Survival strategies in arctic ungulates

Arctic ungulates usually neither freeze nor starve to death despite the rigours of winter. Physiological adaptations enable them to survive and reproduce despite long periods of intense cold and potential undernutrition. Heat conservation is achieved by excellent insulation combined with nasal heat exchange. Seasonal variation in fasting metabolic rate has been reported in several temperate and sub-arctic species of ungulates and seems to occur in muskoxen. Surprisingly, there is no evidence for this in reindeer. Both reindeer and caribou normally maintain low levels of locomotor activity in winter. Light foot loads are important for reducing energy expenditure while walking over snow. The significance and control of selective cooling of the brain during hard exercise (e.g. escape from predators) is discussed. Like other cervids, reindeer and caribou display a pronounced seasonal cycle of appetite and growth which seems to have an intrinsic basis. This has two consequences. First, the animals evidently survive perfectly well despite enduring negative energy balance for long periods. Second, loss of weight in winter is not necessarily evidence of undernutrition. The main role of fat reserves, especially in males, may be to enhance reproductive success. The principal role of fat reserves in winter appears to be to provide a supplement to, rather than a substitute for, poor quality winter forage. Fat also provides an insurance against death during periods of acute starvation

Small scale density variations of electrons and charged particles in the vicinity of polar mesosphere summer echoes

International audienceWe present small scale variations of electron number densities and particle charge number densities measured in situ in the presence of polar mesosphere summer echoes. It turns out that the small scale fluctuations of electrons and negatively charged particles show a strong anticorrelation down to the smallest scales observed. Comparing these small scale structures with the simultaneously measured radar signal to noise profile, we find that the radar profile is well described by the power spectral density of both electrons and charged particles at the radar half wavelength (=the Bragg scale). Finally, we consider the shape of the power spectra of the observed plasma fluctuations and find that both charged particles and electrons show spectra that can be explained in terms of either neutral air turbulence acting on the distribution of a low diffusivity tracer or the fossil remnants of a formerly active turbulent region. All these results are consistent with the theoretical ideas by Rapp and Lübken (2003) suggesting that PMSE can be explained by a combination of active and fossil neutral air turbulence acting on the large and heavy charged aerosol particles which are subsequently mirrored in the electron number density distribution that becomes visible to a VHF radar when small scale fluctuations are present

Reindeer breathe less and save water in the cold

Simultaneous measurements of metabolic rate, respiratory minute volume, respiratory frequency, and oxygen extraction from the inspired air were obtained during treadmill exercise in Svalbard reindeer (Rangifer tarandus platyrhynchus) and Norwegian reindeer (Rangifer tarandus tarandus). The experiments were carried out both in summer and winter at ambient temperatures and running speeds ranging from +12 to -30 °C and 3.7 to 9.0 knvh1, respectively. We found that respiratory minute volume was generally lower in summer than in winter for a similar ambient temperature, and also that respiratory minute volume was reduced at low ambient temperature both in summer and winter. The change in respiratory minute volume was inversely related to oxygen extraction, the latter being at its highest at the lowest ambient temperature and running speed in summer. Reduction of respiratory minute volume, and hence respiratory water loss, at low ambient temperature is likely to contribute significantly to the survival of these species, particularly in winter when the animals can only replace body water with snow at low temperature

Selective cooling of the brain in reindeer

Selective cooling of the brain during hyper-thermia has been demonstrated in several species of mammals (Baker 1979, 1982). Such cooling is achieved by heat exchange between the cooled venous blood returning from the nasal mucosa and the warmer arterial blood entering the brain via the carotid rete. Spot measurements of brain temperature (Tbr) and carotid blood temperature (TCar) were made within 1 min. of death in 40 wild reindeer (Rangifer tarandus tarandus). At Tear lower than 40.5°C Tbr was higher than T c a r. With increasing Tear above 40.5°C Tbr remained at approxima-tely 40.5°C, indicating that selective cooling of the brain had occurred

A review of data on abundance, trends in abundance, habitat use and diet of ice-breeding seals in the Southern Ocean

The development of models of marine ecosystems in the Southern Ocean is becoming increasingly important as a means of understanding and managing impacts such as exploitation and climate change. Collating data from disparate sources, and understanding biases or uncertainties inherent in those data, are important first steps for improving ecosystem models. This review focuses on seals that breed in ice habitats of the Southern Ocean (i.e. crabeater seal, Lobodon carcinophaga; Ross seal, Ommatophoca rossii; leopard seal, Hydrurga leptonyx; and Weddell seal, Leptonychotes weddellii). Data on populations (abundance and trends in abundance), distribution and habitat use (movement, key habitat and environmental features) and foraging (diet) are summarised, and potential biases and uncertainties inherent in those data are identified and discussed. Spatial and temporal gaps in knowledge of the populations, habitats and diet of each species are also identified

