By Julia Eckberg ’21
The concept of “animal personality” has captivated the scientific world, leading to a plethora of research aiming to unravel the mysteries behind what makes all animals seem incredibly human. The majority of this kind of research has focused on where individual animals land on the shy versus bold spectrum and why, which is often tested by gauging an animal’s response to a human approach. Writing in Animal Behavior, DeRango et al. (2019) completed a multi-year field study on Galapagos sea lions, which showed that pup personality is dictated both by the traits its mother, as well as its own physical characteristics.
DeRango et al. performed their study on a population of Galapagos sea lions that have been the subject of scientific research since 2003, which provided the research group with parental information, as many individuals had already been identified and tagged. They predicted that pup personality would vary depending on physical characteristics (sex, age), would remain consistent over a one year period, and would be shaped by the physicality of the mother.
In order to determine a pup’s personality, researchers performed two tests: a novel object and a human approach. Their novel object of choice was a tennis ball, the perfect foreign object to pique pup curiosity, considering its fluorescent coloring would stand out well against the rocky Galapagos landscape. Researchers found that pup response to a novel object was extremely variable within the population, and was dependent upon pup age and sex, with older, male pups exhibiting the most bold behaviors (approach and inspection of the tennis ball). Mothers of these bold pups were often older and larger, and their pups may have been bold because these older mothers have bold personalities themselves, or that the mother-offspring pairs inhabit similar environments, and would therefore develop similar personalities. Both genetics and environmental conditions may play a role in the development of personality in pups, but a unique feature of shy pups is the increased flexibility of their personality. This was shown by their significant increase in boldness when their mother was present, suggesting that maternal presence offers support and protection in a way that encourages pups to get out of their comfort zone. So while bold pups may seem to overshadow their shy counterparts, the flexibility of shy pup personality may help increase their likelihood of survival, as it suggests an increased ability to adjust behavior in response to changing environmental and social conditions.
Results from the human approach tests were very similar, with the older, male pups who were the offspring of older, larger mothers having the most bold response when faced with the prospect of human interaction. That being said, bold responses to humans were less extreme than with the novel object test, with most bold pups simply not reacting to the researcher and very few actually inspecting the researcher. This suggests that human approach presents a more significant threat to pup well-being, which isn’t surprising given humanity’s tenuous relationship with wildlife. Pup response to human approach, as with the novel object test, was found to be repeatable, which suggests that bold versus shy behavior is in fact a personality trait.
To test the consistency of pup personality, researchers returned the Galapagos to rerun these experiments on the same individuals a year after the original assessment. Researchers found little variability in individual pup response to both a novel object and human approach between the 2017 and 2018 breeding season. These results show trait stability, which once again suggests that these kinds of behaviors are part of sea lion personality, and supports the researchers’ prediction that pup relative boldness would experience little change over a short period of time.
DeRango et al. (2019) have shown that sea lions are more similar to humans than we ever thought, with varying personalities that can be dependent on genetics, environment, and social conditions. While some scientists may see the use of the term “personality” as the problematic application of human ideas onto a completely different species, this research may also encourage greater conservation efforts by humanizing these important animals.
DeRango, E. J., Schwarz, J. F. L., Kalberer, S., Piedrahita, P., Páez-Rosas, D., & Krüger, O. 2019. Intrinsic and maternal traits influence personality during early life in Galápagos sea lion, zalophus wollebaeki, pups. Animal Behaviour, 154, 111-120.
