High altitude diving in river otters: coping with combined hypoxic stresses

River otters (Lontra canadensis) are highly active, semi-aquatic mammals indigenous to a range of elevations and represent an appropriate model for assessing the physiological responses to diving at altitude. In this study, we performed blood gas analyses and compared blood chemistry of river otters from a high-elevation (2357 m) population at Yellowstone Lake with a sea-level population along the Pacific coast. Comparisons of oxygen dissociation curves (ODC) revealed no significant difference in hemoglobin-oxygen (Hb-O2) binding affinity between the two populations - potentially because of demands for tissue oxygenation. Instead, high-elevation otters had greater Hb concentrations (18.7 g dl-1) than sea-level otters (15.6 g dl-1). Yellowstone otters displayed higher levels of the vasodilator nitric oxide (NO), and half the concentration of the serum protein albumin, possibly to compensate for increased blood viscosity. Despite compensation in several hematological and serological parameters, theoretical aerobic dive limits (ADL) were similar between high-elevation and sea-level otters because of the lower availability of O2 at altitude. Our results suggest that recent disruptions to the Yellowstone Lake food web could be detrimental to otters because at this high elevation, constraints on diving may limit their ability to switch to prey in a deep-water environment

Appendix A. A description of model selection techniques used to predict occurrence of river otter latrine sites on Yellowstone Lake and tributary streams, along with figures showing frequency distribution distances from all latrines to the nearest non-latrine site and the frequency distribution distances from latrines to the nearest non-latrine site where stable isotope samples were collected.

A description of model selection techniques used to predict occurrence of river otter latrine sites on Yellowstone Lake and tributary streams, along with figures showing frequency distribution distances from all latrines to the nearest non-latrine site and the frequency distribution distances from latrines to the nearest non-latrine site where stable isotope samples were collected

Appendix B. Tables showing final logistic regression models used to predict occurrence of river otter latrine sites on Yellowstone Lake and tributary streams and intercept coefficients for regressions of δ15N vs. fecal deposition rate for plants growing on otter latrine sites compared with δ15N of plants growing on non-latrine sites.

Tables showing final logistic regression models used to predict occurrence of river otter latrine sites on Yellowstone Lake and tributary streams and intercept coefficients for regressions of δ15N vs. fecal deposition rate for plants growing on otter latrine sites compared with δ15N of plants growing on non-latrine sites

Appendix C. Tables showing plant genera and plant species identified on latrine sites and non-latrine sites on Yellowstone Lake and tributary streams and the number of occurrences of selected plant genera on latrine and non-latrine sites.

Tables showing plant genera and plant species identified on latrine sites and non-latrine sites on Yellowstone Lake and tributary streams and the number of occurrences of selected plant genera on latrine and non-latrine sites