Activity budget, pattern and rhythm of maned sloths (Bradypus torquatus): Responses to variations in ambient temperature

Abstract Three-toed sloths ( Bradypus ) are heterothermic, and ambient temperature may have a direct effect on their activity levels. Our goal was to describe the time budget, pattern and rhythm of activity of the maned sloth, Bradypus torquatus (Xenarthra: Bradypodidae), and to evaluate the effect of ambient temperature on its activity. We hypothesized that (1) sloth activity increases with ambient temperature, fluctuating with the circadian temperature cycle, and (2) sloths are more active in the diurnal period during colder seasons than warm seasons due to constraints or avoidance of the colder times within a 24-h cycle. Nine radio-collared individuals were followed in forest remnants in southern Bahia, Brazil from March 2003 to April 2014. Behavior data of 8 sloths were collected during the diurnal period by direct visualization (608 h of record), and the activities of 4 sloths were recorded by an automated system during continuous hours (744 h of record). The maned sloths exhibited low activity levels, resting 77% of a 24-h period. In general, they were cathemeral, although they were twice as active in the diurnal phase (active 32% of the time) compared with the nocturnal phase (15%). The ambient temperature had a significant positive effect on activity levels. The rhythm of activity was circadian and synchronized with the ambient temperature. No difference was detected in the diurnal activity between hotter and colder seasons, most likely reflecting the low fluctuations in climatic conditions of this tropical forest. The narrow relationship between the circadian activity pattern of maned sloths and the ambient temperature cycle highlights their poor thermoregulatory ability. The lower activity levels exhibited during colder times may represent a behavioral adaptation that reduces heat loss, enhances body temperature control and optimizes energetic benefits, a key feature for a species relying on a low energetic diet.

[1]  M. Galetti,et al.  Records of Harpy and Crested Eagles in the Brazilian Atlantic forest , 1997 .

[2]  R. Sikes,et al.  Guidelines of the American Society of Mammalogists for the Use of Wild Mammals in Research , 2007 .

[3]  F. Mendel,et al.  Vision of Two-Toed Sloths (Choloepus) , 1985 .

[4]  Adriano Garcia Chiarello,et al.  Life‐history traits and sexual dimorphism of the Atlantic forest maned sloth Bradypus torquatus (Xenarthra: Bradypodidae) , 2005 .

[5]  Mark S. Boyce,et al.  GPS Based Daily Activity Patterns in European Red Deer and North American Elk (Cervus elaphus): Indication for a Weak Circadian Clock in Ungulates , 2014, PloS one.

[6]  S. Harris,et al.  Activity patterns and feeding behaviour of the tree hyrax, Dendrohyrax arboreus, in the Parc National des Volcans, Rwanda , 1999 .

[7]  S. Mori,et al.  Southern Bahian moist forests , 1983, The Botanical Review.

[8]  S. Lehman,et al.  Feeding Patterns in a Small-Bodied Nocturnal Folivore (Avahi laniger) and the Influence of Leaf Chemistry: A Preliminary Study , 2006, Folia Primatologica.

[9]  D. Gilmore,et al.  Cardiovascular responses to locomotor activity and feeding in unrestrained three-toed sloths, Bradypus variegatus. , 2004, Brazilian journal of medical and biological research = Revista brasileira de pesquisas medicas e biologicas.

[10]  M. Sunquist,et al.  Activity patterns and rates of movement of two-toed and three-toed sloths (Choloepus hoffmanni and Bradypus infuscatus). , 1973, Journal of mammalogy.

[11]  F. R. Santos,et al.  Extreme population divergence and conservation implications for the rare endangered Atlantic Forest sloth, Bradypus torquatus (Pilosa: Bradypodidae) , 2008 .

[12]  D. Faria,et al.  Ferns, frogs, lizards, birds and bats in forest fragments and shade cacao plantations in two contrasting landscapes in the Atlantic forest, Brazil , 2007, Biodiversity and Conservation.

[13]  J. R. Landis,et al.  The measurement of observer agreement for categorical data. , 1977, Biometrics.

[14]  D. Chivers,et al.  A translocation experiment for the conservation of maned sloths, Bradypus torquatus (Xenarthra, Bradypodidae) , 2004 .

[15]  M. Sunquist,et al.  Habitat selection and use by two-toed and three-toed sloths , 1978 .

[16]  M. Goffart.  Function and form in the sloth , 1971 .

[17]  J. Altmann,et al.  Observational study of behavior: sampling methods. , 1974, Behaviour.

[18]  Helane Santos Tito de Oliveira.  Ritmo biológico da temperatura corporal em preguiças (Bradypus variegatus) , 2007 .

[19]  D. Gilmore,et al.  Circadian rhythms in blood pressure in free-ranging three-toed sloths (Bradypus variegatus). , 2003, Brazilian journal of medical and biological research = Revista brasileira de pesquisas medicas e biologicas.

[20]  T. Dayan,et al.  Partitioning of Time as an Ecological Resource , 2003 .

[21]  T. Pleše,et al.  Activity Patterns, Preference and use of Floristic Resources by Bradypus variegatus in a Tropical Dry Forest Fragment, Santa Catalina, Bolívar, Colombia , 2010 .

[22]  B. Urbani,et al.  Feeding ecology and postural behaviour of the three-toed sloth (Bradypus variegatus flaccidus) in northern Venezuela , 2007 .

[23]  G. Donati,et al.  From darkness to daylight: cathemeral activity in primates , 2006 .

[24]  J. Ragle,et al.  IUCN Red List of Threatened Species , 2010 .

[25]  F Halberg,et al.  Methods for cosinor-rhythmometry. , 1979, Chronobiologia.

[26]  S. Halle.  Polyphasic Activity Patterns in Small Mammals , 2006, Folia Primatologica.

[27]  Ary T. Oliveira-Filho,et al.  Patterns of Floristic Differentiation among Atlantic Forests in Southeastern Brazil and the Influence of Climate1 , 2000 .

[28]  D. Gilmore,et al.  An update on the physiology of two- and three-toed sloths. , 2000, Brazilian journal of medical and biological research = Revista brasileira de pesquisas medicas e biologicas.

[29]  Jacob Cohen.  A Coefficient of Agreement for Nominal Scales , 1960 .

[30]  D. Faria,et al.  Activity, movement and secretive behavior of a threatened arboreal folivore, the thin‐spined porcupine, in the Atlantic forest of southern Bahia, Brazil , 2012 .

[31]  Adriano G. Chiarello,et al.  Activity budgets and ranging patterns of the Atlantic forest maned sloth Bradypus torquatus (Xenarthra: Bradypodidae) , 1998 .

[32]  S. E. Huggins,et al.  Sleep and waking in the three-toed sloth, Bradypus tridactylus. , 1983, Comparative biochemistry and physiology. A, Comparative physiology.