Fecal Glucocorticoid Metabolites as Biomarkers in Equids: Assay Choice Matters

From Wiley via Jisc Publications RouterHistory: received 2020-05-06, rev-recd 2021-03-29, accepted 2021-04-09, pub-electronic 2021-06-01Article version: VoRPublication status: PublishedFunder: Royal Society; Id: http://dx.doi.org/10.13039/501100000288; Grant(s): UF110641Funder: Chester Zoo; Id: http://dx.doi.org/10.13039/501100005359; Grant(s): Conservation FellowshipABSTRACT: Free ranging animals are exposed to environmental, demographic, and ecological challenges over time, which can affect their health and fitness. Non‐invasive biomarkers can provide insight into how animals cope with these challenges and assess the effectiveness of conservation management strategies. We evaluated how free ranging ponies (Equus ferus caballus) on the Carneddau Mountain range, North Wales respond to 2 stimuli: an acute stressor of an annual roundup event in November 2014, and spatial and temporal variation in ecological factors in 2018. We evaluated fecal glucocorticoid metabolites using 2 enzyme immunoassays (EIAs): an 11‐oxoetiocholanolone EIA (measuring 11,17‐dioxoandrostanes [11,17‐DOAs]) and a corticosterone EIA. The former assay has been validated in equids, whereas there is limited evidence for the suitability of the latter. We used an additional parent testosterone EIA to measure fecal androgen metabolites in response to the ecological challenges. Following the roundup, the metabolite concentrations measured by the 2 glucocorticoid EIAs were not correlated. The 11,17‐DOAs were elevated from the second day following the roundup and then slowly returned to pre‐round levels over the next 2 weeks. In contrast, the metabolites measured by the corticosterone assay showed no response to the roundup. For the ecological data, all 3 assays detected a positive correlation between metabolites and social group size in males but not in females. The metabolite concentrations measured by the testosterone and corticosterone assays were highly correlated and were temporally associated with the onset of the breeding season, whereas the 11,17‐DOAs were not. The co‐variance of metabolites measured by the corticosterone and testosterone assays, and the lack of an acute response in the corticosterone assay to the roundup, suggests that metabolites detected by the corticosterone assay were not primarily associated with increased glucocorticoid production. We recommend using well‐validated fecal biomarker assays of hypothalamus‐pituitary‐adrenal axis activity to evaluate and compare the effect of different management interventions and environmental change. © 2021 The Authors. The Journal of Wildlife Management published by Wiley Periodicals LLC on behalf of The Wildlife Society

Novel habitat use supports population maintenance in a reconfigured landscape

Given the limited scope of unaltered, protected areas in most regions, understanding the contributions to imperiled species conservation by landscapes in which habitat elements have been reconfigured is critical. Commercial forestry has been a driver of altered structure and composition of forests and of distribution and character of aquatic systems. In eastern North America, extensive historical wetland drainage reconfigured hydrologic environments from low-gradient wet flats and isolated wetlands to connected networks of linear ditches. Landscapes where both uplands and aquatic environments differ from historic conditions may affect most ecological aspects of semi-aquatic species, including reptiles. Our objective was to determine if habitat selection and use decisions by spotted turtles (Clemmys guttata), a rare semi-aquatic species, supported population maintenance in a reconfigured forest landscape in eastern North Carolina, USA. We captured 280 individuals and radiomarked 31 adults to examine habitat selection at multiple spatial scales with paired logistic regression, movements and home ranges with location data and utilization distributions (UDs), survival with a known-fate model, and abundance with N-mixture modeling. Across local and landscape scales, turtles selected features associated with ditches despite abundant, more natural aquatic depressions across the study area. Habitat metrics describing understory closure and substrate characteristics were important at local scales, and closed canopy forest and habitat heterogeneity was positively associated with activity areas at landscape-scale spatial grains. Both movements and home ranges were centered on ditches, and turtles exploited ditches to access mates, nest sites, or uplands for estivation. In this highly reconfigured landscape, this species appeared to have sufficient behavioral plasticity to acquire key resources contributing to high survival and an abundant population. Isolation from road traffic and collection, both which negatively affect turtles elsewhere, was facilitated by limited public access. Our results suggest that conservation and management of rare species should not rely solely on habitat information gained from studies in more pristine areas because such results may not demonstrate the range in variation in behavior that might allow persistence in novel environments, absent key threats

Community occupancy of herpetofauna in roadside ditches in a managed pine landscape

Aquatic habitat types embedded in managed forest can contribute ecological services and suitable conditions for numerous species despite departing from historical baselines. Although prevalent in the Atlantic Coastal Plain, roadside ditches adjacent to pine plantations have had few surveys of vertebrate diversity and little is known about local and landscape level effects of silvicultural activities on species assemblages. Our goal was to investigate richness and occupancy of amphibians and reptiles in an intensively managed forest landscape with a history of silvicultural alterations of aquatic habitat types, including ditching, draining, and periodic maintenance of ditches for optimizing loblolly pine (Pinus taeda) growth. We selected 15 roadside ditches that were maintained 3-17 years earlier and were embedded in a matrix of pine plantations in eastern North Carolina, USA. We conducted repeated, visual encounter surveys of roadside ditches during 2012-2013 and detected 25 species of amphibians and reptiles 447 times including five species of statewide conservation concern. We used a Bayesian, hierarchical, community occupancy model with group-specific hyper-parameters to estimate occupancy probabilities and species richness while accounting for imperfect detection. With our model, we examined effects of time since ditch maintenance, amount of nearby mature forest, and amount of adjacent wet-lands on species richness and occupancy. We predicted species would respond positively to an intermediate period of time since ditch maintenance and positively to landscape covariates related to mature forest and wetlands. Our model estimated species richness of anurans from 0.9 to 7.4 species/ditch segment, snakes and lizards from 0.8 to 9.0 species/ditch segment, and turtles from 0.9 to 5.1 species/ditch segment. Contrary to our predictions, occupancy of herpetofauna showed no evidence of a relationship to time since ditch maintenance, and landscape metrics only influenced occupancy of one turtle species. Detection probabilities were influenced by season for several anurans, snakes, and lizards, but not turtles. Our results indicate that aquatic habitat types embedded in managed forests that were hydrologically and structurally altered for silviculture can support local occupancy of a relatively diverse herpetofaunal community and that temporal proximity to ditch maintenance had little effect on occupancy or richness