Abstract
The New England cottontail (Sylvilagus transitionalis) has experienced range contraction
in recent decades, stemming from habitat loss and fragmentation. As this is an imperiled species,
population monitoring may be both time- and resource-intensive. Integrative, non-invasive
measures, on the other hand, may be beneficial in evaluating habitat quality and better
understanding how environmental changes are impacting physiology and diet, and for guiding
conservation efforts. My dissertation evaluated how environmental stressors shape both the
physiological health and diet composition of New England cottontails in the Hudson Valley, NY.
I used fecal glucocorticoid metabolites (FGMs) to determine how environmental perturbations
impact perceived stress in wild populations, and how energetic demands shift in response to
seasonal changes and life-history events in captive individuals. Because New England cottontails
may engage in resource competition with a non-native species (eastern cottontails, Sylvilagus
floridanus) they may be outcompeted and consequently pushed into suboptimal shrubland
patches (among successional stages other than preferred mid-successional stage shrublands).
Such shifts in habitat may induce shifts in diet composition and breadth, which I evaluated by
means of DNA metabarcoding. My findings indicated that both eastern cottontail prevalence and
Japanese barberry stem density may serve as environmental stressors and thus correlate with
FGM concentrations in wild populations. Specifically, FGM concentrations were negatively
associated with Japanese barberry stem density in shrublands with high eastern cottontail
prevalence, suggesting that suboptimal forage may ameliorate perceived stress stemming from
resource competition. Seasonal shifts and reproductive demands also influenced FGM
concentrations, especially among captive females. Diet analysis revealed that New England
cottontail diets were narrowest in presumably high-quality, mid-successional shrublands
(potentially due to greater availability of preferred forage material) and broadened in ostensibly
suboptimal late-native and late-invasive shrublands in response to environmental pressures. This
finding supported the idea that New England cottontails function as facultative generalists.
Invasive barberry was present in the diet but underrepresented relative to its availability,
suggesting its use as a backup resource rather than preferred forage material. The findings of my
dissertation highlight the value of integrative, non-invasive approaches in evaluating habitat
quality and understanding species responses to environmental change.