Book Description

Semi-fossorial plethodontid salamanders exhibit behavioral plasticity to avoid desiccation, retreating underground to shelter from adverse conditions such as low precipitation and high temperatures. In this study, I used passive integrated transponder (PIT) tag surveys to monitor this behavior in the Del Norte salamander (Plethodon elongatus), a small plethodontid native to northwestern California and southwestern Oregon. Within its range, a climatic gradient exists in which coastal areas experience milder temperatures and high precipitation, while inland areas tend to have colder winters, hotter summers, and lower precipitation. By monitoring the activity patterns of this species in inland and coastal areas, I aimed to observe which environmental variables had the greatest impact on the detection of individuals within the detectable range of the PIT tag antenna (~10 cm underground). Using this method, I obtained a 61.4% overall re-detection rate, compared a 17% recapture rate of above ground salamanders. The likelihood of detecting P. elongatus was significantly related to temperature, with the odds of making a detection increasing by 7.2% for every one-degree Celsius increase in ambient temperature. Relative humidity was also significantly associated with detection, with the odds of making a detection increasing by 12.3% for every one percent increase in humidity. Canopy cover and cloud cover were not significantly related to detection odds. Detection likelihood did not vary based on the body mass index or sex of each individual. Portable PIT tag antenna surveys are significantly less labor intensive than traditional amphibian monitoring techniques and are minimally invasive after the initial tag insertion. Using this method allows for direct monitoring of individual salamanders over time, including near-surface level activity that would be impossible to observe with traditional methodologies. Given that climate projections predict rising temperatures within the range of P. elongatus, monitoring the species’ activity patterns under current climate conditions can help predict how the species may respond to future climate conditions.