This Squirrel Looks Out for Its Friends

Ground squirrels have a good reason to be worried. They have lots of predators and few ways to defend against them. So they watch out for each other.

Unlike some animals that take turns playing sentry, Barbary ground squirrels keep watch together, a new study finds. It’s a behavior known as synchronous vigilance.

Found off the coast of Africa, these squirrels (Atlantoxerus getulus) are an invasive species that were introduced to the Canary Islands from Morocco.

Study lead author Annemarie van der Marel, a postdoctoral researcher at the University of Cincinnati, is fascinated by these small ground squirrels for many reasons. She spent three winters studying them for her research.

“I'm very intrigued by the question of how species navigate their social and physical environment. As Barbary ground squirrels are a social species that is invasive to Fuerteventura, they had to adapt to a different environment. So they represent an interesting study case for me to answer how they are resilient and such successful invaders,” van der Marel tells Treehugger.

“They are relatively short-lived (average lifespan about 2 years), which allows me to analyze data from their full lifecycle in a short period of time. Furthermore, they are small diurnal prey species, therefore many predators try to eat them and it's fascinating to me what behaviors they have evolved to evade predation and increase survival.”

The small rodents with big eyes and bushy tails live in colonies and find shelter in burrows underground like other ground squirrels.

“They’re pretty cute. People had them as pets and that’s how they were introduced to the Canary Islands in 1965,” van der Marel says.

The results were published in the journal Behavioral Ecology and Sociobiology.

Social and Vigilant

Barbary squirrels are very social, says van der Marel, who began studying when and why they were social and how they avoided predators.

“Females share sleeping burrows with related females and males share burrows with unrelated males. We also found that males also group with subadult males and females, which is different from any other ground squirrel species,” she says.

“Although Cape ground squirrels also have separate male and female social groups, the subadults stay in the female social groups. The social organization is different from many North American social species as these often live in family groups.”

When the squirrels set out in the morning to find food, they are vigilant, looking for threats from the land and sky. If something is detected, a squirrel will sound the alarm to send other animals scurrying to safety. Often, the squirrels will hold watch together.

Because they can’t forage and be on alert for predators simultaneously, they’ll often stop throughout the day and scan the environment together, using their keen vision to search for potential predators. They’ll often do it from a higher vantage point, van der Marel says.

Synchronized behavior increases as the group size gets larger. Other situations can also have an impact.

“The factors that influence synchronous vigilance are the behavior of the group members, where individuals copy the behavior of their neighbors or where group members have the same timing to perform certain behaviors, or the anthropogenically altered habitats, where multiple individuals may be necessary to watch on either side of a rock wall for terrestrial predators that are ambush predators, so they watch each other's back,”  van der Marel says.

Being watchful and alerting other group members is the primary defense mechanism these squirrels have, but not their only one.

“Barbary ground squirrels also use low-quality vigilance. Low-quality vigilance is where the squirrels can perform another behavior while being vigilant. Thus, when ground squirrels have found food, they can be vigilant while they are eating. Barbary ground squirrels also alarm call to alert their group members of danger.”