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Radio Telemetry Project: The Case of the Vanishing Squirrels

By Annabelle McCarthy

When I first started my radio telemetry research project as an undergraduate, I wasn’t always entirely confident in my skills, “... Was that ‘beep’ louder here… or here?”. And of course it didn’t help that my subjects, two California ground squirrels (Otospermophilus beecheyi ) at the UC Fort Ord Natural Reserve, were routinely in the same general locations. On the rare occasions where I happened to find a squirrel in the exact same location as the day before, self doubt and worry would creep in, “Am I doing this wrong? Did the squirrel’s collar fall off? Did the squirrel die?”. But then, the next day the squirrel would move three feet in another direction, and I could reassure myself that everything was going okay. The event that truly enforced my radio telemetry skills however, was a mystery as good as any Agatha Christie novel.

Up close and personal with a captured squirrel. Photo by Annabelle McCarthy.

It began on a dark and stormy night. OK, just kidding: this story is set in Marina, California, where the weather is practically perfect in every way. I was at the Ord Reserve around lunch time, slowly walking parallel to the fence line that separates the reserve from a field of brassica, checking the usual hideouts of my furry, collared subjects, two California ground squirrels (Otospermophilus beecheyi). I had no trouble locating squirrel 150.040 (named for the frequency of his collar) among the burrows and poppies that dominated the landscape. Squirrel 150.062 however, didn’t seem to be anywhere near her usual stomping grounds.

I began to worry about the time, knowing I needed to be back on campus to run a tutoring session soon, and unsure of how long it would take me to track down the missing squirrel. There was nothing to do but take a deep breath and try my best. I cranked the receiver volume up, held my yagi antenna up high, and started walking in circles. (I cringe to think what a passerby might have thought I was doing – probably trying to intercept alien signals or perhaps secret government communications). Luckily, I began to hear a faint “beep”, which grew louder as I followed it through thickets of coyote brush and mock heather, all the time watching my step for tiny, endangered sand gilia flowers. Eventually, I emerged clear out of the chaparral, and confronted by a wall of low growing coast live oaks. “Is this normal?” I wondered. “I don’t know that I’ve ever seen a ground squirrel in an oak woodland.”

California ground squirrel captured in a Tomahawk trap. Photo by Annabelle McCarthy.

Stumped, and stopped by the abundance of poison oak growing among the live oaks, I reached out to my research mentor, Dr. Jenny Duggan, and the reserve manager, Joe Miller, for advice about how to proceed. Both agreed that the squirrel may have been captured and eaten by an owl, and that I was likely to find a pellet with an antenna sticking out of it.

After a few days of verifying that the radio signal was coming from the same location, I donned a Tyvek suit and headed into the oak woodland. Walking among the low growing trees and shrubs didn’t prove too difficult, but then the receiver pointed me toward a massive Coast Live Oak, whose branches met the ground. Crawling beneath the tree, avoiding being whacked in the face by a sprig of poison oak, and mediating wrestling matches between the yagi antenna and the oak branches, I braced myself for the inevitable sadness of finding an owl pellet with the live antenna of my dead friend. So, you can imagine my surprise when I finally pinned the source of the signal: a humongous nest of a Monterey dusky-footed woodrat!

Radio-collared squirrel feeding outside a trap. Photo by Annabelle McCarthy.

Woodrats build stunning mound-like dens made of branches, with multiple chambers for all sorts of uses. Nicknamed packrats, they are notorious for collecting and hoarding modern human artifacts, which they use as interior decorations of sorts. One man’s trash is often a treasure to a packrat. The Monterey dusky-footed woodrat is a species of special concern in California, which meant there was now a rat in possession of a $200 necklace that I would never see again. Although I was disappointed that I never got to retrieve the radio collar, I like to imagine the joy that this animal must experience every time it sees what must be its most precious belonging. But most importantly, I felt that my skills in radio telemetry were put to the test by this experience, and I passed.

Squirrel-Net note: We thank Annabelle for writing about her experiences during her radio telemetry project and wish her the best in her future endeavors. As of writing this blog, Annabelle has been accepted to work on a M.S. in Dr. Nick Haddad’s lab at Michigan State University. Congrats Annabelle!

Annabelle McCarthy dressed for work in poison oak. Photo by Isaiah Woodard.


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