Seasonal Changes in Body Composition and Crop Content of Spitzbergen Ptarmigan Lagopus mutus hyperboreus

Mortensen, Atle; Unander, Sigmund; Kolstad, M.; Blix, Arnoldus Schytte

doi:10.2307/3676018

Cited by 57 publications

(61 citation statements)

References 2 publications

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“…Birds had ad libitum access to food and water, and were housed in wooden cages with wire mesh floors. Under these conditions, the birds undergo their natural seasonal physiological changes [39,40]. Experiments were conducted during July.…”

Section: Methodsmentioning

confidence: 99%

Understanding sex differences in the cost of terrestrial locomotion

et al. 2011

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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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Section: Methodsmentioning

confidence: 99%

Understanding sex differences in the cost of terrestrial locomotion

et al. 2011

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“…At their peak, fat stores account for 30% of the animals' total body mass. However, all the fat has disappeared by February, when daylight reappears on the islands (Mortensen et al, 1983). Moreover, these changes also happen when captive birds are fed ad libitum throughout the year (Stokkan et al, 1986).…”

Section: Fat Storagementioning

confidence: 98%

Adaptations to polar life in mammals and birds

Blix

2016

Journal of Experimental Biology

141

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This Review presents a broad overview of adaptations of truly Arctic and Antarctic mammals and birds to the challenges of polar life. The polar environment may be characterized by grisly cold, scarcity of food and darkness in winter, and lush conditions and continuous light in summer. Resident animals cope with these changes by behavioural, physical and physiological means. These include responses aimed at reducing exposure, such as 'balling up', huddling and shelter building; seasonal changes in insulation by fur, plumage and blubber; and circulatory adjustments aimed at preservation of core temperature, to which end the periphery and extremities are cooled to increase insulation. Newborn altricial animals have profound tolerance to hypothermia, but depend on parental care for warmth, whereas precocial mammals are well insulated and respond to cold with non-shivering thermogenesis in brown adipose tissue, and precocial birds shiver to produce heat. Most polar animals prepare themselves for shortness of food during winter by the deposition of large amounts of fat in times of plenty during autumn. These deposits are governed by a sliding set-point for body fatness throughout winter so that they last until the sun reappears in spring. Polar animals are, like most others, primarily active during the light part of the day, but when the sun never sets in summer and darkness prevails during winter, high-latitude animals become intermittently active around the clock, allowing opportunistic feeding at all times. The importance of understanding the needs of the individuals of a species to understand the responses of populations in times of climate change is emphasized.

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“…In particular, the acquisition of fat reserves in winter means that these birds experience a seasonal doubling of M b , from approximately 500g between March and August to approximately 900g in mid-November. At this time, fat content comprises as much as 32% of M b (Grammeltvedt and Steen, 1978;Mortensen et al, 1983;Stokkan et al, 1986). It has previously been found that Svalbard ptarmigan have adaptations for locomotor efficiency in both summer (Nudds et al, 2011) and winter (Lees et al, 2010), and when young (Lees et al, 2012b); however, it is unknown how the cost of incline locomotion is affected by the dramatic seasonal changes in M b .…”

Section: Introductionmentioning

confidence: 97%

The metabolic cost of incline locomotion in the Svalbard rock ptarmigan (Lagopus muta hyperborea): the effects of incline grade and seasonal fluctuations in body mass

Lees

Folkow

Stokkan

et al. 2012

Journal of Experimental Biology

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SUMMARYIn a terrestrial environment animals must locomote over varying terrain; despite this, the majority of studies of animal locomotion focus on level locomotion. The influence moving up an inclined surface has on the metabolic cost of locomotion and the efficiency with which animals perform positive work against gravity is still not well understood. Generally speaking, existing data sets lack consistency in the use of grades, further compounded by differences between species in terms of morphology and locomotor gait. Here we investigated the metabolic cost of locomotion using respirometry in the Svalbard ptarmigan (Lagopus muta hyperborea). The Svalbard ptarmigan provides a unique opportunity to investigate the cost of incline locomotion as it undergoes a seasonal fluctuation in body mass, which doubles in winter, meaning the requirement for positive mechanical work also fluctuates with season. We demonstrate that at the same degree of incline, the cost of lifting 1kg by 1 vertical metre remains relatively constant between seasons despite the large differences in body mass from summer to winter. These findings are consistent with the notion that positive mechanical work alone dictates the cost of lifting above a certain body mass. However, our data indicate that this cost may vary according to the degree of incline and gait.Supplementary material available online at

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Seasonal Changes in Body Composition and Crop Content of Spitzbergen Ptarmigan Lagopus mutus hyperboreus

Cited by 57 publications

References 2 publications

Understanding sex differences in the cost of terrestrial locomotion

Understanding sex differences in the cost of terrestrial locomotion

Adaptations to polar life in mammals and birds

The metabolic cost of incline locomotion in the Svalbard rock ptarmigan (Lagopus muta hyperborea): the effects of incline grade and seasonal fluctuations in body mass

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