Bradypus variegatus - Brown-throated three-toed sloth
The Brown-throated three-toed
sloth, Bradypus variegatus, on average weighs between 2.25 and 6.20kg
for an adult. Body length, with the head
included, ranges from 413 to 700mm, and the tail is approximately 20 to
90mm. Bradypus variegatus’ overall
body pelage color is a grayish brown with a darker brown forehead and
suborbital markings that encircle the eye.
The lengths of the forelimb appendages are longer than the hind
limbs. Both limbs exhibit three digits
of close proximity that extend into the characteristic three curved claws. The head of B. variegatus is small in
size, compared to the rest of the body, with ears reduced beyond visible
perception. The tail, also reduced in
length, is stumpy. Male body coloration
differs from females with the presence of an orange-yellow patch that contains
a brown stripe through the middle. This
patch of fur is of shorter length compared to other areas and is located
between the shoulders, mid dorsum. The
fur of B. variegatus is coarse and thick with the strands longitudinally
grooved. This groove allows for green
algae to grow generating their own camouflage. The orientation of their fur is
ventral to dorsal, opposite than most mammals, providing quick rain
runoff. Another layer of fur is found
underneath the top layer, which consists of finer strands that provide more
variegatus is found only in the neotropics.
They range from eastern Honduras
to the northern regions of Argentina
(Redford and Eisenberg, 50). The climate of this area has a constant warm
temperature, allowing vegetation growth through out the year. The precipitation and humidity also plays a
significant role in the algae growth that serves as camouflage from
variegatus mate once a year before the rainy season and gestation lasts
between four and six months (Taube, 174).
The male’s role in reproduction ends after mating. Litter size is a consistent one offspring per
birth. The young will remain with the
mother through lactation, approximately four months. The young become independent in another two
to four months. During the time when the
offspring and mother are together the young inherits the mother’s dietary
preference. It is thought that this is
facilitated due to the passing of microorganisms found in the stomach that is
specific to the vegetation type consumed.
Once the offspring becomes independent the mother will give the young
part of her territory, thus lowering competition between the two (Taube, 173).
Ecology and Behavior:
Sloths are active both diurnally and nocturnally (Redford
and Eisenberg, 51). A solitary animal, Bradypus
variegatus, is less aggressive than the two-toed sloth, Choloepus. That is not to say that B. variegatus
will not defend itself, their territory, or their young. If they need to defend a resource, they are
well equipped, because their long claws can leave deep wounds (Greene,
369). The only time when two B. variegatus are together with out confrontation is generally when mating. Reports of a male and a female living
together are definitely not the norm.
Being an arboreal specialist, B. variegatus spends the vast majority of their time in the trees. They descend from their tree top homes to
defecate approximately once a week.
Still clinging to the tree they will dig a hole, with their tail,
defecate, cover it and ascend (Emmons, 36).
There is a symbiotic relationship
between the sloth and a moth that forages on the algae growth. The moth not only feeds off the sloth but it
also lays its eggs in the feces of the sloth.
Locomotion of the sloth with in
their arboreal habitat is a hand over hand motion while hanging upside
down. Their long arms and legs are well
suited for this; however, terrestrial movement is more of a challenge. Due to their arboreal movement being energy
efficient they do not have the muscle mass needed for terrestrial
locomotion. Movement on land is carried
about in a crawling fashion, moving on their forearms and the soles of the hind
feet. Though terrestrial movement is
labored, they are skilled swimmers (Nowak, 152).
B. variegatus spends
the greater part of their life in the mid to upper canopies of tropical trees,
hanging upside-down, munching on young leaves, buds, and other shoot
material. As many other herbivores they
need to consume large quantities to obtain the necessary nutrients. This is facilitated by being able to forage
with out having to use their limbs by being able to rotate their head
270°. Most mammals have seven cervical
vertebrae, but sloths possess nine. This
allows for greater mobility of their head for a hands free approach to
dinning. The herbivore diet, as stated above, that is passed on from mother to
offspring is folivorous, a leaf specialist (Taube, 174). Due to the poor nutrient content of this diet
their stomachs are compartmentalized, this extends digestion time extracting
the most nutrients. Slow locomotion and
a poor thermoregulation system is a direct result of this specialized diet,
generally found in the Cecropia tree (Redford and Eisenberg, 51). A tree is suitable if a couple of aspects are
met, a folivorous diet scheme and the canopy cover density needs to be
compatible with the poor thermoregulatory system. Canopy cover density is based on the amount
of sunlight that reaches the crown of the tree. Sloths use these trees as a
means to regulate body temperature by simply moving in and out of the
Bradypus variegatus is
listed as an appendix two species by CITES.
Meaning that they are not listed as endangered, however, they are
regulated (Primack, 473). Ironically
since they are not threatened or endangered, there is not much research on B. variegatus. It is known that this animal
does not handle change well, thus habitat fragmentation or other alterations
will have devastating effects on the survival of this animal.
Adam, Peter J.
“Mammalian Species Choloepus didactylus.” American Society of
Mammalogists No. 621 (1999) : 1-8.
Emmons, Louise H. Neotropical
Rainforest Mammals – A Field Guide. Chicago,
University of Chicago Press, 1990.
A, ed. et al. Mammology: Adaptation, Diversity, and
Ecology Second Edition.
New York, 2004.
Greene, Harry W.
“Agnostic Behavior by Three-toed Sloths, Bradypus variegatus.” Biotropica vol. 21 No. 4 (1989) :
Nowak, Ronald M. Walker’s
Mammals of the World vol. 1 sixth edition. Baltimore, The
Johns Hopkins University Press, 1999.
Primack, Richard B.
Essentials of Conservation Biology. Sunderland, Sinauer Associates Press, 1993.
Redford, Kent H., John F Eisenberg. Mammals of Neotropics
– the Southern Cone vol. 2. Chicago, University of Chicago Press, 1992.
Taube, Erica., Joel
Keravec, Jean-Chistophe Viَe, Jean-Marc Duplantier. “Reproductive biology
and postnatal development in sloths, Bradypus
and Choloepus: review with
original data from the field (French Guiana)
and captivity.” Mammal Review vol 31 No. 3 (2001): 173-188.
Reference written by
Ryan Wittkopf, Biol 378 (Mammalogy), University of Wisconsin – Stevens
Point: Edited by Christopher Luddington. Page last
updated March 4, 2005.