The Sloth Backpack Project – September

25 Sep

This year got off to a great start, with tracking backpacks being deployed on 4 wild sloths during January and February (I introduced these sloths in a previous blog: Burrito, Star, Pancake and Apple/Pie). Unfortunately, we find that far too much research focuses on achieving the largest sample size possible, yet fails to study individual animals for long enough to understand their patterns of behavior. This is particularly important for sloths as everything happens so slowly! It can take an individual up to 30 days to digest one leaf, so you can imagine how much time is needed to document the complete diet of just one sloth. For this reason, I have spent the past 8 months intensely following the 4 sloths that I tagged with backpacks at the start of this year and getting to know their individual habits. This time has also allowed me to perfect the harness design and iron out any faults with the backpack-tagging process. As a result of this, I am excited to announce that we are finally ready to expand the project and there are exciting plans for the next few months.


Left: Burrito, Right: Star

What have we found out so far?

Burrito and Star have been my most predictable sloths and are continuing to show the same cyclic rotation of favoured trees that I observed at the beginning. Their ranging patterns have been fairly consistent and their territories often overlap. In May, three months after Star lost her previous baby, I observed her vocalising – a sure signal that she had entered oestrus. From our previous research on captive sloths, we know that these vocalisations happen for 8 – 10 days every month and correspond with a sudden increase in activity levels. We were unsure exactly how long it would take Star to come into oestrus again following the death of her baby, so this was a great finding. During her days in oestrus, she positioned herself in a tall tree and remained there for 11 consecutive days. To my delight, Burrito also appeared in the same tree and remained with her for much of this time. We didn’t actually witness any mating due to the dense canopy obstructing our view – but if a new baby appears in a few months perhaps we can have a guess at the gestation period for three-fingered sloths!

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Apple (mother) and Pie (baby)

I had a great first four months following Apple (mother) and Pie (her baby). The baby had been approximately 3 months when I tagged them in February and was growing quickly. In June, I sadly found her without her baby. I had located them the day before and Pie was clinging to her chest (he definitely wasn’t old enough to be alone yet), but there was no sign of him the following day. I can only assume that he fell during the night and either died on impact, or that she rejected him. This is now the third female sloth that I have studied with a baby – and all three have lost their babies. Unfortunately, this points to an extremely high mortality rate among baby sloths. This might be very natural, or it may point to a more serious issue in the wild populations. I am continuing to follow Apple and although she initially displayed very random movements in the weeks following her loss, she appears to have settled down recently.

Daily Diary data

I have managed to recapture my tagged sloths 8 times in total since January, allowing me to replace the backpack batteries and download the existing data. In order to do this, I have to count on finding the sloth low down enough to recapture (this requires a lot of patience and good fortune). Unfortunately, this results in a very slow rate of data acquisition. In order to speed things up, I will soon be taking a tree-climbing course that will allow me to get up in the canopy with the sloths and collect a continuous stream of information.

Left: the latest Sloth Backpack Right: the Backpack electronics are sealed inside non-lubricated condoms to protect them from moisture damage

Left: the latest Sloth Backpack
Right: the Backpack electronics are sealed inside non-lubricated condoms to protect against moisture damage

I can’t analyse any of the Daily Diary data whilst in Costa Rica as the files are simply too large to load without a super computer – the Daily Diary tags collect 8 million data points in 24 hours! Last month I returned to Swansea University to begin the long process of data analysis. The team at the university are constantly developing new analysis software, and the latest version is truly impressive. We were able to input the sloths body movement data from the Daily Diary, and when combined with the GPS location data, the software creates a 3D trail showing the sloths exact movements between two GPS points. Furthermore, the software can identify specific behaviours within the trail and colour-code these accordingly. For example, when the sloth is climbing upwards the trail could be blue, and then when he stops to scratch the trail would change to red etc. This basically allows us to visualise and quantify wild sloth behavior for the first time – exciting stuff for sloth science!

The visualisation suite at Swansea University

The visualisation suite at Swansea University

The next stage

I am continuing to closely monitor the 4 sloths that I tagged earlier this year, but I have finally reached the stage where I am ready to expand the project. Over the past 8 months I have managed to perfect the backpack-tagging process (involving lots of trial and error) and I have figured out solutions to the many technical problems associated with tracking sloths – I would like to think that I have become quite good at it! I am excited now to be expanding the study and taking things to the next level.

In my grand plan, I am aiming to tag 25 sloths (both two and three-fingered) with Daily Diary backpacks over the next few months. This isn’t going to be easy and will require a huge amount of time spent out in the forest – but this is what the past 8 months have been building up to. In addition to taking a tree climbing course, I will also be taking on a research assistant(s) which will effectively double the rate at which we can locate the sloths and collect data. More information will be coming on this soon, but things are definitely heading in a very exciting direction!

Valentino: our latest sloth to be tagged with a backpack

Valentino: our latest sloth to be tagged with a backpack

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