You’ve probably seen them as you walk down the street, through a park or among the trees in a forest, and not taken much notice. But the next time you spot a red squirrel, stop and take a closer look because it could be one very moody rodent. Amanda Kelley, a biologist at the University of Alberta and the field coordinator of the Kluane Red Squirrel Project, which has studied the mammal since 1987, explains her work examining its personality, the results of which were recently published in the journal Behaviour.

On why she studies squirrel personality

I was interested in juvenile personality and how personalities change over time in wild critters, which is not something that we look at a lot. We’ve studied changes in personality a lot in humans and in lab animals, but in the wild we don’t really know what goes on under natural conditions. It’s hard to do. Think about trying to follow baby animals as they grow to see how how their behaviour changes. Mortality can be high with the little ones, so you might not have an adequate sample size by the time they’re grown up. And a lot of the time, wild animals will behave differently when there’s a human around. Squirrels are great, though, because they habituate quickly to humans and don’t really care if you’re there or not — they’re just going to do what squirrels do.

On why the red squirrel is a good subject

Squirrels are great to study for a variety of reasons. They’re generally easy to trap and not difficult to handle and put in an environment where you can study them. Imagine trying to do the same thing to a moose or a polar bear; logistically, that’s going to be a little tough! Red squirrels are territorial and maintain individual middens throughout their lives. They have a central food cache, so they have to be there to defend it. Once you locate a red squirrel that’s vocalizing and letting you know where it lives, you can go back and find it for the rest of its life, which allows you to follow the animal across time. Grey squirrels are not territorial in the same way; they’ll hide their food in spots over a broad area.

On what she was looking for

The two personality measures I looked at were activity and aggression, which are separate behaviours. Activity and aggression are often correlated with each other; squirrels that are really active also tend to be really aggressive and vice versa.

On how the study worked

The way you test personality is squirrels is by putting them in a novel environment. We have what we affectionately call the Thunderdome, the technical term for which is the open-field trial arena. It’s just a white box with a clear lid that allows you to videotape the animal’s response to being in a new environment. You can get a measure of their activity — how much time the squirrel spends checking out this new place, how much time it spends walking, how often it’s jumping, how long it’s just sitting there — and the response is really variable across individuals; some immediately start bouncing around in the box, whereas others will just sit and wait for something to happen to them. After the activity test, a mirror is revealed and the aggression test begins. When the squirrel sees its own reflection, it thinks it's seeing another squirrel. And because squirrels are asocial, it perceives the situation as confrontational. As with the activity test, there’s a lot of variability among individuals. Some squirrels respond to the ‘confrontation’ by retreating to the farthest corner of the arena and avoiding eye contact, whereas other, more aggressive individuals rush up to the mirror and attack it. We don't use another live squirrel, or video of a squirrel, for more consistency of experience. The mirror is actually quite elegant because it matches each squirrel’s size and initial level of aggression. As with humans, you might expect a squirrel to be a little less keen to start a fight with a much larger or bolder opponent!

On what she found

With young squirrels, there were really active ones and really inactive ones, just as there were really aggressive ones and really unaggressive ones. But as they matured, the really active, aggressive squirrels became more moderate, and the low-aggression, low-activity squirrels kicked it up a notch. They sort of averaged out.

On what her findings mean

When squirrels are younger, it’s a very turbulent time in their lives. They have to leave their mother’s territory and find their own place, and extreme behaviours may be more beneficial to them. One good strategy could just be for them to go out there, explore really thoroughly, be really aggressive and gain that territory. Alternatively, they might have a greater predation risk if they’re really active and really aggressive, so they might be better off if they weren’t as active or aggressive. Once you have a territory you’re pretty much set for life, so at that point you might not need to have such extreme behaviours.

On her future work

A small proportion of personality in squirrels, and in all animals, is heritable, but there’s a lot of other things that can influence it. One of the other things I’m trying to determine but haven’t published anything on is the early characteristics that relate to personality later on. I have some preliminary results suggesting interactions among siblings are an influence, but there’s a whole bunch of factors that could have an effect, including the mother’s behaviour. You do tend to see a lot of personality variability within litters, and this even comes out when you’re trying to capture them. It was really hard to catch complete litters. There’s always a squirrel that’s super interested in peanut butter right away, that’s really trackable, that I catch every time I go to his mom’s territory. Then there’s the shy squirrel, the one that just sits in the tree looking down at you, not trusting you, the one that won’t get in the trap even though you see them day after day. You can tell there are differences in personality even before you get them in the Thunderdome.