A major project here for the Earthwatch teams at the Pantanal research site is collecting information about small mammals in the area. The group that collects the small mammal data (a.k.a. the "rat pack") surveys four plots of land. Each plot of land contains three to four trails with traps spread across their lengths. Two types of live traps are used, one for the ground and one to put into the treetops. The traps use doors that are triggered by the animal stepping on the other side where the bait is kept. The traps don't harm the animals. The bait used is a mixture of banana, oats, peanut butter, and manioc.

The "rat pack" checks and re-baits the traps twice a day. When an animal is caught, they record the length of the animal's body (head to the base of the tail), the length of the tail, the genus and species, gender, approximate age, and whether parasites are visible. Blood is taken if the animal is large enough.

The "rat pack" estimates the general health of the population using the data they collect on size and parasites as well as analysis of the blood samples taken. They also track the spread of diseases and parasites through the small mammal population of the Pantanal. Based on the mammals they find in their plots, the "rat pack" can also estimate the diversity and density of small mammal species in the Pantanal.