Effects of improved nutrition in pregnant reindeer on milk quality, calf birth weight, growth, and mortality

A group of 35 pregnant reindeer (Rangifcr tarandus) was divided into two groups in mid-February. Until calving in May one of the groups (L) received lichen ad lib., while the other group (IN) received an improved diet, rich in protein and minerals. After calving both groups received the same improved diet. In both groups it was distinguished between young (<3 years) and old (>3 years) animals. At the start of the experiment the body weight of L-young animals was 58.5 ± 4.6 kg, IN-young 56.2 ± 2.8 kg, L-old 70.3 ± 6.0 kg and IN-old 68.2 ± 4.8 kg. At calving the weights of the same animals were 55.9 ± 4.5 kg (L-young), 68.1 ± 2.5 (IN-young), 70.0 ± 6.9 kg (L-old) and 81.6 ± 6.8 kg (IN-old). Birth weight of IN-young calves was 4.5 ± 0.7 kg and of L-young calves 3.7 ± 0.5 kg. Birth weight of IN-old calves was 5.7 ± 0.8 kg and of L-old calves 4.4 ± 0.6 kg. The birth weight of the calves in all groups was correlated to the weight of the female just prior to calving. Growth rates in all but the IN-old group were not different, the IN-old group showing a significantly higher growth rate than the other groups. In mid-September, however, the average body weight for the calves from the L and IN-groups did not differ significantly. Neither chemical composition nor total energy content of the milk differed significantly between the groups. Total mortality in the L-group was 28% as compared to 7% in the IN-group. Two females in the IN-old group had not given birth at the end of the experimental period.Virkningen av bedret ernæring til drektige reinsimler på melkekvalitet, kalvenes fødselsvekt, vekst og dødelighet.Abstract in Norwegian / Sammendrag: En flokk på 35 drektige reinsimler (Rangifer tarandus) ble delt i to grupper i midten av februar. Frem til kalving i mai ble den ene gruppen gitt lav ad lib. (L-gruppe), mens den andre gruppen ble tilleggsforet med 2 kg RF - 71/dag (IN-gruppe). Etter kalving ble begge gruppene gitt 2 kg RF - 71/dag. Innen begge gruppene ble det skilt mellom unge (<3 år) og gamle (>3 år) simler. Ved forsøkets start var kroppsvekten for unge simler ca. 57 kg, og for gamle simler ca. 69 kg, i begge ernæringsgruppene. Ved kalving var kroppsvekten for unge simler 55.9 ± 4.5 kg (L-gruppe), og 68.1 ± 2.5 kg (IN-gruppe) mens kroppsvekten for gamle simler var 70.0 ± 6.9 kg (L-gruppe) og 81.6 ± 6.8 kg (IN-gruppe). Fødselsvekt for kalver etter IN-unge simler var 4.5 ± 0.7 kg, og 3.7 ± 0.5 kg for kalver etter L-unge simler. De tilsvarende fødselsvektene for kalver etter gamle simler var 5.7 ± 0.8 kg (IN-gruppe) og 4.4 ± 0.6 kg (L-gruppe). Fødselsvektene var korrelert til simlenes kroppsvekt like før kalving. Kalveveksten i de første tre ukene etter fødselen var signifikant høyere for kalver etter IN-gamle simler, sammenlignet med kalveveksten i de øvrige tre gruppene, som ikke var innbyrdes signifikant forskjellige. I midten av september var det ingen signifikante forskjeller i kalvenes kroppsvekt gruppene imellom. Det var ingen signifikante forskjeller hverken i totalt energiinnhold eller i kjemisk sammensetning av melken fra simlene i de to ernæringsgruppene. Total dødelighet for kalver i L-gruppen var 28% mot 7% i IN-gruppen i løpet av de tre første ukene etter fødselen. To av de gamle simlene i IN-gruppen hadde ikke kalvet ved forsøkets slutt.Kantavien porovaatimien parannetun ravinnon vaikutus maidonlaatuun, vasojen syntymåpainoon, kasvuun ja kuolleisuuteen.Abstract in Finnish / Yhteenveto: 35 kantavan porovaatimen (Rangifer tarandus) lauma jaettiin kahteen ryhmaan helmikuun puolivålisså. Vasomiseen saakka toukokuussa annettiin toiselle ryhmalle jåkalaa ad. Ub. (L-ryhmå), kun taas toinen ryhma sai lisåravintona 2 kg RF-71 rehua påivåsså (IN-ryhmå). Vasomisen jålkeen annettiin molemmille ryhmille 2 kg RF-71 rehua påivåsså. Molemmissa ryhmisså erotettiin nuoret (< 3-vuotiaat) ja vanhat (> 3-vuotiaat) vaatimet toisistaan. Tutkimuksen alkuvaiheessa oli nuorten vaatimien ruumiinpaino n.57 kg, ja vanhojen vaatimien n.69 kg, molemmissa ravintoryhmisså. Vasomisen aikana oli nuorten vaatimien ruumiinpaino 55,9 ± 4,5 kg (L-ryhmå), ja 68,1 ± 2,5 kg (IN-ryhmå), kun taas vanhojen vaatimien ruumiinpaino oli 70,0 ± 6,9 kg (L-ryhmå) ja 81,6 ± 6,8 kg (IN-ryhmå). Vasojen syntymåpaino IN-nuorten vaatimien ryhmåsså oli 4,5 ± 0,7 kg, ja 3,7 ± 0,5 kg L-nuorten vaatimien ryhmåsså. Vastaavat syntymåpainot vanhojen vaatimien vasoilla olivat 5,7 ± 0,8 kg (IN-ryhmå) ja 4,4 ± 0,6 kg (L-ryhmå). Syntymåpainot olivat vastaavuussuhteessa vaatimien ruumiinpainoon våhåå ennen vasomista. IN-vanhojen vaatimien vasojen kasvu ensimmåisten kolmen viikon aikana syntymån jålkeen oli merkittåvåsti korkeampi, verrattuna niiden kolmen muun ryhmån vasankasvuun, jotka eivåt olleet keskenåån merkittåvån erilaisia. Vasojen ruumiinpainossa ryhmien kesken ei ollut mitåån merkittåviå eroavaisuuksia syyskuun puolivålisså. Nåiden kahden ravintoryhmån vaatimien maidossa ei ollut mitåån merkittåviå eroja kokonaisuudessa ravinnon sisåltoon eikå kemialliseen kokoonpanoon nåhden. Vasojen kokonaiskuolleisuus L-ryhmåsså oli 28% ja IN-ryhmåsså 7% kolmena ensimmåisenå viikkona syntymån jålkeen. Kaksi vanhaa vaadinta IN-ryhmåsså ei ollut vasonut tutkimuksen lopussa

