ESTIMATING REPRODUCTIVE TIMING AND FREQUENCY
We assessed the reproductive status of females of both species
using visual observations of colour-marked individuals. Sloths
provide maternal care for a single young several months following
parturition, and juveniles are readily observed clinging to
their mothers (Taube et al. 2001). We estimated the timing of
birth as the midpoint between the last date a female was observed
without a juvenile and the first date she was observed with a
juvenile. We estimated the timing of juvenile independence as the
midpoint between the last date a female was observed with a
juvenile and the first date she was observed without a juvenile.
We limited these calculations to instances where ≤2 weeks elapsed
between consecutive observations such that the average error in
timing was likely ≤1 week. We considered an adult female to
have successfully reproduced if she was observed with a juvenile
on a single occasion. We used somewhat different criteria to identify
adult females that did not breed for the two species because
(i) C. hoffmanni reared young throughout the annual cycle,
whereas B. variegatus reared young over a considerably shorter
period (see below) and (ii) B. variegatus females were easier to
locate than C. hoffmanni females. As a result, we considered an
adult female B. variegatus to not have reproduced if it was
observed without young on at least five occasions from January
to June (in May 2012), with at least 1 week elapsing between
consecutive observations. For C. hoffmanni, we considered an
adult female to not have bred in a given year if she was not
observed caring for a juvenile at least once in each of the four
annual quarters (i.e. 3-month periods). Choloepus hoffmanni not
meeting this criterion, or that were observed for