Physiology of thermoregulation in the pika, <i>Ochotona princeps</i>

MacArthur, Robert A.; Wang, Lawrence C.H.

doi:10.1139/z73-002

Cited by 96 publications

(97 citation statements)

References 9 publications

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“…Data from our present study indicate that plateau pikas showed no winter reduction in their body mass, which is consistent with the previous Wndings (Wang and Wang 1990and Wang , 1996. It is interesting that the American pikas (Ochotona princeps), which remained active in winter, also showed no seasonal changes in body mass (MacArthur et al 1973), though the ecology of the two pika species is diVerent. American pikas inhabit areas which are covered by snow in winter and they can feed on stored food under the snow cover (Wunder 1992).…”

Section: Seasonal Variations In Body Mass and Body Fat Masssupporting

confidence: 92%

Seasonal thermogenesis and body mass regulation in plateau pikas (Ochotona curzoniae)

2006

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Changes in photoperiod, ambient temperature and food availability trigger seasonal acclimatization in physiology and behavior of many animals. In the present study, seasonal adjustments in body mass and in several physiological, hormonal, and biochemical markers were examined in wild-captured plateau pikas (Ochotona curzoniae) from the Qinghai-Tibetan plateau. Our results showed that plateau pikas maintained a relatively constant body mass throughout the year and showed no seasonal changes in body fat mass and circulating levels of serum leptin. However, nonshivering thermogenesis, cytochrome c oxidase activity, and mitochondrial uncoupling protein 1 (UCP1) contents in brown adipose tissues were significantly enhanced in winter. Further, serum leptin levels were positively correlated with body mass and body fat mass while negatively correlated with UCP1 contents. Together, these data suggest that plateau pikas mainly depend on increasing thermogenic capacities, rather than decreasing body mass, to cope with cold, and leptin may play a potential role in their thermogenesis and body mass regulation.

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Section: Seasonal Variations In Body Mass and Body Fat Masssupporting

confidence: 92%

Seasonal thermogenesis and body mass regulation in plateau pikas (Ochotona curzoniae)

2006

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“…The instantaneous difference between the surface and subsurface environment routinely exceeded 20 C°at some sites. Pikas maintain a high resting body temperature ( x = 40.1°C) and a relatively low upper lethal temperature (x = 43.1°C; [30,84]). Endothermic animals compensate for ambient temperatures that exceed their upper critical temperature (UCT) by increasing metabolism [85], or by taking advantage of convective/conductive heat loss.…”

Section: Discussionmentioning

confidence: 99%

Microrefuges and the occurrence of thermal specialists: implications for wildlife persistence amidst changing temperatures

Hall

Chalfoun

Beever

et al. 2016

Clim Chang Responses

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Background: Contemporary climate change is affecting nearly all biomes, causing shifts in animal distributions, phenology, and persistence. Favorable microclimates may buffer organisms against rapid changes in climate, thereby allowing time for populations to adapt. The degree to which microclimates facilitate the local persistence of climate-sensitive species, however, is largely an open question. We addressed the importance of microrefuges in mammalian thermal specialists, using the American pika (Ochotona princeps) as a model organism. Pikas are sensitive to ambient temperatures, and are active year-round in the alpine where conditions are highly variable. We tested four hypotheses about the relationship between microrefuges and pika occurrence: 1) Local-habitat Hypothesis (local-habitat conditions are paramount, regardless of microrefuge); 2) Surface-temperature Hypothesis (surrounding temperatures, unmoderated by microrefuge, best predict occurrence); 3) Interstitial-temperature Hypothesis (temperatures within microrefuges best predict occurrence), and 4) Microrefuge Hypothesis (the degree to which microrefuges moderate the surrounding temperature facilitates occurrence, regardless of other habitat characteristics). We examined pika occurrence at 146 sites across an elevational gradient. We quantified pika presence, physiographic habitat characteristics and forage availability at each site, and deployed paired temperature loggers at a subset of sites to measure surface and subterranean temperatures. Results: We found strong support for the Microrefuge Hypothesis. Pikas were more likely to occur at sites where the subsurface environment substantially moderated surface temperatures, especially during the warm season. Microrefugium was the strongest predictor of pika occurrence, independent of other critical habitat characteristics, such as forage availability. Conclusions: By modulating surface temperatures, microrefuges may strongly influence where temperature-limited animals persist in rapidly warming environments. As climate change continues to manifest, efforts to understand the changing dynamics of animal-habitat relationships will be enhanced by considering the quality of microrefuges.

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“…As a result, it is possible to compare closely related species in environments that differ markedly in the amount of oxygen available but are comparable in other environmental parameters (Table 1). Pikas are extremely active foragers year-round and have high metabolic rates (MacArthur and Wang, 1973) with no form of metabolic reduction such as daily torpor, aestivation or hibernation (Krear, 1965;MacArthur and Wang, 1973). Thus, their demand for a high rate of ATP turnover is not decreased by metabolic reduction strategies.…”

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confidence: 99%

Metabolic enzyme activities across an altitudinal gradient: an examination of pikas (genusOchotona)

Sheafor

2003

Journal of Experimental Biology

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Changes in metabolic enzyme activities were examined in three species of pikas that occur over a range of altitudes. Because these closely related mammals live in comparable ecosystems and face similar environmental factors regardless of altitude, modifications of metabolic machinery are probably due to differences in oxygen availability. Citrate synthase (CS), β-hydroxyacyl CoA dehydrogenase (HOAD) and lactate dehydrogenase (LDH) activities were measured in heart, diaphragm, vastus lateralis, gastrocnemius and soleus muscles. Additionally, the activity levels of both M-LDH (skeletal muscle type) and H-LDH (heart type) isozymes were quantified in tissue samples. Pikas from high altitude had greater CS and HOAD activities in heart and diaphragm when compared with pikas from low altitude, while activity levels did not differ in skeletal muscles. The increase in oxidative enzyme activities in tissues with high metabolic demand is thought to enhance oxygen utilization when oxygen availability is low and may reflect greater metabolic demand on heart and diaphragm tissue. Pikas from high altitude were also found to have greater total LDH activities in all tissues examined. High altitude animals had dramatically higher H-LDH activity (2.3-3.8 times greater) while M-LDH activity was more comparable (1.8 times lower to 1.7 times greater) when compared with low altitude animals. High total LDH activity enables pikas to perform short bouts of anaerobic activity, while high levels of H-LDH isozymes may serve to enhance lactate removal and decrease recovery time in animals living at high altitude.

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Physiology of thermoregulation in the pika, Ochotona princeps

Cited by 96 publications

References 9 publications

Seasonal thermogenesis and body mass regulation in plateau pikas (Ochotona curzoniae)

Seasonal thermogenesis and body mass regulation in plateau pikas (Ochotona curzoniae)

Microrefuges and the occurrence of thermal specialists: implications for wildlife persistence amidst changing temperatures

Metabolic enzyme activities across an altitudinal gradient: an examination of pikas (genusOchotona)

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