Catching (and Releasing) Squirrels

Toolik Field Station, North Slope, AK
June 23, 2019

Photo of the Day:

Arctic Ground Squirrel (Spermophilus parryii)
Arctic Ground Squirrel (Spermophilus parryii). Toolik Field Station, North Slope, AK.

Today was a change of pace, as I was able to join “Team Squirrel” on their final day at Toolik. This group of researchers consists of Dr. Cory Williams, Dr. Helen Chmura, and graduate student Cassandra Duncan, all from the University of Alaska Fairbanks. The team is specifically interested in the circadian rhythms and circannual cycles of Arctic ground squirrels (Spermophilus parryii).

Team Squirrel
Team Squirrel. From left to right: graduate student Cassandra Duncan, Dr. Cory Williams, and Dr. Helen Chmura. Toolik Field Station, North Slope, AK.

The Arctic ground squirrel (called siksik in the native Inuktitut, a name which references its characteristic vocalization), has a very interesting phenology. There is constant daylight during the summer up here in the Arctic (check out this video I took), yet evidence suggests the Arctic ground squirrel is still able to maintain a circadian rhythm during this time period.1 This species also hibernates from fall to spring and is somehow able to survive despite its body temperature dropping to as low as −3°C.2

To study these cycles, the research team traps Arctic ground squirrels on the North Slope and equips them with collars containing light sensors and temperature loggers, as well as radio transmitters. Using this technology, they are able to obtain an impressive amount of data. Light loggers are used to determine when squirrels go into and come out of their burrows. Temperature loggers allow for analysis of hibernation (temperature drop). In addition, temperature data can be used to analyze timing of reproduction, as females exhibit a spike in temperature when they give birth.

Squirrel Research Collar
Arctic ground squirrel research collar, containing a light sensor, temperature detector, and radio transmitter. Hand of high school science teacher for scale. Toolik Field Station, North Slope, AK.

The team works as part of a long-term study at two different sites, one at Toolik Field Station (started by Dr. Brian Barnes), the other near Atigun Gorge. The Toolik site has been monitored for over 30 years, and data from this site was used to first determine the above-cited circannual and circadian cycles in the Arctic ground squirrel. This summer, the group has also been collecting data for a pilot project investigating seasonal variation in immune investment. In other words, are Arctic ground squirrels equally likely to mount an immune response to a challenge at all parts of the year?

Map of Study Site
Map of Atigun Gorge long-term study site. Toolik Field Station, North Slope, AK.

This morning, I accompanied Dr. Helen Chmura to the Atigun Gorge site to set squirrel traps. With traps strapped to external frame backpacks and fanny packs full of carrots, we explored the tundra to determine the locations of recently used burrows.

Ready to Catch Squirrels
Rigged up and ready to catch Arctic ground squirrels. Atigun Gorge, North Slope, AK.

Atigun Gorge Study Site
Dr. Helen Chmura searches for Arctic ground squirrel burrows at the Atigun Gorge study site. North Slope, AK.

Squirrel Bait
Carrots are the bait of choice for the Arctic ground squirrel. Toolik Field Station, North Slope, AK.

Traps were set as good locations were determined, using carrots as bait. Dr. Chmura was very kind to explain the process to me, which I’ve summarized in the below video and photos:

Setting Trap
Dr. Helen Chmura sets a trap for the Arctic ground squirrel. Atigun Gorge, North Slope, AK.

Trap Site
Completed trap site, next to Arctic ground squirrel burrow. Atigun Gorge, North Slope, AK.

Once we had finished setting all the traps, midday had already set in, and it was time to go back and check them in the order they were set. I’m pleased to report that with a total of one trapped squirrel, we didn’t get skunked! Unfortunately, however, the captive was a female; only males were needed for this portion of the study, so this was a quick catch and release:

In the evening, I returned to the same site with the group to release some squirrels that had been collared at Toolik Field Station. It was great to see these squirrels sprint back out onto the tundra!

Releasing Squirrels
Walking to burrow locations to release squirrels. Atigun Gorge, North Slope, AK.

Returning After Trap Collection
Dr. Cory Williams (left) and graduate student Cassandra Duncan (right) return after collecting traps from the Atigun Gorge study site. North Slope, AK.

Comment below!

  1. National Science Foundation. Arctic Ground Squirrels - Science Nation, ↩︎

  2. Barnes, B. “Freeze Avoidance in a Mammal: Body Temperatures below 0 Degree C in an Arctic Hibernator.” Science, vol. 244, no. 4912, 1989, pp. 1593–1595. ↩︎

Add Comment


Janet Warburton

Oh I love Team Squirrel!

Jennifer took the best videos of these critters two summers ago. Tell Team Squirrel hello and I know you are having fun :-)

David Walker

Will do! Yes, I saw her PolarTREC page, really cool stuff! Team Squirrel was so nice to let me come out for a day.


Hey David,

Just catching up on your journals. Great stuff! I suspect your combination of field and lab experiences this summer will fundamentally change both your Planet Earth and Organic Chemistry classes. And the squirrel research and the Bluethroat video are just plain awesome!


David Walker

Thanks for reading, Tim! Yes, it's amazing how this research directly relates to both of the courses I teach. I might be picking your brain at some point this fall about some lab ideas I have.


Very much enjoyed this post. How similar are these squirrels to the ones that live in backyards in Austin?

David Walker

Thanks for reading, El! Here's the best report I've found -- The formal phylogenetic tree is on page 8. Ground squirrels are in sub-family Marmotini, tree squirrels are in Sciurini. Page 9 indicates how long ago these groups diverged in evolutionary history (in millions of years). Pretty cool stuff!