Forest fragmentation imperils red slender lorises (Loris tardigradus tardigradus) in South-Western Sri Lanka

Abstract

The red slender loris ( Loris tardigradus tardigradus ) is endemic to Sri Lanka's southern rainforests, where less than 2% of their habitat remains in small, fragmented patches. Because of continued encroachment on these small areas, the species is considered Endangered. We present data on red slender loris abundance in nine of the last remaining forest patches in Sri Lanka's Wet Zone and examine the relationship between habitat characteristics and abundance. Slender lorises were present at 7 out of 9 patches, and 44 animals were encountered. Density estimates ranged from 3.4 to 28 lorises/km 2 with linear encounter rates of 0.1-1.1 lorises/km. Patch size heavily in fluenced encounter rate, with the largest patches containing more lorises. Removing the effect of patch size, we explored whether support size, undergrowth continuity, number of lianes/vines, and canopy continuity in fluenced loris density. We found slight evidence that increased numbers of lianes and vines were associated with decreased numbers of lorises. Although lorises rely on continuous substrates for movement, increased numbers of lianes and vines are also associated with the smallest and most disturbed habitats. In order to persist, red slender lorises require continuous forest. Unless forest encroachment can be halted and reforestation programmes started, their future in all but the largest of Sri Lanka's remaining forest patches is bleak.