Mean Standard Metabolic Rate Research Articles

Energy Metabolism and Thermoregulation in Juvenile Harbor Seals (Phoca vitulina) in Air

We measured metabolic rates (mL O₂ h⁻¹, converted to kcal d⁻¹), deep body temperatures ($T_{b}'s$; ° C), and skin temperatures ($T_{s}'s$; ° C), and calculated whole-animal thermal conductances (C; mL O₂ g⁻¹ h⁻¹ °C⁻¹), of five juvenile harbor seals (Phoca vitulina concolor) at ambient air temperatures ($T_{a}'s$) between -10° and 32.5° C. The mean thermal neutral zone (TNZ) of our seals extended from a lower critical temperature ($T_{lc}$) of -2.3° ± 0.03° C to an upper critical temperature ($T_{uc}$) of 25.1° + 0.07° C. Hyperthermia was observed at $T_{a}$ = 32.5° C. Mean standard metabolic rate was 1,399 ± 92 kcal d⁻¹, approximately 1.6 times the value expected for adult animals of similar body mass. Mean $T_{b}$ increased from 38.2° + 0.3° C at $T_{a}$ = 27.5 C and reached 40.2° + 1.4° C at $T_{a}$ = 32.5° C. Skin temperatures decreased with decreasing $T_{a}$ but remained well above $T_{a}$. Mean C decreased from $T_{a}$ = 32.5°C until it reached a minimum value of. 0.012 mL O₂ g⁻¹ h⁻¹°C⁻¹ at 1.0°C; i...

Temperature regulation and water economy in desert wolves

The wolf, Canis lupus, inhabits deserts at the margins of its broad circumpolar, holarctic range. The wolf subspecies C. l. pallipes (adult body mass 18-22 kg) inhabits arid areas in Israel. Other desert-dwelling canids of similar size reduce their internal heat load through low metabolic rate, but must drink water to survive. To ascertain whether desert wolves behave similarly we measured metabolic rate and evaporative water loss in three hand-reared female wolves under controlled conditions, at ambient temperatures between 0 and 40°C. Using tritiated water, we also measured their total body water and water turnover rates while they were kept in a 0·16 ha outdoor enclosure with shade and water available ad lib. The wolves had a wide thermal-neutral zone which included all test ambient temperatures. Mean standard metabolic rate was 1·20 W·kg -1 in winter and 1·59 W kg -1 in summer; winter and summer standard metabolic rates were respectively, 33·6% and 12·15% lower than predicted allometrically. Evaporative water loss was significantly higher in summer than in winter. Total body water averaged 68% of body mass in both seasons, but mean water turnover rate was significantly higher in summer (97·52 ml·kg -1·day -1) than in winter (27·45 ml · kg -1 · day -1). After 21 h of water deprivation in late summer, wolves lost 11·8% of their initial body mass. They made up 44% of their water deficit in their first post-dehydration drink and the rest over 24 h. Morphological examination of kidneys from 2 road-killed males indicated no extraordinary renal concentrating ability. The data suggests that wolves must drink to meet the physiological challenge posed by the hot desert climate.

Metabolic Rate of Bobcats as Influenced by Seasonal Temperatures

We used indirect respiration calorimetry to measure metabolic rate and delineate the lower critical temperature (T,,) of bobcats (Felis rufus) during summer, fall, winter, and spring. The yearly mean standard metabolic rate (SMR) within the thermoneutral zone was 79 kcal/kg body weight (BW)o75/day (range = 69-88 kcal/kg BW075/day). No difference (P < 0.05) was found between winter and summer SMR's. We measured T,, of 22.5, 7.7, -2.2, and 5.0 C for summer, fall, winter, and spring, respectively, which were similar to mean seasonal temperatures in New Hampshire. Bobcat metabolic rate increased linearly below TLC. Metabolic measurements and regional temperature information indicate that northern bobcats are commonly exposed to energy-costly temperatures during winter. This high thermoregulatory cost likely results in behavioral adaptations; e.g., microhabitat selection and sunning. J. WILDL. MANAGE. 53(1):202-205 Energetic information for northeastern bobcats includes food habits (Pollack 1951, Westfall 1956, Litvaitis et al. 1984) and digestibility of several prey species (Golley et al. 1965, Powers 1984); however, bobcat metabolic rate has only been measured during the winter (Gustafson 1984). Our understanding of bobcat energetics is limited beyond the scope of these studies. A knowledge of baseline energy requirements of bobcats, when coupled with food consumption and food assimilation information, allows the calculation of minimum prey budgets of freeranging bobcats. Impacts of climate, changing land-use patterns, and forestry practices on bobcats and their resources can likewise be evaluated through a better understanding of bobcat energetics. The purpose of our study was to determine seasonal metabolic rates and thermoneutral zones of bobcats acclimated to natural ambient temperature and photoperiod. We acknowledge the help of numerous students and the constructive reviews of E. N. Francq and J. A. Litvaitis. This project was supported with Pittman-Robertson funds (PR W-81This content downloaded from 157.55.39.102 on Thu, 23 Jun 2016 07:08:29 UTC All use subject to http://about.jstor.org/terms J. Wildl. Manage. 53(1):1989 BOBCAT METABOLISM * Mautz and Pekins 203 R-1) through the New Hampshire Fish and Game Department and McIntire-Stennis funds. This is Scientific Contribution 1538 from the New Hampshire Agricultural Experiment Sta-

