Body length shrinkage in an endangered amphibian is associated with drought

Abstract

AbstractShrinkage in body length, followed by growth, has rarely been documented in vertebrates and has been associated with stressful energetic and environmental conditions. Here, we document reversible shrinkage in an amphibian for the first time. Jollyville Plateau salamanders Eurycea tonkawae are neotenic (attain maturity while retaining an aquatic larval form) and inhabit springs and caves of a dissected aquifer in Travis County, TX, USA. We conducted mark‐recapture surveys on a spring‐dwelling population before and after an exceptional drought in 2008. Use of unique marks and digital photographs of individuals provided precise information on salamander growth rates during and after a period in which salamanders retreated to underground refugia to avoid desiccation during the drought. Tail width decreased significantly during the drought indicating a reduction in energy stores, a consequence of stressful environmental conditions. Unexpectedly, body length shrinkage also occurred during the drought and was followed by positive growth when spring flow resumed. Body length shrinkage could be an adaptation to coping with long periods of low food availability although its long‐term effects are unknown. Given the influence of body size on many ecological and physiological characteristics of organisms, plasticity in body size may have important consequences that go undetected by researchers if shrinkage is ignored.