Use of stable isotopes in the continental-scale ecology of small mammals

Background/Question/Methods

Extreme events including droughts, severe storms, and fire are increasingly impacting many ecosystems. These disturbances will likely change the water balance of these systems, as well as the structure and function of ecological communities. The National Ecological Observatory Network (NEON) will measure the drivers, responses, and important feedbacks associated with environmental and ecological change at 60 sites across the United States. Terrestrial measurements will include biogeochemistry and organismal diversity. Small mammal sampling is one component of assessing organismal diversity, and focuses on demography, community dynamics, diversity, and prevalence of select pathogens, as they relate to climate and other drivers. In conjunction with live-trapping, we aim to collect and archive a select group of tissues to enable independent PIs to address a diversity of research questions. Here we focus on the interesting and important questions regarding water stress and its effects on small mammals that could be addressed through stable isotope analysis. We present our proposal and associated rationale for archiving small mammal tissue for isotopic analyses by members of the natural sciences community.

Results/Conclusions

We propose to collect fur samples from adult individuals only, in order to avoid confounding effects of juvenile molting. Fur samples (approximately 10 hairs) will be collected with forceps from the dorsal side of each individual’s neck, and then sealed in a coin envelope for dry ambient storage. Long-term storage of these samples will be organized within NEON’s larger archival effort of storing a diversity of samples at various natural history collections. Analysis of isotopes, like nitrogen (δ¹⁵N), oxygen (δ ¹⁸O), and hydrogen (δ D), within the fur samples could provide a seasonal view (on the order of months) of water stress, either by indicating isotopic enrichment in the organisms’ diet or water source, or by elucidating differences in the metabolic responses between obligate drinker and drought-tolerant species. While independently important, this dataset could also help provide a more complete picture of community dynamics by providing insight into a potential mechanistic driver of changes in small mammal abundance and diversity.  It could also allow researchers to draw linkages between community dynamics and factors such as plant productivity, soil biogeochemistry, climatic variables, and the spread of infectious diseases.