Seasonal variations in basal metabolic rate, lower critical temperature and responses to temporary starvation in the arctic fox (Alopex lagopus) from Svalbard |
| |
Authors: | Britt N Fuglesteg Øyvind E Haga Lars P Folkow Eva Fuglei Arnoldus Schytte Blix |
| |
Institution: | 1. Department of Arctic Biology, University of Troms?, 9037, Troms?, Norway 2. Norwegian Polar Institute, 9296, Troms?, Norway
|
| |
Abstract: | Metabolic rates of four resting, post-absorptive male adult summer- and winter-adapted captive arctic foxes (Alopex lagopus) were recorded. Basal metabolic rates (BMR) varied seasonally with a 36% increase from winter to summer, while body mass
was reduced by 17% in the same period. The lower critical temperature (T
1c) of the winter-adapted arctic fox was estimated to −7°C, whereas T
lc during summer was 5°C. The similarity of these values, which are much higher than hitherto assumed (e.g. Scholander et al. 1950b), is mainly due to a significantly (P<0.05) lower BMR in winter than in summer. Body core (stomach) temperature was stable, even at ambient temperatures as low
as −45°C, but showed a significant (P<0.05) seasonal variation, being lower in winter (39.3±0.33°C) than in summer (39.8±0.16°C). The thermal conductivity of arctic
fox fur was the same during both seasons, whereas the thermal conductance in winter was lower than in summer. This was reflected
in an increase in fur thickness of 140% from summer to winter, and in a reduced metabolic response to ambient temperatures
below T
lc in winter. Another four arctic foxes were exposed to three periods of forced starvation, each lasting 8 days during winter,
when body mass is in decline. No significant reduction in mass specific BMR was observed during the exposure to starvation,
and respiratory quotient was unchanged at 0.73±0.02 during the first 5 days, but dropped significantly (P<0.05) to 0.69±0.03 at day 7. Locomotor activity and body core (intraperitoneal) temperature was unaltered throughout the
starvation period, but body mass was reduced by 18.5±2.1% during these periods. Upon re-feeding, locomotor activity was significantly
(P<0.05) reduced for about 6 days. Energy intake was almost doubled, but stabilised at normal levels after 11 days. Body mass
increased, but not to the level before the starvation episodes. Instead, body mass increased until it reached the reduced
body mass of ad libitum fed control animals. This indicates that body mass in the arctic fox is regulated according to a seasonally
changing set point. |
| |
Keywords: | |
本文献已被 SpringerLink 等数据库收录! |
|