SMSC Diary (Week 5): Small Mammal Trapping
WEC concluded the week with a crash course in small mammal trapping led by Leah Card, a level-2 field technician with the National Ecological Observatory Network (NEON). Do not be alarmed, this process was actually very thorough and absolutely no crashes took place.
Leah walked our class through the small mammal trapping training session NEON developed for interns and technicians. We reviewed the extensive checklist of gear required for a normal trapping day, the procedures for trap set up and collection, and the protocol for sample (animal) processing.
Why small mammals and not large?
Widespread
Sensitive to local environmental changes
Carry/transmit zoonic agents (disease)
Represent unique size classes, life histories, and home range size in NEON’s range of study
Interact with other NEON sentinel taxa (ticks, mosquitos, ground beetles, plants, soil microbes, and birds)
NEON utilizes 100 Sherman traps per field site for their long-term monitoring of small mammal populations. A Sherman trap is essentially an elongated metal box with a trap door that closes after an animal enters. This type of trap is preferred as it is very portable allowing technicians to carry large numbers at a time.
After our classroom training session, we practiced identifying areas in the outdoor classroom where NEON might want to set up their Sherman traps. Then, each student identified their own trap location and placed their trap. These traps, however, were only used as demonstrations and were only allowed to sit outside for approximately 5 minutes, as we did not want to accidentally trap an animal.
Small mammal trap placement tips:
Make sure your trap is flat with the ground and does not wobble to make as realistic a route as possible for the animal (no one wants to walk on wobbly ground).
Place trap under tall plant or grass cover, so that the traps are not in direct sunlight or in direct line of sight for aerial predators.
Place traps running parallel and against obstacles such as logs.
Avoid placing traps in areas that may fill with water when if it rains.
Animal safety is a top priority for NEON, so the comfort and health of the animals are always forefront when preparing traps for the survey. Each trap is filled with a fluffy cotton-like substance known as "batting" to keep the captured mammal warm and comfortable until the NEON crew can retrieve them. The traps are set two hours prior to sunset and checked early the next morning around 7 AM. Additionally, an array of seeds are dispersed in the trap to lure in the animals, but also ensure they do not starve following capture. The traps are never set out longer than 24 hours.
Upon capture, each small mammal is given an ear tag with a unique identification number, are checked for ticks, measured for weight and various lengths, and if it is a new capture (did not already have an ear tag) a small drop of blood is collected for processing. The species of interest included meadow voles (Microtus pennsylvanicus), woodland voles (Microtus pinetorum), black rats (Rattus rattus), house mice (Mus musculus), white-footed mice (Peromyscus leucopus), and deer mice (Peromyscus maniculatus). The data collected from these surveys may be used to evaluate a variety of measures such as the role of small mammals as vectors for disease and the distribution of these species within their range.
Prior to this experience, I had never realized how many small mammal species inhabited tall grasses in our area. While I enjoyed seeing the diversity of species, I think that I am too squeamish for the ear tagging and DNA collection aspects of small mammal monitoring. Therefore, I can happily say I have tried small mammal trapping, but will not be pursuing it as a career.