Courtship and mating gifts

bonding techniques for enamored animals

Animal courtship often involves more than fancy displays and songs. Some male animals also give courtship ‘gifts’ to females, to help begin a mating relationship and help it on its way. But the gifts may also contribute to the well-being of the ensuing offspring and the mother. There may be both direct and indirect benefits to both giver and receiver.

Courtship gifts are often a food item; many birds, from songbirds to seabirds, engage in courtship feeding. Once a pair-bond has begun, the gift-giving often continues through the egg-laying period, when the female is fertile. Gifts of food come in a variety of forms. For instance, male kingfishers offer small fish to their females, and male shrikes commonly offer insects. The European great gray shrike with large gifts is reported to obtain better chances of copulating with his mate than one bringing small gifts—and he also gets more mating opportunities with other females when he goes gallivanting!

Females receiving gifts generally are in better condition, may lay more eggs, and are more likely to incubate successfully, so her reproductive success is enhanced. The direct advantage to the gift-giving male includes not only more copulations (and so, more eggs fertilized), but he also gains less direct benefits from the improved success of the female incubating his eggs. His gifts might also help keep her attention from wandering males looking for a chance to mate.

Male dance flies of some species capture another insect and present it to a female, copulating with her while she eats. If the prey is small, she may eat and run, before copulation is finished. Other species of dance fly (genus Hilaria) wrap the prey in a balloon of silk, which the female must unwrap in order to eat the prey. If he finishes copulating before she is finished eating, he sometimes takes back the gift and rewraps it for another female. In a related genus (Empis), some species just present a balloon of saliva bubbles that’s empty—and the females apparently accept that.

Male nursery web spiders in Europe give prey (usually silk-wrapped) to a female, who unwraps and bites it (instead of him). The male then copulates, spider style, by transferring sperm from his genitalia to his pedipalps (modified legs) and inserting the laden pedipalps in the female’s reproductive tract. He may keep one leg on his gift, lest she try to escape with it. However, sometimes the gifts are deceitful, just an inedible item wrapped in silk—that seems to work too, but perhaps not as well. 

Some male insects transfer nutrients to a female along with their sperm, in a package called a spermatophore. Depending on the species, the female may eat the part with nutrients or simply take it up into her reproductive tract. Experiments with fireflies and bush crickets have shown that spermatophore nutrients are indeed taken up by females and soon metabolized. In other species, the spermatophore contains protective substances. For instance, female fire-colored beetles take up spermatophores containing cantharadin (a poisonous and blistering compound); the females cover their eggs with it to protect them from predators.

In some cases, although there may be immediate reproductive advantages to both gift-giver and recipient, there may be other effects as well. For example, in the fruit fly (Drosophila melanogaster), the male’s gift may increase the female’s current reproductive success but decrease her long-term reproductive fitness.

There are still other ways of transferring things from one mating partner to another, such as the transdermal injections used by some invertebrates. For example, earthworms (which are hermaphroditic, the two partners exchanging sperm when they mate) have stiff hairs on the clitellum (the expanded segments near the front end of the body). Those hairs puncture the partner’s skin and may somehow manipulate the partner’s reproductive physiology. The famous ‘love darts’ of terrestrial,hermaphroditic snails and slugs are fired by both partners when they mate, just before sperm is exchanged. Apparently, mucus on the dart helps open the canal to the organ where incoming sperm is stored and improves sperm viability. Most snails produce one dart at a time, but some can produce many of them(they are made of calcium carbonate, chitin, or cartilage). Now the question arises: are these really gifts with the typical reciprocal benefits or does only the donor benefit?

The many uses of urine

courtship and defense, signposts and bragging rights… and a few human uses too

Reading about porcupine courtship made me think about how other animals use this metabolic waste product. Urine is an excellent vector for delivering scents and hormones that are signals involved with courtship (as in porcupines) and territorial defense. Many mammals, as well as some fishes and invertebrates, makes use of this convenient and readily available delivery system for olfactory communication.

We are all familiar with domestic dogs lifting a leg to urinate on a tree or fencepost. Such scent marks are sniffed by other dogs, who can learn the identity of the mark maker from the unique mix of scents, and often leave their own marks atop the original one. We sorry humans, with our relatively poor sense of smell, sometimes have a hard time imagining the scented world of dogs and many other animals, but these other beasts can identify individuals, as well as sexual and social status, from scent marks.

Both members of the dominant pair in a pack of wolves use urine to scent-mark the borders of their territory; newly formed pairs superimpose urine-borne scent marks on each other’s previous marks, probably as a part of courtship. Territorial borders marked with urine deposits are a regular feature of behavior in a variety of mammals, including coyotes and tigers. Beaver families make small, black piles of debris marked with urine and anal gland secretions to establish claims to particular waterways; other beavers are thus given notice that the place is occupied.

Males of many ungulates (such as moose, bison) either urinate over their own legs or wallow in urine-soaked dirt as a way of chemically signaling their status. Stallions urinate on established dung piles to advertise their dominant status. Male elephants and giraffes actually taste a few drops of female urine to detect hormones that signal readiness (or not) to mate. Female crayfish and swordfish send out a chemical signal via urine to attract willing males. Urine is used for certain forms of chemical communication among individuals of some species of primates (the taxonomic group to which humans belong).

Human campers sometimes urinate all around a camp site in hopes of deterring unwelcome four-footed visitors (although I don’t think the efficacy of this boundary marking has been fully determined), but human uses of urine go way beyond simple boundary marks. In the course of history, urine has been used in several inventive ways. Perhaps best known are the roles of urine in tanning hides and as a mordant to bind dyes to cloth. In sixteenth century England, whole casks of urine were shipped across the country for use in the dye industry.

The ammonia in urine can cut dirt and grease, and so it has been used as a cleaner. Even after soap became available, urine from chamber pots was used as a household stain-remover. In ancient Rome, urine collected from public urinals was hauled to laundries, diluted with water, and poured over dirty clothes in a tub; a person then stood in the tub and stomped on the wet pile to thoroughly mix the cleaner with the dirty clothes. Commercial persons who made a business of collecting and selling vats of urine were even subject to Roman taxes.

A traditional Scottish way to treat woven wool was to soak a length of the cloth in household urine to clean it and set the dye, and then pound it on a board. The process is called ‘waulking’ and still continues in the Hebrides (and in Nova Scotia by descendants of Scottish emigrants) as a cultural celebration.

Urine has been used as a tooth-whitener and for making gun-powder. Hormones extracted from pregnant mare’s urine are one way of treating fertility and menopausal problems. More recently, stem cells extracted from urine have been re-programmed to grow new nerves and other tissues. Many other medical applications are part of folklore, and indeed may be efficacious, but they could use verification by scientific study.

Very versatile stuff!