Modeling the response of cave hibernating Myotis species to white-nose syndrome mitigation tactics

Science Center Objects

Bat Research

Research collaboration: Robin Russell (NWHC), Tonie Rocke (NWHC), Wayne Thogmartin (UMESC), Evan Grant (PWRC)

White-nose syndrome is a fungal disease devastating cave-hibernating bat species (Myotis spp.) in the eastern United States. Several mitigation tactics have been proposed to alleviate the effects of white-nose syndrome on bats including probiotics and vaccination. Questions remain regarding how effective a treatment should be to result in population-level effects, and what proportion of a population would need to receive the treatment. For example, effective vaccination often relies on “herd immunity”- the concept that not all individuals need to receive treatment, but that a critical mass should be vaccinated to prevent the spread of disease in a population. In addition, bats can travel large distances between summer roosting habitat and overwintering hibernacula locations, making our ability to designate distinct “populations” for treatment difficult.

Efforts are underway to develop decision support models for managers faced with the challenge of trying to conserve white-nose syndrome-affected populations. Missing from these models is a population-level model of bat dynamics that can provide more detailed information of expected responses of bats to mitigation tactics. For example, useful population models should address questions such as what proportion of the population would need to be treated to observe an effect on population viability? What is the spatial scale that treatments should be applied? Are there tradeoffs between within and among hibernacula tactics for mitigation? When are treatments most effectively applied (spring emergence, summer roosting, fall swarming)? If a population is only accessible in the summer at roost locations what is the optimal strategy? We build on previously developed models of population dynamics of Myotis species combined with information on mitigation strategies to address these questions. This project ties together the vaccination trials being conducted at NWHC with the structured decision-making efforts at PWRC.

The PIs previously developed population models of cave-hibernating Myotis species including little brown bats and Indiana bats (Thogmartin et al. 2013, Russell et al. 2014, Erickson et al. 2014, Russell et al. 2015). These models are spatially explicit, birth-death-immigration-emigration models, and include two life stages (juvenile and adult). Bat movements, including hibernacula switching events (i.e., a bat overwintering in a different hibernacula than the previous winter), are simulated based on distance between hibernacula and published myotis fidelity rates. These models previously addressed the recovery potential of little brown bats under different mechanistic scenarios (i.e., the effects of white-nose syndrome abate over time, the effect of white-nose syndrome do not abate over time, the effects of white-nose syndrome are density-dependent). These models can be modified to address different mitigation scenarios (including the potential for small populations to recover, different hypothesized mechanisms of recovery, and the potential for mitigation tactics to speed recovery). 

Little brown bat (Myotis lucifugus) in the Shipp Room, Hellhole cave

Little brown bat (Myotis lucifugus) in the Shipp Room, Hellhole cave

(Credit: Dave Riggs. Public domain.)

 

Literature Cited

Russell, R.E., W.E. Thogmartin, R.A. Erickson, J. Szymanski, and K. Tinsley. 2015. Estimating the recovery potential of little brown bats in the eastern United States in the face of white-nose syndrome. Ecological Modeling 314:111–117.

Russell, R.E., K. Tinsley, R. A. Erickson, W.E. Thogmartin, and J. Szymanski. 2014. Estimating the spatial distribution of wintering little brown bat populations in the eastern United States. Ecology and Evolution 4:3746–3754.

Thogmartin, W.E., C. Sanders-Reed, J.A. Szymanski, R.A. King, L. Pruitt, P.C. McKann, M.C. Runge, and R.E. Russell. 2013. White-nose syndrome is likely to extirpate the endangered Indiana bat over large parts of its range. Biological Conservation 160:162–172.

Erickson, R. A., W.E. Thogmartin, R.E. Russell, J.E. Diffendorfer, and J. A Szymanski. 2014. A stage-structured, spatially explicit migration model for colonial species with a focus on Myotis bats. Letters in Biomathematics 1:157‒172.