Mikko Harri

Hypothermia in mice tested in Morris water maze

The Morris water maze, one of the most common behavioral tasks to assess learning and memory in rodents, exposes the animals to cold water for a few minutes. Unlike rats, young healthy mice can become severely hypothermic during the task. Five swims of 45 s in 20 degrees C water with 30s between the trials was enough to cause up to 9 degrees C drop in the rectal temperature. The decline in core temperature was accompanied by slowing of the swimming speed. Moreover, the effect was dependent on the sex and genotype of the mice, such that females were more susceptible to hypothermia than males and transgenic mice carrying Alzheimer-associated APP and PS1 mutations more vulnerable than their nontransgenic littermates. Raising the water temperature from 20 to 24 degrees C alleviated the hypothermia, but did not remove the significant drop in core temperature when using 30-s inter-trial interval. However, increasing the break from 30 s to 13 min removed the net cooling effect of five trials on the core temperature and swimming speed. We conclude that the currently most common water maze protocol renders mice hypothermic, which may confound the test results, especially when transgenic female mice are used. We recommend monitoring of the swimming speed on a trial-by-trial basis and using longer inter-trial intervals.

Thermoregulation of polecat and raccoon dog: A comparative study with stoat, mink and blue fox

1. Oxygen consumption (ml X kg0.75 per min) in relation to ambient temperature (Ta) in the raccoon dog (Nyctereutes procyonoides), polecat (Mustela putorius), mink (Mustela vison) and stoat (Mustela erminea) is described by equations y = 14.2 - 0.23x, y = 26.3 - 0.47x, y = 26.9 - 0.33x and y = 39.0 - 1.06x, respectively. Resting metabolic rate (RMR) of blue fox (Alopex lagopus) could be measured only at thermoneutrality. 2. In polecats, calorigenic response to noradrenaline was about 40% above the RMR, while in raccoon dogs it was absent. 3. The cooling constant (per min) of deceased raccoon dogs was similar to that measured for blue fox (0.0008), but considerably higher than that measured for dog (beagle 0.0016) or polecats (0.0023-0.0031).

Seasonal changes in thermoregulation of the raccoon dog (Nyctereutes procyonoides Gray 1834)

Oxygen consumption (ml X kg-0.75/min) in relation to ambient temperature (Ta) in the raccoon dog whelps at the ages of 7-9 weeks and 17-19 weeks is described by equations y = 32.9-0.69x and y = 26.2-0.49x, respectively. The corresponding equations to adults in summer and winter pelages are y = 19.6-0.46x and y = 14.5-0.32x, respectively. The cooling constant (min-1) of deceased raccoon dogs decreased exponentially with increasing body mass, while M-0.75 specific heat transfer coefficient (W X kg-0.75/degrees C) regressed linearly on body mass, y = 0.124-0.00066x. Cooling rate of deceased animals were more dependent on body mass than on pelage quality.

Heat loss of farmed raccoon dogs and blue foxes as evaluated by infrared thermography and body cooling

Infrared thermographs showed that heat loss of the raccoon dog (Nyctereutes procyonoides Gray 1834) is greatest from the chest, the head, the abdomen and the feet. The blue fox (Alopex lagopus) seems to be somewhat better insulated. Mass-0.75 specific heat transfer coefficients (W/kg 0.75 per degrees C) in both species were similar. The wooden nest was able to decrease it significantly. The results support the conclusion that heat loss, and thus the energy costs, of studied species could be reduced by providing them with either a winter nest or a rest-shelf in the cage.

Preferences of farmed blue foxes for different floor types

In the first experiment, farmed blue foxes were allowed to choose for 1 week between four standard farm cages equipped with different floor materials: plastic-coated wire mesh, dry wood, dry sand and wet (summer) or icy (winter) sand. Resting consisted of 10-15 separate bouts/day occupying 50-60% of the total 24-h. There were no other differences in the use of the cages except that the time spent on, and the duration and number of resting bouts were lower on wet or icy sand, resting periods being more affected than activity. In the second experiment, two cages were connected with a 1.2 m tunnel. One cage was always elevated (50 cm) compared to that one which was lower. One cage of each pair had a wire floor whereas the other cage either had sand or wire floor. Sand floor was preferred for active behaviours and wire floor for resting if these were on elevated level. Of two identical wire-floored cages, the elevated one had the priority. Foxes preferred to rest on the same floor where they had finished their previous resting bout, often exclusively and independently of floor material or floor level.

Seasonal changes in energy economy of farmed polecat as evaluated by body weight, food intake and behavioural strategy

An analysis of seasonal changes in energy budget of the farmed polecat (Mustela putorius) was performed in subarctic climate. Cyclical variations were found in the body weight of male polecats from maximum values in February (2.1 kg) to minimum values in June-July (1.5 kg). There were only minor seasonal changes in the body weight of females. There was a direct relationship between body weight and voluntary energy intake on one hand (r = 0.89) and an inverse relationship between body weight and locomotor activity (r = -0.88) on the other hand. Energy intake was significantly (p less than 0.05) higher during winter (224 kcal/animal/day) than during summer (142 kcal/animal/day). Total time spent outside the nest was at its maximum during the winter months (60 min/day). The results suggest that in male polecats, changes in absolute food intake induce seasonal changes in body weight. Seasonal changes in locomotor activity seem to be less important in energy balance regulation. The fact that the body weight of females showed only minor seasonal variation supports the role of sexual hormones in the control of the body weight.

