| 1. |
- Lees, John J, et al.
(författare)
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Understanding sex differences in the cost of terrestrial locomotion.
- 2012
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Ingår i: Proceedings of the Royal Society of London. Biological Sciences. - : The Royal Society. - 0962-8452 .- 1471-2954. ; 279:1729, s. 826-32
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Tidskriftsartikel (refereegranskat)abstract
- Little is known regarding the physiological consequences of the behavioural and morphological differences that result from sexual selection in birds. Male and female Svalbard rock ptarmigans (Lagopus muta hyperborea) exhibit distinctive behavioural differences during the breeding season. In particular, males continuously compete for and defend territories in order to breed successfully, placing large demands on their locomotor system. Here, we demonstrate that male birds have improved locomotor performance compared with females, showing both a lower cost of locomotion (CoL) and a higher top speed. We propose that the observed sex differences in locomotor capability may be due to sexual selection for improved male performance. While the mechanisms underlying these energetic differences are unclear, future studies should be wary when pooling male and female data.
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| 2. |
- Nord, Andreas, et al.
(författare)
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Ambient temperature effects on stress-induced hyperthermia in Svalbard ptarmigan
- 2019
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Ingår i: Biology Open. - : The Company of Biologists. - 2046-6390. ; 8
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Tidskriftsartikel (refereegranskat)abstract
- Stress-induced hyperthermia (SIH) is commonly observed during handling in homeotherms. However, in birds, handling in cold environments typically elicits hypothermia. It is unclear whether this indicates that SIH is differently regulated in this taxon or if it is due to size, because body temperatures changes during handling in low temperature have only been measured in small birds ≤0.03 kg (that are more likely to suffer high heat loss when handled). We have, therefore, studied thermal responses to handling stress in the intermediate-sized (0.5-1.0 kg) Svalbard ptarmigan (Lagopus muta hyperborea) in 0°C and −20°C, in winter and spring. Handling caused elevated core body temperature, and peripheral vasoconstriction that reduced back skin temperature. Core temperature increased less and back skin temperature decreased more in −20°C than in 0°C, probably because of higher heat loss rate at the lower temperature. Responses were qualitatively consistent between seasons, despite higher body condition/insulation in winter and dramatic seasonal changes in photoperiod, possibly affecting stress responsiveness. Our study supports the notion that SIH is a general thermoregulatory reaction to acute stressors in endotherms, but also suggests that body size and thermal environment should be taken into account when evaluating this response in birds.
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| 3. |
- Nord, Andreas, et al.
(författare)
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Reduced immune responsiveness contributes to winter energy conservation in an Arctic bird
- 2020
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Ingår i: Journal of Experimental Biology. - : The Company of Biologists. - 1477-9145 .- 0022-0949. ; 223:8
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Tidskriftsartikel (refereegranskat)abstract
- Animals in seasonal environments must prudently manage energyexpenditure to survive the winter. This may be achieved throughreductions in the allocation of energy for various purposes (e.g.thermoregulation, locomotion, etc.). We studied whether such tradeoffsalso include suppression of the innate immune response, bysubjecting captive male Svalbard ptarmigan (Lagopus mutahyperborea) to bacterial lipopolysaccharide (LPS) during exposureto either mild temperature (0°C) or cold snaps (acute exposure to−20°C), in constant winter darkness when birds were in energyconservingmode, and in constant daylight in spring. The innateimmune response was mostly unaffected by temperature. However,energy expenditure was below baseline when birds were immunechallenged in winter, but significantly above baseline in spring. Thissuggests that the energetic component of the innate immuneresponse was reduced in winter, possibly contributing to energyconservation. Immunological parameters decreased (agglutination,lysis, bacteriostatic capacity) or did not change (haptoglobin/PIT54)after the challenge, and behavioural modifications (anorexia, massloss) were lengthy (9 days). While we did not study the mechanismsexplaining these weak, or slow, responses, it is tempting to speculatethey may reflect the consequences of having evolved in anenvironment where pathogen transmission rate is presumably lowfor most of the year. This is an important consideration if climatechange and increased exploitation of the Arctic would alter pathogencommunities at a pace outwith counter-adaption in wildlife.
