Sloth Deformities – a genetic study

21 Dec

The Sloth Sanctuary of Costa Rica just received their fifth baby sloth showing severe birth defects. This baby was found on Isla Uvita; a tiny island off the coast of mainland Costa Rica covering just 0.8 km². This uninhabited island was previously thought to be too small to support a viable sloth population, however the discovery of this little baby proves otherwise. This special little sloth was called Onesie: he has only one finger and one toe on each hand and foot. Unfortunately, Onesie is not an isolated case – the incidence of congenital disorders in the wild sloth population appears to be increasing, and we want to do something about it. Click here to help us!

The five affected sloths were all C.hoffmanni infants originating from the Limon province on the Caribbean Coast of Costa Rica. The deformities have all been strikingly similar; missing fingers/toes, malformed ears and misshapen limbs. High numbers of birth defects like this in any population are a warning sign that something is seriously wrong. We are confident that the defects shown by Onesie are probably a result of inbreeding due to being isolated on an island. Considering the marked similarity between Onesie’s deformities and those observed in the mainland babies, we are growing increasingly concerned about the potential impact that habitat fragmentation and inbreeding are having on the genetic health of the wild sloth populations.

We want to raise enough funds to carry out the necessary scientific research to assess the genetic status of the wild sloth populations, and to ultimately determine the cause of the observed congenital birth defects. 

For more information or to donate, please visit:

My name is Rebecca Cliffe and I am a biologist working at the Sloth Sanctuary of Costa Rica in the Limon province. I am currently studying the ecology of sloths for my PhD under the supervision of Professor Rory Wilson at Swansea University. Last year I ran the Save Our Sloths Indiegogo campaign, raising funds to develop a release program for hand-reared orphans at the Sloth Sanctuary of Costa Rica. The incredible response that we received to that fundraiser has motivated us to expand our efforts in order to develop conservation strategies to protect wild sloth populations. This project will be completed in collaboration with Dr Sofia Consuegra, a geneticist from Swansea University.



Habitat fragmentation

With the rapidly expanding human population driving deforestation to an unprecedented level, the rainforest habitat that the sloths depend on is becoming more and more fragmented. Roads, farms, towns and cities now dominate the landscape, cutting the once continuous forest into smaller and more isolated segments. For animals such as sloths that have limited dispersal abilities, habitat fragmentation can be quite detrimental to the species. Through a reduction in population size, lack of immigration and inbreeding, the loss of habitat connectivity can quickly result in the extinction of whole populations due to a loss of genetic diversity. This is one of the most important factors that determines the adaptability and survival of a species. One of the major warning signs associated with a loss of genetic diversity in a population is a high incidence of congenital birth defects.


Unfortunately, we suspect that the observed birth defects are just the tip of the iceberg. Humans are not only encroaching on the rainforest in this region; it is happening daily throughout central and South America. Furthermore, the deformed sloths that arrive at the sanctuary are just the lucky few who were found and rescued – they will be a tiny percentage of a much bigger number. By identifying the root cause of the observed congenital disorders, this opens the door for us to mitigate the problem through the development of targeted conservation strategies. If we can identify habitat fragmentation and inbreeding as the driving factor, we can then aim to increase genetic diversity within the populations by promoting habitat connectivity.



We want to use molecular, isotopic and GSI techniques to determine the genetic status of wild sloth populations on the Caribbean Coast of Costa Rica where the Sloth Sanctuary is located. We will collect hair samples from distinct populations of wild B.variegatus and C.hoffmanni sloths in the Limon region, including those animals currently inhabiting Isla Uvita. With the collaboration of Dr. Consuegra at Swansea University, we will screen for genetic diversity using microsatellite analysis. We have successfully trialed DNA extraction and amplification protocols using non-invasive sloth hair samples, and so we are confident in our methodology.

We will also genetically analyse hair samples from the five sloths showing congenital deformities. By assessing the levels of homozygosity in these individuals, we aim to identify whether the observed malformations are indeed a direct result of potential inbreeding due to habitat fragmentation.

Finally, we will identify the genetic status of the captive sloths currently maintained at the Sloth Sanctuary of Costa Rica by combining the details from our location records with a hair sample analysis on each animal. By incorporating this knowledge with the genetic background of the local wild sloth populations, we will be able to improve the Sanctuary’s release program in terms of recipient population suitability and dispersal conditions.

Before we can do any of this, we need your help to fund the necessary scientific equipment to make this study possible.



100% of the money raised through this fundraiser will go directly towards supporting the study of sloth population genetics. In order to complete this project, the major areas that we need to fund are:

Consumables for genetic analysis:

DNA extraction kit (minimum 100 samples)

Primers for 15 microsatellites (labelled)

Multiplex amplification kit

Fragment analysis in sequencer (2 multiplexes)

In-field and operational costs:

Permits and fee’s (research and sample export)



Field assistants for sample collection



You can help us to conserve these incredible animals by donating whatever you can – no donation is too small, every dollar is a step closer to reaching our goal.

I passionately believe that your contribution can help to make a huge difference to the conservation of sloths throughout Central and South America. Together we have the chance to discover more about these amazing animals and help to protect them in the future.

As well as donations, please help us to spread the word and share this page with all of your friends.


If you would like to keep up to date with the project I will report our progress here.

You can also follow us on Facebook and twitter.


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