) long, but the teepee can be as extensive as 1.6 meters (63 inches) across. This little teepee comes complete with a low entranceway overlooking a “garden,” consisting of brightly colored flowers and objects that are diligently replenished as soon as they fade. There are about nineteen species of bowerbirds, and they all have similarly elaborate courtship displays.

Mammal Courtship

Mammals have evolved to have the most sophisticated sexual apparatus of all animals, yet in general, mammals do not spend as much time in courtship as birds do. Mammals also have the most highly evolved manner of parenting. Therefore, the relationships between mates are diverse. Lower mammals, such as some rodents, practice promiscuous polygamy without any particular selection process by the female. The females are left to rear the young on their own. In bears, both the male and female are promiscuous. There are others where the male appears to have a harem. The California sea lion may have up to forty females, the Pribilof seal from forty-five to a hundred. Many deer and antelope have harems, too. Even the sedate koala may monopolize several females. These are also examples of dominance. Dominance can also extend toward other males, so that the dominant male can have all the females to himself.

Monogamy is rarer in mammals. A few canines are monogamous, but only for a particular season. Some monkeys and apes, not including chimpanzees, follow this rule. Foxes may be monogamous, and the American beaver is one rare mammal that practices monogamy for life. Even in the higher mammals, including humans, monogamy causes a decline in sexual interest for the partner, and eventually, sexual relations may cease if there is no stimulus of novelty. There is also the other extreme, where the animals are solitary and only meet for copulation, such as the titi monkey.

Most mammals tend to be complacent in their efforts at enticement, and rely on simpler stimuli such as secretions, color changes, and odors. For mammals, arctic foxes have an elaborate and rather graceful courtship dance. They rear up on their hind legs and face each other as though they are playing. The elephant has a most gentle approach to courtship. The female is attracted to the male by the strong scent of the two glands near his ears, which start to secrete during rut. Once the male and female have found each other, they caress one another with their trunks and intertwine these sensitive organs. They express their affection and confidence by placing the tips of their trunks in each other’s mouths.

In some species, the female takes the initiative for mating. A small number of primates will do so. When the female is ready, she entices the male to attend to her. The female hedgehog will lift her tail up and lay all her spines down to solicit the male for mating.

Odor marking is very common in placental mammals. Most male mammals, even pack animals, will mark out their territory by odor glands, urine, or feces. Some will mark the female as a sign of ownership. There are others that display color, signaling a potential partner of the opposite sex of its interest in mating. The female gelada baboon, which mostly spends her time sitting, develops a red patch on her chest similar to the one in her genitals, so that both markings can be easily observed by other baboons.

In many different animals, migration is required as part of the courtship and breeding process. Migratory rituals exist in just about all types of animals: fish, birds, and mammals. Some fish, such as the salmon or sturgeon, will travel thousands of miles to return to their ancestral waters to spawn. The urge is so strong that the fish will die trying to reach this place rather than give up.

Ultimately, nature’s most primordial instinct is to continue the species. Every living organism feels the irrepressible compulsion to perpetuate its genes. This necessitates sexual selection, Darwin’s other type of natural selection. The consequence is sexual dimorphism, including different size, color, and traits in the sexes. There are two types of sexual selection: intrasexual selection, where males contend among themselves through contests and displays for the favor of a female, and epigamic selection, where the females accept males with certain characteristics. The male may monopolize the females by practicing polygamy, thereby effecting a much more intense sexual selection for procreation purposes. Courtship behavior is about sexual selection, which eventually leads to the proliferation of the species.

Principal Terms

Arachnid: A class of arthropods with jointed legs and hard external skeleton that includes mites, scorpions, spiders, and ticks

Estrus: The period during a female’s sexual cycle when she is sexually receptive

Lek: A territory used by certain animals for mating

Monogamy: A mating system in which one male pairs with one female

Pheromone: A chemical produced by one animal that influences another animal of the same species

Polygamy: A mating system in which an individual of one sex pairs with several of another sex

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