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Title: A syndrome of mutualism reinforces the lifestyle of a sloth

item Pauli, Jonathan - University Of Wisconsin
item Mendoza, Jorge - University Of Wisconsin
item Steffan, Shawn
item Carey, Cayelan - University Of Wisconsin
item Weimer, Paul
item Peery, Zachariah - University Of Wisconsin

Submitted to: Proceedings of the Royal Society B
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/20/2013
Publication Date: 1/22/2014
Publication URL:
Citation: Pauli, J., Mendoza, J., Steffan, S.A., Carey, C.C., Weimer, P.J., Peery, Z. 2014. A syndrome of mutualism reinforces the lifestyle of a sloth. Proceedings of the Royal Society B. 281:20133006.

Interpretive Summary: Three-toed sloths are South American mammals that live in trees and subsist on nutrient-poor diets, and are subject to intense predation when they return to the ground to defecate. We show here that the risky act of defecation indirectly provides additional nutritional benefits through a relationship with moths, algae, and bacteria. The sloths are colonized by ground-dwelling moths whose waste provides essential nitrogen to algae living on the sloth hair. The sloths consume this algae, which can be fermented by bacteria in the foregut to provide a supplemental source of nutrition to the sloth. The results are of interest to animal nutritionists concerned with nutrient balances in plant-eating mammals, and to entomologists, wildlife ecologists, and evolutionary biologists interested in mutualisms between insects and animals.

Technical Abstract: By regularly descending a tree to defecate, sloths transport phoretic “sloth moths” to their oviposition sites in sloth dung, which promotes moth colonization of sloth fur. Moth detritus, in turn, acts as fertilizer and increases levels of inorganic nitrogen in sloth fur, which fuels algal growth. Sloths consume at least some of the readily digestible algae growing on their fur, presumably to augment their limited and nutritionally poor diet. This important and complex syndrome of mutualisms between moths, sloths and algae may reinforce fundamental aspects of the sloth’s behavior, and help to explain why sloths engage in such a risky and energetically costly behavior of descending to the forest floor weekly to defecate.