New Sloth Crossing Wildlife Bridges

This month we are delighted to have installed 2 new Sloth Crossing wildlife bridges in the South Caribbean region of Costa Rica!

‘Sloth Crossings’ are artificial bridges that we install between trees to link fragmented habitats together and allow wildlife a safe route of passage. Behind power line electrocutions, the biggest threats to the survival of wild sloths in Costa Rica are dog attacks and road traffic collisions. Both occurrences stem from habitat fragmentation forcing sloths to descend to the floor and crawl across the ground where they are extremely vulnerable. In order to keep the sloths safely up in the trees and away from danger, we build Sloth Crossing bridges across roads and in places where the once-continuous rainforest has been disturbed by development.


These wildlife bridges also mitigate a much less talked about problem – inbreeding. Sloths are very vulnerable to habitat loss because it makes travelling to find a mate very difficult. As the world’s slowest mammal, sloths cannot run nor jump, and so any gap in the forest canopy represents a major barrier to movement.

Image of sloth crossing road
A sloth risks it’s life to cross a road – a daily sight in the South Caribbean of Costa Rica

Why is this a problem?

Well, it is very important that sloths are able to move far enough away from their immediate relatives to avoid accidentally breeding with them in the future. When inbreeding happens, it causes something called ‘a loss of genetic diversity’ in the population, and this is really bad news for the health of wild sloths. All species rely on genetic diversity for survival because it allows them to evolve in response to things such as changing environmental conditions, shrinking habitats, or new diseases.

Inbred offspring are also more likely to be born with fertility issues and physical deformities. If you have a small patch of forest in a semi-urban area, and it is surrounded by roads and development, then the sloths living in that patch of forest are going to become isolated and will breed with each other over generations. Throughout the South Caribbean region, we are already starting to see the detrimental effects of inbreeding on the genetic health of wild sloth populations, with young sloths frequently being born with congenital defects (including missing digits, malformed limbs, jaw deformities, albinism etc.). As a part of our sloth conservation efforts we have been researching this issue over the last 6 years and we will be publishing the scientific paper later this year. Click here to read more about our sloth genetics projects!

Baby sloth with deformities
Sloths are being born with physical deformities due to inbreeding caused by habitat fragmentation. This sloth has missing fingers.


Our most basic Sloth Crossing design consists of a single rope secured between two hardwood trees. We then grow carefully chosen species of native vine (which can grow up to 3 feet per day and reach a diameter of over 1 foot) along the rope, which will eventually create a natural bridge for wildlife. This is the cheapest and easiest option, but does have some drawbacks. The maximum distance that we can span with a single rope is limited to about 30 meters and some animals do not like to use this style of bridge. We suspect this is because the rope moves too much which makes them nervous, and they likely feel very exposed and vulnerable while crossing without any canopy cover.  Our more extensive design consists of support posts and a flat metal grid, along which we grow plants and vines. The added stability and vegetation cover make this an optimal choice for wildlife, however building costs are higher and logistics of installation more difficult.

A single rope Sloth Crossing wildlife bridge
A single rope Sloth Crossing wildlife bridge

For all of our Sloth Crossing installations we like to monitor what animals use the bridges by using camera trap technology. These special wildlife cameras are programmed to start recording video whenever the sensors detect heat or movement. Unfortunately, however, we have discovered that sloths move too slowly to trigger the motion detector, and their body temperature is too low to trigger the heat sensor! They sneak past undetected! We are still trying to find cameras that will work for detecting sloths when they use our Sloth Crossing canopy bridges.

camera trap on a sloth crossing
We use camera traps to monitor the use of the bridges by different species

Thank you to our community partners and to all of our supporters who make this work possible – we couldn’t do it without you!

We would like to extend special thanks to Tasty Dayz Hostel and Geckoes Lodge for hosting the latest Sloth Crossing bridges on their properties! Community participation and support is essential to the success of any conservation effort, and we strive to maintain a strong community-based approach to all of our programs. We have many more Sloth Crossings being built over the next few months, so we will be sure to provide further updates here as they happen!


Each “sloth crossing” bridge costs $200 to construct (in the most basic form: a single rope design without a camera trap). If you would like to help us to build more bridges (or personally sponsor your own sloth crossing), you can do so by donating via the PayPal link below (be sure to include your preference as “sloth crossings” in the optional box!

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