DNR QUESTION OF THE WEEK ?

[Lee Borgersen]

December 2012

The DNR communications team works with agency experts to develop the weekly questions and provide the answers. This feature addresses current DNR issues, interesting topics, or the most frequently asked questions from around Minnesota.

Dec 3

Q: Given the drought situation over most of Minnesota, how will turtles and frogs fare in finding suitable places to hibernate?

A: Drought can have significant impacts locally and regionally on aquatic reptiles and amphibians, depending on the length of the drought.

Species that breed in seasonal wetlands and ponds may be forced to find alternative breeding and overwintering sites. These alternative sites are often larger wetlands, ponds or lakes that have a more permanent water source. These sites often have fish and other predators that prey on amphibians and amphibian larva. Local populations can be depleted as a result of this use of alternative breeding and wintering sites.

Another concern with prolonged drought is low oxygen levels. Species that can breathe air can survive in lower oxygen conditions during no-ice conditions. However, many species can only exchange oxygen with the water. In low oxygen conditions caused by prolonged drought, local populations can be lost. During winter, it is harder for amphibians and aquatic reptiles to get oxygen due to ice conditions. As a result, it is common to see frog and turtle die-offs in ponds when they thaw in spring.

Overall, most species can survive short-term droughts, with some localized impacts. Many species can re-inhabit seasonal wetlands and ponds as conditions improve, provided there is a permanent water source in proximity to these seasonal sites.

Prolonged droughts over three to four years can have larger-scale negative impacts on aquatic species.