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 metamorphosis, but slightly increased time to metamorphosis and mass at metamorphosis for Northern Leopard Frogs. Behavioral assays revealed that while structure addition increased the number of tadpoles in shallow regions for both species, these increases were small. Most tadpoles were observed on a shallow, built-in lip present on the walls of all of our mesocosms, which are a common feature of most available mesocosms. Post-hoc choice tests revealed that American Toads preferred the lip to both structure types and Northern Leopard Frogs displayed a preference for platforms but no preference when choosing between ramps and the lip. Furthermore, while Rusty Crayfish reduced survival for toads and altered metamorphic responses for both species, they did not alter tadpoles' use of structure. Although access to shallow water may be important for anuran larvae, our study suggests that it may not be necessary to augment shallow water access in cattle tank mesocosms if a shallow lip is already present.

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