Seasonal changes in standard metabolic rates in the white-browed scrubwren Sericornis frontalis (Acanthizidae) from arid, semi-arid and mesic environments

1. 1. Standard metabolic rates (SMRs) of S. frontalis from resident populations at three sites in Western Australia, ranging from arid, through semi-arid to mesic environments, were measured in summer and winter. 2. 2. Significant seasonal differences in the mean SMR were observed only in scrubwrens from the arid environment where the mean (±SE) SMR was 31.3 ±1.7 ml O 2/10g·h in summer compared with 38.6 ±3.5 ml O 2/10g·h in winter. 3. 3. SMRs recorded in the arid zone were markedly lower than those measured in semi-arid and mesic areas in summer only. The lowered SMR appears to be an adaptation for (a) reducing energy expenditure as, although there is only a slight reduction in the available food supply in summer, foraging time is reduced by the need to shelter from the heat, (b) reducing production of body heat, and (c) conservation of body water. 4. 4. Possible causes of a high mean SMR recorded in scrubwrens in the semi-arid region in one summer sampling period are discussed.

Energetics of Concertina Locomotion in Bipes biporus (Reptilia: Amphisbaenia)

Rates of oxygen consumption and whole-body lactate concentrations were measured in adult Bipes biporus (x SVL = 171.6 mm; x mass = 5.19 g; x body temperature = 25 C) during: 1) minimal activity (standard metabolic rate); 2) 30 min of voluntary, concertina locomotion; and 3) 2 min of intense, forced exercise. Mean rate of oxygen consumption during concertina locomotion (Vo2 conc = 0.214 ml 02/g'h) was significantly greater than mean standard metabolic rate (Vo2 stan = 0.035 ml 02/g h), and was 36% of that during forced exercise (Vo2 exer = 0.601 ml O2/g h). Mean lactate concentration during concertina locomotion (0.115 mg lactate/g body mass) did not differ significantly from that during minimal activity (0.129 mg/g). However, forced exercise resulted in a significant increase in mean lactate content (0.442 mg/g). Mean locomotor speed during constant, voluntary concertina locomotion was 0.1 km/h. The total cost of transport (=TCT) for B. biporus at 0.1 km/h and 25 C was 2.1-2.2 ml O2/ g km and is estimated to be, at similar speed and temperature, approximately as energetically efficient as lateral undulation in the snake, Thamnophis sirtalis (TCT = 2.2 ml O2/gkm), and from 58-67% as expensive as quadrupedal lomotion in two species of lizards (Cnemidophorus murinus: TCT = 3.2 ml 02/g km; Dipsosaurus dorsalis: TCT = 3.7 ml 02/g km).

Rates of oxygen consumption in four species of seabird at Palmer Station, Antarctic Peninsula

1. 1. We determined standard metabolic rates (SMR) of wild-caught adults of the Adelie penguin, southern giant fulmar, blue-eyed shag, and South Polar skua at Palmer Station, Antarctica, during January and February 1981. Oxygen consumption was measured volumetrically in a closed system at temperatures between 2 and 12°C. 2. 2. Mean SMR varied between 0.82 1 O 2/kg per hr for male fulmars and 1.301 O 2/kg per hr for unsexed adult skuas. Values were 174–198% of those predicted by the Lasiewski-Dawson equation for nonpasserines. 3. 3. The SMR of the Adelie penguin was considerably higher than that reported in other studies and higher than most values for other species of penguins. 4. 4. Our measurements of oxygen consumption agree with some estimates of metabolism based upon loss of mass by fasting birds during incubation.

