A discussion on the growing attention being paid by the scientific community to the role of personality in animal populations.
The question of whether or not animals possess personalities has long been a topic of debate. We have all heard devoted pet-owners gush about the personalities that they believe their feline or canine companions have. I can admit to often being guilty of this myself! For example, I regularly tell newcomers in my house that my dog is a ‘scaredy-cat’ who would run away from friend or burglar alike. However, for the longest time, science was not enamoured with the concept of animal personality. The terms ‘personality’ and ‘conscience’ seemed to come hand-in-hand, and the subject of animal conscience has been under fire from scientists, psychologists and philosophers alike for decades. Yet, in recent years, the concept of animal personality has begun to gain traction and its place in population survival is now being explored.
In order to better understand this concept of animal personality, we must first investigate what this term really means. In humans, personality can be referred to as individual differences in characteristic patterns of thought, emotion and behaviour (1). In other words, personality can be described as a repeated series of behaviours by an individual. This repeatability must occur across a variety of contexts and time for it to be deemed a ‘personality trait’ (2). Once we separate personality from the sticky topic of conscience, and begin to focus on it in its true form as the distinct behavioural patterns of an individual in a population, suddenly it begins to become evident throughout the animal kingdom.
These repetitive behaviours can be grouped into broad definitions of ‘personality type’. These types can be grouped into five general categories; shyness or boldness, aggressiveness, exploration, activity and sociability. So, in other words, in groups of animals you will encounter the bold and the shy, the aggressive and the passive, the brave explorers and the wary, the active and the inactive, and the social and antisocial. Also, similar to what we see in humans, individuals don’t all possess extremes in personality. That is to say; while some individuals might be starkly ‘bold’ and others entirely ‘shy’, some do fall comfortably in between. This creates a nice gradient of personality types within a group of the same species, which it is believed is integral to the species’ overall survival (3).
Personality has always existed in animals, but it is only in recent years that we have begun to identify it for what it is. Species that have had personality types successfully identified and studied include sea anemones, limpets, fish, birds, rodents, primates, ungulates, spiders and lizards, with research continuing across many other species (4).
Elk, and other deer, are amongst the most closely monitored species when it comes to investigating the presence and role of animal personality. It has been noted by journalists that they appear to be becoming braver; individuals are often seen grazing on the lawns of gardens and town centres across their native home range within Alberta (4). Another example includes an elk in the Smoky Mountains National Park that was euthanised due to consistently approaching humans. This case garnered media attention due to a viral video in which the elk repeatedly head-butted a photographer (5). Even recently, a hunter was killed when a stag gored him with his antlers after being cornered in the Compiegne Forest, France (6).
These cases of acute boldness would appear to indicate that the species is changing or adapting. However, we must note that these personality types have always been present in these populations. Therefore, it may be possible that we are seeing subtle shifts in the dynamics of personality due to the effects of human activities.
For example, we can document the flight response of individual elk, ie. their readiness to flee on the approach of a human observer. A personality test can then rank the relative boldness or shyness of each animal (4). Researchers have shown that human activities can select for certain traits, depending on what that activity is. For instance, studies have shown that human hunters tend to remove bold traits from a population (7). Logically, this makes sense; bolder individuals utilise open areas more and show a higher level of motility than their shyer counterparts. In turn, this exposes them to human hunters more readily and can lead to them being killed more regularly.
Likewise, it may be that human lawns and other food sources provide bolder individuals with an advantage. For example, the grass present around human houses and town squares is often well tended, nutrient rich and cropped short, which makes it ideal for easy grazing. The elk that are brave or bold enough to enter human habitats to feed on this grass, or on human food waste, will have access to richer nutrition than shyer individuals. They, therefore, will have a fitness advantage over these shy individuals and may reproduce more successfully. As personality is heritable (4), it would make sense that we would then see a spike in bold elk within an area.
So, are humans affecting the natural gradient of personalities in a population? Not just through active removal in hunting, but even passively through our food waste and lawns? We have, historically, selected for morphological characteristics (eg. antler size, colour) in hunted and breeding stock. Could it be that we are also unintentionally selecting for certain personality types by accidentally providing them with different advantages and selective forces?
This question does not just apply to deer or elk, but to an entire range of species. For example, we have also identified personality types in songbirds, such as the Great Tit. When birds are captured from the wild and brought into a captive environment that they have not seen before, they display different types of exploratory behaviour. Some individuals will explore the entire fake environment and investigate every false tree and item that has been placed there. Whereas, others will fly to a single tree and remain there without displaying much tendency towards exploration (4, 8).
The advantages for each side are clear; the wary are less susceptible to predation, while the brave are more inclined to find better food sources. However, how can humans affect this natural balance of behavioural types? Do fowl hunters remove the brave explorers? Does humans’ leaving out feeders provide them with an advantage? As we cut down trees, are the less exploratory also less likely to successfully migrate and survive? As humans continue to have such a strong influence on the world around us, it is time for us to investigate every aspect of what we are affecting. This includes how we can affect the balances of personality traits in animal populations.
But why is this balance, or gradient, of personalities important to a population? Previously, animal personality would simply have been considered background noise during studies, and would have been disregarded. However, now we are beginning to understand the key ecological and evolutionary roles that it plays within populations in an ecosystem (9).
