A gift for all times

In the semiaquatic Zeus beetle,the female is about twice the size of the male.

Written by New York Times | Published: December 29, 2013 5:08 am

Natalie Angier

Here are some last-minute gift ideas to suit even the most discriminating individuals on your list. For the female scorpionfly: an extremely large,glittering,nutrient-laced ball of spit,equivalent to 5 to 10 per cent of a male fly’s body mass. Gentlemen: Too worn down by the holidays to cough up such an expensive package? Try giving her a dead insect instead.

For the male Zeus bug: A month long excursion aboard the luxury liner that is the much larger female’s back,with its scooped-out seat tailored to his dimensions and a pair of dorsal glands to supply the passenger with all the proteinaceous wax he can swallow.

For the bonobo you’ve just met: half your food,at least. Sharing is fun!

We may denounce the hyper-consumerism of the Christmas season until we’re Hanukkah blue in the face,but much of our economy relies on the strength of the gift-giving impulse and with good reason: The drive to exchange presents is ancient,transcultural and by no means limited to Homo sapiens. Researchers have found striking examples of gift-giving in insects,spiders,mollusks,birds and mammals.

Many of these donations fall under the rubric of nuptial gifts,items or services offered during the elaborate haggle of animal courtship. Nuptial gifts can also be a gift for researchers,allowing them to precisely quantify a donor animal’s investment in mating and reproduction and to track the subtleties of sexual competition and collusion by analysing the chemical composition of a given bag of courtship swag. “This is an incredibly cool and important topic in sexual selection that we’re just beginning to explore,” said Sara M Lewis,a professor of biology at Tufts University who has written extensively about nuptial gifts. “The bright side of nuptial gifts is,here’s a way that males can contribute things that are essential to his mate and to his future offspring. “The gifts can also be a source of sexual conflict,a way of manipulating the female into doing what he wants,” she said.

Other researchers are studying how animals use gifts socially to foster alliances or appease dominant members of the group. Grooming among primates is considered a form of gift-giving,and,in most cases,it’s the subordinates who do the tick-picking: betas groom alphas,females groom males.

Gifts can be costly to make or acquire. The salivary mass that a male scorpionfly secretes to lure in a peckish female is packed with so much protein and nutrients that a less-robust suitor may forgo the effort and resort to offering a female a dead insect,instead. Unlike a spitball,the insect corpse can be reclaimed after mating is through.

Among Pisaura mirabilis garden spiders,males risk their lives to give gifts. The first thing they do as adults is look for suitable prey,which they kill and wrap in silk. They then march through the forest looking for females,their bulky gifts held high in their mouthparts. Reporting recently in the journal Animal Behaviour,Pavol Prokop of Trnava University in Slovakia and Michael R Maxwell of National University in La Jolla,Calif,showed that gift-carrying cut down on a spiders running speed by 60 per cent,potentially putting the male along with his precious bundle at risk of being eaten.

On occasion,females are the ones playing Santa Claus. In the semiaquatic Zeus beetle,the female is about twice the size of the male. Not only does she allow a male to piggyback on top of her for weeks at a time,she also has a depression on her back seemingly designed to accommodate him while he feeds on rich wax that she secretes for his convenience.

As they reported this year in the journal PLoS One,Jingzhi Tan and Brian Hare of Duke University and their colleagues showed that bonobos may be alone among apes,if not among animals,in preferring to share food with strangers over friends and family. When wild-born bonobos were placed in a room and supplied with treats like slices of apples and bananas and given the choice of opening a gate to admit either a familiar or an unknown bonobo,the provisioned bonobo would lift the latch of the strangers enclosure and then push food in the unfamiliar ape’s direction. Researchers propose that bonobos use food gifts to expand their social network.

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