Further Observations on Thermoregulation in the Brooding Female Python molurus bivittatus (Serpentes: Boidae)

in ambient temperature (TA) with an increase in oxygen consumption and contraction rate and was able to maintain a stable body temperature (TB) above 33 C until TA fell below 26 C. At a TA of 23 C the temperature differential TB - TA was 8.3 C and oxygen consumption had increased to a mean of 169 ml 02 kg-lhr-1, 20 times that of the non-gravid animal at the same TA. An increase of TA caused a decrease of contraction rate and oxygen consumption. Mean daily oxygen consumption of the eggs during the last 9 days of incubation ranged from 110 to 130 ml 02 kg-lhr-1. Mean standard metabolic rate of day-old hatchlings was 124 ml 02 kg-lhr-1 at a TA of 28 C. Air samples from among the eggs inside the body coil during incubation had a CO2 concentration of 1%. Standard metabolic rate of the non-gravid animal increased with temperature, but not in a simple, exponential fashion.

Temperature regulation in the Dusky Munia, Lonchura fuscans (Cassin) (Estrildidae)

Dusky munias are small (9.5 g) tropical seed-eating members of the family Estrildidae. Adaptations of munias to hot-humid conditions were examined by measuring body temperatures (Tb), rates of oxygen consumption [V(O2)] and evaporative water loss (Mwe) at night at ambient temperatures (Ta) between 17 and 44�C. Within the zone of thermal neutrality (30-39�C) night-time Tb averaged 38.9�C (range 37.6-41.l�C). Above 30�C, Tb increased with increasing To, reaching a maximum of 44.1�C at a Ta of 43.8�C. For the most part, dusky munias were unable to maintain Tb lower than Ta at high temperatures. The mean standard metabolic rate of munias was 1.87 ml O2 g-1 h-1. This is only 51% of the value predicted for passerine birds of comparable size. Below thermal neutrality, V(O2) (in ml g-l h-1) varied with Ta (�C) in accordance with the equation V(O2) = 8.37-0.218Ta. The slope of the line relating V(O2) to Ta below thermal neutrality is 19% lower than predicted, indicating that munias are better insulated than other birds of comparable size. Dusky munias have relatively high rates of Mwe at Ta's below 34�C (mean 7.68 mg water g-1 h-1), but exhibit little capacity to increase the rate of evaporation at high Ta's. Review of metabolic data for birds reveals that the standard metabolic rate of tropical species averages 67% of the level predicted from body mass. Thus, adaptation to hot-humid climates appears to have involved a reduction in the level of metabolism.

Respiration in relation to ion uptake in the crayfish Austropotamobius pallipes (Lereboullet).

1. O2 uptake was determined for periods of 23-46 h in salt-depleted crayfish held in deionized water (DW) or Na-free media at 10 degrees C. These media were replaced by artificial lakewater media (ALW) containing 0-2-0-6 mM Na and O2 uptake was again determined for periods of 24-66 h. 2. During net ion uptake in ALW the metabolic rate was either elevated or depressed. Standard metabolism in ALW altered by amounts equivalent to 0-1 - 15-5% (mean 6-4 (15) +/- 4-4% S. D.) of the metabolic rate measured during salt-depletion. On three occasions the metabolic rate was elevated by 22-0 - 66-7%, but some of this increase may have been due to locomotor activity. 3. The calculated values for thermodynamic work involved in ion transport were 0-056 - 0-268 J/10 g. h at 10 degrees C, or 1-5 - 7-2% of the mean standard metabolic rate. Most of the observed changes in metabolic rate lie within the limits of experimental error (ca. +/- 7%). Hence the energetic cost of ion transport is too small for direct measurement in intact crayfish.

Metabolic and Behavioral Thermoregulation in the Long-Tailed Vole, Microtus longicaudus

The difference between the mean standard metabolic rates of Microtus longicaudus acclimated to 15°C (2.62 cubic centimeters 02 per gram-hour) and those acclimatized at natural temperatures averaging 11°C (2.67 cc 02/g-hr) is not statistically significant. These values are 60 to 70 per cent higher than predictions based on body weight. The relationship of oxygen consumption to ambient temperature (0 to 40°C) was determined for voles in and out of their nests. The zone of thermoneutrality while in the nest (20 to 30°C) was 5° wider than when not in the nest (25 to 30°C). The relationship of oxygen consumption to ambient temperature below thermoneutrality was linear, described by the equation Y = 5.54 − .146 X (in the nest) and Y = 7.26 − .181 X (out of the nest). Above thermoneutrality, the relationship becomes curvilinear and is described by the equation log Y =.455 − .017 X . Visual observations at temperatures above thermoneutrality revealed no special behavioral patterns for thermoregulation. Body temperature of M . longicaudus was independent of ambient temperature between 5° and 25°C, averaging 37.4°C.