Where to go when all options are terrible: ranging behavior of brown-throated three-toed sloths (Bradypus variegatus) in central Amazonian flooded igapó forests

Abstract

Ranging behaviors performed by animals are influenced by both biotic and abiotic factors. For herbivorous mammals, seasonality in forage production is considered to be the main driver of movement patterns. Here, we investigated the home range and movement of one of the most abundant herbivores in the Americas and their relationship with plant phenology in an Amazon igapó — a seasonally flooded riverine forest with strongly pulsed leaf production phenology. Using a combination of telemetry and phenological analysis, the study recorded movement patterns of five brown-throated three-toed sloths (Bradypus variegatus Schinz, 1825) over a 6-month period and related these to seasonal and within-forest differences in food availability through monitoring young leaf production of 570 trees. All monitored animals were shown to be permanently resident within the igapó flooded forest, maintaining their home range even during flood periods when most trees lacked leaves. We found that seasonal variation in leaf production had no effect on the extent of displacement of the sloths. Accordingly, for herbivores with low metabolism, variation in young leaf availability may not be the main driver of their ranging behavior. In addition, an arboreal habit and well-developed swimming capacity allow igapó sloths to occupy a niche ecologically inaccessible to other mammals.