Primates in Peril

San Martín Titi Monkey
Callicebus oenanthe Thomas, 1924
Peru
(2012, 2014)
Jan Vermeer
light variant
The San Martín titi monkey was discovered in 1924,
but until 2007 was only known from six museum
specimens and scarce observations, all from the Alto
Mayo Valley in northeastern Peru (Thomas, 1924, 1927;
Hershkovitz 1990; Mark 2003; Rowe and Martinez 2003;
De Luycker 2006). Extensive surveys by the team of
Proyecto Mono Tocón have shown that the distribution
of the species extends from the Alto Mayo Valley in
the south, restricted largely (but not completely) by
mountain ranges in the west, south and north, and the
Río Huallaga in the east (Boveda-Penalba et al. 2009).
It inhabits the lowland forest on the eastern foothills of
the Andes, rarely occurring at altitudes above 1,200 m
above sea level.
dark variant
Callicebus oenanthe is endemic to the department of
San Martín, which has the highest deforestation rates
in Peru. Although its original range was estimated to
have been approximately 14,000 km², its habitat has
been reduced to less than 6,500 km², of which only
1,900 km² is thought to be covered with good habitat
(Shanee et al. 2013). The forest cover data used for this
study were from 2007/2008; meanwhile deforestation
has continued at high speed and the situation is even
worse today.
The San Martín titi monkey is highly variable in
coloration (Boveda-Penalba et al. 2009; Vermeer et al.
2011). Most animals in the north are brownish with a
white mask, while in the south many lack the typical
mask and have a darker or more orange color (Proyecto
Mono Tocón unpublished data).
San Martín titi monkey (Callicebus oenanthe)
(Illustrations: Stephen D. Nash)
Only a few larger populations are living in protected
areas, and it is doubted that these populations are
viable. Most San Martin titi monkeys were found to live
in isolated populations in small forest fragments, with
little chances for survival. Connecting isolated forest
patches is mostly impossible due to human presence.
The situation is even more complicated as the San
Martín titi monkey seems to have a preference for the
edges between primary and secondary forest, where
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