A massive occupancy monitoring programme has been initiated over the past 18 months to assess the persistence of lorises in over 100 of the remaining fragmented rainforest patches spread across south-western Sri Lanka. The principal threat facing the slender loris is habitat change, resulting from nearly two centuries of over exploitation for coffee, tea, rubber, and cinnamon. Combine with the facts that the species is endemic to central and south-western Sri Lanka, and is typically found in the southern “wet zone” of the island, up to the central “intermediate zone”, and the picture is bleak.
Fortunately, the ZSL EDGE programme has teamed up with the Open University of Sri Lanka and
FOGSL of the University of Colombo wildlife experts to develop a species conservation strategy. The overall programme is being monitored by the National Steering Committee on slender loris appointed by the Ministry of Environment and Natural Resource, Sri Lanka.
A major objective of the project is to provide the first spatial data on loris species at this scale in Sri Lanka allowing questions regarding habitat use, forest preferences, and distribution to finally be answered. To focus attention and resources on this mammoth task, seven hypotheses were selected for slender loris occupancy monitoring:
1 – Loris occupancy is highest in lowland rainforest ecotype compared to sub-montane and montane, 2 – Loris occupancy is related to connectivity to other habitat patches 3 – Protected and managed areas have greater loris occupancy than gazetted but unmanaged and unprotected areas, 4 – Loris occupancy is highest in secondary forest compared to primary forest and agroforestry systems, 5 – Loris occupancy changes according to patch size, 6 – Loris occupancy is highest in forest with highest substrate connectivity than moderately connect and no connection; 7 – Different loris species has difference occupancy.
The first round of the occupancy monitoring programme for slender lorises was completed in March 2010. Nocturnal transect surveys (2km each) were repeated across some 115 forest patches in the wet zone and intermediate zone of the country – totaling over 1000 surveys!
The team are now beginning to process and interpret a huge amount of data, to reveal some of the secrets of loris life. One early success has been the rediscovery the virtually unknown Horton Plains slender loris (Loris tardigradus nycticeboides). Originally documented in 1937, there have only been four known encounters in the past 72 years. The rediscovery and capture by the team (working under the ZSL EDGE programme) has resulted in the first detailed physical examination of this sub-species.
The Horton Plains slender loris is evidently extremely rare and was only found after more than 200 hrs of nocturnal transect surveys in the known habitat. The red slender loris is a focal EDGE species, and the rarity of L. t. nycticeboides resulted in it being listed as one of the world’s 25 most endangered primates.
More results of the fieldwork will follow in the next blog………