This post is written by MSU grad student Lily Johnson-Ulrich
Spotted hyenas are found in just about every habitat in sub-Saharan Africa including human-disturbed areas and fully urbanized ones (i.e., cities) (Yirga Abay, Bauer, Gebrihiwot, & Deckers, 2010). While most large carnivores in Africa are decreasing in number, spotted hyenas are thriving. One reason for this inconsistency may be their high degree of behavioral flexibility; they’re dietary generalists eating everything and anything from termites to elephants (Holekamp & Dloniak, 2010). Spotted hyenas also exhibit social complexity and social cognition that are similar to the cercopithicine primates (a group that includes baboons and vervet monkeys) (Holekamp, Sakai, & Lundrigan, 2007). Living in novel or urban environments and complex sociality are factors that are thought to drive the evolution of large brains and intelligence in primates. This makes the spotted hyena an ideal model organism for confirming the relationship between these factors and cognitive abilities outside of primates.
I’m a graduate student in Dr. Kay Holekamp’s lab at MSU where Dr. Holekamp has been studying the lives of spotted hyenas for almost thirty years. This long-term data set provides a unique pool of information on hyena relationships that goes back several generations. I’m interested in looking at how social and environmental conditions may affect cognition in wild spotted hyenas in order to understand the adaptive function of intelligence in a natural system.
One of the things that we think makes humans unique is our large brains and intelligence (think human culture, innovation, science, and technology!). However, large brains are metabolically expensive and we’re still not sure just what the adaptive pay-off for extreme intelligence was in our ancestral environment. In today’s modern world, we no longer experience the same selective forces or live in the same habitat that we did when our large brains were evolving so it’s difficult to retrace the steps that led us to where we are today. I think it’s important to try and understand the adaptive function of intelligence because it can help us understand how to foster intelligent behavior such as creativity and innovation in today’s society. One way to try and understand both how our large brains evolved and how intelligence is adaptive is to take a look at its function in wild extant populations of other species that may share evolutionary pressures with ancestral humans, like spotted hyenas. In other words, we can try to understand the origins of intelligence by studying it in other species.
Figure 1. A hyena interacting with the multi-access box used to test innovative problem-solving. The box has four doors that a hyena may manipulate to retrieve bait from the interior.
For my graduate research I am testing two specific cognitive abilities that are related to intelligence, innovation (Figure 1) and inhibitory control (Figure 2), in three populations of wild spotted hyenas, one urban, one disturbed, and one protected. Innovation is the ability to solve a novel problem or solve a familiar problem in a novel way and. It has a strong relationship with brain size, behavioral flexibility, and also the ability to survive in novel environments across many animal taxa (e.g. Cognitive Buffer Hypothesis (Sol, 2009)). Cities are becoming more widespread and urbanization creates dramatic changes across a landscape, posing evolutionarily novel problems for animals to cope with. Spotted hyenas are among the few species that are actually able to thrive in urban environments and I suspect this may be related to their innovative abilities. To test this idea, I’m studying the innovative abilities of fully urbanized hyenas and comparing them to the abilities of hyenas in a fully protected national reserve and to those of an intermediate population. The intermediate population also resides inside a national reserve but the population’s boundaries overlap the border of the reserve and a growing human town where the impacts of tourism and cattle grazing are increasing.
Figure 2. A hyena successfully detours to the side of the transparent cylinder during an inhibitory control test.
Inhibitory control is the cognitive ability to resist a prepotent, but ultimately incorrect, response. In humans, strong inhibitory control in childhood is related to later life success (Meldrum, Petkovsek, Boutwell, & Young, 2017). Inhibitory control is thought to be important to other cognitive abilities like innovation, because it allows individuals to “stop and think” prior to making a decision (Hauser, 2003). In the social world of spotted hyenas, each group member is part of a linear hierarchy, or “pecking order” that determines access to food. An alpha female and her children are at the top, followed by other females, and then the males are at the bottom. Adult male hyenas fall at the bottom of this hierarchy because male hyenas will leave their natal clan when they reach sexual maturity and join a new clan in search of mating opportunities while female hyenas remain in the clan they were born in (and benefit from the support of their mother and sisters). Male hyenas, on the other hand, when they join a new clan don’t have the support of family members they had in their natal clan and they begin their new lives at the very bottom of the social hierarchy along with other immigrant males. At the bottom of the hierarchy individuals must inhibit all aggression towards higher ranking clan members or risk strong retaliation (Kruuk, 1972). Since all male hyenas are “doomed” to live their adult lives as the lowest ranking members of a clan we suspect that they will possess better inhibitory control than female hyenas. If so, it would support the idea that many advanced cognitive abilities evolved in challenging social contexts, an idea known as the Social Intelligence Hypothesis (Dunbar, 1998).
In sum, I hope to examine if individual hyenas with better inhibitory control are also more innovative and if these two cognitive abilities are related to the environment hyenas live in or if they are related to social factors such as group size, sex, and rank. Ultimately, I plan on relating variation in both innovation and inhibitory control to heritability and fitness. If variation in innovation and inhibitory control is heritable and related to annual reproductive success this would suggest that evolutionary selection is currently acting on cognitive abilities in spotted hyenas. I hope that my research can shed light on where and why intelligence is adaptive, which in turn can give us clues about where and why human intelligence might have evolved. I also hope to highlight the fact that many animals, even distantly related ones, share many of the same cognitive abilities with humans. Increasingly, it looks like the difference between human and non-human animal minds is one of degree, not kind.
Dunbar, R. I. M. (1998). The social brain hypothesis. Evolutionary Anthropology: Issues, News, and Reviews, 6(5), 178–190. http://doi.org/10.1002/(SICI)1520-6505(1998)6:5<178::AID-EVAN5>3.3.CO;2-P
Hauser, M. D. (2003). To innovate or not to innovate? That is the question. In S. M. Reader & K. N. Laland (Eds.), Animal Innovation. Oxford University Press.
Holekamp, K. E., & Dloniak, S. M. (2010). Intraspecific Variation in the Behavioral Ecology of a Tropical Carnivore, the Spotted Hyena. In Behavioral ecology of tropical animals (1st ed., Vol. Volume 42, pp. 189–229). Elsevier. http://doi.org/http://dx.doi.org/10.1016/S0065-3454(10)42006-9
Holekamp, K. E., Sakai, S., & Lundrigan, B. (2007). The spotted hyena (Crocuta crocuta) as a model system for study of the evolution of intelligence. Journal of Mammalogy, 88(3), 545–554.
Kruuk, H. (1972). The spotted hyena: a study of predation and social behavior.
Meldrum, R. C., Petkovsek, M. A., Boutwell, B. B., & Young, J. T. N. (2017). Reassessing the relationship between general intelligence and self-control in childhood. Intelligence, 60, 1–9. http://doi.org/10.1016/j.intell.2016.10.005
Sol, D. (2009). The cognitive-buffer hypothesis for the evolution of large brains. Cognitive Ecology Ii, 111–134.
Yirga Abay, G., Bauer, H., Gebrihiwot, K., & Deckers, J. (2010). Peri-urban spotted hyena (Crocuta crocuta) in Northern Ethiopia: diet, economic impact, and abundance. European Journal of Wildlife Research, 57(4), 759–765. http://doi.org/10.1007/s10344-010-0484-8