A gory 12 days of Christmas

It’s Christmas shopping time again, and the biggest-selling item at Wal-Mart on Black Friday was a 29-cent towel that is sure to disappoint many recipients this year. Wal-Mart sold 2.8 million of them, and I’m really hoping I don’t get one.

But if I do, at least it won’t be a spitball. Or a vole on a stick. Those are just a couple of the gifts given in the wider animal world, and they aren’t even the most disgusting ones (by human tastes, that is; to a most animals I’m sure the vole on a stick would be way better than a new car with a giant ribbon on top). Insects and spiders are among the biggest gift-givers, often as part of mating, and anything from cyanide to a wad of saliva can become a present. But birds and mammals are no Scrooges, presenting their own pre-mating food offerings or even a well-timed blood meal to help a hungry buddy out. In their honor, here’s a gory version of a gift list for the 12 days of Christmas, including a few of the most fascinating recent findings about animal gifting.

1. Spermatophores: sperm and a nutritious meal all in one

Fireflies don’t eat as adults, so nutrition is the best gift a female firefly can get during breeding season. Luckily male fireflies, like many insects, produce sperm packages called spermatophores that contain both sperm and much-needed nutrients. Males give the packets to females as a nuptial gift, meaning it’s related to mating. In the case of fireflies the spermatophore is decorative too, shaped like a coiled spring. In 2012 researchers reported that the mating success of Photinus greeni fireflies depends largely on presenting females with a large spermatorphore.

2. Cyanide for you and your children this holiday season

In six-spot burnet moths (Zygaena filipendulae), male moths transfer cyanide-producing compounds to females. The poison is hard to make and comes in handy; females use it for their own defense and store some in their eggs for larvae to use later. In November, researchers in Denmark reported that male moths throw a stocking stuffer into the transfer, giving females a compound, 5-hydroxytryptophan glucoside, that may cause females to copulate longer and delay egg-laying, which reduces the odds she’ll mate with another male. 

 

3. Voles on a stick

Some birds give food gifts just before mating, and birds called shrikes takes it a step further by making those gifts into kabobs. The birds impale insects or smaller birds or mammals on sharp sticks or thorns to hold them in place as the bird dismembers them. Great grey shrike males are faster and more efficient at impaling prey, researchers reported last year, and build up caches of their dismembered prey that they offer as goodie piles for females.

 

4. Spitwads as the bait in a bait-and-switch

Scorpionfly females prefers a long courtship, sometimes several hours long, followed by the gift of a salivary secretion from the male. If a male Panorpa cognata scorpionfly is in poor shape and can’t make enough saliva, he may switch gifts and offer a dead insect, even stealing it back from the female after mating.

 

5. Silk gift wrap can’t make up for an empty package

The nursery web spider Pisaura mirabilis wraps its presents. Males usually wrap an insect in silk as a nuptial gift, and females often reject males who don’t bring a gift. So some males just find any old thing and wrap it up instead, as researchers reported in 2011: “Dissection of 16 gifts carried by males in the field showed that 62 percent contained fresh prey, while the remaining 38 percent contained empty arthropod exoskeletons, i.e. prey already sucked out, probably by the male itself.” Males that give good gifts get to mate with females longer and transfer more sperm, scientists report October 23 in the Proceedings of the Royal Society B.

 

6. This fluffy willow seed is pretty, but what am I supposed to do with it?

A fluffy present sounds nice, but this one is just another dirty trick. Male dance flies (Empis opaca) typically give females a gift of a dead insect before mating, but some males cheat. A 2006 study found males swapping out a worthless willow seed for a nutritious insect. They don’t exactly get away with it, though; the cheaters had lower mating success rates than better gifters, the researchers found.

7. Here’s a dead eel, and thanks for all the fish

Researchers studying dolphins in Australia report that a pod of dolphins has been presenting them a variety of prey items. From 1998 to 2012, the team says, dolphins have on 23 occasions offered cephalopods such as squid or fin fish to biologists who had been feeding them. It’s not clear if the behavior is some type of play or possibly related to food sharing.

 

8. Look, ma, a dead bird!

Housecats are famous for bringing home dead or dying prey to generally ungrateful owners. But this one isn’t actually a gift; we humans just like to think it is. The leading idea for the behavior is that it mirrors the behavior of cats in the wild, which bring prey home to kittens to feed them and allow them to practice hunting skills. Even with no kittens to teach, the behavior sticks. The feline practice has created a heated debate about the extent to which cats harm native bird populations. As Science News reported earlier this year, Smithsonian biologists published a controversial estimate that feral and domestic cats kill between 1.4 billion and 3.7 billion birds each year.

9. Vomit drops, the smallpox blankets of animal gifting

A drop of regurgitated fluid serves as a nuptial gift for the fruit fly species Drosophila subobscura. Females in poor health strongly preferred males in good health who provided a vomit gift before mating, researchers reported in 2009. Males of the fruit fly species best known for laboratory experiments, Drosophila melanogaster, give females a gift of proteins that may actually shorten females’ life span. Called a Medea gift for the poisoned wedding robes that Medea gave to an enemy in Greek mythology, the proteins appear to boost ovulation and egg-laying evolutionary fitness in the short term, at the expense of females’ long-term evolutionary fitness.

 

10. Cricket nog recipe: chew hole in leg, sip gently

Crickets don’t have blood per se, but instead have a circulatory fluid called hemolymph that sometimes becomes a nuptial gift. A female southern ground cricket chews off a specialized spur on a male’s leg and sips his hemolymph through the opening. A study published in Ethology earlier this year showed that the gift increases the number of eggs females lay by more than 40 percent, suggesting it provides a nutritional boost.

 

11. Well, I did enjoy that monkey meat …

Female chimps are more likely to mate with males that share meat from colobus monkeys and other animals that the chimps hunt down as packs. “Our results strongly suggest that wild chimpanzees exchange meat for sex on a long-term basis,” anthropologist Cristina Gomes told Science News in 2009. It’s not an immediate quid-pro-quo exchange, but males that bring home the monkey meat are playing the long game.

 

12. Blood saves lives, so regurgitate some today

Vampire bats need to eat blood to survive, and skipping just a few meals could kill a bat. This year researchers reported that vampire bats not only regurgitate blood for starving roostmates, they offer blood to nonrelatives. Such acts of altruism that don’t benefit an animal itself or gene-sharing relatives are uncommon in the animal world. But as we can see from this list, sometimes it’s better to give than to receive.