Torbjørn Severinsen

Activity pattern of arctic reindeer in a predator-free environment: no need to keep a daily rhythm

Arctic Cervids face considerable challenges in sustaining life in a harsh and highly seasonal environment, and when to forage is a key component of the survival strategy. We predict that a cervid maximizes net intake of energy to change the duration of feeding-ruminating cycles depending on season, and pays no attention to light or other activity-entraining cues. Still, in periods of bad weather it may pay energetically to reduce exposure and heat loss. We investigated environmental impact on the seasonal and daily activity pattern of a food-limited, predator-free arctic deer, the Svalbard reindeer. We found that the reindeer indeed had season-dependent feeding-rumination intervals, with no distinct peaks in activity at sunrise and sunset, as would be expected if animals maximize energy intake rates in predator-free environments. However, they temporarily reduced activity when exposed to low temperature and increased precipitation during winter, possibly to conserve energy. We provide insight into the behavioural strategy of Svalbard reindeer which enables them to cope with such an extreme environment.

Continuous and discrete extreme climatic events affecting the dynamics of a high-arctic reindeer population

Climate at northern latitudes are currently changing both with regard to the mean and the temporal variability at any given site, increasing the frequency of extreme events such as cold and warm spells. Here we use a conceptually new modelling approach with two different dynamic terms of the climatic effects on a Svalbard reindeer population (the Brøggerhalvøya population) which underwent an extreme icing event (“locked pastures”) with 80% reduction in population size during one winter (1993/94). One term captures the continuous and linear effect depending upon the Arctic Oscillation and another the discrete (rare) “event” process. The introduction of an “event” parameter describing the discrete extreme winter resulted in a more parsimonious model. Such an approach may be useful in strongly age-structured ungulate populations, with young and very old individuals being particularly prone to mortality factors during adverse conditions (resulting in a population structure that differs before and after extreme climatic events). A simulation study demonstrates that our approach is able to properly detect the ecological effects of such extreme climate events.

Determination of toxaphenes in fish and marine mammals.

An analytical method for the determination of toxaphene in biological materials using gas chromatography with an electron capture detector (GC-ECD) has been established and validated for three single congeners (chlorinated bornanes (CHB) 26, 50 and 62). The analytical method was based on a method for determination of PCB, DDT and other chlorinated pesticides. To include toxaphene congeners an extra step, adsorption chromatography on silica columns, was introduced to separate the pesticides from PCB. The recovery of CHB-26, 50 and 62 were 97+/-11%, 94+/-10% and 99+/-12%, respectively. Samples from cod, ringed seal and polar bear from the Norwegian arctic environment have been analysed. The levels of CHB-26 and 50 found were 13-55 ng/g fat in cod, 1.3-7.7 ng/g fat in ringed seal and 0.4-119 ng/g fat in polar bear. The levels of CHB-62 were 2.0-13, 0.8-3.4, 0.2-11 ng/g fat in cod, ringed seal and polar bear, respectively.

Endotoxin induced prolonged fever in rats

Abstract 1. 1.| E. coli endotoxin (3.0 mg/kg) was injected intraperitoneally (i.p.) at 09:00 h for one group and 17:00 h for a second group of male Wistar rats. 2. 2.|Deep body temperature ( T b ) was monitored with a small temperature sensitive radiotransmitter located in the abdomen. 3. 3.|After 2–4 h latency the endotoxin injections resulted in elevated T b in both groups for a period of more than 24 h. 4. 4.|The results indicate that male Wistar rats will develop prolonged fever after a single i.p. injection of E. coli endotoxin.

Resting metabolism during the stable phase of fever in rats

Abstract 1. 1.|The effect of a drop in ambient temperature ( T a ) on deep body temperature ( T b ) of normal rats and rats in the stable second phase of fever were investigated. 2. 2.|The resting metabolisms of normal rats and of rats in the stable second phase of fever were measured. 3. 3.|A 20°C drop in T a gave an average rise in T b of normal rats of 0.3°C. The same treatment did not result in a significant change in the T b of the febrile rats. 4. 4.|The metabolism of the rats in the stable second phase of fever was significantly higher than that of the normal rats at all temperatures. 5. 5.|The energy expenditure during the stable second phase of fever was higher than could be caused by normal Q 10 -effects of the increased deep body temperature. This indicates an increased heat loss in the febrile animals, which was balancing out the increase in heat production.