Breeding Migrations, Survivorship, and Obligate Crayfish Burrow Use by Adult Crawfish Frogs (Lithobates Areolatus)

Abstract

Movements are risky behaviors to animals, and amphibians are no exception. Being unable to cover long distances quickly, amphibians may find migrations challenging, yet many if not most species exhibit cyclic annual migrations. Crawfish Frogs (Lithobates areolatus), are a relatively understudied species of North American amphibian listed as endangered in Indiana and Iowa, and considered a species of conservation concern throughout much of their range. To better understand the biology of this species, and in particular, to assess the role that movements play in affecting survivorship, I radio tracked 48 Crawfish Frog adults, in 2009 and 2010. My study encompassed a total of 7,898 telemetered-frog days; single frogs were tracked for up to 606 days. These data demonstrate two behaviors previously undocumented in this species: 1) migration distances that averaged nearly ½ km, and for one frog was > 1,187 m; and 2) fidelity to upland burrows excavated by crayfish. Together, these findings indicate that Crawfish Frogs have a remarkable ability to home to distant upland burrow sites. Burrow fidelity in Crawfish Frogs involves, in part, frogs following similar migration routes to and from breeding wetlands. Burrow fidelity also occurs after ranging movements, and often involves individual frogs following the same circuit across years. Further, I demonstrate that movements are risky for Crawfish Frogs (about 12 times riskier than burrow dwelling), and therefore have survival consequences. My data also suggest that adult Crawfish Frogs are likely not dispersing to colonize new sites; instead, it seems more likely that juveniles represent the dispersing stage. To ensure the least impact to Crawfish Frog populations several conservation measures should be taken. First, core habitat and buffers should be established that exclude or limit roads for at least a 1.1-km radius around breeding wetlands. Secondly, burrow destruction should be minimized by limiting new cultivation and other ground disturbance within the core habitat and buffer. Thirdly, prescribed burns should be avoided from mid-March to mid-May, when frogs are out of their burrows migrating to and from wetlands.