Methods of Mammal Research

Most mammals, especially small mammals like squirrels, are extremely difficult to observe in the wild because they only come out at night or because they are so skittish and avoid contact with people. Not every critter is like the friendly Eastern Grays found on UW campus, so animal researchers must take measures to trap them, outfit them with collars to track their movements, tag them, and other methods in order to study their behavior. Below are three examples of how scientists carry out their research: trapping, radio telemetry, and the use of "dummy" robotic squirrels to measure social interactions.

Trapping
Trapping is usually the first step before performing other types of animal research such as attaching collars or determining gender. It is important to note that trapping should only be done with the proper permits and with proper knowledge on the type of trap to use and on setting the trap to avoid hurting the animal. All sorts of things can go wrong if the trap is too large or too small (the animal could hurt itself crashing into the walls of the cage) and if one is not prompt in checking the trap, as an animal left in the cage for too long will be exposed to predators of all kinds, even ants, and will probably die if left overnight. 

Simple live cage trap

The most common and easy to use kind of trap is the live cage trap. First, the researcher will bait the trap over the course of a few weeks using, if attempting to catch squirrels, walnuts, which they love and which won't attract other animals. The squirrels will come to the trap gradually and become accustomed to finding food there. Once the researcher is certain the squirrels will keep coming back, he or she will bait the trap one more time, let the squirrels come, bait it again, and then set off the trap. The cage door is rigged open and, when the squirrel enters and goes for the walnuts in the back, it will step on the pressure plate and shut the cage door behind it. The researcher will not leave the squirrel in the trap for longer than two hours at maximum for the aforementioned reasons. They must then employ other methods to get the squirrel out of the trap and into their hands for whatever purposes needed for their research. 

Tessa showing off the capture cone.

One such method is the capture cone, which, in this picture, is just a piece of denim with velcro along the seams that forms a cone shape. The capture cone is fitted around the entrance to the cage and the cage is opened, releasing the squirrel. The squirrel will run into the cone and get its head stuck in the smaller end. The researcher can then get a good grip on the squirrel and open the velcro to check the animal's gender, attach a tag or a collar, or whatever their research entails. The squirrel can then be released with no harm done to it if the trapping and handling has been done properly. 

Capture cone and cage trap

Trapping is an important part of researching smaller mammals like squirrels. There are always risks for both the animal and the humans, so I would not recommend the average person attempting to trap animals in their backyard. Our information came from PhD student Aaron Johnston, who uses trapping as part of his work on radio telemetry with Eastern and Western Gray squirrels at Ft. Lewis (for more information on Aaron and his research, see the "Competiton" tab and the "Learn More: Helpful Websites and Experts at the home page!) and is very experienced in the process. For extra information on the process of trapping, check out the "Learn More" tab for an extremely helpful website!




Radio Telemetry

Source: www.redsquirrel.ca
A baby red squirrel fitted with a tracking collar.

Using the aforementioned trapping methods, collars can be placed on animals, squirrels in the case of Aaron's study, and radio telemetry can be used to track them down so that their locations can be added to a map using GPS. Squirrels are captured, fitted with collars, and released again. A small portable transmitter that emits radio waves is then used as well as a special antenna that picks up the waves. Each squirrel is assigned its own frequency and the researcher can tune to that frequency when searching for that squirrel. The transmitter will emit beeps as the researcher gets closer and closer to the squirrel and the antenna is designed so that the beeps will be louder if a certain part of the antenna is pointing directly towards the squirrel. Triangulation is another method requiring the radio collars that is commonly used on larger, more dangerous mammals like lions. Researchers will get within a certain distance from the animal and record that location. They will do this three times and plot them on a map, which will form a triangle. The animal will be in the center of that triangle. This method is much less precise unless one is very experienced in the technique, but it is essential for tracking mammals considerably larger and more of a potential threat than squirrels.


Robotics and Social Interactions

The two robotic squirrels. 

One final technique demonstrated to our group by Aaron Johnston was the use of stuffed squirrels outfitted with robotics to make their tails move. These dummy squirrels (one Eastern and one Western Gray) can be used along with recorded calls from both species to see how squirrels (or other mammals) interact with their own species and with different species. For example, the Western Gray dummy would be placed in an area known to be populated by Eastern Grays and the researchers would watch how the Eastern Grays would react when Western Gray calls were played and the dummy's tail would twitch. The Eastern Grays would bark at the dummy, but would never attack it or approach it. In contrast, if a Western Gray were to encounter the dummy, it would merely inspect it, but would not bark or attack. This technique is an excellent way to observe social interactions without having to sit and wait for one species to enter the other's territory. For more information on the study Aaron conducted, please see the tab titled "Competiton". For more on social interactions between squirrels, simulated or otherwise, please see the tab titled "Social Interactions."


Written by Tessa