Why not all animals are equally innovative
A new study in Current Biology shows how mate choice helps preserve behavioural diversity
Results of the linear models show that: the interaction between female and male problem-solving skills ultimately influences female choice in the controlled experiment, with innovative females (green) choosing non-innovative males and vice versa. Only innovative females (green) base their choice on male weight, in contrast to non-innovative females (orange), for whom male weight played no role in how much time they allocated to potential mates.
To the Point:
- Females do not all choose the same way: Depending on their own problem-solving ability, females prefer different males.
- Mixed pairs are common: In near-natural populations, innovative and less innovative animals pair up more often than expected by chance.
- Innovativeness comes at a cost: Males that solve problems well are, on average, lighter and less physically dominant.
Being innovative is usually seen as an advantage. Animals that find new ways to access food or overcome obstacles often cope better with change. One might therefore expect such behaviour to spread until everyone is equally innovative. Yet this is not what we see in nature. Many animal populations show persistent differences: some individuals are highly innovative, others rarely attempt new solutions.
A new study by researchers at the Max Planck Institute for Evolutionary Biology, published in Current Biology, explains why these differences can persist over time. By combining long-term observations in near-natural conditions with controlled mate-choice experiments, the researchers show that partner choice itself can maintain diversity in behaviour.
In the study, wild-derived house mice lived for six months in semi-natural enclosures. The animals could voluntarily attempt several simple tasks to obtain food. Only a subset of mice regularly solved these tasks. Using genetic analyses, the researchers later identified which individuals had successfully reproduced. When compared with a model of random mating, the pattern was clear: pairs consisting of one innovative and one less innovative individual occurred more often than expected by chance.
To understand how this pattern arises, the team examined female choice more closely. Rather than treating female choice as a single, uniform preference — as mate-choice studies often do — the researchers asked whether females with different problem-solving abilities value different benefits in a partner. In standardised mate-choice tests, females could choose between an innovative and a non- innovative male. The results mirrored the patterns seen in the enclosures. Innovative females tended to prefer heavier, more physically competitive males, regardless of whether those males were innovative themselves. Less innovative females, by contrast, preferred innovative males, largely independent of body size.
The study also uncovered an important biological constraint. Innovative males were, on average, lighter, while heavier males tend to be more dominant in direct competition. This suggests that being good at solving problems comes with costs that limit investment in physical strength. Together, these trade-offs and differing female preferences help explain why no single behavioural type dominates.
Crucially, the findings show that mate choice cannot be understood by looking at one trait in isolation. Whether innovativeness is attractive depends on who is doing the choosing. By taking the abilities of both females and males into account, the study helps reconcile conflicting results from earlier research and offers a clearer picture of how behaviour evolves.
The full paper in Current Biology provides detailed data from both near-natural populations and controlled experiments and will be of interest to readers seeking a deeper understanding of how behaviour, mate choice and evolution interact.