New study takes closer look at how environment affects daily life of
sloths

Date:
July 21, 2020
Source:
University of Notre Dame
Summary:
Scientists studying brown-throated three-toed sloths, where
predators are extinct and food is more accessible, have found that
the animals adapt to have a primarily diurnal, or daytime, schedule.



FULL STORY ========================================================================== Scientists studying brown-throated three-toed sloths, where predators
are extinct and food is more accessible, have found that the animals
adapt to have a primarily diurnal, or daytime, schedule.


==========================================================================
The study was conducted in a highly disturbed section of the Atlantic
forest, in Northeastern Brazil. Researchers recorded the sloths' behaviors
and circadian rhythm during the course of 29 days. The results, published
in the journal Mammalian Biology, present a unique take on the impact of
human activity in the area. While deforestation, development, intentional
fire setting and nighttime hunting have been detrimental to various
tree and animal species, brown-throated three-toed sloths may benefit in shifting from nocturnal tendencies to becoming primarily daytime active.

"These environmental disturbances are in no way an ideal scenario
from a conservation perspective but the results -- fewer predators,
easier access to primary food sources -- clearly had a positive impact
based on our observations," said Giles Duffield, associate professor in
the Department of Biological Sciences at the University of Notre Dame,
and a co-author of the study. "With less competition for food and fewer predators these animals developed a more synchronous pattern of activity." Previous studies have focused sloth activity in undisturbed forests. The research, led by Antonio Rossano Mendes Pontes at the National Institute
of Amazonian Research, is unique in that researchers not only monitored
sloths in a highly disturbed setting but their behavior -- rest, travel, movement, feeding and grooming -- was observed over a complete 24-hour
cycle.

"In all other studies, sloths have been found to be nocturnal or
cathemeral," Duffield said. "We did not expect to see such clear and
distinct diurnal behavior." Sloths spend a majority of their time
at rest -- up to 90 percent in some cases. A number of factors can
influence a sloth's tendency toward diurnal or nocturnal activity,
including temperature, competition and the threat of predators. Rest was
still the dominant activity, even in a highly disturbed environment. The
sloths spent an average of 75 percent of their time resting.

Females rested significantly more than the males and infants rested 79
percent of the time on average. Peak activity took place in the early
morning and late afternoon hours.

There is no preserved land left within the Atlantic forest, according
to the study. An estimated 98 percent of its woodland has been lost,
so researchers can't compare activity between highly disturbed and
undisturbed sections of the forest. For the same reason, the study asserts
the assumption that the daytime activity observed by this group of sloths
is an adaptive response to changes in their environment.

While found in a few unique cases in nature, "it's generally rare to
observe such flexibility in an organism that allows it to switch from predominately nocturnal to daytime active," Duffield said. "These results highlight that a more variable or nocturnal activity pattern might
be a strategy that improves chances of survival in a more challenging environment, one with predators such as eagles and large snakes, heavier competition for food sources produced by other herbivores, and where the
sloth has to move around more to find its preferred food. It's ironic,
but these results suggest that when conditions are 'easier' for the
iconic slow-moving sloth, as we find in this disturbed forest habitat,
it reverses the time of its preferred activity within the 24-hour day.


========================================================================== Story Source: Materials provided by University_of_Notre_Dame. Original
written by Jessica Sieff. Note: Content may be edited for style and
length.


========================================================================== Journal Reference:
1. Diogo de Oliveira Bezerra, Leandro Ricardo Rodrigues de Lucena,
Giles E.

Duffield, Dominic J. Acri, Antonio Rossano Mendes
Pontes. Activity pattern, budget and diurnal rhythmicity of
the brown-throated three-toed sloth (Bradypus variegatus) in
northeastern Brazil. Mammalian Biology, 2020; 100 (4): 337 DOI:
10.1007/s42991-020-00047-5 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/07/200721114739.htm

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