title: High-altitude diving in river otters: coping with combined hypoxic stresses.
abstract: 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-O(2)) 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 O(2) 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.
authors.affiliation: Department of Zoology and Physiology, University of Wyoming, Laramie, WY 82071, USA. craitj@uwyo.edu
authors.forename: Jamie R
authors.initials: JR
authors.lastname: Crait
authors.forename: Henry D
authors.initials: HD
authors.lastname: Prange
authors.forename: Noah A
authors.initials: NA
authors.lastname: Marshall
authors.forename: Henry J
authors.initials: HJ
authors.lastname: Harlow
authors.forename: Clark J
authors.initials: CJ
authors.lastname: Cotton
authors.forename: Merav
authors.initials: M
authors.lastname: Ben-David
mesh_terms: D000531:Altitude; D000818:Animals; D001774:Blood Chemical Analysis / Q000662:veterinary; D004242:Diving / Q000502:physiology*; D005260:Female; D006454:Hemoglobins / Q000378:metabolism; D008297:Male; D010041:Otters / Q000502:physiology*; D010100:Oxygen / Q000097:blood / Q000378:metabolism; D014861:Washington; D014959:Wyoming
chemical_list: D006454:Hemoglobins; D010100:Oxygen