Team Squirrel

 In Biology and Wildlife

By Sara Wilbur

Second-year Masters student in the Department of Biology and Wildlife
Advisor: Dr. Brian Barnes

Copyright © 2013 Øivind Tøien/Institute of Arctic Biology. A curious Arctic ground squirrel stares at the photographer.

I don’t think Team Squirrel could do it without the Wall of Candy.

Besides the gorgeous landscape, the friendly staff, and the decades-long projects devoted to monitoring arctic health, Toolik Field Station (TFS), located just north of the Brooks Range, is also known for its delicious cuisine. Along with three gourmet meals prepared and served daily by an incredibly creative kitchen staff (think Vietnamese pork chops, or pan-fried rock fish, or stuffed portabella-eggplant-goat cheese cakes, or savory sweet potato pies, or, or, or…), there are baked goods (banana cake with maple frosting and candied bacon bits!), freshly-prepared ice cream (bitter orange chocolate chip!), and fermented delicacies (fresh sourdough baguettes!). The abundance of homemade eats ensures that every researcher and staffer is well fed and fully satisfied while stationed at TFS.

However, when one is considering what to supplement his or her substantial lunch with to support a long day of squirrel trapping, one need not look further than the Wall of Candy, stocked with all your favorite high fructose corn syrup, fractionated palm kernel oil, and Blue Lake #40 favorites: M&Ms, Snickers, Reese’s, Baby Ruth, Kit Kat, Almond Joy, Skittles, etc., etc., etc. These babies pack a sugary punch that can get any Squirrel Girl or Guy through the tussocks, crusty cages, and squirrel-laden schleppers that are necessary components of “trapping for keepers”, or capturing squirrels to later truck back down to UAF for the upcoming winter’s research.

Copyright © 2013 Øivind Tøien/Institute of Arctic Biology.

In early July of 2017 four members of Team Squirrel covered large areas of habitat to the north and south of TFS. In theory, trapping an arctic ground squirrel (AGS; Urocitellus parryii) is easy: find an active burrow (evidence of footprints, feces, smells like squirrel), open and set a live trap, cut up some carrot, toss it in, and “let it soak”, as one Team Squirrel member refers to the wait period necessary to lure the squirrels in. In reality, it is often more difficult. Aforementioned tussocks, unpredictable weather (snow can fall literally any day of the year), soggy soil, awkward hillsides, and the distance covered while carrying heavy, unwieldy schleppers and traps can make for an exhausting day. Ironically, although AGS can survive subzero ambient temperatures for up to eight months without eating or drinking and can lower their core body temperature to below freezing (Barnes 1989), their summer activity patterns are very much influenced by weather; AGS will not leave their burrows if it is too hot, too sunny, too cold, too rainy, or too windy. Furthermore, when conditions are unfavorable, cages have to be checked frequently, as the animals are prone to hypo- or hyperthermia. At the end of the day, any successfully trapped animals are trucked to the lab at TFS and cared for until the trip back down to Fairbanks.

Copyright © 2013 Øivind Tøien/Institute of Arctic Biology.

Why put so much effort into trapping AGS? For decades, scientists at UAF and around the world have been fascinated by the extreme thermophysiology exhibited by these hibernating rodents. AGS are obligate hibernators; that is, they are programmed to drop into a deep hibernation every autumn. Facultative hibernators, on the other hand, may drop into hibernation only if environmental conditions are unfavorable, such as during times of low food abundance or cold ambient temperatures (Drew et al. 2007). Hibernators like AGS experience two distinct physiological phenomena while in hibernation: torpor, or an extended period of very low metabolic rate, body temperature, and respiration (around two to three breaths a minute); and arousal, characterized by a brief (12-24 hour) return to normal, summer-type physiology (Buck & Barnes 2000). A common misconception regarding hibernation is that hibernators “sleep” while in their hibernaculum, or hibernation chamber. It is actually during an arousal that hibernators are thought to be “sleeping”; that is, brain activity over an arousal closely resembles brain activity during sleep (Daan et al. 1991). AGS fluctuate between these two states throughout the hibernation period, arousing several times before the final exit from torpor and reentry into the world above ground. How AGS can adjust their metabolic demand, entering stasis for months, yet keep track of time to emerge to the surface at just the right moment in spring are research topics of several labs at UAF.

AGS are charmingly cute, very diverse in their vocalizations, and very opportunistic in their diets, from berries to fungi, roots to grasses, and baby ptarmigan to baby AGS! (Males may eat the young sired by other males). They are solitary hibernators, unlike the closely-related marmots, which hibernate communally (Lee et al. 2016). They are prey to gyrfalcons, golden eagles, foxes, wolves, and bears. Young will stay with their mothers until weaning, and the following spring juvenile males from the year prior will leave in search of new territory while the young females are likely to stay close (Byrom & Krebs 1999). Much of the active season is spent fattening for the upcoming winter, and both males and females turn into little furry butterballs as their fall immergence time approaches.

Although the days are long and the work is challenging, trapping in the incredible beauty of the north slope of Alaska and the comradery one feels with the other scientists and staff at TFS make for a highly rewarding experience. Working so closely with these fascinating animals and attempting to understand the mechanisms and limits of their unique physiology is also a source of deep fulfillment. May the legacy of research with arctic ground squirrels at Toolik Field Station, and the essential abundance provided by the Wall of Candy, continue for many years to come.

Literature cited:

Barnes, B.M. (1989). “Freeze Avoidance in a Mammal: Body Temperatures Below 0°C in an Arctic Hibernator.” Science 244(4912): 1593-1595.

Buck, C.L. & B.M. Barnes (2000). “Effects of ambient temperature on metabolic rate, respiratory quotient, and torpor in an arctic hibernator.” American Journal of Physiology: Regulatory, Integrative, and Comparative Physiology 279: R255-R262.

Byrom, A.E. & C.J. Krebs (1999). “Natal dispersal of juvenile arctic ground squirrels in the boreal forest.” Canadian Journal of Zoology 77(7): 1048-1059.

Daan, S., B.M. Barnes, A.M. Strijkstra (1991). “Warming up for sleep? Ground squirrels sleep during arousals from hibernation.” Neuroscience Letters 128(2): 265-268.

Drew, K.L., C.L. Buck, B.M. Barnes, S.L. Christian, B.T. Rasley, M.B. Harris (2007). “Central nervous system regulation of mammalian hibernation: implications for metabolic suppression and ischemia tolerance.” Journal of Neurochemistry 102(6): 1713-1726.

Lee, T.N., F. Kohl, C.L. Buck, B.M. Barnes (2016). “Hibernation strategies and patterns in sympatric arctic species, the Alaska marmot and the arctic ground squirrel.” Journal of Mammology 97(1): 135-144.

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