Small mammals, big personalities

Personalities of animals, including the smallest woodland mammals, dictate how they behave and, ultimately, impact their habitat. Understanding how the critters respond in environments being altered by humans and climate change is at the core of research by Alessio Mortelliti, an assistant professor of wildlife habitat ecology at UMaine.


Alessio Mortelliti:
Small mammals play a really critical role in forest regeneration.

Like humans, animals have personalities. We have bold individuals, shy individuals, more aggressive individuals. It’s the same for animals. There’s shyer mice, more aggressive mice, more curious mice, more active mice.

Allison Brehm:
It’s important to have a lot of diversity in population for them to be healthy. A population that has animals with all the same behavioral type, it’s not going to be as able to withstand change as a population of animals with all sorts of behavioral types.

A bold mouse, it might have advantages in some instances, but a shy mouse may also have advantages in some circumstances. It’s important to have that diversity.

Humans influence animals when we clear forests, when we urbanize, but we may not be affecting all of the animals the same way.

Sarah Boone:
The small mammals like to move when it’s raining because predators can’t hear their feet scurrying around as easily.

Alessio Mortelliti:
We’re looking at whether, by modifying the environment, we’re actually giving an advantage to certain types of individuals, so we are somehow modifying the course of evolution and advantage in certain personality traits compared to others.

Allison Brehm:
This is a woodland jumping mouse.

We use three different behavioral tests right now to help us gauge personality. The first is called an open field test. It’s used to measure an individual’s response to a novel environment.

Second test is called an emergence test. It lets us see who the bold individuals are.

The last test, it’s called a handling bag test. Basically, it measures stress response. Then I can eventually look and see how personality influences body condition, survival, and how this change all plays into it. Depending on the type of forest treatment, animals are either advantaged or disadvantaged.

Alessio Mortelliti:
People think, who cares about small mammals? They’re not an important species. Because their job in the ecosystem is to eat seeds and disperse them, they can really harvest up to every tip.

For example, we’re finding that they really do not like paper birch. They do not like balsam fir. I’ve seen squirrels spitting seeds of balsam fir because they don’t like them.

I’m not surprised that balsam fir, paper birch are the most common species in regenerating forests. They can really have a very substantial role on the composition of the forest.

Allison Brehm:
Basically, an animal passes through this area, they go in here, and start eating whatever seeds I have. It’ll read the pit tag. Then these two cameras will show me what they’re doing. I can see what sort of decisions that they make and how long it takes them to make those choices.

I am giving them different size and weight options. They all taste the same, they smell the same, and the same shape. The only thing that’s different is their size. I’m looking to see how different individuals make different choices based on the size of the seeds and the weight of the seeds.

Obviously, bigger seeds, they give you more resources. They’re better to a point, because you’ve got to lug that big thing away and you can’t be vigilant during that time. Then there’s a cost to even spending the energy to disperse that seed.

I want to see whether or not personality plays into this choice, whether or not the bolder, more active individuals are the ones who decide to go for that big seed versus the smaller seed.

Alessio Mortelliti:
In the long term, if we want to manage viable populations, we need to also start looking at things such as the variation of personalities. If we want these populations to be able to adapt to the changes in climate, land use changes of the future, we need to preserve this variation behavior.