My research focuses on understanding the demography, distribution, and trend of wildlife populations. Understanding these relationships is crucial because habitat and environmental variables are critical drivers of species’ abundances. In particular, I am interested in how variation in abiotic factors throughout the annual cycle impacts the population dynamics of migratory species. Quantifying which environmental and anthropogenic factors drive population dynamics at regional scales is further complicated because it depends on the extent of migratory connectivity, the integration of population processes throughout the annual cycle, and the quantity/quality of data available.
My current research program combines empirical data (both researcher-collected and citizen science) with innovative quantitative methods to address problems such as:
- How do anthropogenic changes influence habitat quality and populations?
- How do events and conditions in different stages of the annual cycle influence subsequent stages and consequently survival and reproduction rates?
- What types of management actions can mitigate declines in species’ abundances?
My work spans a broad range of taxa, as demonstrated by my projects involving birds, butterflies, and mammals. I am always eager to establish new collaborations to expand these research areas!
Recent research highlights:
In a soon-to-be published study in Ecography (coming mid-May 2017), my co-authors and I analyzed monarch butterfly monitoring data collected by citizen scientists in Illinois. We developed negative binomial regression models to estimate monarch abundance during recruitment in Illinois as a function of local climate, site-specific crop cover, and county-level herbicide (glyphosate) application. We also incorporated cross-seasonal covariates, including annual abundance of overwintering monarchs in Mexico and climate conditions during spring migration and breeding in Texas.
We provide the first empirical evidence of a negative association between county-level glyphosate application and local abundance of adult monarchs, particularly in areas of concentrated agriculture. We also found that wetter, and to a lesser degree, cooler springs in Texas were associated with higher summer abundances in Illinois. Site-specific abundance of monarchs averaged approximately 1 fewer butterfly per site from 2004 – 2013 than from 1994 – 2003, suggesting a recent decline in local abundance of monarch butterflies on their summer breeding grounds in Illinois.
I recently co-authored a publication with fellow Zipkin Lab member Dr. Sam Rossman (and others) in which we introduced a new model (‘dynamic N-occupancy‘) capable of providing accurate estimates of local abundance, population gains (reproduction/immigration), and apparent survival probabilities while accounting for imperfect detection using only detection/nondetection data.
We validated our model using simulations and then applied it to estimate spatiotemporal heterogeneity in abundances of barred owls within a recently invaded region in Oregon. In our paper, we discuss the potential conservation implications of our findings. Our dynamic N-occupancy model greatly improves inferences on individual-level population processes from occupancy data by explicitly modeling the latent population structure. Check out the MSU press release here!
In a 2016 publication, my co-authors and I analyzed data collected by citizen scientists (via state-wide butterfly monitoring networks) to estimate climate impacts on monarch butterflies breeding in the Midwest. The aims of this study were two-fold:
- To develop a quantitative method to evaluate confidence in predictions of ecological responses to changing climate conditions
- To use this approach to assess spatio-temporal synchrony among distinct study regions within the breeding range of migratory monarch butterflies
We used Bayesian negative binomial regression models to estimate weekly site-specific summer abundances of monarchs in the Midwest as a function of climate conditions experienced during a shared spring migration/breeding phase in Texas and separate summer recruitment periods in Ohio and Illinois. Check out the MSU press release here!
Graduate studies research questions:
At the heart of my dissertation research was the fundamental question: How can studying variation within and among individuals be used to conserve a population effectively? Using banding data, I aimed to improve management of the Great Lakes piping plover by:
- Determining how parental experience influenced reproductive success
- Learning which fitness-related traits were heritable and which were environmentally-determined and thus susceptible to impacts of global climate change
- Teasing apart the relative influences of various environmental factors at pre-fledging, post-fledging, and adult stages to more precisely inform recovery actions
- Improving the captive-rearing program by determining causes of the lower survival rates of captive-reared birds post-release
List of publications (does not include in press or in review; see CV):
Rossman, R., Yackulic, C.B., Saunders, S.P., Reid, J., Davis, R., Zipkin, E.F. 2016. Dynamic N-occupancy models: estimating demographic rates and local abundance from detection-nondetection data. Ecology 97:3300-3307.
Saunders, S., Ries, L., Oberhauser, K., Zipkin, E. 2016. Evaluating confidence in climate-based predictions of population change in a migratory species. Global Ecology & Biogeography 25:1000-1012
Saunders, S., Cuthbert, F. 2015. Chick mortality leads to male-biased sex ratios in the endangered Great Lakes piping plover. Journal of Field Ornithology 86:103-114
Saunders, S., Cuthbert, F. 2014. Genetic and environmental influences on fitness-related traits in an endangered shorebird population. Biological Conservation 177:26-34
Claassen, A., Arnold, T., Roche, E., Saunders, S., Cuthbert, F. 2014. Factors influencing nest survival and renesting by piping plovers in the Great Lakes region. The Condor: Ornithological Applications 116:394-407
Saunders, S., Arnold, T., Roche, E., Cuthbert, F. 2014. Age-specific survival and recruitment of piping plovers (Charadrius melodus) in the Great Lakes region. Journal of Avian Biology 45:437-449
Saunders, S., Harris, T., Traylor-Holzer, K., Goodrowe-Beck, K. 2014. Factors influencing breeding success, ovarian cyclicity, and cub survival in zoo-managed tigers (Panthera tigris). Animal Reproduction Science 144:38-47
Saunders, S., Wei Ying Ong, T., Cuthbert, F. 2013. Auditory and visual threat recognition in captive-reared Great Lakes piping plovers. Applied Animal Behaviour Science 144:153-162
Brudney, L., Arnold, T., Saunders, S., Cuthbert, F. 2013. Survival of piping plover chicks in the Great Lakes region. Auk 130-150-160
Saunders, S., Roche, E., Arnold, T., Cuthbert, F. 2012. Female site familiarity increases fledging success in piping plovers (Charadrius melodus). Auk 129:329-337