The influence of environmental factors on pond activity of aquatic red-spotted newts Notophthalmus viridescens

Abstract

Many important components of animal behavior, growth, and reproduction are tightly linked to environmental conditions, particularly for ectothermic freshwater organisms. For amphibian species, factors such as temperature and rainfall can be physiologically limiting and alter activity levels. The effects of environmental conditions on terrestrial amphibian movement have been well characterized, but less is known about the importance of these factors in aquatic habitats. Here we investigate the impact of temperature and rainfall on the activity of a pond-dwelling amphibian using capture patterns of aquatic adult red-spotted newts (Notophthalmus viridescens). Data on newt captures, air temperature, and rainfall were collected for 6 years (2009, 2011, 2013–2016) during the winter breeding season at a wetland in the Piedmont region of North Carolina, USA. In 2016, we collected more detailed data on the size and sex of captured newts, as well as recording water temperature. Overall, temperature played a significant role in determining newt activity, while rainfall had little effect. As expected, and consistent with findings on amphibian activity in terrestrial systems, newt captures increased with increasing air temperature. During the 2016 breeding season we found sex-based changes in activity in response to temperature, with a higher proportion of males captured during warmer temperatures and a reduction in the male capture bias during colder temperatures. We found no evidence of size-based shifts in activity in response to temperature. This study increases our knowledge of amphibian responses to temperature while in aquatic habitats. Although the duration of time spent in aquatic habitats can be highly variable between species, these breeding locations are critical for the persistence of populations and activity levels, and reproductive success in these wetlands can be highly impacted by future changes in environmental conditions.

Keywords

• Aquatic amphibian
• ectotherm
• capture sex ratio
• minnow trap
• water temperature
• North Carolina
• wetland