Biology subjects

Storm, D. J.

Publications and source records attributed to Storm, D. J..

3 recordsLinked to original sources

bioRxiv2025

A system dynamics model to understand the integrated ecological and human dimension aspects of wildlife health and disease management

Chronic wasting disease (CWD) presents an ongoing challenge for the management of deer populations and sustaining harvest opportunities across North America. Existing disease models often fail to fully capture the complex interplay between disease dynamics, host ecology, and socio-economic factors. We developed a comprehensive system dynamics (SD) model that integrates demographic, epidemiological, ecological, and socio-economic processes within a single model to more fully characterize the complex network of causal feedbacks throughout the system. The model was calibrated using a Bayesian approach that incorporates prior knowledge to generate biologically interpretable outcomes, even with sparse data. For estimating the joint posterior distribution of model parameters, we leveraged time series of deer abundance, harvest composition, genetic profiles, CWD surveillance, and hunter demographics and behavior. Model outputs reproduced key system behaviors, including observed CWD prevalence trends, deer population dynamics, and hunter license purchasing patterns. Model predictions were most sensitive to parameters governing initial deer population size and recruitment. While model predictions generally aligned with observed data, discrepancies in early CWD detection and overestimation of the reactivation of long-inactive hunters reflect data limitations and modeling challenges. Key results suggest that indirect transmission is necessary to explain observed prevalence, that transmission is moderately density-dependent, and that observed population-level genetic shifts driven by CWD may play a role in transmission and progression. The SD modelling approach enabled estimation of difficult-to-measure parameters and identified potential leverage points for management--such as prioritizing increasing participation in antlerless harvest of existing hunters over the recruitment of new hunters. This integrated modeling approach offers a flexible foundation for adaptive wildlife disease management and emphasizes the value of unifying biological and human dimension processes to better inform effective, evidence-based policy.

ecology↗

bioRxiv2025

Incorporating habitat selection does not account for nonrandom camera deployment in a design-based viewshed density estimator

Camera trap-based abundance estimators are increasingly used for population size estimation in the absence of marked individuals. One approach is to relate animal detections to the space sampled by each cameras viewable area, which results in viewshed density estimates that can be extrapolated to the broader sampling area to obtain abundance. The assumption is that spatial variation in local abundance corresponds to the collective viewsheds of cameras. Therefore, these design-based viewshed density estimators require that camera locations be representative of the study area. This assumption can be met with spatially balanced probability sampling, such as a generalized random tessellation stratified design. However, the random placement of cameras can be restrictive in practice. Using simulations and an empirical study, we evaluated an extension of the instantaneous sampling estimator to account for unmodeled spatial variation in local abundance using independent predictions of relative habitat use from GPS telemetry data. We applied this approach to a fenced population of white-tailed deer (Odocoileus virginianus), some of which were GPS collared, where timelapse photography data were collected using random and nonrandom camera placements simultaneously during two consecutive winter seasons. Our simulations showed that this approach neither reduces bias nor improves the precision of abundance estimates considerably. Specifically, we found little support that calibrating estimates based on habitat selection analysis would produce unbiased results when sampling is spatially unbalanced and focused on areas of high animal use instead of being representative of the study area. Our findings underscore the need for randomized sampling when the goal is to provide unbiased population size estimates for unmarked wildlife populations using design-based viewshed density estimators. Attempts to relax the model assumptions must be both theoretically sound and practically feasible, otherwise there would be a risk of misleading management decisions by using unreliable estimates of population size.

ecology↗

bioRxiv2023

Prions in carnivore feces: recovery from spiking experiments and detection in free-ranging carnivores

Chronic wasting disease (CWD) is a highly contagious, fatal neurodegenerative disease caused by infectious prions (PrPCWD) affecting wild and captive cervids. Although experimental feeding studies have demonstrated prions in feces of crows (Corvus brachyrhynchos), coyotes (Canis latrans), and cougars (Puma concolor), the role of scavengers and predators in CWD epidemiology remains poorly understood. Here we applied the real-time quaking-induced conversion (RT-QuIC) assay to detect PrPCWD in feces from cervid consumers, to advance surveillance approaches, which could be used to improve disease research and adaptive management of CWD. We assessed recovery and detection of PrPCWD by experimental spiking of PrPCWD into carnivore feces from 9 species sourced from CWD-free populations or captive facilities. We then applied this technique to detect PrPCWD from feces of predators and scavengers in free-ranging populations. Our results demonstrate that spiked PrPCWD is detectable from feces of free-ranging mammalian and avian carnivores using RT-QuIC. Results show that PrPCWD acquired in natural settings is detectable in feces from free-ranging carnivores, and that PrPCWD rates of detection in carnivore feces reflect relative prevalence estimates observed in the corresponding cervid populations. This study adapts an important diagnostic tool for CWD, allowing investigation of the epidemiology of CWD at the community-level.

ecology↗