The Back Patch Mystery

Sloths have many weird and mysterious behaviors that we are constantly trying to understand... Why are they so slow? Why do they come down to the ground to defecate? How long do they sleep for? These are all the common questions. The fact that male three-fingered sloths have evolved bright orange patches on their backs seems to have been completely overlooked! Considering a sloths survival strategy is camouflage, this sticks out like a neon flashing light!

Why have these bright back patches evolved? What is the benefit? Why don't females have them? Why does patch size and color differ so much between individuals? This begs so many questions that we are hoping to answer here at the Sloth Sanctuary.

We have learnt over time that male three-fingered sloths develop these patches as they reach sexual maturity at approximately 1 - 2 years old.  They are always yellow or orange in color and divided by a central black stripe with additional black markings in a pattern unique to each individual.The type of hair within the patch is completely different in texture to the rest of the sloths hair and doesn't grow any algae. Interestingly, the patch appears to be covered in an unknown oily secretion and if you touch it, the yellow/orange pigment rubs off! 

The result of rubbing the patch with a cloth:

The (infuriating) video below was posted by a man who studies sloths in Panama. They claim that if a female sloth smells the oily back patch of a male, she will produce a loud vocalization. Unfortunately this is nothing but a fairy-tale, yet another example of terrible sloth science!  

We have studied female vocalizations here at the Sloth Sanctuary and we know that they produce these screams for 10 days every month while they are in oestrus - regardless of any males present! The vocalizations attract male sloths into the area. It wouldn't make any sense for a female to scream if she was already with a mate! We did however test this theory out just to be sure - we rubbed the back patch of a wild male and held it under the noses of both a female who was in oestrus and a female who wasn't. Surprise surprise neither vocalized upon smelling the patch! Unfortunately this video is completely faked and probably explains the strange camera angle...!

 So the mystery continues. I am determined to find the reason for these big bright back patches and so have recently begun a study looking at this. Do bigger stronger males have bigger brighter patches? Does the patch size simply relate to body size? Do the patches get darker with age due to the continuous secretion of oily pigment? 

To test this, I am on a mission to find as many different male sloths as I can. Luckily as the females come into oestrus here at the Sanctuary we get an influx of testosterone fueled males from the surrounding forest. I catch them and take measurements of body size, weight, patch size, pattern and color intensity. 

We are building a male sloth back patch library!! 

If you would like to donate to fund sloth research or the sloth backpack project you can do so safely and securely through our sloth research Paypal account:

The sloth backpack solution!

I have learnt a valuable lesson this week: always have a back-up plan! We recently discovered that the 3D printer we had been planning on using to create our backpacks was 'temporarily unavailable' - not great when I only had 3 weeks back in the UK to figure this out! 

After a brief panic my lovely sister saved the day with a bright idea: my old high school, Penwortham Priory Academy, had an excellent technology department... perhaps they could help! After a quick visit it was clear that the staff at the school were up for the challenge, what a relief! (although trying to explain that I needed help making a sloth backpack without sounding absolutely crazy was difficult enough!)

By this point, I only had 3 days left before I was due to fly back to Costa Rica (armed with the backpacks...) so we had no time to waste! The technology department staff immediately began brainstorming ideas and before long, they had developed 2 winning designs.

The first is a waterproof backpack that will be used to house the original, larger Daily Diary... This design consists of an existing plastic container, modified with holes for the harness and a silicon sealed lid - tough, waterproof and functional!

The second backpack design will contain our tiny new Daily Diary and VHF transmitter. Because this is a much smaller device, we used a vacuum form machine to mold a plastic sheet into exactly the right shape.  This worked like a dream!

Of course, things couldn't just be that simple - the new Daily Diary contains a barometer which will allow us to track the height of the sloth in the tree. This feature requires a constant air supply in order to work, yet the whole backpack needs to be waterproof! To solve this dilemma, we have created a waterproof sloth backpack with a... snorkel! Essentially this is just a tiny bendy rubber tube that air can pass through but water can't.

I want to say a HUGE thank you to all the staff at Penwortham Priory Academy who made all of this possible by kindly donating their time and expertise to the project.