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BEHAVIORAL DIFFERENCES AND EFFECT OF ENVIRONMENTAL TEMPERATURE ON THE ACTIVITY OF TWO SPECIES OF THREE-TOED SLOTHS (BRADYPUS TORQUATUS AND BRADYPUS VARIEGATUS) IN THE ATLANTIC FOREST
Unlike most mammals, the three-toed sloths (Bradypodidae) are heterothermic, presenting low and unstable body temperature, which can vary widely throughout a circadian cycle. Thus, we might expect their behavior to be markedly affected by thermal changes in the environment. Although Bradypus variegatus and the threatened Bradypus torquatus occur syntopically in some regions and are potential competitors, no study has evaluated their behavioral differences. We aim to compare the daily activity time-budget, pattern and rhythm between B. torquatus and B. variegatus occurring in syntopy in the Atlantic Forest of the south of Bahia, as well as to compare the effect of environmental temperature on the levels and rhythm of activity of these two species along the circadian cycle. Seven free-ranging individuals of B. torquatus and six of B. variegatus were monitored between February and November of 2017. The animals were tagged with radio-collars containing activity sensors and data were obtained remotely by automated registers. Both species presented circadian rhythm and low level of activity (<14%). There was no significant difference in the daily level of activity between B. torquatus and B. variegatus. The two species were cathemeral, active during both day and night, but they concentrated their activities in the daytime period. The general activity level of B. variegatus and B. torquatus at each hour of the day was positively related to the environmental temperature and there were no differences in the activity rhythm of these species. The acrophase of the rhythm curve of temperature and activity differed only for B. variegatus. Thus, we conclude that there was no significant temporal difference between the activity of these species living in syntopy, and both respond similarly to temperature variations throughout the day. It remains unclear what niche differences may allow the coexistence of these species and whether one can negatively affect the other.
Bradypodidae, syntopy, heterothermic, behavior, activity pattern, time-budget, circadian rhythm, threatened species
We thanks CNPq (proc. 563216/2010-7), CAPES (proc. 552198 / 2011-0), FAPESP (proc. 2014/16320-7) and UESC (proc. 00220.1100.1735) for financial support, as well as we are grateful the FAPESB for providing fellowships for C. C. Santos. We thanks CEPLAC for authorizing and supporting the conduct of the research. This research received the legal permit (license number 52971-4) from the Instituto Chico Mendes de Conservação da Biodiversidade (ICMBio).
Cinthya Chiva Santos, Camila Righetto Cassano, Ariovaldo Pereira Cruz-Neto, Gastón Andrés Fernandez Giné