No abstract

1973. Physiology of thermoregulation in the pika, Ochotona princeps. Can. J . Zool. 51: 11-16.The mean body temperature of pika measured by radiotelemetry under field and laboratory conditions was 40.1°C (range = 37.942.7) over an ambient temperature range of -9.3 to 24°C. The maximum daily fluctuation in any one individual was less than 2.6"C and no seasonal difference in the level of body temperature maintained was observed. Hypcrthermia and death occurred after a 2-h exposure to ambient temperatures higher than 28"C, inclusive.The basal metahl~c ratc was 1.53 cc 0 2 / g h and the thermal conductance was between 0.096 and 0.050 cc Ol/g h 'C, 143% and 101-53F1, sespecrively, of their predicted weight-specific values. The relatively high body temperature of pika 15 attributed to its high basal metabolic rate and good insulation. The low thermal conductance, which ind~cates a reduction of energy consumption at ambient tenlperaturc~ below the lower critical temperature (21°C), favors the overwinter survival of this species when only limited food storage is available. MACARTHUR,R.A., et L. C. H. WANG. 1973. Physiology of thermoregulation in the pika, Ochotona princeps. Can. J. Zool. 51 : 11-16. La tempkrature moyenne de l'ochotone, mesurk par radiotklkmktrie en nature et en laboratoire, est de 40.1°C (ktendue = 37.9 a 42.7) ii des tempkratures ambiantes allant de -9.3 a DOC. La !ariation maximale enregistree chez un individu, dans la m8me journk, est de moins de 2.6'C et le nlveau de tempdrature du corps est le meme en toutes saisons. Une exposition de 2 h ii des temperatures de 28°C ou plus cause l'hyperthermie et la mort. Le m6tabolisme de base est de 1.53 cc 0 2 / g h et la conductibilitk thermique varie entre 0.096 et 0.050 cc Oz/g h "C, reprhentant respectivement 143% et 101-53% des valeurs prkvues d'aprks le poids del'animal. La temperature relativement dlevk de l'ochotone est due ii son mktabolisme basal 8evk et son isolation efficace. La faible conductibilitk thermique, indice d'une reduction de la consommation d'dnergie une temp6rature ambiante infkrieure A la tempkrature critique minirnale (21°C), permet la survie de I'animal durant l'hiver, alors que les ressources alimentaires disponibles sont limitkes.praduit par le journal]

The telemetered heart rates (HR) of unrestrained female bighorn sheep (Ovis canadensis canadensis) were recorded under various behavioral and environmental circumstances. In all ewes HR varied positively with activity level and inversely with distance to a road traversing the study area. The HR recorded from animals moving at night or through timber by day were higher than during daytime movement across open slopes.Responses to transient stimuli varied greatly. The appearance of free-ranging canids evoked maximal increases in HR in all ewes. Vehicular traffic and aircraft elicited HR responses only at close range (< 200 m). Most (78.1%) HR responses to disturbing stimuli preceded or occurred in the absence of overt behavioral reactions. The HR usually peaked within 60 s of the onset of the response and recovered to predisturbance base line in less than 200 s. The appearance and continued presence (1–10 min) of a human within 50 m of the sheep resulted in a 20% rise in mean HR. The significance of these findings is discussed in relation to the behavior, ecology, and bioenergetics of bighorn sheep.

1974. Behavioral thermoregulation in the pika Ochotona princeps: a field study using radiotelemetry. Can. J. Zool. 52: 353-358. When either the level or duration of spontaneous activity is increased over an ambient temperature range of 2-2PC, tlie body temperalure of the ~k a shows e slight increase; the maximum Ourtua~ion obrerved war I.OC. Hawurer. none o?thr changer in body temperature proved to be significantly different from thal of the resting state (P < 0.05).In nature, pihas avoid hyperthermia I?y means of precise behavioral thermoregulation in which both dura~ion and levcl OF actlrity are regulated. A negative correlation was observed between the duration of time spent on the surface of the rocks, and the surface ambient temperature, over R range of 3-27C. Between 0930 and 1930 h, as the surface ambient temperature increased. ihe percentage of obscrvat~ons I n which the pika was below the rocks increased. and vice versa. By engaging in short bursrs of surface ac~ivity (usually Iess than a 3.5-min duration) followed by retreal to the cooler micrmlima~e beneath the rocks. pikas 8Fe able lo regulate their lmdy temperature precisely at a level only 2-?C hlow the upper lethal temperature. -MACARTHUR, R. A., et L. C. H. WANG. 1974. Behavioral thermoregulation in the pika Ochotona princeps: a field study using radiotelemetry. Can. J. Zool. 52: 353-358. Chez I'ochotone, lorsque l'intensitt ou la durCe de I'activitt spontank augmente, h une tempirature ambiante situte entre 2-28C, la temperature du corps augmente lkgkrement, la fluctuation maximale observk &ant de l.O°C. Ce ndant, aucun des changements de temphature du corps nest signfiativement different de etempirature au repos (P < 0.05). En nature, les ochotones Bvitent I'hyperthermie ar une r y l a t i o n thermique ricise.~socik au comportement et pendant laquelle sont c o n t r k s et la uree et I'intens~ti fe I'achv~tk. On constate une correlation negative entre la d u r k du tem s pass6 i la surface des rochers et la temperature arnbiante de surface, entre 3-27C. Entre 09f0 et 1930 h, ti mesure qu'aumente la temperature ambiante de surface, le pourcenta e de temps pass6 sous les rocheis au-pente et vice verw. En se limitant 21 de courtes ~eriodes jactivitt! en surface (ordinairement moms de 3.5rnin) suivies d'un retour i un microclimat plus frais, sous les rochers, les ochotones arrivent ? i contrbler la temperature de leur corps de fafon prkise, B un niveau de seulement 2-3C sous la tempirature letale supirieure.vraduit par le journal]

Muskrats experienced a steady decline in abdominal and subcutaneous body temperature (ΔTh) during unrestrained dives of 0.5- to 4-min duration. Extent of body cooling, postdive O2 consumption [Formula: see text], and metabolic recovery time increased both with time submerged and declining water temperature (3 – 30 °C). For each additional minute that a muskrat remained submerged, cost increased by 99 mL O2∙kg−1 in 3 °C, compared with 71 and 43 mL O2∙kg−1 in 20 and 30 °C water, respectively. Postdive [Formula: see text] correlated strongly with ΔTh incurred during diving. Mean [Formula: see text], during spontaneous activity in water, when animals were free to swim, dive, or float quietly on the surface, varied inversely with water temperature and directly with ΔTh. Temporal decline in Th during 25-min immersion was matched by a concurrent reduction in voluntary dive time. Mean [Formula: see text], immediately following withdrawal from water exceeded that during an equivalent period of immersion.