A Week In the Life of The Sloth Census
Sloths are masters of camouflage, blending seamlessly into the dense rainforest canopy to avoid predators – and, unfortunately, researchers. Because of this, information on population size, distribution, and status is severely lacking, with some sloth species having virtually no data at all. While four of the seven sloth species are currently classified as “least concern” on the IUCN Red List, this classification is based on incomplete or outdated information. The reality is, we don’t know enough to assess how sloths are really doing, which is why this census is so critical.
To fill this data gap, we are using three different sloth detection methods:
- A trained scat detection dog
- Human observers
- Thermal drone technology
Conducting a scientific sloth census sounds simple – until you try doing it in the jungle. Every single survey must follow the exact same process to ensure the data is repeatable and scientifically robust. There’s just one catch: if it rains at any point, the entire census is called off and we have to try again the following week. And it rains a lot in the rainforest.
We constantly run into issues like Keysha the dog getting confused, the GPS not detecting signals, drone malfunctions, the joy of working next to dozens of hidden venomous snakes, difficult terrain, and, of course, unpredictable weather.
Every time we attempt to conduct a census, something likely goes wrong, leading us to jokingly call it the “Curse of the Census.” But in true sloth-like fashion, we refuse to give up, and things are finally starting to come together. This is what a week working on the Sloth Census really looks like:
Monday – Site Selection
We start by identifying a 0.5-hectare area (5,000 m², roughly the size of 12 tennis courts) with consistent habitat, that’s walkable (sort of), and with landowner permission. This step can take several days, and even then, the “best” location is often far from ideal – think steep slopes, tangled jungle, and the occasional river crossing thrown in for good measure.
Wednesday – Transect Setup
Using GPS and measuring tapes, the team marks out a grid with sticks placed every 10 meters. Sounds easy – but this is usually in dense jungle. The GPS drifts, the tape measure gets tangled in vines and trees, and the layout ends up wonky. It takes a team of 7 people all day and must be done exactly two days before the census to avoid confusing the detection dog.
Friday – The Big Day
4:00 AM | Thermal drone survey
This survey must happen before dawn -it’s the only time the temperature contrast is strong enough for the thermal camera to detect sloths hidden in the canopy. That means the team hits the road by 3:00 AM. We fly the drone in a precise lawnmower pattern over the grid marked out two days earlier. Sounds straightforward, except it’s pitch black, the jungle is dense, and the drone is completely out of sight.
When we spot a heat signature, we have to carefully fly in closer to confirm whether it’s a sloth. Dodging branches in the dark, with a drone you can’t see, takes remote piloting to the next level. More than once, we’ve lost signal mid-flight and watched the drone drop straight out of the sky – or disappear completely into the jungle.
5:30 AM | Sloth Scat Detection Dog
Tamara and Keysha begin their transect, following the grid of marked sticks through the jungle. One team member walks ahead with a machete to clear a path through the dense vegetation. When Keysha signals, the search begins for sloth poop (yes, they bury it). In the dark. In the undergrowth. If we find it, it’s carefully collected in bags to be dried and weighed later in the lab.
This stage also comes with the added excitement of venomous snakes, which is why every step is taken with caution – and a healthy dose of respect for the forest floor.
8:00 AM | Human observer transect
Once the detection dog survey is complete, three of our most experienced sloth spotters begin their work. They walk slowly through the study area, spaced 10 meters apart, stopping every 10 meters to scan the canopy for sloths over a two-minute period.
If they spot something, they must first confirm it’s actually a sloth – and not, as often happens, a suspiciously sloth-shaped termite nest – before recording data. This process continues until the entire 5,000 m² area is covered, usually taking several more hours under the increasingly hot jungle sun.
12:00 PM | Vegetation survey
Once all sloth spotting is complete – and the team is thoroughly exhausted – we move on to habitat assessment. Five 10×10 meter plots are randomly selected within the study area. In each one, we record every tree, bush, vine, bromeliad, and anything else rooted in the ground. Tree species are identified, height is measured, canopy cover is estimated, and tree basal area is calculated. It’s detailed, time-consuming work, but essential for understanding the habitat conditions sloths depend on.
Pack up and reset
Finally, the marker sticks come out, the team heads home muddy and worn out—and then it all starts again at the next location. Each site is surveyed three times to ensure data consistency. In the days between, the team jumps straight back into our other projects. There’s no such thing as downtime in sloth conservation.
