What television-watching tits can tell us about predators and prey

Image credit: Francis C. Franklin

Most of us can easily understand how camouflaging abilities go a long way in helping prey stay alive– the less visible a species is, the lower the chance of it being spotted by a predator. But what about brightly coloured species– what some scientists term “conspicuous prey”– which lack the more visible advantage of their counterparts? Such conspicuous prey often have defence mechanisms like a foul or toxic taste, but if predators only learn by consuming them first then how do they have the chance to survive at all?

A recent study has used the great tit as a “model predator” to reveal the way predator species learn through observation of others on which types of prey to avoid. In an interesting twist, it employed a television in order to show how such conspicuous prey ultimately have the chance to develop defence tactics and warn off predators.

The study, which was published in the journal Nature Ecology & Evolution, was headed by Cambridge University fellow Dr Rose Thorogood. For research, the scientists captured wild great tits in Finland, and then trained them to open white paper packages containing almond pieces– these modelled as prey. The paper packages were then placed in aviaries which the scientists covered with black crosses on white paper, and the packages were marked with either a cross or a square. Those with crosses acted as camouflaged prey and those with squares as conspicuous prey.

The conspicuous prey contained almonds soaked in a bitter fluid, and a tit’s unpleasant experience eating one was filmed. The clip was then played on a television to other tits. It was discovered that tits that had watched it were 32% less likely to choose conspicuous prey during a subsequent meal selection than those that had not.

The predator-prey relationship, it thus appears, is much more complex than a simple trial-and-error process. The survival of both conspicuous prey and predator is instead founded on cultivated instinct. Predators need not encounter unpalatable prey individually in order to learn, but can look instead to imitation for a quicker, less distasteful method.

Television-watching habits aside, it appears that these predators have something in common with us: “Just as we might learn to avoid certain foods by seeing a facial expression of disgust,” Thorogood said, “observing another individual headshake and wipe its beak encouraged the great tits to avoid that type of prey.” Great tits themselves are popular as a test species because of their ability to forage in flocks, and use intelligent insight rather than trial and error in problem solving.

So if you think camouflaged prey have a better chance of surviving, you might actually be wrong. With the help of a mathematical model, scientists found the point at which enough social transmission has to occur for conspicuous prey to actually have a better survival chance than camouflaged ones. Bright colours then prove to be repulsive rather than attractive to hungry predators. In the long run, this might have evolutionary consequences on the ecological community and its inhabitant species– quite a revelation from one video of a tit’s unappetizing meal!

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