Tuesday, February 06, 2007

Just Science day 2: They're only after one thing

Before we begin, I notice that the aggregator at Just Science has given yesterday's post the date of 31 December 1969. Can anyone help with why this has happened, and how to stop it happening again?

Anyway, on with the madness. With Valentine’s day just a week away, this paper in the new issue of Ethology is a must-read. In it, self-proclaimed ‘media friendly expert’, Karim Vahed, of the University of Derby, looks at nuptial gifts — the tasty morsels that many male animals (especially insects and spiders) bring to their intended mates.

The orthodox view of this is that everyone wins — the female gains a meal that increases her fertility, the male gets a mating. Vahed, however, has a rather more cynical take on things:

In this review, I explore the proposition that nuptial gifts act as sensory traps: by exploiting the female's gustatory responses, the male may be able to entice females to accept superfluous matings and/or transfer greater volumes of ejaculate than are in the female's reproductive interests.

Gift composition is more likely to be tailored to increasing the attractiveness of the gift to the female and/or maximizing gift handling time than to suit the female's nutritional needs … evidence suggests that the gift enables the male to overcome the resistance of the female to accepting an extra large ejaculate.

There is some evidence for this notion. Experiments in the fly Rhamphomyia sulcata suggest that females are almost as enthusiastic about worthless gifts as they are about a full dinner. Such indiscrimate behaviour leaves the door open to an invasion of cheating males.

And if Dr Vahed gives you a box of chocolates next Wednesday, beware.

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