Sex, beetles and barbed penises

The male seed beetle is equipped with a barbed penis, so that once he has found a mate she cannot escape from his clutches. Unfortunately, whilst a barbed penis may be good for the male it isn’t a lot of fun for the female. In fact the damage caused can be enough to kill the female.

Earlier this week a post looked at the tragedy of the commons.

We know this can happen when humans are arguing over, and potentially destroying, a limited resource; but it can also happen in nature with animals such as the seed beetle.

Clearly males killing females during mating is a problem for the long-term survival of the species. The most aggressive males tend to be more successful in reproducing which leads to a new generation of beetles which is, on average, more aggressive than the last one. Ultimately this could reach the point where the aggressive males kill all the females and the species dies out.

This is a ‘tragedy of the commons’ where the female beetle is the limited resource which is being ‘overused’ by the male beetles. If there is no controlling mechanism then the males will kill all the females.

Luckily for the beetles there is a slight difference between this situation and the ones that we normally see as examples of the tragedy of the commons. Normally the overused resource will not have any choice in the matter, for example fish who are being over-fished really can’t do much about it.

In this case the females can influence the situation with their own behavior. Whilst the females will sometimes be caught by an aggressive male, when they are able to choose they will, understandably, seek out a male who is less likely to kill them.

This seems to be enough to avert the tragedy of extinction for the beetles.

Today’s takeaway: If there is a way for a resource to adapt to protect itself then it can avoid the tragedy of the commons…or maybe just avoid males with barbed penises!

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