Curious Nature

Ladyman's Selfish Toad Theory

Hamilton's Selfish Herd Theory states that individuals within a population attempt to reduce their predation risk by putting others of their species (i.e. their buddies) between themselves and predators. This theory, to explain the gregarious nature of many animals, is said to contrast the more popular idea that animals grouped for some mutual benefit.

I wonder how often, in how many species or situations the real causation behind the grouping of animals has been completely overlooked. Sure, for a flock of lambs the fluffy little nipper in the center of the flock is the last to get eaten by the big bad wolf. And it is probably warm and cozy in there too.

What if you are not hiding from predators? What if predators were the least of your worries? Take the Cane Toad for instance. Cane Toads give nary a thought to predators and don't make any particular effort to disperse when you come upon them of a night (or during the day for that matter). Grouping to avoid predation? I think not.

At the end of the dry season water is scarce and from my experiences today (traipsing around the Kimberley looking for pooling water for Gouldian Finch) Cane Toads are living breathing divining rods. So when you come across a bakers dozen all crammed into a crevice that is seeping the ever-so-slightest amount of moisture you can be sure they are grouping in competition for a limited resource - water! They are not grouping to avoid predation.

If you are not a social beast but your survival depends on a resource that is in very limited supply you are going to do whatever it takes to get access to that resource. And if you are not prone to aggression you are probably not going to fight your nearest neighbor to the death to get what you want.

So when Cane Toads find some moisture the result is a bit of a case of 'stacks on the mill'.

BUT the big question is do they confer any other advantages from their gregariousness?? I'd wager that these clever little buggers would benefit from the massively reduced water loss that occurs as a direct function of the reduction of exposed surface area when they are all piled on top of one another in a close confined space.

Have a look and decide for yourself. Cane Toad Crush

And for those who are not big fans of this feral (though I am not happy about their impact, as a biologist I do admire their capacity for survival) here are a few around the periphery that did not make it.