June 2016 Summary
Behavioral study of spider monkeys at Los Arboles Tulum
Dr. Filippo Aureli & Dr. Colleen M. Schaffner
Universidad Veracruzana, Mexico
Since November 2016 we have run phase 2 of the spider monkey project at LAT. This phase consists of finding the monkeys, following them for as long as we can each day to identify them individually and document their behavior.
Our research team is small, but has a lot of experience in studying spider monkeys. The main team member to carry out this work is Cecilia Cahum Cahum, who was born in a small Maya village between Coba and Nuevo Xcan and has received a bachelor degree in Biology from the Instituto Tecnológico de Chetumal, Quintana Roo. For the first few months, she has been accompanied by Andrea Díaz Alonso, who is an undergraduate Biology student of the Instituto Tecnológico de Conkal, near Merida.
Every day we follow spider monkeys for several hours and use binoculars, digital voice recorders and gps to collect data on the monkeys´ activities and their ranging behavior. We have discovered several areas where the monkeys tend to sleep, so we can check them in the evening and start the following morning from one of them where we found monkeys. Some of the LAT residents have been very helpful by telling us about their monkey sightings.
Spider monkey groups split in small subgroups that change composition several times a day. That is why we see them in subgroups of different size and composition. The first two months have been very rewarding because we could regularly find large subgroups, which are easier not to lose when attempting to follow them. As you know, the LAT monkeys are used to people and do not run away. Still, they were not used to be followed. Cecilia and Andrea did an excellent job in habituating the monkeys to be followed, and so we could be with them several hours a day. We have also started individually identifying some of them based on size, hair color and spots, especially around the eyes.
When the dry season started, things became more difficult for us as spider monkeys started to split in smaller subgroups to adjust to decreased food availability and travel farther away in search for food. This is a seasonal change typical of spider monkeys, but it made it more difficult for us to locate them, especially as we knew only a handful of their sleeping sites at LAT. And even when we were able to follow a small subgroup after dark, we often could not find them in the same location in the morning as they probably moved to an unknown sleeping site when it was already dark. The rainy season has started and more food should soon be available at LAT. Therefore, we hope to find and follow spider monkeys at LAT on a more regular basis. Still, the data collected during the dry season are useful as they confirm that LAT spider monkeys follow the typical species pattern of splitting in smaller subgroups in the dry season when there is less food available to reduce competition.