Furthermore, the researchers wanted to correlate their findings with the gene variants in the mice. Female mice of the t-haplotype, one of the two genetic variants on chromosome 17, are known to live longer. The t-haplotype in house mice is transmitted by t-carrying males to 90 percent of their offspring. However, embryos that inherit a t-copy from both parents die before birth. With his experiment, Yannick Auclair wanted to investigate whether there was a correlation between this so-called "selfish genetic element" and the personality of the mice; "selfish" in this case is a technical term and has nothing to do with a selfish personality trait.
The research team could show that the t-haplotype females that lived longer were also less active than the shorter-lived non-carrier females. These older mice also consumed less food, were less explorative and thus expressed reactive personality traits favouring cautiousness and energy conservation, as predicted by the theory. "For the first time, we can report personality traits associated with a selfish genetic element that influences life expectancy", Auclair concludes. According to the research team, female mice with a longer life expectancy follow the strategy "live slow, die old", whereas those with a shorter life expectancy live according to the popular slogan "live fast, die young".
Contrasting to the predictions of the life-history theory, there are no extremely cautious individuals among the t-haplotype female mice. The researchers suppose that selection does not favor mice that are too cautious. "In order for a mouse to find food and be able to reproduce, clearly a minimum level of boldness is required", Auclair explains. "In such a situation, large variation will not develop." (© University of Zurich, AcademiaNet)