The Sloth Backpack Project

02 Mar

It has been a rather un-slothful start to the new year, with a lot of progress being made on the sloth science front. Since Christmas, I have managed to tag an additional four wild sloths with tracking backpacks (including a mother with a baby!), and I am beginning to build up a nice picture of their ranging patterns, and perhaps most importantly, their diet.

The all-new Sloth Backpack:

1Our Sloth backpack designs are constantly changing and being updated as we gain access to new technology. Our latest design features a much smaller VHF and GPS transmitter, a longer-life battery and a brand new Daily Diary model. We have also reduced the size of the housing and added a ‘snorkel’ – a tiny bendy rubber tube that allows air to enter the backpack but keeps water out. This allows the pressure sensor to measure the height of the sloth in the tree. Finally, the long VHF antenna now wraps around the chest strap of the harness to prevent it from catching on branches as the sloth climbs.


The sloths:

The first wild sloth to be tagged with this new-design backpack was Burrito. He is a big, male three-fingered sloth who frequents a tree within the sanctuary grounds. I first tagged him in January and his backpack collected behavioral data continuously for four weeks. Yesterday he climbed down low enough for me to re-catch him and I managed to replace the batteries in the Daily Diary- this means that we have at least another 4 weeks of behavioral data to come! The tracking device will run continuously for 12 months so I will be following his exact movements over the coming year. Whilst putting on his backpack, we were also able to collect valuable hair samples for genetic testing. I am interested in looking at the level of genetic diversity in the wild sloth population surrounding the sanctuary, and finding out how sloths (who aren’t thought to disperse very far) avoid inbreeding.



Next came Star. She is a female three-fingered sloth that I have been wanting to tag for a long time. She tends to hang out in the tree’s surrounding the Estrella  river and up until 2 months ago, she had a baby. I had been keeping an eye on her and waiting for the perfect opportunity to tag her, but frustratingly she never came down low enough. Unfortunately, when she finally came down to the ground in January, she no longer had the baby with her. I have tagged her with a backpack and it will now be interesting to see how quickly she comes into heat and how her behavior changes during this time.



Late in January I tagged Pancake. She was crossing the road outside of the sanctuary, and a well-meaning passer-by had picked her up and put her into a nearby tree. Unfortunately, their choice of trees wasn’t great – it was a huge palm tree in somebody’s garden surrounded by barbed wire – not good sloth territory at all! It took a very long ladder and some hair-raising moments, but we finally got her down. I tagged her with a backpack and released her deep in the forest away from any roads or barbed wire. We try to avoid releasing sloths away from their original territory, but in some cases it is necessary. Pancakes old habitat was divided by a very busy road – an accident waiting to happen. The data we collect from her will help us to see how sloths adapt and establish a new territory following release in a new area.

Last but definitely not least I tagged Apple (mother) and Pie (baby). Now I know what you are thinking – there seems to be a food theme developing with these sloth names (Burrito, pancake and now Apple Pie!) This simply reflects the tendency of wild sloths to finally come down from their trees just as I sit down for lunch. Pancake turned up just as I was about to eat a pancake etc.



I tagged Apple and Pie just a couple of days ago. I spotted her hanging out in a Cecropia tree within the sanctuary grounds and immediately realised that she was nursing a tiny baby. I constructed a looping harness design that wouldn’t obstruct the nipples and sat underneath her tree patiently waiting for her to move down low enough. When I finally managed to tag her, the baby was clinging tightly to her chest with his head buried in her hair. We had her tagged and released within 3 minutes so as to minimise stress on her and the baby. We estimate Pie to be no more than 3 months old – probably closer to 8 weeks but it is quite hard to tell. Apple’s tracking device will run for 18 months and so we are incredibly excited to learn exactly how she raises Pie and what happens when it finally comes to the weaning stage. Does the mother leave the baby in her territory or is the baby expected to find its own space? We will soon find out!



What have we found out so far?

Well both Burrito and Star have surprised me by how small their home ranges appear to be. In the past 3 weeks, both have displayed the cyclic rotation of favored trees that we expected, but have only covered approximately 200m in total – usually moving 10 – 20m per day. There was one exception. Last week Burrito made an interesting move. In 24 hours he traveled almost 300m directly away from the sanctuary, and then he traveled back again the following day. I have no idea why he did this, but I suspect he may have caught the scent of a female in heat.

Pancake on the other hand has ranged much further. She moved almost 800m in two weeks, but has more recently settled down and can usually be found in a flowering Cecropia tree (a favorite food of all sloths it seems). We have already identified several new trees and vines that have been used for feeding that we previously weren’t aware of. Now the challenge is having these identified down to species level so we can piece together the fine components of the sloths natural diet. In the meantime, I also have my eye on a beautiful male two-fingered sloth that is currently snoozing in an almond tree within the sanctuary grounds. As soon as he drops down low enough he will also be equipped with a backpack and our study will expand further!

Posted in: General, Sloths
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