Delineation of core terrestrial habitat for conservation of a tropical salamander: The Hong Kong newt (Paramesotriton hongkongensis)

Abstract

Core terrestrial habitat, sometimes called fixed-width riparian buffer or life zone, is defined as the spatial delineation of 95% of an amphibian population that encompasses all breeding, overwintering, and terrestrial foraging habitats. It has been proposed as a measure of the extent of terrestrial habitat use by amphibians, from which speciesspecific guidelines on buffer zone width can be derived. The Hong Kong newt (Paramesotriton hongkongensis), one of few tropical salamandrids, is endemic to southern China and categorized by the IUCN as Near Threatened. Populations of P. hongkongensis have declined due to habitat degradation and overexploitation for the pet trade. Previous studies of aquatic habitat use by P. hongkongensis revealed distinctive patterns, with juveniles using terrestrial habitats exclusively and most adults remaining on land for about 10 months each year. However, other information on the terrestrial stage is incomplete. We combined radio telemetry and terrestrial transect surveys to study habitat use and quantify movement and distribution patterns of P. hongkongensis during its terrestrial stage with the goal of delineating core terrestrial habitat for the species. Fifty-two P. hongkongensis radio-tracked during the wet season primarily used forest, maintained small home ranges (mean = 0.04 ha), and made frequent short distance movements (< 7m/day) between cover objects. From transect surveys that detected 117 P. hongkongensis, we estimated that the core terrestrial habitat extends 113 m from the nearest stream margin. Currently, there are no guidelines in place for establishment of fixed-width buffer zones to protect semi-aquatic animals in Hong Kong. We recommend that buffer zones of at least 113 m be designed to protect the terrestrial stages of P. hongkongensis.

Does forest extent affect salamander survival? Evidence from a long‐term demographic study of a tropical newt

“…Because only adults were captured in selected breeding pools, we have no knowledge of juvenile/subadult survival rates and their influence on overall population dynamics. Subadult P. hongkongensis are cryptic and rarely observed in the wild (only 24% of 117 newts found during terrestrial transect surveys were subadults; Lau et al., ), and little is currently known about their habitat requirements or growth rates. Juvenile survival rate of salamanders is notoriously hard to estimate directly because of difficulty in relocating juveniles on an annual basis, but it is an important parameter in staged‐based demographic models built to predict population trends (Harper et al., ; Trenham & Shaffer, ).…”

“…To further advance the conservation of this species in mainland China, we recommend 1) breeding site monitoring in selected mainland sites to access the statuses of these populations, 2) quantification of forest cover in core terrestrial habitat surrounding these breeding sites, and 3) increasing patrol in protected areas to discourage activities such as illegal logging, electrofishing, and collection of newts. Locally, we recommend establishing a buffer of at least 113 m around streams outside of protected areas where this protected species occurs (Lau et al., ). A similar approach should be considered for other threatened Asian salamandrids (e.g., L. laoensis ) for which similar patterns of terrestrial habitat use and forest dependency have been observed or are suspected.…”

“…We quantified forest cover by calculating the mean satellite‐derived normalized difference vegetation index (NDVI) of the terrestrial habitat within a 113 m radius of each breeding pool. This value represents core terrestrial habitat occupied by P. hongkongensis during its nonbreeding season (Lau et al., ). NDVI is a remote sensing index used to differentiate vegetated and nonvegetated land cover types (Glenn, Huete, Nagler, & Nelson, ; Pettorelli et al., ) and is commonly used as a measure of forest cover (Carlson & Ripley, ; Carreiras, Pereira, & Pereira, ).…”

“…This value represents core terrestrial habitat occupied by P. hongkongensis during its nonbreeding season (Lau et al, 2017). NDVI is a remote sensing index used to differentiate vegetated and nonvegetated land cover types (Glenn, Huete, Nagler, & Nelson, 2008;Pettorelli et al, 2005) and is commonly used as a measure of forest cover (Carlson & Ripley, 1997;Carreiras, Pereira, & Pereira, 2006 (Pettorelli et al, 2005).…”

“…Such geographic bias is not limited to newts, as studies on plants, invertebrates, and vertebrates from Southeast Asia, which is characterized by high species diversity and high threat levels, accounted for only 6% of the conservation literature published from 2011 to 2015 (i Marco et al, 2017;Sodhi, Koh, Brook, & Ng, 2004). Recent work on tropical salamandrids has largely centered on species discovery, distributions, and threats (Lau, Karraker, Martelli, & Dudgeon, 2017;Phimmachak, Stuart, & Sivongxay, 2012;Rowley et al, 2016), but confronting declining populations with conservation action requires an understanding of demography.…”