The Animals That Give Each Other Gifts

 

We may think that gift giving is a purely human trait, but it turns out many other animals also treat their mates and companions.

If on Christmas morning, upon opening your annual gift of novelty socks, your feeling is that of crushing disappointment, you can at least be thankful that you're not a female scorpionfly.

If you were, then the best you could look forward to at yuletide would be a ball of spit from the love of your life. Far from being disappointed though, female scorpionflies relish the tasty treat, rewarding their suitors with the opportunity to mate with them.

Nuptial gift giving – when the male presents the female with a nutritious morsel during courtship and mating – has been noted in species as diverse as snails, earthworms and squid. Birds have been known to enjoy gift giving too, with male great grey shrikes impaling small creatures on thorns and twigs to impress mates, before offering them as presents during courtship.

However, the phenomenon is most common amongst insects and arachnids. Male six-spot burnet moths, for example, give their female partners cyanide delivered via their sperm. Nursery web spiders, on the other hand, present potential mates with prey wrapped up in silk, with added chemicals to make it more attractive. If the female refuses, the male simply adds more wrapping to the gift, before offering it again.

Sometimes the males try to trick the females by wrapping up low-quality prey, or even paltry half-consumed morsels. While the female is busy unwrapping what she thinks is a thoughtful gift, he'll mate with her and run off before she realises. One study found that as many as 70% of gifts given by male nursery web spiders are fake.

"You do get males attempting to cheat. They might wrap up an old, dried-up leg of a cricket, or something," says Darryl Gwynne, a behavioural ecologist at the University of Toronto in Canada.

Other insects have been known to try to skimp on gifts too.

"Down the road from my house in spring there's a really beautiful thing where male dance flies go out over the river and catch aquatic insects," says Gwynne.

"They bring it back, and females compete for the prey because they can't feed themselves, and they need this nutrition to produce their eggs. On one occasion, I saw a male come in with a ball of willow fluff that comes off the willow seed and attempt to present that."

While presenting a worthless gift may benefit the male in the short term, as soon as the female has unwrapped her gift and realises that she has been deceived, she will reject him. This means that he will only get to mate with her for a brief period. As female insects usually mate with several suitors, the dishonest male's sperm will be less likely to fertilise her eggs, meaning he loses out in the long term.

- Author: Jasmin Fox-Skelly, BBC