Please cite this article as: Giné, G.A.F., Cassano, C.R., Almeida, S.S., Faria, D.,Activity budget, pattern and rhythm of maned sloths (Bradypus torquatus): responses to variations in ambient temperature, Mammalian Biology (2015), http://dx.A c c e p t e d M a n u s c r i p t 1 Activity budget, pattern and rhythm of maned sloths (Bradypus torquatus): 1 responses to variations in ambient temperature 2 Abstract 25 Three-toed sloths (Bradypus) are heterothermic, and ambient temperature may have a 26 direct effect on their activity levels. Our goal was to describe the time budget, pattern 27 and rhythm of activity of the maned sloth, Bradypus torquatus (Xenarthra: 28 Bradypodidae), and to evaluate the effect of ambient temperature on its activity. We 29 hypothesized that 1. sloth activity increases with ambient temperature, fluctuating with 30 the circadian temperature cycle, and 2. sloths are more active in the diurnal period 31 during colder seasons than warm seasons due to constraints or avoidance of the colder 32 times within a 24-h cycle. Nine radio-collared individuals were followed in forest 33 remnants in southern Bahia, Brazil from March 2003 to April 2014. Behavior data of 8 34 sloths were collected during the diurnal period by direct visualization (608 h of record), 35 and the activities of 4 sloths were recorded by an automated system during continuous 36 hours (744 h of record). The maned sloths exhibited low activity levels, resting 77% of 37 a 24-h period. In general, they were cathemeral, although they were twice as active in 38 the diurnal phase (active 32% of the time) compared with the nocturnal phase (15%). 39 The ambient temperature had a significant positive effect on activity levels. The rhythm 40 of activity was circadian and synchronized with the ambient temperature. No difference 41 was detected in the diurnal activity between hotter and colder seasons, most likely 42 reflecting the low fluctuations in climatic conditions of this tropical forest. The narrow 43 relationship between the circadian activity pattern of maned sloths and the ambient 44 temperature cycle highlight their poor thermoregulatory ability. The lower activity 45 levels exhibited during colder times may represent a behavioral adaptation that reduces 46 heat loss, enhances body temperature control and optimizes energetic benefits, a key 47 feature for a species relying on a low energetic diet.48 49