Turbulent small-scale neutral and ion density fluctuations as measured during MAC/Epsilon

During the MAC/Epsilon campaign (Fall 1987, from Andoya, Northern Norway, 69 N, 16 E) a total of four altitude profiles of neutral gas number densities and six profiles of ion number densities were measured with high spatial resolution in the height range from 60 to 120 km. First results of these rocket-borne experiments are presented with emphasis on small scale turbulent density variations and related turbulent parameter as structure function constants and energy dissipation rates

Rocket measurements of positive ions during polar mesosphere winter echo conditions

On 18 January 2005, two small, instrumented rockets were launched from Andøya Rocket Range (69.3° N, 16° E) during conditions with Polar Mesosphere Winter Echoes (PMWE). Each of the rockets was equipped with a Positive Ion Probe (PIP) and a Faraday rotation/differential absorption experiment, and was launched as part of a salvo of meteorological rockets measuring temperature and wind using falling spheres and chaff. Layers of PMWE were detected between 55 and 77 km by the 53.5 MHz ALWIN radar. The rockets were launched during a solar proton event, and measured extremely high ion densities, of order 1010 m−3, in the region where PMWE were observed. The density measurements were analyzed with the wavelet transform technique. At large length scales, ~103 m, the power spectral density can be fitted with a k−3 wave number dependence, consistent with saturated gravity waves. Outside the PMWE layers the k−3 spectrum extends down to approximately 102 m where the fluctuations are quickly damped and disappear into the instrumental noise. Inside the PMWE layers the spectrum at smaller length scales is well fitted with a k−5/3 dependence over two decades of scales. The PMWE are therefore clearly indicative of turbulence, and the data are consistent with the turbulent dissipation of breaking gravity waves. We estimate a lower limit for the turbulent energy dissipation rate of about 10−2 W/kg in the upper (72 km) layer

Structure and function of respiratory turbinates in phocid seals

Abstract: In terrestrial mammals, the respiratory turbinate bones within the nasal cavity are employed to conserve heat and water. In order to investigate whether environmental temperature affects respiratory turbinate structure in phocids, we used micro-computed tomography to compare maxilloturbinate bone morphology in polar seals, grey seals and monk seals. The maxilloturbinates of polar seals have much higher surface areas than those of monk seals, the result of the polar seals having more densely packed, complex turbinates within larger nasal cavities. Grey seals were intermediate; a juvenile of this species proved to have more densely packed maxilloturbinates with shorter branch lengths than a conspecific adult. Fractal dimension in the densest part of the maxilloturbinate mass was very close to 2 in all seals, indicating that these convoluted bones evenly fill the available space. The much more elaborate maxilloturbinate systems in polar seals, compared with monk seals, are consistent with a greater need to limit respiratory heat loss