Gonzalez Monge, Alvaro
The Annamese silvered langur (Trachypithecus margarita) is a
recently recognized as a separate species and considered
Endangered by the IUCN. It
lives in Indochina, east of the Mekong River. There are some
studies on its morphology,
distribution and diet. Information on the species’ ranging,
social behavior and
organization, habitat use and reproduction is scarce. The effects
of human disturbance on
langurs are unknown, a reason...[Show more] for concern given the current
biodiversity crisis in the
region. Information on the habitats where the species is found in
the wild is scarce, with
some sources conflicting. I aim to expand our current knowledge
on the socioecology of
T. margarita and the effects of human activities on it.
Research was done at Veun Sai Siem Pang Conservation Area,
Province, Cambodia, from April 2013 until May 2014. An
unhabituated group was
followed for five days every week. Group size was estimated and
position was marked every 30 minutes until the end of the day or
the group was lost.
Canopy layer and forest type were noted every time an individual
was seen. When eating,
plant part and species were identified to species level. Eight
botanical transects of 5x200
meters were set up, classified by forest type and anthropic
disturbance. Plants with a DBH
of 12 cm or over were identified to species level. Biodiversity
and Evenness indices were
calculated for the habitat and each transect and compared. Langur
visits to a mineral lick
were recorded using camera traps. Group size, sex and age classes
were counted, and
morphological characters analysed for individual variability.
Chainsaw numbers, length
of logging in hours and distance from logging spots to the group
were calculated daily.
Mixed evergreen forest is more heterogeneous than mixed deciduous
presents more canopy layers and smaller stems. Logging tracks
affect habitat structure
but not diversity, while intensive logging strongly affects
structure and diversity.
Vertebrate populations at VSSPCA are resilient to small scale
T. margarita at VSSPCA are morphologically uniform. Group size is
at least 61
individuals and the social organization is multi-male
multi-female. Langurs associate
with other sympatric species of primates at the site, especially
M. leonina and P. nemaeus.
Langurs fed mainly on seeds, (69% of their diet), but also ate
other fruit parts; leaf
consumption was low. Focus on plant parts, food species and
families varied between
seasons. Dipterocarps were highly consumed, but Willughbeia and
oak trees were highly
Home range size reached 256 ha, being larger in the dry season
than in the rainy
season, likely because of different food availability. The high
canopy was most frequently
used, although juveniles used the mid canopy more frequently.
Langurs preferred mixed
deciduous forest during the rainy season but avoided it during
the dry season, probably
for a lack of canopy to hide and feed. Langurs were strongly
affected by logging, moving
higher in the canopy as intensity increased, and abandoned areas
of their home range
where it was most destructive. While T. margarita tolerates human
target key tree groups and law enforcement must be maintained.
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