Small migratory birds employ a wide range of behavioural and physiological strategies to accelera... more Small migratory birds employ a wide range of behavioural and physiological strategies to accelerate their fuel accumulation rate at migratory stopovers. Although they could potentially reduce their rest-phase energy requirements by huddling with conspecifics, to date only anecdotal information exists about this behaviour. We found that resting Blackcaps (Sylvia atricapilla) regularly huddled in groups of two to six individuals in aviaries during migratory stopover. This occurred in spring migration in the Negev Desert and in autumn migration in central Poland. On some nights, huddling Blackcaps used rest-phase hypothermia, but on other nights, huddling birds maintained higher body temperatures at night than solitarily roosting individuals. Since many species of migrating passerine birds congregate at migratory stopovers, we anticipate huddling to be a common energy saving phenomenon among them.
As photoperiod shortens with the approach of winter, small mammals should reduce their energy exp... more As photoperiod shortens with the approach of winter, small mammals should reduce their energy expenditure to survive periods of food limitation. However, within seasons, animals should balance their energy budgets as abiotic conditions change, sometimes unpredictably; cold spells should increase heat production, while warm spells should do the opposite. Therefore, we addressed specific questions about the possible interactions between seasonal acclimatization and the intra-seasonal phenotypic flexibility of metabolic rate. We hypothesized that phenotypic flexibility in small mammals differs seasonally and is greater in summer than in winter, and predicted that seasonal adjustments in energetics, which are driven by photoperiod, overwhelm the influence of variations in the thermal environment. We measured body mass, basal metabolic rate (BMR), facultative non-shivering thermogenesis (fNST), body temperature, and calculated minimum thermal conductance in Siberian hamsters Phodopus sungorus. Animals were acclimated to winter-like, and then to summer-like conditions and, within each season, were exposed twice, for 3 weeks to 10, 20 or 28 °C. We used differences between values measured after these short acclimation periods as a measure of the scope of phenotypic flexibility. After winter acclimation, hamsters were lighter, had lower whole animal BMR, higher fNST than in summer, and developed heterothermy. After these short acclimations to the above-mentioned temperatures, hamsters showed reversible changes in BMR and fNST; however, these traits were less flexible in winter than in summer. We conclude that seasonal acclimation affects hamster responses to intra-seasonal variations in the thermal environment. We argue that understanding seasonal changes in phenotypic flexibility is crucial for predicting the biological consequences of global climate changes.
Journal of physiology and pharmacology : an official journal of the Polish Physiological Society, 2006
The aim of our study was determine torpor use in the Siberian hamsters (Phodopus sungorus) tested... more The aim of our study was determine torpor use in the Siberian hamsters (Phodopus sungorus) tested in a wide gradient of ambient temperatures (T(a)). Experiments were done on fed and food-deprived animals acclimated to winter-like and summer-like conditions. We found that neither fed nor unfed hamsters acclimated to winter-like or summer-like conditions selected low T(a)'s and entered torpor. Instead, food deprivation led to selection of higher T(a)'s and slight lowering of body temperature (T(b)), especially during the rest-phase of the day. Our calculations show that this strategy may lead to higher energy savings than torpor would. We argue that torpor use is not a fixed strategy but is determined primarily by a thermal conditions available in the environment.
Small migratory birds employ a wide range of behavioural and physiological strategies to accelera... more Small migratory birds employ a wide range of behavioural and physiological strategies to accelerate their fuel accumulation rate at migratory stopovers. Although they could potentially reduce their rest-phase energy requirements by huddling with conspecifics, to date only anecdotal information exists about this behaviour. We found that resting Blackcaps (Sylvia atricapilla) regularly huddled in groups of two to six individuals in aviaries during migratory stopover. This occurred in spring migration in the Negev Desert and in autumn migration in central Poland. On some nights, huddling Blackcaps used rest-phase hypothermia, but on other nights, huddling birds maintained higher body temperatures at night than solitarily roosting individuals. Since many species of migrating passerine birds congregate at migratory stopovers, we anticipate huddling to be a common energy saving phenomenon among them.
As photoperiod shortens with the approach of winter, small mammals should reduce their energy exp... more As photoperiod shortens with the approach of winter, small mammals should reduce their energy expenditure to survive periods of food limitation. However, within seasons, animals should balance their energy budgets as abiotic conditions change, sometimes unpredictably; cold spells should increase heat production, while warm spells should do the opposite. Therefore, we addressed specific questions about the possible interactions between seasonal acclimatization and the intra-seasonal phenotypic flexibility of metabolic rate. We hypothesized that phenotypic flexibility in small mammals differs seasonally and is greater in summer than in winter, and predicted that seasonal adjustments in energetics, which are driven by photoperiod, overwhelm the influence of variations in the thermal environment. We measured body mass, basal metabolic rate (BMR), facultative non-shivering thermogenesis (fNST), body temperature, and calculated minimum thermal conductance in Siberian hamsters Phodopus sungorus. Animals were acclimated to winter-like, and then to summer-like conditions and, within each season, were exposed twice, for 3 weeks to 10, 20 or 28 °C. We used differences between values measured after these short acclimation periods as a measure of the scope of phenotypic flexibility. After winter acclimation, hamsters were lighter, had lower whole animal BMR, higher fNST than in summer, and developed heterothermy. After these short acclimations to the above-mentioned temperatures, hamsters showed reversible changes in BMR and fNST; however, these traits were less flexible in winter than in summer. We conclude that seasonal acclimation affects hamster responses to intra-seasonal variations in the thermal environment. We argue that understanding seasonal changes in phenotypic flexibility is crucial for predicting the biological consequences of global climate changes.
Journal of physiology and pharmacology : an official journal of the Polish Physiological Society, 2006
The aim of our study was determine torpor use in the Siberian hamsters (Phodopus sungorus) tested... more The aim of our study was determine torpor use in the Siberian hamsters (Phodopus sungorus) tested in a wide gradient of ambient temperatures (T(a)). Experiments were done on fed and food-deprived animals acclimated to winter-like and summer-like conditions. We found that neither fed nor unfed hamsters acclimated to winter-like or summer-like conditions selected low T(a)'s and entered torpor. Instead, food deprivation led to selection of higher T(a)'s and slight lowering of body temperature (T(b)), especially during the rest-phase of the day. Our calculations show that this strategy may lead to higher energy savings than torpor would. We argue that torpor use is not a fixed strategy but is determined primarily by a thermal conditions available in the environment.
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