What If Gone

Species → Brown-throated Sloth

Brown-throated Sloth

Bradypus variegatus

no global estimate available; local densities measured between 0.6…
Extinction risk Least Concern
Tropical forestObligate mutualismScientific controversy
Brown-throated Sloth (Bradypus variegatus)
Photo: Charles J. Sharp, Wikimedia Commons (CC BY-SA 4.0)

What if it disappeared?

Impact Low
1 year

Moths live almost exclusively in the sloth's fur and rely on its weekly descent to the ground to lay their eggs there. Without it, these moths would instantly lose their only known egg-laying site — a habitat that doesn't exist anywhere else in the same way.

Extrapolated
Detail

Extrapolation à partir de Pauli et al. (2014), qui documente la dépendance des papillons de fourrure du paresseux au comportement de descente au sol pour la ponte — l'étude ne mesure pas directement ce qui arrive aux papillons si le paresseux disparaît, seulement la corrélation chez des animaux vivants.

Pauli et al. (2014) establish a statistical correlation between the number of moths present in the fur and how often the sloth descends to the ground, in animals captured and released in Central America. Ground descent is presented as the key behavior that lets the moths lay their eggs. No study has followed a population of these moths after the disappearance of a host sloth.

What's missing to confirm it: Monitoring of fur-moth populations in an area where the sloth has disappeared, to confirm they actually lose their egg-laying site.

10 years

Over ten years, these sloth-fur-specific moths would likely decline to local disappearance, for lack of another known host able to replace this very particular niche — a case of cascading extinction limited to a handful of insect species, not the whole forest.

Hypothesis
100 years

A century later, this loss would likely remain confined to that handful of ultra-specialized insects. A critical re-evaluation of the original scenario showed that the sloth doesn't groom itself, that 83% of its digesta samples contain no trace of algae at all, and that ground predation risk is far lower than predicted — links to the rest of the forest too thin for a century of absence to measurably change the vegetation itself.

Extrapolated
Detail

Extrapolation à partir de Monge-Nájera (2021), qui montre que le paresseux à gorge brune ne se toilette pas et que 83 % des échantillons de bol alimentaire analysés ne contiennent aucune algue — aucune étude ne mesure directement l'état de la forêt un siècle après la disparition de l'espèce.

Monge-Nájera (2021) raises several inconvenient facts against Pauli et al.'s (2014) three-species mutualism scenario: no grooming in the brown-throated sloth, no algae in 83% of analyzed digesta samples, and ground predation risk 5.5 times lower than the original model predicted. If the nutritive links between sloth, algae, and the rest of the forest are as thin as this re-evaluation suggests, the species wouldn't carry the ecological weight needed to change the vegetation at a century scale — only the fur-moth niche would remain affected.

What's missing to confirm it: A direct comparison of forest structure between an area that lost its sloths long ago and a comparable area that still hosts them.

1000 years

Over a thousand years, this gap would likely remain permanent for the fur moths themselves: without another mammal as slow-moving and as thickly furred to recreate this very particular niche, this insect lineage would likely never return — even as the rest of the forest carried on largely unchanged.

Hypothesis

Documentation

Last verified: August 16, 2026