RSS Feeds

Email a Friend Printer Friendly

Should Opposites Attract? - Bird Success Depends On Personality

November 07, 2003

Your personality determines how successful you are, in both survival and reproduction. Personality is to a large extent hereditary and also influences partner choice. Biologists from the Netherlands Institute of Ecology (NIOO-KNAW) found this in great tits. The research project on the evolution of personalities will be finalised this month.

Why do we all differ in personality? Even when we live in the same environment we are different. And how is this variation preserved? These are the questions that Kees van Oers, Niels Dingemanse, and colleagues of NIOO started their research on. An animal - FROM APE TO OCTOPUS - reacts in the same way in a certain stressful situation. Personality is fixed, like the way body size is, for instance. The two extremes are: fast and aggressive versus slow and careful. Earlier NIOO research showed that about 50 percent of the type of behaviour, or personality, is hereditary.

Kees van Oers: "The genetic background of personality is obvious, so evolution can influence it. Determining the genetics of personality forms an essential starting point for research on the evolution." Without this information you cannot predict what kind of personality great tit chicks have, only based on their parents. Ph.D. student Van Oers tested families of great tits on different qualities. He concluded that different characteristics largely depend on the same genes: you inherit these together. In brief: you receive a 'personality package'. Furthermore, the behaviour of the offspring proved to be more than a simple sum of father and mother, because some genes dominate. Also important is the 'MOTHER EFFECT': young tits look a bit more like their mother than like their father. Van Oers: "This is all accounted for in our models and this way we can predict the personality of the young after all."

Niels Dingemanse and post-doctoral researcher Christiaan Both were able to reach conclusions on personality in nature based on the information of Van Oers. Dingemanse carried out the fieldwork with populations. He tested 1342 wild great tits on their personality. Following, he investigated the effect on survival and reproduction. His conclusion: "Opposites should attract!"

When looking at the highest survival and the highest reproduction (the fitness) at a time scale of several years, the 'average types' are the winners. Not the extreme fast or slow animals. This is probably caused by the fact that average types experience less fluctuation in survival chances and eventually live longer. They also have the best chances in BEECHNUT POOR WINTERS that are the most common winters in the Netherlands.

Dingemanse: "They do not have the largest number of children, I think, but they eventually have the most grandchildren." And how do 'average animals' emerge: because many fast males mate with slow females, and the other way around. "This seems like a well-considered partner choice," says Dingemanse, who takes his Ph.D. at Utrecht University on the 10th of November.

Personality has important consequences for your chances in the wild, but the environment at the spot determines the winners. In years with poor winters (few beechnuts) fast females, slow males, and juveniles of average parents encounter higher chances. A nutritious winter shows a totally different view. The fattest chicks are produced by couples of fast x fast an slow x slow, but this only yields victory in rich years. NOT EVERY YEAR, and not on every spot, the same partner forms the best choice.

Dingemanse: "You could say that the fluctuating chances for all the different personalities make that they coexist. But it is not that simple."

Another effect is that young, fast, aggressive animals do not thrive in the community at their place of birth. They are all the way down the social ladder, cannot cope with the stress, and fly away to try their luck somewhere else.

The Netherlands Organisation for Scientific Research (NWO) supported the research programme. The total programme was composed of three Ph.D.'s and one post-doctoral project. This is THE FIRST personality research ever illustrating the genetic structure and the resulting effects on survival in the wild. The findings of Van Oers and Dingemanse match very well. (Is this due to a successful combination of personalities?)

The NIOO-KNAW is the research institute for ecology of the Royal Netherlands Academy of Arts and Sciences (KNAW). It is composed of three centres for: coastal and marine ecology, freshwater ecology, and ecology on land. In the NIOO Centre for Terrestrial Ecology in Heteren scientists are studying life on land.

Netherlands Institute of Ecology (NIOO-KNAW)