Sloths need more than just Cecropia for survival

Sloths need more than just Cecropia for survival

Why do scientists sometimes feel the need to jump to extra conclusions, just so that they can have an eye-catching story for the media? This can be incredibly dangerous for the conservation of a species, particularly when the extra conclusion is wildly incorrect.  Here at SloCo we are dedicated to correcting the inaccurate information on sloths that is frequently published! Here is the latest one:

Recent research that has been picked up in the media this week concludes that sloths are “more adaptable to urban areas than we previously thought”. This is an eye catching tagline, but is unfortunately a complete misinterpretation of the studies results (…again)! In fact, sloths might be one of the least adaptable species imaginable, and to incorrectly claim otherwise is damaging for conservation efforts. The conclusion was based on genetic research in a cacao plantation which found that sloths with a high number of a particular tree species (cecropia) in their home ranges had higher survival rates and sired more offspring. That by itself is an interesting finding and suggests that planting cecropia trees could be useful for the conservation of sloths in urbanised areas (although this is already being done, as we have known for a long time that sloths utilise these trees when they are available). Either way, it is a nice result and gives scientific evidence to the benefit of these trees. They should have left it there. The story might not get picked up by the Conversation or the New York Times, but it is good science and helpful for conservation. Unfortunately, however, the authors and associated media went one step further and have insinuated that as long as cecropia trees are present in a given area then sloth populations should thrive (i.e. sloths can adapt perfectly well to the urbanisation of the rainforest and we have no need to worry, as long as we make sure there are enough cecropia trees dotted around). This tunnel-vision conclusion is where the problems arise.

Brown-throated Three-toed Sloth Wild sloth crossing pavement at Sanctuary Aviarios Sloth Sanctuary, Costa Rica

Anybody that has worked with sloths in the wild for a significant length of time will know that they are not resource limited i.e. they do not struggle to find enough food, even in urban areas. It takes a sloth approximately 1 month to digest a single leaf and so they really can’t eat very much on a daily basis due to their constantly full stomachs. They subsist on a handful of leaves per day to meet their minimal energy requirements. Furthermore, they are known to feed from over 90 different tree species (i.e. a pretty diverse diet), and so as long as some of these trees are available, they won’t starve to death. It has been scientifically proven for a long time that sloths consume a wide variety of leaves, and so the groundbreaking discovery that they feed on trees other than cecropia isn’t actually a discovery at all – it’s just reiterating what we already know. Just because the authors noticed juvenile sloths utilising trees other than cecropia definitely doesn’t make sloths “more adaptable than previously thought”.

Sloths don’t NEED cecropia in their home range for survival at all – indeed these trees rarely grow in healthy rainforests (which is actually the sloths ideal habitat for survival and where they likely sire even more offspring). Similarly, however, many scientists do not like to study sloths in healthy rainforests because of the remote / difficult tracking conditions and dense canopy cover obscuring observations. As a result, there is very little data from pristine sloth habitats for comparison! To therefore conclude that “cecropia trees are critical for the survival and reproductive success of adult sloths” becomes a little ridiculous.

Cecropia trees are already very common in urban areas as they are a fast growing, pioneering species. For this reason we use these trees in our reforestation and canopy connectivity projects, however sloth numbers are still declining at an accelerating and alarming rate. Despite the abundance of cecropia trees, rescue centres in Costa Rica are receiving 1-2 sloths every single day. The truth is that sloth populations are in rapid decline for 3 reasons that have nothing to do with cecropia tree availability (but everything to do with the sloths inability to adapt to habitat disturbance):
1. Power line electrocutions
2. Dog attacks
3. Road traffic collisions

Sloths irrefutably need all of the help they can get, regardless of how many cecropia trees there are. We do not deny that the basic findings of the publication are useful, but to publish them with the associated tagline that “sloths are more adaptable to deforestation than previously thought” (just to make the story attractive for the media) is potentially catastrophic to sloth conservation, awareness and fundraising efforts.

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