Migration phenology and fertility of imperiled Illinois salamander (Ambystoma) species

Abstract

Habitat loss is the primary driver of global amphibian declines. Habitat restoration and management of aquatic and terrestrial habitats are underway in Illinois, where over 90% of wetlands have been lost. Demographic and phenologic data are needed to inform land management decisions, such as the timing of controlled burns, to help avoid causing harm to amphibians moving between aquatic and terrestrial habitats (and vice versa). Interfering, stressing, or causing mortality of migrating adults could result in cascading effects on reproduction and recruitment. The Jefferson Salamander (Ambystoma jeffersonianum), Silvery Salamander (A. platineum), and Blue-spotted Salamander (A. laterale) are three species of conservation concern in Illinois that migrate annually from upland habitat to wetlands for reproduction. Juveniles (metamorphs) subsequently emigrate from wetlands to terrestrial habitats after metamorphosis. I conducted a census for each species over three years to understand the environmental factors influencing adult and juvenile movements. Minimum air temperature and 24-hr. precipitation influenced adult A. jeffersonianum and A. platineum movements, whereas wetland depth (a surrogate for hydroperiod) influenced metamorph emigration. Increases in soil inversion strength promoted A. laterale adult movements. To estimate A. jeffersonianum population reproductive characteristics, I combined census and fertility data over three years. Fertility estimates for two wetlands ranged from 0.29 to 1.94, possibly due to hydroperiod. Fertility estimates for both wetlands surveyed were larger than previous studies conducted in the same region. A potential reason for the higher fertility is the restoration efforts aimed at wetland creation and increasing the hydroperiod of existing wetlands. Ultimately, my results can inform future restoration efforts on the timing of prescribed burns and illustrate the potential benefits of habitat restoration on population demographics for wetland-breeding amphibians.