Monkeys in the house

Monkeys in the house

By: Amor Aline Saldaña Sánchez, Denise Spaan & Filippo Aureli. 

The project on the spider monkeys within the Los Árboles Tulum (hereafter LAT) began in 2017. Since then, more than 10 researchers, students and field assistants have been involved in the project. Over the years, our team has been dedicated to monitoring the behavior of and following the groups of spider monkeys that live within LAT. The team has also been involved in tasks as diverse as collecting monkey feces for genetic analyses, surveying trees to learn about the forest structure and availability of spider monkey food (mostly a wide array of different fruits), helping inform where to build new houses within the lots before the start of construction, flying drones to count monkeys, climbing trees to install camera traps, recording spider monkey vocalizations to examine how they communicate, teaching classes at the “Escuelita” in Macario Gómez, and more. We even did a study at night and found that the spider monkeys are active, at least part of the night. Maybe you have heard them at night too?

Every team member has had a lasting impact not only on the project by bringing new ideas, energy, skills, and enthusiasm, but also on the knowledge they helped to generate about the monkeys, plants, and animals of LAT.

Throughout these 6 years, we have learnt several interesting things about the spider monkeys. For example, we discovered that there are at least three groups that use part of LAT for their daily activities such as eating, travelling and resting. The Coba group spends a lot of the time in the northwest part of LAT, the Tulum group in the northeast part and the Macario group to the south, that is, next to the road by the two entrances. Over the years, the groups of spider monkeys have shown some fluctuations in their space use within LAT, and sometimes they disappeared from LAT for a while! Typically, spider monkeys use all suitable habitat that is available, and two groups may even take turns to use parts of the same area. In LAT, instead, we discovered that groups leave some areas unused, possibly as a buffer to reduce the probability of encountering neighboring groups. This discovery is a unique contribution our team made as it has never been reported in any other spider monkey study.

We also established that monkeys within LAT feed on some different tree species than those used by monkeys in other regions. For example, within LAT, monkeys search for and consume fruits, flowers and/or leaves of trees they do not use in Punta Laguna (just 40 km from LAT). As such our research in LAT contributes to an overall understanding of the dietary flexibility of spider monkeys in the Yucatan Peninsula.

Because researchers are a constant presence at LAT, it may look like LAT residents are just spectators of the work the researchers do, and of course, of the beauty of having monkeys in their backyards. However, residents are far from mere spectators!!! LAT residents are a primary source of information and invaluable support to our team! Thanks to your reports, we know when the monkeys of the different groups are sighted around LAT, even when the researchers are absent. It is thanks to your reports that we can locate the monkeys during the day when they have gone out of sight of the researchers or leave the limits of LAT. As a result, on many occasions, you helped us to to collect more data, just when we thought our work day was already over. And don´t get us wrong, that is a very good thing!

Below we summarized some of the information provided by yourselves, the LAT residents, to us during 2023. Throughout 2023 we have had 288 reports from LAT residents on spider monkey whereabouts.

In the following graph we can see the areas of LAT in which the monkeys have been seen and reported the most by residents.

The mean number of monkeys that neighbors reports in their lot is 7 individuals and usually included moms and babies. Now, it is normal that sometimes one just sees the monkeys and doesn´t actually count them. And even when we count them, we may miss some. So, there are certainly more monkeys than those spotted at any one time.

The day of the week with most reports is Wednesday. However, the distribution among the days of the week is more or least uniform, meaning that you report monkeys every day of the week. Especially in the weekends your reports are a great source of information as our research team is usually taking their days off. This means we have full week coverage of where the LAT monkeys are, thanks to you! We can see that the hours when there are the most reports of sightings are between 16 and 19 hours. This makes sense as it is much easier to see spider monkeys when they come to sleep next to your house than by chance when moving around LAT.

LAT residents send us also photos and videos of the monkeys. These are great illustrations of their behavior. Although we were not there, it gives us an idea of what the monkeys did. They may have eaten a particular fruit, made a bridge between branches to allow a juvenile to cross the canopy gap, or were excited about something and make alarm calls. They may have gone for a stroll on the ground, elegantly swung from branch to branch before going to sleep, or shared some fruit with coatis on the same tree. These images provide insight into the monkeys’ behavior that may inspire new research ideas!!! So please keep sharing them. 

It is crystal clear that LAT residents are so important to our project, as you provide us with a lot of information and images that we cannot get otherwise. In the end, all the efforts made by both residents and the research team, are in favor of the conservation of spider monkeys within and outside of LAT. LAT is an important refuge for spider monkeys, especially if we take into account the exorbitant amount of construction near Tulum (for example, the Tren Maya project and the new neighborhoods that pop up in and around the town). 

If you would like to contribute by recording spider monkey sightings in LAT, we have a WhatsApp group for this purpose that we are very happy to add you to (if you are not on it yet), or you can send us messages privately with sightings of monkeys. The when and where of the monkey sighting are really important!!! 

Thanks again for all your support this year and see you in 2024. 

Happy Holidays! 

Amor, Denise, Filippo