Ask anyone with a pet (or animal companion, if you prefer that term), animals have personality. Anthropomorphism aside, there seems to be something to it. In recent years, research in animal behavior has resulted in the suggestion that there are indeed behavioral differences between animals in a population that persist through time and across contexts. Animal personality became a legitimate field of study. Substantial study has been done, hoping to get some grip on the different personalities and their causes. Less work, however, has been done on understanding how these persistent behavioral differences might affect ecology and evolution.
A recent review aims to draw attention to this and suggests 14 potential ecological/evolutionary implications of animal personalities. (Warning: long list. Get a drink. And a snack.)
- Life history and demography: animal personality can have a fairly obvious impact on survival and reproduction. If you’re a fighter rather than a ‘flighter’, you are perhaps more likely to end up between the jaws of some predator. But also, different personalities often find themselves in slightly different habitats, which, in turn, can affect their survival and reproduction.
- Population density and productivity: dietary preferences can differ, which may reduce competition and lead to facilitating effects (say, for example, shy types can only settle in habitats previously colonized by their bolder population mates).
- Stability, resilience and persistence of populations: in general, genetic variation in a population is good, so perhaps behavioral variation is good also. Variation can allow a population to deal with changes in environment.
- Dispersal, colonization, and invasion: personality might affect settlement success. And a group that settles/colonizes might benefit from having different personalities aboard.
- Distribution within habitats: animals with different personalities might make their home in different locations within the population’s habitat.
- Transmission of disease and information: behavioral types can differ in their susceptibility for a disease, and the difference in the number of interactions can affect the spread of disease as well as of information.
- Social evolution: some animals might be more prone to cooperate, or more capable of coordinating their efforts with others. Some are perhaps more prone to cheating than others.
- Evolutionary speed and potential: populations with many different personalities might be capable of responding better to environmental changes, because of variation in genes and/or phenotype (basically, observable traits).
- Evolutionary constraints: in contrast with the previous point, perhaps some personality traits are inextricably ‘bound together’, which means that if one changes, the others have to do so, too, which might limit the amount of change that’s possible.
- Evolvability: another possibility is that these personality traits were bound together after being ‘tried and tested’ by evolution, and fit well together. So, rather than having each trait evolve independently, changing one might ‘automatically’ change the other. (Note that this is the opposite of the previous point, but that doesn’t mean that they can’t both be possible. Different traits can be stuck together in different ways, and in response to one change, being stuck together might be good, whereas in response to another, it might not.)
- Eco-evolutionary dynamics: sometimes, evolution can happen fairly quickly, on ecological timescales. In such cases, ecological and evolutionary change can affect each other. Since animal personalities can affect both ecology and evolution, bringing them into the mix might be a good idea.
- Speciation: behavior can be quite relevant in the formation of new species. Since behavior can differ in populations, animal personality can potentially have an impact on the process leading to new species, speeding it up, or slowing it down.
- Species interactions: if different animal personalities have different dietary preferences, or live in slightly different places, or are more or less susceptible to parasites and disease, this obviously affects other species.
- Community structure and ecosystem processes: different behavioral types might affect community structure (think of, for example, the food web) and ecosystem services.
It’s important to note that these are possibilities and that, since animal personality is a young field of study, much more empirical research is needed to figure out which ones happen in which conditions, and so on. Luckily, the authors are aware of this.
We are aware of the fact that several of the above implications are based on plausibility arguments and suggestive case studies rather than on firm evidence.
The next step, then, is clear.
What is needed now is the development of models translating verbal arguments on the consequences of personality differences into clear-cut (quantitative) predictions, and empirical research to test these predictions.
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Wolf, M., & Weissing, F.J. (2012). Animal personalities: consequences for ecology and evolution. Trend in Ecology & Evolution, 27 (8), 452-461 DOI: 10.1016/j.tree.2012.05.001
It also seems possible that personality isn’t all that connected to evolution and the complexity of growth and development of animal brains inevitably leads to variation in personality from “cultural” and environmental factors. It seems like it would be extraordinarily difficulty for a species DNA to ensure that every brain would develop in exactly the same manner, even if it was somehow beneficial.
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