Newsroom: Does what’s On the Inside Count?

Swiping on Tindr is undoubtedly fun. Judging potential mates based only on physical characteristics—hello 6’3’’ man with those soulful eyes—has its definite merits, but inevitably the first date comes around and something else becomes abundantly clear. Personality matters. The same is true for the ladies of the animal kingdom. While animal behaviorists have long studied the physical traits that females use to make mate choice decisions (a male peacock’s tail, for example, is the avian equivalent of the gym selfie), behavior is also a key component of what a male has to offer. UC Davis Animal Behavior graduate students Amelia Munson and Cameron Jones along with Hannes Shraft (University of Quebec) and Dr. Andrew Sih (UC Davis) investigated whether there is evidence that female animals use consistent differences in the behavior of potential mates to help them decide who to settle down with.

It may come as some surprise that scientists talk about animal personality. While Buzzfeed has yet to come up with the perfect quiz to figure out if an individual guppy is more of a Samantha or Carrie, scientists have discovered that animals (everything from spiders to pandas) exhibit consistent individual differences in behavior [1]. It is these consistent individual differences in behavior that make up an animal’s personality. If a black widow is bolder than its neighbor today, then it is likely to be bolder tomorrow as well. This consistency is important for mate choice decisions, because it allows a female to predict a male’s future behavior based off what she sees him doing in the present. Humans do this too. When we see a picture of someone hiking on their Tindr, we might be attracted to that because we assume it means that they will want to go hiking in the future (hopefully with us!). Without that consistency of behavior, what we see now means nothing for what we can expect in the future.

Female animals may consider both physical attributes and personality traits in assessing potential mates.

Considering personality in mate choice decisions can benefit females in two main ways. One way is from the direct benefits she receives. These are things that directly improve her quality of life. Humans also receive direct benefits from mate decisions; watching a potential mate play with kids makes us hopeful that he will engage in a similar behavior in the future and help us to take care of our future children. Similarly, in house wrens, aggressive males are less likely to help provide food to their offspring [2], so females may prefer less aggressive mates.

Some males may provide females with direct benefits, such as food for the new offspring.

Females can also receive indirect benefits. These are the genetic traits that a potential mate passes to his offspring that can make them more likely to survive and reproduce (indirectly increasing a female’s reproductive output). We may like that a partner is hard working and intelligent with the hope that these traits are passed to our children, because our children’s success indirectly benefits us. Animal personality is heritable [3], so choosing a mate based on personality is a good way for females to affect her children’s personality. Female common lizards, for example, choose less active mates in the presence of predators [4]. This means she will have less active offspring that are less likely to be eaten (so glad I am more concerned with my future children’s work ethic than whether they are going to be eaten!).

Mates can pass on their personality traits to their future offspring.

Just like in humans, not all female animals prefer the same personality type. Females may prefer different males depending on their own personality. A shy female may prefer a shy male and vice versa.  This is particularly true for species that engage in coordinated parental care like zebra finches [5].  Mating with someone who is the same personality type as yourself may make parenting decisions easier to coordinate. Alternatively, mating with someone with a very different personality could allow you to balance out any short comings in your own strategies—this is particularly true for species, like some fish [6], where the male and females fulfill different parenting roles.  Additionally, females may prefer different males depending on the quality of the environment they are in. If food is scarce, females may prefer males that promise to be good at foraging.

Females may be forced to consider the state of the environment in choosing a potential mate.

Personality-dependent mate choice is more important than just for avoiding having another fight over the unwashed dish in the sink. The authors of this paper argue that understanding the benefits of mate choice based on personality could help explain why we see personality in animals. If females show a preference for males that behave consistently and this consistency benefits them or their offspring, then we would expect both the preference for consistency and consistency itself to increase in a population. So, if your next Tindr match advertises his hiking prowess, hold him to it, and take that hike!

For more information:

*Munson, A. A., *Jones, C., Schraft, H., & *Sih, A. (2020). You’re Just My Type: Mate Choice and Behavioral Types. Trends in Ecology & Evolution.

*Stars denote UC Davis Animal Behavior Graduate Group affiliated authors

References:

[1] Sih, A., Mathot, K. J., Moiron, M., Montiglio, P. O., Wolf, M., & Dingemanse, N. J. (2015). Animal personality and state–behaviour feedbacks: a review and guide for empiricists. Trends in Ecology & Evolution30(1), 50-60.

[2] Barnett, C. A., Thompson, C. F., & Sakaluk, S. K. (2012). Aggressiveness, Boldness and Parental Food Provisioning in Male House Wrens (Troglodytes aedon). Ethology118(10), 984-993.

[3] Dochtermann, N. A., Schwab, T., & Sih, A. (2015). The contribution of additive genetic variation to personality variation: heritability of personality. Proceedings of the Royal Society B: Biological Sciences282(1798), 20142201.

[4] Teyssier, A., Bestion, E., Richard, M., & Cote, J. (2014). Partners’ personality types and mate preferences: predation risk matters. Behavioral Ecology25(4), 723-733.

[5] Schuett, W., Dall, S. R., & Royle, N. J. (2011). Pairs of zebra finches with similar ‘personalities’ make better parents. Animal Behaviour81(3), 609-618.

[6] Scherer, U., Kuhnhardt, M., & Schuett, W. (2017). Different or alike? Female rainbow kribs choose males of similar consistency and dissimilar level of boldness. Animal Behaviour128, 117-124.

[Drawings by Amelia Munson; Edited by Meredith Lutz]

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