Squirrel Project Update

With trapping all wrapped up and 15 fresh collars fitted to TA's squirrels, it is time to begin phase two of our annual squirrel monitoring project. During this phase of our mark/recapture study, we monitor feeders with trail cameras, keeping track of the number of squirrels visiting the feeder and whether or not they are wearing a collar. A typical mark/recapture study would use a second round of trapping to gain an idea of the ratio of collared to non-collared squirrels in the population. When I designed the study, I chose to use the trail camera technique with the idea that squirrels that have been previously handled would be less likely to be trapped again. One of the major assumptions in this research is that all squirrels have the same likelihood of being captured. Those educated squirrels avoiding our traps would be a major source of error. The trail camera allows us to "capture" any squirrel that climbs onto the feeder without them ever realizing it. The basic formula we use to estimate our population (known as the Lincoln-Petersen Index) is shown below.

  M (Number of Marked Individuals)                R (Collard Squirrels Recaptured on Camera)

        ----------------------------------------------       =       --------------------------------------------------------

     N (Total Number of Squirrels in Pop.)             T (Total number of "captures" on Camera)

My lab aide, Cody Agro, is tasked with keeping the feeders full and sifting through thousands of photos of squirrels, looking closely for collars, and recording data in our shared spreadsheet. He is off to a great start with some interesting findings already. 

Cody sifting through photos and recording data

A week in, we have had plenty of activity on our campus feeder but only two individual squirrels have been documented. This aspect of our research is really cool. Many people wonder if they are seeing the same squirrels in their backyard day after day and in this case it seems as though we are. Both squirrels are wearing collars. One is a male collared on October 2nd sporting a yellow collar (2018) with all white beads. The other is a squirrel wearing an orange collar from 2016! This means this squirrel is at least 2.5 years old, an old timer by squirrel standards, we think. This individual has been seen around campus a few times this fall. I was really hoping to get a fresh collar on it this year but we never caught it during our initial trapping. It seems as though this is one of the those previously educated squirrels our trail camera method seeks to make up for. If not for a distinct scar on its back and a notch in its left ear, it would be hard to tell if this was the same individual over and over again. 

An orange collared squirrel from 2016 on the feeder last week

A male from the class of 2018 on the feeder last week 

We are just a few days into phase two of the research this year and the big questions are already popping up? Where are the other nine squirrels collared within 100 yards of this feeder site this year? Having only collared individuals on camera suggests we have caught and collared every squirrel in the population, something we know from daily observation is not the case. I suspect that as the season rolls along and food becomes limited, our feeder site will draw more squirrels. Only time will tell, stay tuned!