If male budgerigars can successfully open a puzzle box with food, they become more attractive to females. Biologist Carel ten Cate and Chinese colleagues publish experimental evidence for this in a paper in Science on 11 January .

More children for smart animals

Budgerigars live in the Australian outback, where it can be hard to obtain food and where food extraction skills can be valuable. Scientists believe that such skills can evolve when smart partners are preferred over partners with fewer skills. In this way, smart animals more often get the chance to mate, they will have more offspring and the skill is spread throughout the population.

Ladies’ choice

Leiden professor of Animal Behaviour Carel ten Cate, together with researchers from the Zoology Institute of the Chinese Academy of Sciences, studied whether female budgerars actually have a preference for males with good skills. Female birds first performed a preference test, in which they were placed near two males and could choose how much time they spent in the vicinity of each. Next, the least preferred males were trained to open two puzzle boxes containing food. After that, females could observe the opening skills of these males. The females also watched the initially preferred male being unable to open the boxes.

Preference for smart male

When the preferences were tested again, the females spent more time with the males they had seen opening the boxes. Control experiments could rule that the preference shift was due to observing that one male, but not the other, had access to food. Also, females showed no shift in preference when exposed to female instead of male examples, indicating a sexual and not a social effect.

Direct proof

'For the first time, we looked directly at whether seeing smart behaviour influences partner choice', says Ten Cate. Scientific evidence for this hypothesis was mainly indirect up to now. Researchers have looked at another, clearly visible trait that they know will often occur in combination with good cognitive skills, for example the intensity of the color of the head of the great tit. They studied whether there was a connection between such a derived trait and partner choice.

Partner choice in people

So far, scientists have hypothesised that the evolution of cognitive skills is influenced by partner choice mainly referring to humans. Correlations are known in humans between cognitive capacities and attractiveness for partners. This study does not prove whether people actually choose partners based on cognitive skills, says Ten Cate. 'But we do show that these underlying mechanisms exist in the animal kingdom, and that the hypothesis can therefore be true.'