Evaluating the Need for Supplemental Shallow Water Access for Amphibians Reared in Mesocosms

Abstract

Mesocosms are an important tool in experimental aquatic ecology, but have been criticized for failing to effectively mimic natural habitats. Identifying contrived features of mesocosms that affect endpoints of interest is a prudent step in ensuring the reliability of mesocosm data. Because anuran larvae actively regulate their exposure to a suite of biotic and abiotic conditions by positioning themselves at various depths in natural ponds, the steep walls and minimal access to shallow regions in common cattle tank mesocosms may force tadpoles into sub-optimal patterns of habitat use. We tested whether adding angled ramps or horizontal platforms to increase access to shallow regions affected survival, time, or mass at metamorphosis of American Toads (Anaxyrus americanus) or Northern Leopard Frogs (Lithobates pipiens) in the presence or absence of Rusty Crayfish (Orconectes rusticus), a common predator that may influence habitat use. Addition of structure had no effect on American Toad survival or metamorph...