Bioenergetics and thermal physiology of American water shrews (Sorex palustris)

Gusztak, R. W.; MacArthur, Robert A.; Campbell, Kevin L.

doi:10.1007/s00360-004-0465-x

Cited by 19 publications

(33 citation statements)

References 27 publications

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“…The estimated field MR of free-ranging little brown bats during summer was 29.9kJday -1 (Nagy et al, 1999), while that measured for solitary, captive bats was 17.4kJday -1 (O'Farrell et al, 1971). Thus, assuming a digestible energy efficiency of 91.2% (O'Farrell et al, 1971) and urinary energy losses of 5% (Gusztak et al, 2005), bats in our study fed to 50% and 100% satiation obtained 12.9-22.2% (0.862ϫ4.49kJ 3.87kJ) and 22.8-39.2% (6.82kJ), respectively, of their estimated daily energy requirements. Despite this relatively small proportion, they were still able to closely match their total energy expenditure with their energy intake under both the 'cold' and 'warm' ambient conditions.…”

Section: Discussionmentioning

confidence: 98%

Feasting, fasting and freezing: energetic effects of meal size and temperature on torpor expression by little brown batsMyotis lucifugus

Matheson

Campbell

Willis

2010

Journal of Experimental Biology

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Torpor is an adaptation for energy conservation employed by many species of small-bodied endotherms. However, surprisingly little is known regarding proximate factors influencing day-to-day variation in torpor expression in the wild. We used open-flow respirometry to quantify torpor expression in nine little brown bats (Myotis lucifugus, LeConte 1831) at two ambient temperatures (7 degrees C and 17 degrees C) following either sham feeding or consumption of a high-protein meal (50% or 100% of the mass required to reach satiation for each individual). Food consumption significantly increased the time spent normothermic before torpor entry but did not affect either the rate of body cooling or torpid metabolic rate. Bats did not fully exploit potential energy savings by maximising their use of torpor. Instead they varied torpor expression such that total energy expenditure over the course of each 22-h trial was balanced against gross energy intake immediately before the trial, independent of ambient temperature. This was accomplished by adjusting the timing of entry into torpor (thus altering the time spent torpid), rather than by modulating torpid metabolic rate. However, pre-trial body mass was also a significant predictor of torpor expression, which suggests that energy reserves combine with recent foraging success to influence individuals' decisions about depth and duration of their torpor bouts. We also present evidence that little brown bats use the heat generated through digestion (i.e. the heat increment of feeding) to substitute for active thermogenesis at sub-thermoneutral temperatures, thereby reducing the energetic costs of thermoregulation prior to torpor entry.

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Section: Discussionmentioning

confidence: 98%

Feasting, fasting and freezing: energetic effects of meal size and temperature on torpor expression by little brown batsMyotis lucifugus

Matheson

Campbell

Willis

2010

Journal of Experimental Biology

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“…Water shrews have predatory abilities that seem extraordinary given their small size and habit of diving in search of prey (11).…”

Section: Discussionmentioning

confidence: 99%

“…These latencies are remarkably short, and the behaviors include accurate directional responses suggesting the shrew's nervous system might be specialized for rapid processing of sensory information. In addition to facilitating prey capture, moving and foraging quickly may be required, because small size dictates low O 2 storage capacity and high mass-specific metabolism, limiting water shrews to short dives (11).…”

Section: Discussionmentioning

confidence: 99%

Water shrews detect movement, shape, and smell to find prey underwater

Catania

Hare²,

Campbell³

2008

Proc. Natl. Acad. Sci. U.S.A.

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American water shrews (Sorex palustris) are aggressive predators that feed on a variety of terrestrial and aquatic prey. They often forage at night, diving into streams and ponds in search of food. We investigated how shrews locate submerged prey using highspeed videography, infrared lighting, and stimuli designed to mimic prey. Shrews attacked brief water movements, indicating motion is an important cue used to detect active or escaping prey. They also bit, retrieved, and attempted to eat model fish made of silicone in preference to other silicone objects showing that tactile cues are important in the absence of movement. In addition, water shrews preferentially sniffed model prey fish and crickets underwater by exhaling and reinhaling air through the nostrils, suggesting olfaction plays an important role in aquatic foraging. The possibility of echolocation, sonar, or electroreception was investigated by testing for ultrasonic and audible calls above and below water and by presenting electric fields to foraging shrews. We found no evidence for these abilities. We conclude that water shrews detect motion, shape, and smell to find prey underwater. The short latency of attacks to water movements suggests shrews may use a flush-pursuit strategy to capture some prey.insectivore ͉ olfaction ͉ somatosensory ͉ tactile ͉ whiskers

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“…Conversely, red-toothed shrews are not known to enter torpor and are believed to be Holarctic in origin. Members of this clade further possess relatively high, stable core body temperatures, and exhibit the highest mass-specific rates of basal O 2 consumption recorded among eutherian mammals (Gusztak et al 2005;McNab 1991). In this light, it is surprising that-apart from a single O 2 affinity measurement (oxygen half-saturation pressure or P 50 = 32.8 mmHg at 37°C, pH 6.8) of a dilute hemolysate solution from a short-tailed shrew, Blarina brevicauda (Foreman 1954)-no information appears to be available on the functional properties of the hemoglobin (Hb) of any red-toothed shrew.…”

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confidence: 98%

Molecular and physicochemical characterization of hemoglobin from the high-altitude Taiwanese brown-toothed shrew (Episoriculus fumidus)

et al. 2012

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Red-toothed shrews (subfamily Soricinae) exhibit the highest mass-specific rates of O₂ consumption recorded among eutherian mammals, though surprisingly no data appears to be available on the functional characteristics of their hemoglobin (Hb). As a first step in addressing this shortcoming, we investigated the O₂ binding characteristics of Taiwanese brown-toothed shrew (Episoriculus fumidus) Hb and its temperature and pH dependence in the absence and presence of anionic red blood cell effectors. Although comparative data regarding the intrinsic O₂ affinity of other shrew species are currently unavailable, our data suggest that the sensitivity of this high-elevation endemic species' Hb to allosteric effector molecules is similar to that of the two lowland species of white-toothed (crocidurine) shrews examined to date. The efficient exploitation of blood O₂ reserves by E. fumidus appears to be achieved via synergistic modulation of O₂ affinity by Cl⁻ and organic phosphates that moreover dramatically lowers the overall enthalpy of oxygenation of their Hb. Oxygen unloading is presumably further enhanced by a relatively high Bohr effect (ΔLog P₅₀/ΔpH = -0.69) and marked reduction in the titratable histidine content (predicted low proton buffering value) of the component globin chains relative to human HbA. Notably, however, the limited data available suggest these latter attributes may be widespread among shrews and hence likely are not adaptations to chronic altitudinal hypoxia per se.

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Bioenergetics and thermal physiology of American water shrews (Sorex palustris)

Cited by 19 publications

References 27 publications

Feasting, fasting and freezing: energetic effects of meal size and temperature on torpor expression by little brown batsMyotis lucifugus

Feasting, fasting and freezing: energetic effects of meal size and temperature on torpor expression by little brown batsMyotis lucifugus

Water shrews detect movement, shape, and smell to find prey underwater

Molecular and physicochemical characterization of hemoglobin from the high-altitude Taiwanese brown-toothed shrew (Episoriculus fumidus)

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