Mexican Mammal Study in Coffee Farms

February 19, 2014 by Amanda Caudill


Rice rat (Handleyomys sp.)

We wrapped up Session 2 with the highest trap success rate that I have had in my research career thus far! The trap success rate is a measure of the effectiveness of the sampling effort. For small mammal studies, it is the total number of captures (including recaptures) divided by the sampling effort which is the number of traps set out times the number of sampling nights.

Trap success rates in coffee are usually quoted as approximately 1 to 4 %. In the shade coffee, we had trap success rates ranging from 5.6 to 12.8 %!

We found about 6 different species of small mammals for this second session. I say "about" because there are a few that we have captured that may be 2 different species or may be a subspecies of the other. This will be sorted out when we analyze the DNA samples.

Many of these little critters are not distinguishable from each other in the field, so it is important to have DNA samples so that we can understand the diversity of mammals. Personally, I use the least invasive methods possible for my research. We take salvia samples by swabbing the mouse's mouth with a tiny cotton swab which is about the size of a felt-tipped pen and also by taking a couple hairs of fur. It is amazing that we can identify the species in the lab just based on these samples.

Traps drying.

At the end of each session, we rinse and clean all the traps. I think that I can safely say that this is the least favorite activities of my field crew. We open up all the traps, then rinse and scrub them with a toothbrush. This ensures that there is no bait molding behind the trap door and that all the hinges and corners are clean and functioning, ready for the next round. We first set the traps out to dry, then comes the task of pinning them all back together. It is a time-consuming, tedious task—especially when we have 300 traps to clean and pin.

We are at the midpoint of this field research project. We have 5 sampling sessions total and we are right in middle of session 3. I have noticed in my past field work that the midpoint is one of the toughest parts. The novelty of the project is starting to wear off and you still have a lot more field work ahead of you—you know the area a little bit, are familiar with the sites, have seen a lot of different animals, the camera traps have lost their luster, your muscles are getting tired.

This is when it is important to revisit your focus and motivation, to be aware that you are a little worn out and make sure that you are paying attention to details as much now as you were at the beginning. For example, I always notice that at the beginning of a field season, I take photos of everything. I have multiple pictures of all the sites from all different angles, all the coffee plants, tons of mice photos…then as the research progresses, the number of photos slowly begins to decrease.

I make a conscious effort at this point to take multiple photos each session (it is on one of the many to-do list on the wall for each site) and I also make sure to take a step back when doing our daily hikes and notice our beautiful surroundings and appreciate the fact that we are able to be here and hopefully contribute to the conservation of these important habitats.