title: Movement, demographics, and occupancy dynamics of a federally-threatened salamander: evaluating the adequacy of critical habitat.
abstract: Critical habitat for many species is often limited to occupied localities. For rare and cryptic species, or those lacking sufficient data, occupied habitats may go unrecognized, potentially hindering species recovery. Proposed critical habitat for the aquatic Jollyville Plateau salamander (Eurycea tonkawae) and two sister species were delineated based on the assumption that surface habitat is restricted to springs and excludes intervening stream reaches. To test this assumption, we performed two studies to understand aspects of individual, population, and metapopulation ecology of E. tonkawae. First, we examined movement and population demographics using capture-recapture along a spring-influenced stream reach. We then extended our investigation of stream habitat use with a study of occupancy and habitat dynamics in multiple headwater streams. Indications of extensive stream channel use based on capture-recapture results included frequent movements of >15 m, and high juvenile abundance downstream of the spring. Initial occupancy of E. tonkawae was associated with shallow depths, maidenhair fern presence and low temperature variation (indicative of groundwater influence), although many occupied sites were far from known springs. Additionally, previously dry sites were three times more likely to be colonized than wet sites. Our results indicate extensive use of stream habitats, including intermittent ones, by E. tonkawae. These areas may be important for maintaining population connectivity or even as primary habitat patches. Restricting critical habitat to occupied sites will result in a mismatch with actual habitat use, particularly when assumptions of habitat use are untested, thus limiting the potential for recovery.
authors.affiliation: Watershed Protection Department, City of Austin , Austin, TX , United States of America.
authors.forename: Nathan F
authors.initials: NF
authors.lastname: Bendik
authors.affiliation: Watershed Protection Department, City of Austin, Austin, TX, United States of America; Current affiliation: Warnell School of Forestry and Natural Resources, University of Georgia, Athens, GA, United States of America.
authors.forename: Kira D
authors.initials: KD
authors.lastname: McEntire
authors.affiliation: Watershed Protection Department, City of Austin, Austin, TX, United States of America; Current affiliation: Natural Resources, Travis County, Austin, TX, United States of America.
authors.forename: Blake N
authors.initials: BN
authors.lastname: Sissel
keywords: Caudata; Dynamic occupancy models; Endangered species; Eurycea tonkawae; Multi-strata capture-recapture; Plethodontidae