Breeding Dynamics, Diet, and Body Condition of the Hong Kong Newt (Paramesotriton hongkongensis)

Abstract

Paramesotriton hongkongensis has a highly restricted distribution in southern China, and a comprehensive study of the species' basic ecology in aquatic and terrestrial habitats has not been previously undertaken. Using mark-recapture methods, we assessed seasonal patterns of breeding populations in four streams in Hong Kong every 3 wk over 18 mo (2007–2009). We examined diet and body condition of newts in the four focal and six additional streams. We surveyed transects radiating outward from breeding pools to determine the extent of terrestrial habitats used. In the four focal streams, we made 3436 captures of adult newts, comprising 1312 unique individuals. Breeding occurred primarily during the dry, cool season and extended over 8 mo. Individuals remained in breeding pools for an average of 45 days, suggesting that populations in pools were changing throughout the breeding season and that most individuals had a 10-mo terrestrial phase. Sex ratio changed across the breeding season, with males making up larger proportions of populations earlier in the season. Breeding site fidelity averaged 24% and was density-dependent. Among the 47 identified prey types identified in the diet of 406 newts, the most important prey were Brotia snails, Caridina shrimp, newt eggs, baetid mayflies, and calamoceratid caddisflies, in composite making up 63% of total prey volume and 82% of total prey abundance. Cannibalism of eggs and larvae, primarily by females, largely explained differences in diet between sexes. We documented no systematic difference in adult body condition (size-weight relationship) among streams. Fifteen individuals were found in forested habitats within 100 m of the nearest stream, except a single individual located 228 m away. Our work demonstrates that P. hongkongensis occurs at relatively high densities in stream pools during a protracted breeding season, in which individuals show site fidelity but probably do not breed every year. The species appears to be a generalist predator in most aquatic habitats. Although individuals spend most of the year on land, we still have little understanding of the spatial extent of terrestrial habitat use by the species. Future investigations should focus on the species' ecology in terrestrial habitats and on determining the amount of forest cover around breeding sites necessary to protect P. hongkongensis populations in Hong Kong.