SloCo Expedition to La Selva for GPS Collaring and Sample Collection

SloCo Expedition to La Selva for GPS Collaring and Sample Collection

The SloCo team visited  La Selva Biological Station and Reserve to place GPS collars on the sloths that live there. We met with our colleagues Ezequiel Vanderhoeven and Mady Florida from Brown University, with whom we collaborate on scientific studies, for an intense work week. In this blog, we tell you the chronicles of that week!



La Selva

La Selva (“The Jungle”) is located in the Heredia province of Costa Rica and is a prestigious biological station, a center for scientific studies, and a reserve of 1,500 hectares of primary forest, which borders the Braulio Carrillo National Park.



La Selva is well known in the community of researchers, as it is an important site worldwide for studies of tropical flora and fauna.

The Urban Sloth Project moves to La Selva

Until now, we have fitted VHF collars on sloths living in urban areas for The Urban Sloth Project (USP). However, to know how much urbanization and habitat disturbance affects them, we need to compare data from these sloths and contrast it with data from sloths living in healthy habitats such as old-growth primary forests.


sloth on a powerline
We predict that sloths living in urbanized areas will spend more time and energy looking for resources. Photo: Suzi Eszterhas


In this second stage of the USP, we will collect data on 16 wild sloths living in forests that humans have not affected in any way. Due to its location and protection, La Selva was a safe and convenient choice.

Monitoring sloths in town versus monitoring sloths in the jungle

In the urbanized areas of the South Caribbean, we can use VHF collars and backpacks with daily data loggers, but we must take the GPS coordinates manually. This is why we must go out with our radio antenna every day to locate the sloths.



The devices we use on the sloths in La Selva are GPS collars. These collars have an automatic release system, so after a stipulated time, they open and fall to the forest floor, avoiding a second capture to remove the collar from the sloth. With GPS collars, it is also not necessary for researchers to monitor daily.


A sloth with a GPS collar

Sampling hair and feces

Ezequiel and Mady from Brown University study sloth feces for parasites and dietary composition; They also study their blood and perform various pathogen tests to determine if sloths can spread diseases to humans or vice versa.



We are also collaborating with Max Chavarría, a researcher at the University of Costa Rica, to further study the hair of sloths. Chavarría has recently published a study on the antibiotic potential of sloth fur.

Dogs and Drones

Sloths in the primary forest are very difficult to find since they are very well camouflaged. Primary forests also have dense foliage, so it’s not easy to detect sloths with the naked eye as we do in the South Caribbean. We had to develop new strategies to find them.

Keysha is our detection dog: her job is to find the sloth feces. Feces on the ground indicate the potential presence of a sloth in the treetop. Keysha’s work is also central to the studies of our colleagues at Brown University.



Additionally, Deyber, our climber for our Sloth Crossing Project, is also our certified drone pilot. Dayber uses our drone with thermal cameras to find sloths in the treetops.


This is one of the first images we capture of a sloth using our drone! This image was taken in May in the South Caribbean.


This should be done as early as possible in the early morning when the ambient temperature is relatively low and contrasts best with the body temperature of sloths. Sloths do not maintain a constant temperature of 36° like all mammals, and their body temperature can fluctuate by about 10°, so detecting them with thermal drones is also somewhat tricky.

The week at La Selva

Day 1: Monday

The SloCo team traveled about 5 hours from Puerto Viejo de Talamanca, arriving at La Selva around noon. After meeting with colleagues from Brown University, they went out with the La Selva park rangers to check the trails and the site.


Dayber is setting up the drone, while Keysha is taking a break.


They found a male three-fingered sloth almost at the end of the day, when it was already getting dark, so capturing the sloth was not possible.


Day 2: Tuesday

At 5 a.m., the team was ready to start the workday: Dayber flew the drone, and Keysha did her work in the early morning hours while it was still cool.

After that, the team returned to the same trail to look for the sloth they had seen the day before but could not find him. They found another three-fingered male on a different path, but it was too high up and impossible to climb up to catch it.



After several hours and going through several trails, locating a sloth at a comfortable height for Dayber to climb was possible. Climbing on a tree in the tropical jungle is not an easy task since many animals may live among the plants on the trunk: spiders, snakes, and centipedes, among other creatures, some dangerous. This time, Dayber was attacked by bullet ants, considered to have one of the most painful stings! Ouch, Dayber! However, Dayber captured the sloth despite the ants and lowered it from the tree.



After taking his weight, various measurements, and hair samples, the GPS collar was placed on the sloth, and the team released him in the same tree. The day was a success!


Day 3: Wednesday

The team split into two groups: Keysha, Tamara, and Mady headed out on a bike-friendly trail; This way, Tamara could transport Keysha for several kilometers on a bicycle cart so that Keysha didn’t get tired.


On the other hand, José, Dayber, Diego, and Ezequiel entered more challenging trails. That day they saw many other animals, such as snakes and peccaries, but without success, to see sloths.

Tamagá Porthidium nasutum. Rainforest Hog-nosed Pitviper
Tamagá (Porthidium nasutum), also known as rainforest Hog-nosed Pitviper.

Day 4: Thursday

That morning the team saw two sloths, but again, at a very high altitude, with no chance of climbing. A severe electrical storm began around noon when the team was in the station cafeteria, ready for lunch. In the distance, they could hear some trees falling. In these dangerous weather conditions, the team took shelter at the station for safety.


Moments before the storm


Day 5: Friday

The team returned to look for the two sloths they had seen the day before but were still high up in the treetops. They found a third sloth: Dayber climbed the tree, but the sloth, contrary to what most might think of these animals, slipped away and went to another tree.


Mady, Dayber, José, Ezequiel, and Diego


Around noon, the team receives a report of a female in a tree near the station rooms. They managed to capture her, take data and samples, and after fitting her with the GPS collar, they released her in the same tree.


An atypical week

Science is one of the fundamental initiatives of our organization, and collaborating with scientists and fellow conservationists from other institutions and universities is always a source of joy!

We will continue to bring updates and news about our trips to La Selva. We would like to warmly thank our colleagues at Brown University and all the staff at La Selva for their outstanding support.


Cecilia Pamich

Communications & Outreach


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