Crawfish frog research

With the harsh winter weather and snow preventing many Refuge activities, we have devoted some time to analyzing data from the last 12 years of our crawfish frog project. Some interesting trends have come up in this analysis. We have showed that the success of crawfish frogs on the refuge has increased over the years, as shown both by egg mass counts and by metamorph success (metamorphs being the frogs that have just grown legs and begin to emerge on land).

This is encouraging news, as the crawfish frog is a state-endangered species in Indiana. The increase in population is likely due to the creation of many new ponds which are managed with water control structures that allow the ponds to be drained in the fall, keeping fish and predatory green frog and bullfrog tadpoles out and creating the ephemeral wetlands preferred by the crawfish frog. The managed ponds in particular seem to be much more successful as seen by the number of metamorphs emerging from them.

There is certainly a sizable difference between ponds which were managed (drained) and those which were not, which is not surprising considering the crawfish frog's biology. The tadpoles are rather delicate and do not fare well with predators, making them more dependent on relatively ephemeral and predator-free waters than some other frogs. Other data seems to show that recent prescribed fire does not damage the frogs' success the following year.

Despite this encouraging news, the frog project at Big Oaks has had some setbacks. The largest breeding population at Karns pond has had mass die-offs caused by the Perkinsia parasite. Relatively little is still known about the parasite, though it is thought that the parasite load could be increased by a dense tadpole population year after year until it reaches levels fatal to the tadpoles, causing a die-off. To combat this, we have instituted rigorous equipment bleaching protocols when moving between ponds. We have also tried draining Karns pond for a year, burning straw on top of it, and letting vegetation grow up. We hope that when it is flooded again after lying fallow a year, it will provide a safe home for tadpoles once again.