Evaluating otter reintroduction outcomes using genetic spatial capture–recapture modified for dendritic networks

• Published in: Ecology and evolution Vol. 11; no. 21; pp. 15047 - 15061
• Main Authors: Murphy, Sean M., Adams, Jennifer R., Waits, Lisette P., Cox, John J.
• Format: Journal Article
• Language: English
• Published: England John Wiley & Sons, Inc 01.11.2021; John Wiley and Sons Inc; Wiley
• Subjects: Aquatic mammals; Assessments; Capture-recapture studies; Demographics; Demography; dendritic network; Dendritic structure; Divergence; Endangered & extinct species; Environmental protection; Evaluation; Founder effect; Genetic diversity; Genetic effects; Genetics; Lontra canadensis; Lutrinae; Networks; Otters; Population decline; Population density; Population genetics; Population growth; Population number; Population statistics; recapture; Reintroduction; river otter; River systems; Rivers; Sampling; spatially explicit capture; Translocation; Wildlife conservation; Rio Grande River; New Mexico; United States > US; population density; Lontra canadensis; founder effect; river otter; dendritic network; spatially explicit capture; recapture
• ISSN: 2045-7758; 2045-7758
• DOI: 10.1002/ece3.8187

Monitoring the demographics and genetics of reintroduced populations is critical to evaluating reintroduction success, but species ecology and the landscapes that they inhabit often present challenges for accurate assessments. If suitable habitats are restricted to hierarchical dendritic networks, such as river systems, animal movements are typically constrained and may violate assumptions of methods commonly used to estimate demographic parameters. Using genetic detection data collected via fecal sampling at latrines, we demonstrate applicability of the spatial capture–recapture (SCR) network distance function for estimating the size and density of a recently reintroduced North American river otter (Lontra canadensis) population in the Upper Rio Grande River dendritic network in the southwestern United States, and we also evaluated the genetic outcomes of using a small founder group (n = 33 otters) for reintroduction. Estimated population density was 0.23–0.28 otter/km, or 1 otter/3.57–4.35 km, with weak evidence of density increasing with northerly latitude (β = 0.33). Estimated population size was 83–104 total otters in 359 km of riverine dendritic network, which corresponded to average annual exponential population growth of 1.12–1.15/year since reintroduction. Growth was ≥40% lower than most reintroduced river otter populations and strong evidence of a founder effect existed 8–10 years post‐reintroduction, including 13–21% genetic diversity loss, 84%–87% genetic effective population size decline, and rapid divergence from the source population (FST accumulation = 0.06/generation). Consequently, genetic restoration via translocation of additional otters from other populations may be necessary to mitigate deleterious genetic effects in this small, isolated population. Combined with non‐invasive genetic sampling, the SCR network distance approach is likely widely applicable to demogenetic assessments of both reintroduced and established populations of multiple mustelid species that inhabit aquatic dendritic networks, many of which are regionally or globally imperiled and may warrant reintroduction or augmentation efforts. Monitoring the demographics and genetics of reintroduced populations is critical to evaluating reintroduction success, but species ecology and the landscapes that they inhabit often present challenges for accurate assessments. Using genetic detection data collected via fecal sampling at latrines, we demonstrate applicability of the spatial capture–recapture (SCR) network distance function for estimating the size and density of a recently reintroduced North American river otter (Lontra canadensis) population in the Upper Rio Grande River dendritic network in the southwestern United States, and we also evaluated the genetic outcomes of using a small founder group for reintroduction. Combined with noninvasive genetic sampling, the SCR network distance approach is likely widely applicable to demogenetic assessments of both reintroduced and established populations of multiple mustelid species that inhabit aquatic dendritic networks, many of which are regionally or globally imperiled and may warrant reintroduction or augmentation efforts.