First Record of the Critically Endangered Vandeleuria nolthenii from Hakgala Botanical Garden, Central Highlands of Sri Lanka

Abstract

Rodents of the genus Vandeleuria are small, nocturnal, arboreal members of the family Muridae, distinguished by partially opposable digits and flat nails on the first and fifth toes. Sri Lanka hosts two species: the widespread V. oleracea and the Critically Endangered, montane-endemic V. nolthenii. During a citizen science survey in urban and semi-natural habitats, we recorded V. nolthenii for the first time from Hakgala Botanical Garden (1,700-1,800 m Above Sea Level), adjacent to Hakgala Strict Nature Reserve. The objective of this study was to document and verify the occurrence and nesting-site characteristics of V. nolthenii within human-modified montane habitats. On May 5, 2023, during an opportunistic survey, a dead Cupressus macrocarpa tree (Girth at breast height=135 cm) near the botanical garden exit gate was examined for nesting activity. The trunk had two oval-shaped openings: the lower at 90 cm above ground (28×44 mm) and the upper 40 cm above it (24×17 mm). The lower cavity was covered with dead cypress leaves and other plant matter. Examining it led to the sequential emergence of five small, brownish, long-tailed mice from the upper opening. Based on their external morphology and behaviour, the individuals were identified as V. nolthenii. Previous studies reported females with four half-grown young occupying bird nests in early April; the present observation of five similarly sized individuals in early May is consistent with a mother accompanied by nearly grown offspring. This record highlights the value of citizen science in documenting elusive small mammals and indicates that V. nolthenii can utilize exotic vegetation and persist in modified habitats. The finding extends the known distribution of the species within the montane zone and unveils the biodiversity present in human-managed landscapes. Continued collaboration among visitors, naturalists, and researchers can support monitoring and conservation of Sri Lanka’s lesser-known mammals.

Keywords: Vandeleuria nolthenii, Citizen science, Distribution record, Sri Lanka