Data from: Multiscale threats shape the occurrence dynamics of a threatened aquatic salamander and reveal a possible extinction debt

Freshwater ecosystems are impacted by anthropogenic stressors, resulting
in roughly one-third of freshwater fauna being threatened with extinction.
The Neuse River Waterdog (Necturus lewisi) is a large aquatic salamander
endemic to the Neuse and Tar-Pamlico River basins of eastern North
Carolina, USA, and it was listed as threatened under the federal
Endangered Species Act in 2021. Habitat degradation has been identified as
the dominant threat driving N. lewisi occurrence, and its effect may be
delayed. The USFWS Draft Recovery Plan classified investigation into the
species’ occurrence dynamics (colonization/extinction) as a high-priority
action. We hypothesized that extinction probabilities would decrease in
high-quality local instream habitats, increase with high proportions of
disturbed land cover in the contributing watershed, and increase in years
with intense droughts. We evaluated these hypotheses within a dynamic
occupancy modeling framework using five consecutive years of
detection/non-detection data collected across 176 locations. We derived
estimates of annual occurrence, turnover, and equilibrium occupancy
(stability) to investigate if spatial responses to threats were delayed –
an extinction debt. The top-ranked model supported the hypotheses on
drivers of site-specific extinction probabilities, including a negative
effect of habitat quality, a positive effect of developed land cover in
the watershed, and a positive effect of annual drought intensity. The
derived estimates broadly indicated that annual occurrence was highest in
rural subpopulations (i.e., management units), turnover was highest in
urban subpopulations, and equilibrium occupancy was lower than required to
maintain stability in most subpopulations of the Neuse River basin. The
estimated occurrence dynamics and their derived quantities suggested an
extinction debt in urban subpopulations that may be accelerated by
stochastic drought events. This study describes a novel use of the dynamic
occupancy model framework within an extinction debt context and provides
partnering conservation agencies with information important to guiding
recovery of the Neuse River Waterdog.