title: Evaluating Multi-Level Models to Test Occupancy State Responses of Plethodontid Salamanders.
abstract: Plethodontid salamanders are diverse and widely distributed taxa and play critical roles in ecosystem processes. Due to salamander use of structurally complex habitats, and because only a portion of a population is available for sampling, evaluation of sampling designs and estimators is critical to provide strong inference about Plethodontid ecology and responses to conservation and management activities. We conducted a simulation study to evaluate the effectiveness of multi-scale and hierarchical single-scale occupancy models in the context of a Before-After Control-Impact (BACI) experimental design with multiple levels of sampling. Also, we fit the hierarchical single-scale model to empirical data collected for Oregon slender and Ensatina salamanders across two years on 66 forest stands in the Cascade Range, Oregon, USA. All models were fit within a Bayesian framework. Estimator precision in both models improved with increasing numbers of primary and secondary sampling units, underscoring the potential gains accrued when adding secondary sampling units. Both models showed evidence of estimator bias at low detection probabilities and low sample sizes; this problem was particularly acute for the multi-scale model. Our results suggested that sufficient sample sizes at both the primary and secondary sampling levels could ameliorate this issue. Empirical data indicated Oregon slender salamander occupancy was associated strongly with the amount of coarse woody debris (posterior mean = 0.74; SD = 0.24); Ensatina occupancy was not associated with amount of coarse woody debris (posterior mean = -0.01; SD = 0.29). Our simulation results indicate that either model is suitable for use in an experimental study of Plethodontid salamanders provided that sample sizes are sufficiently large. However, hierarchical single-scale and multi-scale models describe different processes and estimate different parameters. As a result, we recommend careful consideration of study questions and objectives prior to sampling data and fitting models.
authors.affiliation: Weyerhaeuser, Federal Way, Washington, United States of America.
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Kroll
authors.affiliation: Department of Fisheries and Wildlife, Oregon State University, Corvallis, Oregon, United States of America.
authors.forename: Tiffany S
authors.initials: TS
authors.lastname: Garcia
authors.affiliation: Weyerhaeuser, Federal Way, Washington, United States of America.
authors.forename: Jay E
authors.initials: JE
authors.lastname: Jones
authors.affiliation: U.S. Geological Survey, Oregon Cooperative Fish & Wildlife Research Unit, Department of Fisheries and Wildlife, Oregon State University, Corvallis, Oregon, United States of America.
authors.forename: Katie
authors.initials: K
authors.lastname: Dugger
authors.affiliation: Port Blakely Tree Farms LP, Tumwater, Washington, United States of America.
authors.forename: Blake
authors.initials: B
authors.lastname: Murden
authors.affiliation: Weyerhaeuser, Lebanon, Oregon, United States of America.
authors.forename: Josh
authors.initials: J
authors.lastname: Johnson
authors.forename: Summer
authors.initials: S
authors.lastname: Peterman
authors.affiliation: Weyerhaeuser, Lebanon, Oregon, United States of America.
authors.forename: Summer
authors.initials: S
authors.lastname: Peerman
authors.affiliation: Department of Statistics, Oregon State University, Corvallis, Oregon, United States of America.
authors.forename: Ben
authors.initials: B
authors.lastname: Brintz
authors.affiliation: Weyerhaeuser, Lebanon, Oregon, United States of America.
authors.forename: Michael
authors.initials: M
authors.lastname: Rochelle
mesh_terms: D063147:Animal Distribution; D000818:Animals; D065928:Forests; D015233:Models, Statistical; D015983:Selection Bias; D014562:Caudata / Q000502:physiology*