Tag Archives: squirrels

Understanding squirrel personalities can help us better protect endangered species

Do animals have personalities? We don’t tend to think that they do, but new research brings more evidence that we’ve been too hasty to assume this.

Golden-mantled ground squirrel at a camp-site in Prineville Reservoir State Park, Oregon, USA. Image via Wikimedia.

Researchers at the University of California, Davis have produced the first evidence of personality in golden-mantled ground squirrels (Callospermophilus lateralis), a species whose range includes the western U.S. and certain areas of Canada. While we most likely can’t talk about personalities with the same complexity as those seen in humans, the team explains that at least four main traits — boldness, aggressiveness, sociability, and activity levels — differ among individual squirrels, shaping the way each one interacts with their peers and environment.

Little personalities

“This adds to the small but growing number of studies showing that individuals matter,” said lead author Jaclyn Aliperti, who conducted the study while earning her Ph.D. in ecology at UC Davis. “Accounting for personality in wildlife management may be especially important when predicting wildlife responses to new conditions, such as changes or destruction of habitat due to human activity.”

The species itself is not currently considered threatened from a conservation standpoint, but the findings have value in helping us better protect others that are. The field of animal personality is still young, the team explains, and so is the understanding that these personalities have very real implications for ecological and conservation efforts. How individual animals interact with their environment, their peers, the ways in which they use available space, and feed, are all tied into their particular personalities.

The findings were made possible by research that has been performed at the Rocky Mountain Biological Laboratory in Gothic, Colorado, over the last three decades. For the study, Aliperti and her team used data gathered during these last 30 years, as well as results from experiments they performed with squirrels at the site during the last three years.

Although the study of animal personalities is still in its infancy, there are standardized approaches we can employ to investigate individual critters, the authors explain. In broad lines, they employed four types of tests during their experiments. These were ‘novel environment’ tests, where squirrels are placed in an enclosed box with holes and gridded lines; the ‘mirror’ tests, where squirrels are presented with their mirror image (which they do not recognize as being themselves); the ‘flight initiative’ tests, during which the squirrels are approached slowly in the wild, to check how long they wait before fleeing; and the ‘behavior-in-trap’ tests, where squirrels are caught in a simple and non-dangerous trap, and their initial behavior is recorded.

Beyond ascertaining that different squirrels will, in fact, have different responses or performances during these tests, they were also able to link differences in personality to particular behaviors. For example, bold and active squirrels moved faster than their peers. But squirrels that were bold, active, and more aggressive had an overall better command of their territory — they had higher levels of access to perches (vantage points). This type of access is very important for squirrels, as it allows them to better monitor their surroundings for predators, translating directly into safety.

But this was not the only combination of traits that correlated with greater perch access. More social squirrels also had greater access to these spots compared to their peers.

This is particularly interesting as golden-mantled ground squirrels are considered to be an asocial species. They are small and live short lives, relative to other species of ground squirrels, so they only have limited time to spend with their family units before adulthood, when they move to their own territories. That being said, the team notes that individuals who are more sociable tend to have an advantage over their peers. Being more social, in this particular case, can improve an individual’s chances of survival (through increased perch access). This would improve their chances of reproducing, thus forming a comparative advantage.

“Animal personality is a hard science, but if it makes you relate to animals more, maybe people will be more interested in conserving them,” said Aliperti. “I view [the squirrels] more as individuals. I view them as, ‘Who are you? Where are you going? What are you up to?’ versus on a species level.”

This isn’t the first sign that animals can have unique personalities, although it is the first time it has been reported in squirrels. Cetaceans, fish, chimpanzees, and even spiders have shown they can and do develop personalities. All this (growing) body of evidence points to the fact that the animals around us aren’t simple beasts, and efforts to protect endangered species should take this into account. Individual animals will react to any measures designed to protect them according to their personal traits, so understanding these would definitely help us implement better conservation strategies.

The paper “Bridging animal personality with space use and resource use in a free-ranging population of an asocial ground squirrel” has been published in the journal Animal Behaviour.

Prairie dogs murder ground squirrels to stave off competition for food

Many wars have been fought for to resources such as precious minerals, oil and in the not so distant tribal past — food. Humans aren’t the only ones to kill competitors for food. Among their own kind, many animals resort to infanticide, killing the babies of rivals so their own offspring have a better chance to endure. There’s also inter-species warfare. Some insects, for instance,  engage in a bit of biological warfare, carrying a fungus that kills their competitors but which they can tolerate. What’s surprising is that even fluffy and seemingly benign animals use warfare. Researchers report how the white-tailed prairie dog is ruthlessly killing the Wyoming ground squirrel. They do this so they have more access to food, but do not eat the ground squirrels. They just leave the squirrels to rot. This is the first time such a gruesome behaviour has been documented among omnivores.

A white-tailed prairie dog caught red-handed murdering a ground squirrel. Credit: JOHN HOOGLAND

A white-tailed prairie dog caught red-handed murdering a ground squirrel. Credit: JOHN HOOGLAND

For more than a decade, John Hoogland of the University of Maryland Center of Environmental Sciences and his students have been following prairie dogs in  the scrublands of western Colorado’s Arapaho National Wildlife Refuge. In 2007, Hoogland first spotted a prairie dog tossing a rodent. He thought the prairie dog was attacking some pup of their own kind, but soon found the victim was a ground squirrel. Was this some isolated incident or just one in a series of killing sprees?

This first murder prompted the team to investigate closely. They eventually documented 101 ground squirrel murders, plus 62 suspected cases. One prolific individual, aptly nicknamed Killer Supreme, was seen killing nine ground squirrels over four years. Most of these killings happened in May which is when the young squirrels come out of their nests in search for food. Occasionally, the prairie dogs would chew the chests and brains of their victims, but Hoogland says they never ate them — they were just checking the job was done properly. Carcasses are left where they stand, which birds later scavenge.

“In my 43 years of research, this is perhaps the most provocative, puzzling, and far-reaching discovery I’ve ever made,” Hoogland said. “The results are just staggering.”

This all works very well for the prairie dogs. After the researchers followed prairie dogs that killed squirrels, as well as those that didn’t, they found the killers’ offspring had much better survival odds. The findings were reported in  Proceedings of the Royal Society B.

“The condition of the female, her longevity—the factors that normally influence [success]—none of them apply to this case,” says study co-author Charles Brown of the University of Tulsa.

“It seems to me is that there are major, major benefits to killing these ground squirrels.

As climate change intensifies, it’s possible that we’ll witness similar behaviour between other species for control over food. As for us humans, things don’t look too well either. The World Bank and the United Nations say there won’t be enough food to feed the global population when it jumps from the current seven billion people to nine billion by 2050. “The food scarcity problem is serious. I think the next world wars could be fought over resources like food and water,” said  Usha Haley, a professor of business management at West Virginia University, who studies food supplies.