Estimating Survival for Elusive Juvenile Pond‐Breeding Salamanders

Abstract

Juvenile vital rates have important effects on population dynamics for many species, but this demographic is often difficult to locate and track. As such, we frequently lack reliable estimates of juvenile survival, which are necessary for accurately assessing population stability and potential management approaches to conserve biodiversity. We estimated survival rates for elusive juveniles of 3 species, the ringed salamander (Ambystoma annulatum), spotted salamander (A. maculatum), and small‐mouthed salamander (A. texanum), using 2 approaches. First, we conducted an 11‐month (2016–2017) mark‐recapture study within semi‐natural enclosures and used Bayesian Cormack‐Jolly‐Seber models to estimate survival and recapture probabilities. Second, we inferred the expected annual juvenile survival rate given published vital rates for pre‐metamorphic and adult ambystomatids assuming stable population growth. For all 3 species, juvenile survival probabilities were constant across recapture occasions, whereas recapture probability estimates were time‐dependent. Further, survival and recapture probabilities among study species were similar. Post‐study sampling revealed that the initial study period median estimate of annual survival probability (0.39) underestimated the number of salamanders known alive at 11 months. We therefore appended approximately 1 year of opportunistic data, which produced a median annual survival probability of 0.50, encompassing salamanders that we knew to have been alive. Calculation from literature values suggested a mean annual terrestrial juvenile ambystomatid survival probability of 0.49. Similar results among our approaches indicated that juvenile survival estimates for the study species were robust and likely comparable to rates in nature. These estimates can now be confidently applied to research, monitoring, and management efforts for the study species and ecologically similar taxa. Our findings indicated that similarly robust vital rate estimates for subsets of ecologically and phylogenetically similar species can provide reasonable surrogate demographic information that can be used to reveal key factors influencing population viability for data‐deficient species. © 2020 The Wildlife Society.

Life history traits and reproductive ecology of North American chorus frogs of the genus Pseudacris (Hylidae)

“…There is considerable uncertainty in survival probabilities of juvenile chorus frogs, a pattern that is observed for many amphibians [ 229 , 230 ]. The complexity of marking and recapturing metamorphic and juvenile anurans make estimating survival very difficult [ 225 ].…”

Subterranean movement inferred by temporary emigration in Barton Springs salamanders (Eurycea sosorum)

“…We also included individual covariates of body size on survival and temporary emigration. We expected survival to be lower for juvenile salamanders compared to adults ( Lee et al, 2012 ; Messerman, Semlitsch & Leal, 2020 ). Furthermore, lower swimming performance in smaller salamanders (e.g., in Eurycea bislineata , Azizi & Landberg, 2002 ) may inhibit them from migrating back through flowing spring orifices, thus limiting their potential for temporary emigration away from the study site.…”

The contributions of individual traits to survival among terrestrial juvenile pond‐breeding salamanders

“…We measured juvenile survival by conducting a mark–recapture study of the tagged individuals using an array of 40 4‐m 2 outdoor enclosures (hereafter ‘pens’) arranged in five blocks of eight pens (Figure S1 in Supporting Information; see Messerman et al., 2020 for pen details). Messerman et al.…”

“…Juveniles reach sexual maturity in 1–4 years (Semlitsch & Anderson, 2016; Semlitsch et al., 2014; Trenham et al., 2000), and evidence indicates that this is the primary dispersing life stage (Gamble et al., 2007). Adult and juvenile migrations and surface activity levels are strongly correlated with warm, humid conditions (Messerman et al., 2020; Semlitsch, 1985; Timm et al., 2007). Given their fossorial life history, small body size and long maturation period, we know relatively little about the biology of juvenile ambystomatids compared with breeding adults and the aquatic life stages.…”

“…maintenance metabolism) and the physiological rate of water loss. Body mass is predictive of survival among juveniles of many species (Civantos et al., 1999; Craig & Ragen, 1999; Garnett, 1981) and is positively correlated with survival among juvenile ambystomatids (Messerman et al., 2020). We thus hypothesized that juveniles with larger initial body masses would have a higher likelihood of survival than smaller juveniles.…”