I am not currently engaged in any small mammal research (beyond simple inventorying of species) but I teach proper capture and handling techniques in my classes. Let's review the equipment first.
|Sherman trap at a forest location|
Naples, NY (7/14)
Traps such as these require bait to increase the capture rate. I mean, a small mammal could stumble in and investigate, but bait is needed to really make this work. Much has been written regarding various bait effectiveness. We use the following recipe ( I believe credit goes to SUNY ESF???):
|Sasha makes this for us but I believe this is a SUNY ESF recipe|
We also place cotton balls in the traps along with the bait. Cotton serves several purposes. It acts as insulation against the cold of the bare metal and it also gives the captured animal something to do. In my experience, captured rodents often shred the cotton balls and create a "nest".
Other useful equipment for setting traps includes plastic gloves for handling bait, GPS receiver for marking trap locations and a notebook. Please note that there is a different equipment list for checking traps.
To increase capture rate, we typically pre-bait traps for about a week. This entails setting the traps in their transects, adding cotton balls (I like to use two) and bait and leaving the back door open so any animal that enters the trap is free to leave. This can increase capture rate by getting the animals used to visiting the trap for a reward (bait). We try to re-bait every second or third day. It also gives us a chance to see the activity level in the area. If many traps are being cleaned out, we expect a bigger capture when the traps are finally set. One disadvantage of pre-baiting is that larger animals can also find your traps. We have had problems with raccoons, striped skunks and gray squirrels finding and raiding traps. Here are some examples:
|Striped skunk raiding a Sherman trap|
Canandaigua, NY (11/13)
Each May we offer a Conservation Field Camp course and small mammal trapping is part of that. Here, two technicians set and bait a Sherman trap specifically targeting flying squirrels.
It only took about five and a half hours for this coon to visit. He found this set during the pre-baiting period. In this photo he is starting to reach into the trap.
It is difficult for him to reach the bait without triggering the trap. By now, I bet this guy has enough experience with these traps to know that if he pulls out his arm without the bait, he won't get a second chance as the door will close.
The rock wall transect was getting hit as well. Here is a pre-bait photo. Notice first that you are looking at an open back door. The back door is not spring loaded so animals are free to move in and out. To try to increase the camera trap captures at this photo, Sasha placed some natural bait (hickory nuts and mushrooms) on a rock.
Less than two hours later, an eastern chipmunk enters the trap and presumably takes some of the bait.
As hoped, there were lots photos at this location, including some mice in the genus Peromyscus. Check out this mouse in mid-leap with an open Sherman trap in the background. I thought "What a lucky shot! That'll never happen again." Well.....
And then a third... Here I present them to you in the order they were taken. All were captured on different nights. But when I use these in class, I will be putting them in "order" to make it look like a sequence of three photos of one mouse making one jump :)
Since the last photo, Sasha has closed the back door, set the spring loaded front door, re-baited the trap and turned it around so that the opening is still in the same direction as it was during the pre-bait week. Can you see how the edge of the opening looks different than in the photo above? The front door opening has a bit of a lip that the door closes against.
Here is the very next photo captured. The door is closed and the mushrooms have been moved. Obviously, the camera missed some things.
Not far behind was this raccoon. When we checked the traps, this one was tossed open and empty. Was there a critter in the trap when the coon opened it? Probably, but we will never know for sure.
Once we capture a small mammal, the handling protocols we use are designed to assure a safe and quick experience. For example, shrews are particularly susceptible to trap-stress, so our protocol calls for processing them first. Students are instructed to keep noise to a minimum. We still talk, but we use our inside voices. Students work in pairs with one wielding the clipboard while the other processes the animal. And as mentioned previously, animals are returned to the exact location of their capture.
Removing an animal from the trap is not difficult, but does take some practice.
Sometimes an animal is reluctant to leave a trap even after shaking it a little. A nice trick is to aim the opening up. Often an animal will scoot right out.
|Author removing a flying squirrel from a live trap|
Photo credit: Alyssa Johnson
|Weighing a mouse with a spring scale|
Canandaigua, NY (4/14)
The next step is removing the animal from the bag. Here, Clinton holds the bag against his leg and uses one
If we are holding an animal for any length of time (to let students observe it), we place it in a jar. The jar
|Male with enlarged testes and large distance from the|
anus to the genital
Naples, NY (7/14)