The high cost of movement in an arid working landscape for an endangered amphibian

Connectivity is essential for the maintenance of genetic diversity and
stability of wildlife populations. Drought and changing precipitation
regimes have caused natural aquatic amphibian breeding habitats to
disappear or become isolated and have led to the replacement of natural
surface water with artificial livestock water tanks. Terrestrial movement
is the only means of responding to aquatic threats in arid landscapes and
to allow population connectivity. Aridity may present an impenetrable
barrier in hydrologically fragmented environments. We used a facultatively
paedomorphic and federally endangered salamander to assess the challenges
of movement across arid working lands. Sonoran tiger salamanders
(Ambystoma mavortium stebbinsi) are endemic to the San Rafael Valley of
southeastern Arizona, United States of America, where they depend on
livestock water tanks as breeding habitat. The ecology of this species’
metamorphs outside of stock tanks is virtually unknown. To assess survival
on the landscape during terrestrial movement we used radio transmitters to
track 78 adult metamorphosed salamanders over two years. Sonoran tiger
salamanders moved up to 1 km from the tank edge, and average distances
moved of over 400 m were higher than most Ambystoma species. However,
during the study period, none reached neighboring stock tanks. We found
high mortality due to predation and desiccation. Individuals that
dispersed to terrestrial habitat in summer survived longer than
individuals that dispersed in spring. High mortality suggests terrestrial
movement is exceptionally risky and may contribute to isolated
subpopulations and elevated levels of inbreeding. Conservation actions
that improve and maintain artificial aquatic habitats as well as increase
connectivity may improve long-term management for pond-breeding amphibians
in arid regions.