Habitat Characteristics, Relative Abundance and Conservation Threats of Himalayan Bull Frogs (Nanorana leibigii Günther, 1860) in Primary Tributaries of Simkhar River, Bhutan

Abstract

Nanorana leibigii Günther belongs to Dicroglossidae family. Its population in Bhutan is declining due to over collection for its medicinal values. This study documents the habitat characteristic and assesses the relative abundance and conservation threats within the six primary tributaries of Simkhar river under Sarpang District. Opportunistic visual encounter survey was used within the time span of 8:00–11:00 hours in the morning and 17:00–20:00 hours in the evening during the month of March-May of 2015. Systematic hand search within 5 m radial distance in potential habitats were conducted to categorize the niche habitats. Water samples were collected from each tributary and tested using Digital Hanna instrument and conservation threats assessed in their niche habitat. The results show that habitat of N. leibigii is characterized by permanent stream flows (28%), piled-up substrates (26%), moss-laden rock crevices (25%), and decaying vegetable matters (21%). Relative abundance (RA) was highest in Thortneykhola and Gurungkhola, and lowest in Darzhanikhola. RA was higher in habitat with 7.73 pH, 7.6 mg/L Dissolved Oxygen (DO), and 15 ppm Total Dissolved Solid (TDS). Overall, the study recorded intensive cattle grazing in the catchment areas as the highest conservation threat followed by lack of conservation awareness of nearby communities, and collection for medicine. Occurrence of N. leibigii was relatively higher in water with 7.73 pH, 7.6 mg/L DO, and 15 ppm TDS. Similar studies are recommended for an in-depth understanding of the frog’s habitat ecology and conservation need.