Long-term effects of tryptophan on behavioural response and growing-furring performance in silver fox (Vulpes vulpes)

Abstract The effects of dietary tryptophan (TRP) supplementation on behavioural response, body weight, feed consumption, and winter fur development was assessed on silver fox pups from July 28 until December 5. Ten males and ten females received a commercial fox ration (control) and 10 males and 10 females the same ration supplemented with TRP (1.2 g/MJ ME). Dietary TRP supplementation increased the consumption of protein and gross energy in September and November and total DM in September. The male foxes also consumed more feed and gained more weight than the females throughout the trial. Dietary TRP supplementation did not affect body weight gain, initiation of winter fur growth or fur quality in the test groups. There was a trend toward later priming of fur in the TRP supplemented group. The number of contacts with the novel object increased and the latency time until contact with the tidbit and the novel object reduced towards the end of the experiment. In the tidbit test, dietary TRP supplementation reduced the latency time of the females (40.4 s) compared with the non-supplemented females (58.0 s), the TRP supplemented males (51.7 s), and the non-supplemented males (47.6 s, P=0.001). In the novel object test, the latency time of the TRP females (32.5 s) was likewise reduced compared with the control group females (46.9 s) and TRP group males (44.0 s) being comparable to the control group males (38.5 s, P=0.029). It appears that dietary TRP supplement reduces fear and enhances exploratory behaviour in the female silver fox. This is likely due to the female being more sensitive to the imbalance between TRP and other large neutral amino acids, the supplement leading to increased brain serotonin synthesis. Further research needs to elucidate the effects of dietary TRP on the pineal function due to potential interference with seasonal breeding and furring controlled by the photoperiod.

Preferences of farmed silver foxes (Vulpes vulpes) for four different floor types

Farmed silver foxes were allowed to choose between four standard farm cages, each of which was equipped with a different floor material: plastic-coated wire mesh (WM); dry wood (DW); dry sand (DS); and wet wood (WW) or icy sand (IS). Six males and six females were placed in the test environment singly in winter; and the same individuals, again in spring. The use of the different floors was videorecorded and analysed from the tapes for active periods and resting period on 5 or 6 d. Resting consisted of 14–20 separate bouts d−1, occupying 58–62% of the total 24 h. In winter, the active periods of the animal’s day were spent as follows: DW (34%) = DS (33%) > IS (17%) = WM (15%). The resting periods were spent as follows: DW (59%) > WM (26%) = DS (15%) > IS (1%). In spring, the order of active time was DS (36%) > DW (25%) = WW (24%) > WM (15%) and of resting time was DW (51%) > WM (19%) = WW (16%) = DS (15%). Different individuals preferred different floors, leading to large variance in the group means. This ...

Factor analysis of behavioural tests in farmed silver and blue foxes

Abstract We recorded and analysed behaviour of farmed silver and blue foxes in the open-field with a computer-based system. In addition, the reaction towards humans and the capture time were recorded for the animals in their home cage. Factor analysis with VARIMAX rotation produced four independent factors. In the silver fox, the first factor was loaded from general activity in the open-field and accounted for 42% of the variance; the second factor was mainly loaded from initial activity (24%). The third factor was related to the reaction towards humans (19%) and the fourth was the capture time (15%). In the blue fox, the factors were: general (41%) and initial activity in the open-field (26%), capture time (17%) and reaction towards humans (15%). A 5 min exposure to the open-field was sufficient to provide the information needed. In the spring in comparison with the autumn a higher proportion of silver foxes did not come out of the start box to the open-field at all, while fewer young blue foxes emerged than old ones, such reaction thus being an additional behavioural test. The open-field Factor 2 (initial activity) was higher in adult silver foxes and in the autumn compared with juveniles or the same adults about 5 months earlier. The adult individuals in this group were more passive towards humans in the spring. Adult blue foxes were more active in the open-field than the young and their initial activity was higher in the spring. In the spring there were more passive blue foxes while in the autumn the number of fearful individuals was greater. In the autumn, juveniles were more aggressive than adults. Adult blue foxes were more easily accessible to a capturer than young blue foxes. The effect of cage environment on behaviour of the foxes was assessed in animals housed in empty wire-mesh cages or in cages provided with resting platforms and nest boxes or platforms only. There were no other differences between these groups in their open-field behaviour except that the initial activity was lower in the control blue foxes. Blue foxes in the control group were more fearful and passive towards humans, whereas no differences were found among silver foxes. The capture time was always longest in the nest box groups, due to the obstacles that the nest boxes presented to the capture. Our results confirm that behaviour of foxes is subject to changes detectable by the behavioural tests used. However, in this study the behaviour of both fox species appeared to be affected more by season and age than by housing conditions.

Use of nest boxes by young farmed silver foxes (Vulpes vulpes) in autumn

Abstract Traditionally farmed silver foxes are raised in their cages without next boxes, with the exception of vixens in their breeding season. However, according to the European recommendations for keeping foxes, each weaned fox shall have available a secluded area, such as a resting platform or a nest box, for resting, hiding and observing. The aim of the work was to study a simple alternative to enrich the traditional housing system of juvenile foxes by providing a standard wire-mesh cage (length 112 cm × width 107 cm × height 70 cm) with a wooden nest box. The extent to which the nest boxes (dimensions of the main chamber 40 cm × 40 cm × 40 cm; or diameter 38 cm, height 32 cm) were used by silver foxes was assessed in two long-term experiments in practical farming situations, i.e. one or two juvenile foxes per standard cage. The nest boxes were situated in the wire-mesh cages where the animals were kept. Foxes (36 kept in pairs and eight kept singly) spent most of their time (> 50%) on the roofs of the nest boxes and only 1–2% of their time inside the nest boxes. The wire-mesh floor was used very little for resting in August–October, but in November some foxes started to rest there sporadically. When resting on the floor, the animals always occupied a small area from which the view of the surroundings was best. Preference for the nest box roof with a good view may result from non-preference for the much worse cage floor view.