A nuptial gift is a material presentation to a recipient by a donor during or in relation to sexual intercourse, other than gametes, which increases the reproductive fitness of the donor. Such a gift will usually improve the fitness of the recipient as well, though they can also be neutral or costly.
Males may relinquish body parts, produce glandular secretions, or share prey or other food to gain fitness benefits, a process of natural and sexual selection. The study of nuptial gifting links sexual selection, nutritional ecology, and life history theory.
Different types of gifts Nuptial gifts are usually edible tokens: nutrition for the recipient. Many species of birds, insects, and spiders engage in courtship feeding: the gift of a food item from a male to a female just prior to copulation. Inedible tokens may be items such as a leaf or twig, a seed tuft, or a silk balloon, which may serve as an indicator of male fitness. More generally, in many species of insects, birds and mammals, males acquire and donate food to females either before, during, or after copulation, termed mate provisioning.
The source of the gift may be endogenous (produced by the donor) or exogenous (captured, collected or found by the donor). Exogenous gifts are often food items captured or collected by the donor to feed to the recipient. Endogenous gifts often carry great cost to the donor and usually contain hemolymph or body parts. Endogenous oral gifts are secreted by the donor’s glands (salivary, reproductive, etc.), often carrying nutrients or other substances benefiting the recipient or offspring. In the moth Utetheisa ornatrix, the male feeds the female defensive alkaloids to deter predation on their future eggs and larvae.
A gift may be received as an oral gift placed into the recipient's digestive system, a genital gift absorbed through the reproductive tract, of a transdermal gift injected into the body wall of the recipient. In some insects such as katydids and ground wētā, a nutritious genital gift is packaged with the sperm as a spermatophore.
In some species, mating can include gifts that benefit the donor but not the recipient. In hermaphroditic land snails, both partners to the courtship produce sperm and eggs, and it is in the interest of each to impregnate the other. Each partner attempts to shoot a mucus-covered love dart into the flesh of the other before attempting to give sperm into the other's ovipore. A dart may cause severe injury, but if it penetrates safely, pheromones in the mucus promote sperm retention in the ovipore, leading to fertilization in the recipient.
Occurrence Nuptial gifts are common in insects and other invertebrates, such as butterflies, fruit flies and katydids. They seem less common in spiders, though the spider species Pisaura mirabilis is known for nuptial gift giving. However, this may reflect experimental bias due to the ease of rearing this species in the laboratory, so more research is required to evaluate the scope of nuptial gifts among arachnids.
Courtship feeding is particularly common in bird species.
Role reversal
Species in which the male presents the nuptial gift to the female are more common, but the reverse does occur. Female Zeus bugs, Phoreticovelia disparata, present the male with a food item before copulation. The male will then ride in a small depression on the back of the female, as she secretes wax from a gland on the back of her head, which he eats for up to a week. After the sperm is deposited and the male leaves, the female can lay fertile eggs for up to two weeks. Although it is difficult to see any advantages to the female in this scenario, some scientists believe that allowing one male to remain deters other males from violent attempts to copulate with her.
Vertebrates
Great grey shrike
The male great grey shrike, a raptor-like passerine bird, gives prey (rodents, birds, lizards, or large insects) to females immediately before copulation. Shrikes are well known for impaling prey on thorns and sharp sprigs. Great grey shrike females select a mate according to the amount of prey impaled, with larders thus serving as an extended phenotype of the males. A large larder may make a mate more attractive as a regular mate and for occasional copulation with other females.
Invertebrates
Arachnids
Pisaura mirabilis In spiders, nuptial gifts in the form of prey are restricted to a few species from two families belonging to the superfamily Lycosoidea: Pisauridae and Trechaleidae. In both families, the male courts the female by offering a prey wrapped in silk and mating occurs while the female consumes the gift. In the species Pisaura mirabilis (Pisauridae), the gift functions as a mating effort that increases male mating success. The nuptial gift consists of a prey the male has caught and wrapped up in silk. The male offers this gift during courtship, and if the female accepts the invitation, she grabs the wrapped prey. While the female is eating, the male inserts the mating organ, and sperm is transferred.
A similar function was recently suggested for the trechaleid spider, Paratrechalea ornata. In both species, males can obtain mating without a gift, but male mating success increases dramatically when a gift is offered. There is a positive correlation between male size and mating duration, and an increasing mating duration when there is a gift offered. In Pisaura mirabilis, the male pushes up the female during mating and performs alternate pedipalp insertions into the female sperm storage organ, located ventrally on the abdomen. After each insertion the male returns to a face-to-face position with the female, grabbing the gift in the chelicerae. Females often control mating duration and they often attempt to run away with the gift upon terminating the copulation.
