Range Extension and Vocalisation of Endangered Shrub Frog, Pseudophilautus zorro (Amphibia: Rachophoridae) in Sri Lanka

Abstract

Gannoruwa shrub frog, Pseudophilautus zorro, is an endemic species known only from four locations in and around Kandy, Gannoruwa forest, home gardens in Triverton estate, Hanthana and Udawaththakele forest reserves. Despite their cryptic nature calling males are conspicuous once identified their vocalisation. Hence, we describe their vocalisation and acoustic characters. We recorded P. zorro from Hanthana (80.6141° E, 7.2497° N; 700 m a.s.l.) and measured six common call characters of 92 calls from four males. We identified four call types based on wave form structure and spectrogram. Type 1 calls were the most frequently emitted call type (93% of 518 calls recorded) having the average call duration 5.1±1.2 mili-seconds. Vocalising frequency of the species ranged between 3,100 Hz and 3,600 Hz. During our field excursions in 2014-2017, we heard similar vocalisation in two sites well away from its known range, Katugasthota (80.6199° E, 7.3302° N; 470 m a.s.l) and Ovilikanda (80.5926° E, 7.4538° E; 470 m a.s.l). We confirm the identity as P. zorro using the morphological characters. Again, on 18th September, 2014 we sighted the species during an excursion to Kukulamalpotha (80.7819° E, 7.5527° N; 460 m a.s.l) in Knuckles reserve. Since the site was very far from the known range of P. zorro, we obtained toe tips from two individuals and confirm their identity genetically by having 0% uncorrected pairwise genetic distance for 16S gene fragment (~510 bp). With three new found locations their Extent of Occurrence and Area of Occupancy has been increased by 14 times (from 20 km2 to 291 km2) and by 2 times (from 16 km2 to 28 km2) respectively. New found populations considerably expanded the species-range and the knowledge of their vocalisation can further use to explore new populations. This study confirms that P. zorro is not restricted as previously thought.
Keywords: New population, Bioacoustics, Shrub frogs, Extent of occurrence