When there is no forest left: fragmentation, local extinction, and small population sizes in the Sri Lankan western purple-faced langur

[摘要] ABSTRACT: The western purple-faced langur Trachypithecus vetulus nestor is a Critically Endangered primate endemic to Sri Lanka according to the International Union for Conservation of Nature (IUCN). Its population decline is inferred mainly due to vast habitat loss. Few recent data are available regarding its distribution or abundance. The aim of our study was to assess the conservation status of T. v. nestor throughout its known historical range by establishing presence/absence and correlating these data with semi-structured interviews determining human perceptions and threats. Twenty-six sites were investigated, with presence of T. v. nestor being confirmed at 11 and indicated through questionnaires only at 2 additional sites. The present distribution of T. v. nestor is severely fragmented both locally and regionally. More than half of the populations comprised 1 or 2 groups only and, being isolated in a matrix of urban landscapes, are close to unviable. Conflicts between local people and T. v. nestor were identified at such sites, where reports of troops crop-raiding gardens and plantations were associated with negative perceptions. Consequences for crop-raiding langurs ranged from shouting to (infrequently) shooting and killing by dogs. Negative views towards T. v. nestor were significantly related to the length of time they spent in anthropogenic landscapes, while more positive views were significantly associated with the length of time T. v. nestor spent in forested areas. Evidence of local extinctions means that the remaining, yet increasingly fragmented habitat of the highly arboreal T. v. nestor is critical for survival. Intervention to manage this human–wildlife conflict is vital. An integrated approach using international and local conservation authorities is highly recommended.

[学科分类] 动物科学

[关键词] Habitat loss;Conservation;Sri Lanka;Western purple-faced leaf monkey;Trachypithecus (Semnopithecus) vetulus nestor