October 4, 2012
Fox Squirrels Invest In Their Future With Long-Term Hoarding
[ Watch the Video: Fox Squirrel Caching For The Long Run ]
Lawrence LeBlond for redOrbit.com - Your Universe OnlineSquirrels running rampant, foraging for food, gathering nuts--it is a common sight throughout much of North America. But these little critters´ habits have long gone unnoticed in the scientific community. That is, until now.
Researchers at the University of California, Berkeley, have been studying the antics of these furry little rodents as they scamper about the campus grounds foraging for their favorite treats. However, the researchers have found that these fox squirrels are not merely hunting for their next meal, but are engaging in a long-term strategy, investing in their future.
The team notes that humans could learn a few things about building their nest eggs from the diverse efforts seen in these squirrels. But of course, with squirrels, it´s not about money, its about nuts.
“Think of them as little bankers depositing money and spreading it out in different funds, and doing some management of those funds,” said lead author Mikel Delgado, a doctoral student in psychology at UC Berkeley.
Lucia Jacobs, a psychologist who runs a lab at UC Berkeley where the team conducted part of their studies, said the group started a Cal Squirrels website to promote their work.
“We really think that campus squirrels are an ideal system to understand cognition in the wild, especially at Berkeley, with our year-round potential for field work,” said Jacobs, a leading expert on squirrel cognition.
“To understand how their mind has evolved, you want to have a species that faces big cognitive problems — like making decisions about thousands of acorns and then remembering where you hid them three months ago – and still faces normal challenges, such as escaping from predators, outwitting your competitors and seducing those of the opposite sex —and most important, you need to watch them without disturbing their behavior,” explained Jacobs.
Using the campus grounds as an open-range animal behavior laboratory, Delgado and colleagues have tracked upwards of 70 fox squirrels, mapping out their territories and studying their “caching behavior,” the system squirrels implement in hoarding and retrieval efforts. The squirrels are identified by a gentle squirt of fur dye on their backs by the team members.
“We´re trying to find out what kinds of strategies they might be using to assess the quality of each nut and what kind of investment they want to make in it,” said Delgado. “And we want to know how they remember where they hide all those nuts.”
Delgado´s research is funded by the National Science Foundation. A paper on the study is in the works.
While the antics have amused study researchers, they do note that fox squirrels are not native to the area. They were first introduced on and around the campus in the 1930s and are quite distinguishable from their more rat-like eastern gray squirrel kin, having more of a reddish hue, big bushy tails and a level of cuteness not seen in some other species.
Fox squirrels are diurnal--meaning they are most active during the daytime--and do not hibernate. They are typically unsocial and live life as loners. Mating is a brief encounter and “involves a lot of chasing, squeaking, biting and scrambling around trees,” said Delgado.
Over the past few months, Delgado and her team have followed the cute critters across meadows, hillsides and undergrowth, and have even given them names like Rocket and Flame. The little foragers most often subsist on a diet of acorns, pine nuts, walnuts, almonds and hazelnuts. Among their favorite treats, however, are peanuts that team members carry around in their knapsacks.
Hoarding nuts is a necessity, especially around the campus, because not all the trees produce food year-round. And since squirrels do not hibernate, they need to stock up for winter. The team members have recorded the squirrels carrying nuts as far 330 feet to hide their food.
The team wanted to know more“¦like what kinds of spatial cues do these critters use to find their nuts once they hide them?
To track down the answer, the researchers are using GPS technology to record all the burials and, in the process, are creating an elaborate map showing every campus tree, building and garbage can.
“We´ve compiled a list of more than 1,000 locations where the nuts are buried,” Delgado said.
In an experiment tied to the squirrel hoarding study, the team is following the caching abilities of humans by timing them as they bury Easter eggs on campus and then try to find them.
“We´re using humans as a model for squirrel behavior to ask questions that we can´t ask squirrels,” Delgado said.
The team also completed another experiment, looking at how squirrels respond to frustration when given a particular problem to solve. The team trained squirrels to open boxes with their noses. In a group of several regular boxes, included a locked box, which left squirrels frustrated when they couldn´t open it up. However, instead of giving in to defeat, the squirrels persisted, trying different tricks to get the box open, such as dragging it and biting it, techniques that display the building blocks of intelligence, explained Delgado.
She added that these squirrels are “clever and very persistent” when it comes to solving problems.
Squirrel behavioral expert Jacobs has found evidence that, when holding a nut in a shell, squirrels shake their heads to assess the quality of the nut, and that this “head-flicking behavior” increases when they plan to store the nut rather than eat it.
She also was the first to discover that squirrels remember the location of their own buried nuts more so than of nuts buried by other squirrels. Sense of smell could be key to finding the nuts, according to several experts. However, Jacobs´ research suggests there could be other factors.
“That is something we are trying to ascertain with the GPS data,” Delgado said. “They may be using a combination of landmarks and memory to narrow down their search, and then using their sense of smell for a final bit of searching.”
For now, Delgado and her team are continuing to track the squirrels to hopefully ascertain the mystery of their navigational nut-tracking skills.