Reproductive timing of Eurycea naufragia at two spring sites

Background/Question/Methods

The Georgetown salamander, Eurycea naufragia, is an endemic, spring dwelling, neotenic salamander found only at 15 sites in Williamson County, Texas. Little is currently known about the life history of this species. We conducted monthly visual encounter surveys at two sites, Swinbank Spring (starting in 2007) and Twin Springs Preserve (starting in 2008). During the visual encounter surveys, each salamander observed was assigned to one of three size classes; 1(less than 2.5 cm), 2 (2.5 - 5.1 cm), or 3 (greater than 5.1 cm). Starting in June 2010 we captured salamanders and examined them for the presence of eggs to determine the timing of reproduction.  

Results/Conclusions

A significantly greater proportion of gravid females was observed from November to April than May to October at both Swinbank Spring (X² = 47.225, df = 1, P < 0.0001) and Twin Springs (X² = 17.279, df = 1, P < 0.0001). Very few salamanders in the smallest size class were observed throughout the study, and therefore analysis of size classes was restricted to size classes 2 and 3. A higher proportion of size class 2 salamanders was observed from May through October, as compared to November through April, at Twin Springs (P < 0.001), but this trend was not observed at Swinbank Spring (P = 0.4068). These results support a winter reproductive season for the species, although other environmental factors (e.g.. water flow) may also influence reproduction. An understanding of reproductive timing is important for conservation efforts. Continued research and observations may help to better delineate the timing of reproduction and the potential importance of environmental factors in reproductive events.