Females are less likely to succeed in stealing a wrapped – rather than an unwrapped – gift due to the silk wrapping of the gift. The silk wrapping facilitates male handling and control over the gift, as it facilitates a stronger hold of the silk covered package versus an unwrapped insect. Male spiders have a unique opportunity for gift manipulation through the gift wrapping trait, for example by preventing female assessment of the gift content. By disguising the gift content, males may deceive females to copulate, while the female attempts to consume the gift. In Paratrechalea ornata, males were observed wrapping prey carrion and occasionally inedible items such as plant seeds. In Pisaura mirabilis, males have been reported to carry gifts containing empty arthropod exoskeletons or plant parts: gifts of no nutritional value. However, some studies have shown that male spiders rarely cheat in nature. Cogent reasons for this disparate behavior are being explored. It is possible there are confounding factors which do not account for ecological implications. Other research suggests that sensory bias is not the main contributing force behind gift selection in P. mirabilis. Females did not preferentially select unwrapped gifts over wrapped gifts.
Pisaurina mira Similar to its cousin P. mirabilis, male P. mira also offers nuptial gifts to court the females. The gifts typically consist of an insect wrapped around in silk. Acceptance of the nuptial gift leads to completion of copulation, and male P. mira retrieves the gift from the female.
Paratrechalea ornata Nuptial gift behavior has been seen in the spider species Paratrechalea ornata, a Neotropical spider belonging to the Trechaleidae spider family. Paratrechalea ornata males may present either a wrapped or an unwrapped nuptial prey gift. Prey wrapping seems to be triggered by perception of cues on the female's silk and increases in frequency according to the male's age.
Insects
Balloon flies Some Empididae, such as the European species Hilara maura, have an elaborate courtship ritual in which the male wraps a prey item in a silk "balloon" and presents it to the female to stimulate copulation.Hamm, A. H. 1928. On the epigamic behaviour of Hilara maura Fab. and two allied species. Proc R. Soc. B. Lond. 102: 334–337. Empididae show diverse mating systems, ranging from species in which males aggregate in mating swarms, and compete for choosing females to sex-role reversed species in which females aggregate and compete for the attention of choosing males. In some species, such as the North American species Rhamphomyia longicauda, competition for the food provided by males is so strong that females have developed elaborate ornaments, including feathery "pennate" scales on their legs, darkened wings, and inflatable abdominal sacs that enhance their attractiveness. Across the group, nuptial balloons of species in the family range from small balloons containing large prey items (e.g., Empis aerobatica, E. bullifera, Hilara wheeleri), to balloons stuck to inedible dried prey items (e.g., E. geneatis), to completely empty balloons made of silk or saliva (e.g., H. sartor, H. granditarsis).Sadowski, J. A., A. J. Moore, and E. D. Brodie III, 1999. The evolution of empty nuptial gifts in a dance fly, (Diptera: Empididae): bigger isn't always better. Behav. Ecol. Sociobiol. 1999: 161–166.
Decorated crickets In decorated crickets, Gryllodes sigillatus (Orthoptera: Gryllidae), the nuptial food gift is a spermatophylax (a large, gelatinous, sperm-free mass) that surrounds a smaller, sperm-containing ampulla. Together, the spermatophylax and the ampulla constitute the male's spermatophore, which is transferred to the female during copulation and remains attached outside her body at the base of her ovipositor. After mating, the female detaches the spermatophylax from the ampulla and feeds on it while the ampulla remains attached and is emptied of sperm. Once the female has consumed or discarded the spermatophylax, she removes the sperm ampulla, terminating sperm transfer. Female cooperation is required for successful spermatophore transfer, and thus, males cannot impose copulations on females.
Bushcrickets Bushcricket males offer a spermatophylax containing an ampulla. The nuptial gift is also protein-rich, which the females ingest into their reproductive tract. The size of the nuptial gifts positively influences the females refractory period and the males reproduction success. The size of the gift depends on the ampulla and serves as a sperm protection. In the bushcricket Ephippiger ephippiger, the females prefer older males, who have larger spermatophores offering better nutritional value during mating. The nutritional value is related to the female's metabolic needs, and stands as a benefit for females feeding on the spermatophores. Sometimes males produce lower dosages of sperm with a lower nutritional value the fourth time they mate. It may be possible the females are using age and gift quality as a proxy for mates with good genes as their offspring are likely to have high relative fitness. The spermatophore provides protection to the ampulla by preventing it from being removed prematurely.Jay McCartney, Murray A. Potter, Alastair W. Robertson, Kim Telscher, Gerlind Lehmann, Arne Lehmann, Dagmar von-Helversen, Klaus Reinhold, Roland Achmann and Klaus-Gerhard Heller, 2008, Understanding Nuptial Gift Size in Bush-Crickets: An Analysis of the Genus Poecilimon (Tettigoniidae: Orthoptera), Journal of Orthoptera Research, Volume 17, pages 231-242 It is also hypothesized to provide direct nutritional benefit to the offspring through the paternal investment hypothesis.
Ornate moth