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| 4. |
- Nord, Andreas, et al.
(författare)
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Seasonal changes in plumage density, plumage mass, and feather morphology in the world’s northernmost land bird, the Svalbard Rock Ptarmigan (Lagopus muta hyperborea)
- 2023
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Ingår i: Polar Biology. - : Springer Science and Business Media LLC. - 1432-2056 .- 0722-4060. ; 46:4, s. 277-290
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Tidskriftsartikel (refereegranskat)abstract
- The Svalbard Rock Ptarmigan, Lagopus muta hyperborea, is the only year-round resident terrestrial bird in the high Arctic. Many of the physiological and morphological adaptations permitting its winter endurance in this harsh environment are well understood. However, it remains unknown how the conspicuous moult from a greyish brown summer to a white winter plumage, and any underlying changes in plumage structure and feather morphology, contribute to seasonal acclimatisation. We used standard morphometric techniques to describe the seasonal change in plumage and feather characteristics in six body regions. Then, we investigated whether winter plumage traits differed between first-winter and adult (second winter, or older) birds, because a difference in coat insulation has been suggested as an explanation for why first-winter Svalbard Ptarmigan loose more heat than adults. Plumage feather density (i.e., feathers × cm−2) and mass density (i.e., mg feathers × cm−2) were higher in winter, particularly on the head and feet where individual feathers were also heavier, longer, and downier. Seasonal changes in other regions (back, tarsi) indicated acclimatisation primarily to resist physical wear and wind. First-winter and adult birds had similar feather densities. However, mass density in first-winter birds was significantly lower than in adults in all but one body region (back) because individual feathers weighed less. This can explain previous observations of higher heat loss rates in first-winter birds. Our study suggests that plumage acclimatisation contributes to optimising the winter phenotype of Svalbard Rock Ptarmigan, both through higher insulative capacity and by improved resistance to harsh weather. The extent of these adaptations may be determined by the time or energy available for feather growth, exemplified here by inferior insulation in first-winter birds.
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| 5. |
- Nord, Andreas, et al.
(författare)
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Seasonal variation in the thermal responses to changing environmental temperature in the world's northernmost land bird
- 2018
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Ingår i: Journal of Experimental Biology. - : The Company of Biologists. - 0022-0949 .- 1477-9145. ; 221:1
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Tidskriftsartikel (refereegranskat)abstract
- Arctic homeotherms counter challenges at high latitudes using a combination of seasonal adjustments in pelage/plumage, fat deposition and intricate thermoregulatory adaptations. However, there are still gaps in our understanding of their thermal responses to cold, particularly in Arctic birds. Here, we have studied the potential use of local heterothermy (i.e. tissue cooling that can contribute to significantly lower heat loss rate) in Svalbard ptarmigan (Lagopus muta hyperborea) °C the world's northernmost land bird. We exposed birds kept under simulated Svalbard photoperiod to low ambient temperatures (Ta; between 0 and -30°C) during three seasons (early winter, late winter, summer), whilst recording resting metabolic rate (RMR), core temperature (Tc) and several cutaneous temperatures. Leg skin temperature varied the most, but still only by up to 15°C, whereas body trunk skin temperature changed 1°C when Ta decreased from 0 to -30°C. At the same time, Tc increased by 0.9°C, concomitant with increased RMR. This was probably driven by the triggering of cerebral thermosensors in response to cooling of the poorly insulated head, the skin of which was 5.4°C colder at -30°C than at 0°C. Thermal conductance in winter was higher in yearlings, probably because they were time/resource constrained from acquiring a high-quality plumage and sufficient fat reserves as a result of concomitant body growth. In conclusion, Svalbard ptarmigan do not employ extensive local heterothermy for cold protection but instead rely on efficient thermogenesis combined with excellent body insulation. Hence, cold defence in the world's northernmost land bird is not mechanistically much different from that of its lower latitude relatives.
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