Reproductive ecology of the Taliang crocodile newt ( Liangshantriton taliangensis )

The Taliang crocodile newt(Liangshantriton taliangensis) is a rare urodelean species that is endemic to China. Its population has significantly decreased, but studies of the reproductive ecology of the species, which contribute to its conservation, are limited. By introducing the quadrat method, which involved pitfall trapping and marked-recapture, we evaluated the migration of courting adults and metamorphosed larvae, population size of mature individuals, and operational sex ratio change during the breeding season at the Liziping National Nature Reserve in Shimian County. We used the Jolly-Seber model to estimate the population size of breeding males. One-way analysis of variance and Kruskal-Wallis test were used to examine the differences in the snout-vent length and body mass of male newts that entered the breeding pond at different periods. Sexual dimorphism between male and female was tested by Student′s t-test and Wilcoxon rank-sum test. Additionally, t-test, t′-test, or Wilcoxon rank-sum test was used to compare morphological parameters between amplectant and unamplectant male L. taliangensis, which we observed in the field. Pearson correlation coefficient was calculated to determine the relationship between egg-laying number and morphological traits in the female. We also examined incubation of the spawn. The results showed that the breeding season of L. taliangensis was from late April to late July and the first batch of hatched larvae finished metamorphosis and landed in early August. The population size of breeding males at the studied site was approximately 391. Male newts entered the breeding pond earlier than the female and stayed longer, while males with lighter body masses accessed the pond at a later time. The operational sex ratio skewed to male from 0.03 to 0.10 during the entire breeding season. Sexual dimorphism was overt in this species, with female newts possessing significantly longer snout-vent lengths, heavier body masses, and bigger fatness indices than males, whereas males had higher tail fins and higher tail proportions. We also found that amplectant males had greater snout-vent lengths and body masses and higher tail fins than unamplectant males, suggesting that these morphological characters play important roles in intrasexual competition for mates. Additionally, we counted the egg-laying number of 28 individual females in captivity: the average was 176, the spawning period lasted for 2-4 days for an individual female, and t