A gradient of personality types is necessary as a sort of ‘safety net’ for a population’s survival. First of all, a variety of personality types allows a single population to fill different niches. This means that members of the same species will not compete with each other, which could affect the population’s overall, long-term survival (9). Also, this variation in personality types means that, if a new threat is introduced to the system, there are individuals that may not be targeted. For example, if a new disease appears in a system, it may require physical contact in order to be transferred. Individuals that are highly sociable and regularly interact with others will, therefore, be more susceptible the disease. However, individuals that avoid interactions, are shy, or are unsociable may be more likely to survive. Therefore, the entire population won’t be wiped out from an area.
This is only a very simple and specific example, but scientists have found that the logic behind it is applicable across a range of scenarios. Introduction of a new disease is not the only threat facing the animals of today, but also invasive species, changes in climate, habitat loss and many others. We also need to better understand how human activities can go on to affect this balance. As previously mentioned, personality is heritable. If any of our activities is removing a personality type from a population, or providing one with fitness or mating advantage, then we could be influencing the population’s long-term survival and resilience. Understanding personality in animal populations, and our role in removing personalities, may also help to inform captive breeding, reintroductions, and the conservation of endangered species, as well as potentially shedding light on disease transmission to humans (4).
It must be noted that personality traits are very different to learned behaviours; plenty of evidence exists to support the concept that animals do learn to adapt. Personality can be referred to as a ‘behavioural phenotype’, meaning the behaviour that an animal is predisposed to present. However, individual animals have been shown to alter these behaviours to cope with environmental conditions that change within their lifetime. For example, bold individuals in elk populations have been shown to adopt shy behaviours, such as avoiding open areas, in order to avoid being hunted by humans (7). It’s an interesting case of nature vs. nurture, but one that we must understand better if we’re to truly understand the role of personality in animals.
Overall, the role of personality is gaining a huge amount of attention from the scientific community, and for obvious reasons. The importance of a balance or ‘gradient’ of personality types in a population for its ultimate survival and success is obvious; the presence of different personality types forms a better chance of overall survival from new threats. However, now we must begin to focus on how we, as humans, are influencing this balance. In a world where human-stimulated habitat and climate change is wreaking havoc on species everywhere, we must begin to pay precise attention to all the ways in which we may further weaken their resilience. In this way, how our activities remove or favour certain personality types, and create an imbalance in the population, is something we need to better understand and avoid. I would, therefore, encourage researchers everywhere to focus their attentions on the vital world of animal personality and how we can use it to make our conservation efforts even more effective.
References:
1) American Psychological Association, 2017. Psychology Topics: Personality. http://www.apa.org/topics/personality/
2) Biro, P.A. and Stamps, J.A., 2008. Are animal personality traits linked to life-history productivity?. Trends in Ecology & Evolution, 23(7), pp.361-368.
3) Dingemanse, N.J., Kazem, A.J., Réale, D. and Wright, J., 2010. Behavioural reaction norms: animal personality meets individual plasticity. Trends in Ecology & Evolution, 25(2), pp.81-89.
4) Ogden, L. E., 2012. Do Animals Have Personality? The importance of individual differences. BioScience, 62(6), 533-537.
5) Davis, J., 2013. Great Smoky Mountains National Park: Elk had to be euthanized. The Daily Times. http://www.thedailytimes.com/news/great-smoky-mountains-national-park-elk-had-to-be-euthanized/article_f6557f18-4160-55fa-9cdd-427ccaafc41d.html
6) Baynes, C., 2017. Hunter gored to death by cornered deer in rare attack. The Independent. http://www.independent.co.uk/news/world/europe/hunter-deer-gored-death-antler-attack-regis-levasseur-france-paris-a8042311.html
7) Ciuti, S., Muhly, T.B., Paton, D.G., McDevitt, A.D., Musiani, M. and Boyce, M.S., 2012. Human selection of elk behavioural traits in a landscape of fear. Proceedings of the Royal Society of London B: Biological Sciences, p.rspb20121483.
8) Dingemanse, N. J., Bouwman, K. M., Van De Pol, M., van Overveld, T., Patrick, S. C., Matthysen, E., & Quinn, J. L. (2012). Variation in personality and behavioural plasticity across four populations of the great tit Parus major. Journal of Animal Ecology, 81(1), 116-126.
9) Bergmüller, R., & Taborsky, M. (2010). Animal personality due to social niche specialisation. Trends in Ecology & Evolution, 25(9), 504-511.
Image References:
1) Tony Beck, 2012. Timber wolves play. FineArtAmerica.com. https://fineartamerica.com/featured/timber-wolves-play-tony-beck.html
2) National Geographic, 2013. National Geographic Photo Contest 2013. https://www.somepets.com/national-geographic-photo-contest-2013/
3) Katharine Shcroeder, 2014. With $225K to spend, USDA cull kills 192 deer. The Suffolk Times. http://suffolktimes.timesreview.com/2014/08/51598/fewer-than-200-deer-killed-in-225k-cull-that-didnt-work/
4) Dale Sutton, 2017. Blue Tit (Parus caeruleus) flying from hole in tree. Getty Images/The Spruce. https://www.thespruce.com/identify-birds-in-flight-387322
5) Paul Goldstein, 2015. A calf holds on to its [playmate]’s tail as the as the elephants take a stroll around Masai Mara in Kenya. Daily Mail. http://www.dailymail.co.uk/femail/article-2993250/Baby-animals-snuggle-mothers-wild-touching-photos-world-melt-hardest-heart.html
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