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The toque macaque o f Sri Lanka is classified into 3 sub-species; Macaca sinica sinica (dry zone),
M. s. aurifrons (wet zone) and M. s. opisthomelas (hill zone), based on a combination o f
phenotypical traits and climatic and ecological habitat distribution. We investigated the
relationship between altitude and sub-species on relative tail length. Digital profile photographs
were taken of 167 individual toque macaques from 27 localities distributed along elevationaf'
(2~2129 masl) and climatic zones across the island. From these photos we created a pixelated
proxy for tail length (base to tip) and body trunk length (base o f neck to base o f tail) o f each
individual macaques using “Home o f LibreCAD, 2D-CAD” free ware
(http://librecad.org/cms/home.html). From these measurements, we calculated a tail-to-trunk
index (IT index) for the relative proportion o f tail to body length. A statistically significant
relationship was found between T-T index and elevation (LMM 15.45, p < 0.0001). With
every 100 m o f elevation increase, the TT index decreased by 0.031 (SE + 0.007). This
morphological variation seems to be an adaptation to environmental conditions. This simple
method is a promising new application for the non-invasive morphometric analysis o f species
traits in the field.
