Silver Fox Vixens Research Articles

Two's company? Solitary vixens’ motivations for seeking social contact

The flexible social organisation in red foxes ( Vulpes vulpes) suggests that social contact could enrich the housing of silver fox vixens (a selected line of red foxes) farmed for their fur. To investigate their social motivation, adult vixens housed in an operant apparatus were allowed to pull a loop for full physical contact with a same-aged vixen. The access cost was increased daily and their maximum price paid (MPP) measured. Five test and five stimulus animals were pair housed long-term in separate apparatuses over 5 weeks in November/December wherein each pair could have 12 h daily physical contact in a shared compartment. Prior to the operant trials, two food competition tests were completed to establish dominance relations within pairs. To examine vixens’ motives for contact, social behaviour during interaction was also recorded. Subsequently, the test foxes’ MPP for a comparator resource, food, was also measured and their relative price paid (RPP, %) for contact calculated. When access to the resource cage was free (FR1), at the start and end of the experiment, time spent in contact averaged approximately 1/6 (2 h) of the available time; this was stable between these periods. Neither visit rate to nor time spent in the shared compartment differed between the start and the end of the trial, indicating that the test subjects’ social motivation remained stable during the experimental period. The MPP (mean ± SE) for social contact averaged at 560 ± 160.6 pulls; this was significantly lower ( P = 0.015) than the MPP for food (2108 ± 526.6 pulls), representing a RPP of 24.8 ± 3.36%. During social interaction agonistic gaping signals occurred (though never serious fights requiring intervention), but there were also bouts of play, social exploration and high levels of synchronous resting. Aggressive behaviour during the second food test predicted the levels of aggression during operant trials. RPP positively correlated with the total time spent together ( r = 0.87, P = 0.054), and with the time spent resting together ( r = 0.89, P = 0.046). Differences in RPPs for contact and levels of agonism between pairs illustrate that social contact between adult vixens is enriching for some, but may put welfare at risk for others, especially if they have no opportunity to retreat from aggression. However, levels of agonistic behaviour during, e.g. food competition tests may be a possible indicator of the compatibility between potential cage mates. Due to the low number of animals the result must now be replicated with further animals.

Group housing of adult silver fox ( Vulpes vulpes) vixens during autumn and its consequences for body weight, injuries and later reproduction: A field study

Usually, farmed silver foxes are housed singly throughout adulthood. Due to the flexible social nature of wild foxes social grouping may act as an alternative housing procedure for adult vixens. However, sociality may involve increased levels of aggression during competition for e.g. dominance with negative impact on foxes’ welfare and future reproduction, in particular for subordinate individuals. In this study we examined consequences of housing adult vixens in triplets for 13 weeks from September to December on their body weight development, occurrence of wounds and future reproduction. To evaluate effects of social competition dominance relations were recorded. Three-hundred-and-fifty-eight one to four year old silver fox vixens housed in six different commercial farms participated in the study. In each farm half of the vixens were housed in single cages as controls whereas the other half were housed in triplets in three connected cages consisting of one one-year-old, one two-year-old and one three- or four-year-old vixen. After the triplets were separated in December all animals were housed singly until they were mated in February and throughout the breeding period. Socially housed vixens gained more weight compared to the singly housed controls during the group housing period, however, the lowest ranked vixen were significantly lighter (7.0 ± 0.11 kg) compared to the second ranked vixens (7.4 ± 0.11 kg), indicating possible food competition. Yet, the body weight of subordinate vixens was not below that of singly housed controls (6.9 ± 0.05 kg) at the end of the group housing period. Thirty-six % of the group housed vixens had scabs or injuries 3 weeks following the start of the experiment whereas this was 2.3% in the controls. 1.7% ( N = 6) of the group housed vixens were excluded from the experiment due to infectious bite wounds. Damaging aggression seemed to decrease with succeeding time as 6.7% of the group housed vixens had injuries at the end of the experiment. There were no effects of social housing on the vixens reproductive output apart from heat development that occurred on average two days earlier in group housed vixens. Dominant vixens weaned approximately one more cub (4.3 ± 0.33) compared to the lower ranked vixens (3.2 ± 0.34, P = 0.036). To conclude, aggression during social housing in autumn may jeopardize foxes’ welfare and have negative consequences for future reproduction in subordinate vixens. Future studies are needed to clarify how various housing procedures affect social dynamics in group housed foxes.

Group housing of adult silver fox ( Vulpes vulpes) vixens in autumn: Agonistic behaviour during the first days subsequent to mixing

Due to farmed foxes’ ( Vulpes vulpes) social flexibility and possible motivation for intraspecific contact, group housing may act as an alternative housing procedure. Because initial social contact between silver foxes usually involves agonistic displays as a part of foxes’ social dominance assessments and owing to their territorial motivation, the incidence of serious aggression may put foxes’ welfare at risk. The aim of this study was to investigate the consequences of housing adult silver fox vixens in triplets of various age compositions on their agonistic behaviour, body weight gain and bite injury level following the first hours and days after mixing in triplets. Ninety 1.5 and 2.5-year old vixens were housed in triplets consisting of four different age compositions ( N = 3 × 6 × 4 = 72) and in one singly housed control group ( N = 18) in September. Group 112 consisted of two 1.5-year olds and one 2.5-year old; Group 221 of two 2.5-year olds and one 1.5-year old; Group 111 of 1.5-year olds and Group 222 of 2.5-year olds. The triplets were housed in standard wire mesh cages connected with openings and with access to top nest boxes. The foxes’ behaviour was recorded continuously the three first hours after mixing, 1 h day 2 (26th hour) and 1 h day 3 (50th hour) after mixing. One and two weeks following mixing, the number and severity of bite injuries were assessed. There was no overall difference between groups in observed agonistic behaviours. In all experimental groups aggression was most frequent the first hour (chasing = 7.7 ± 1.2; physical aggressive signals = 2.3 ± 0.32; fights = 2.0 ± 0.23). Overall, number of aggressive interactions was reduced with time ( P < 0.001). Scabs and/or bite injuries were recorded in 58.3% of the animals the first week and in 42% the second week. Social grooming and play was only observed at very few occasions. About 35% of the animals, except for controls, lost weight the first week. Vixens with injuries gained less weight compared to unharmed animals ( P = 0.03). A negative correlation between weight asymmetry and number of fights was found ( r = −0.57, P < 0.01). Although a clear effect of age composition was not found the triplets consisting of 2-year olds might have experienced less negative consequences of group housing because of absence of serious wounds. Due to the frequency and intensity of aggression and the fact that several vixens lost weight during the first week it is most likely that adult silver fox vixens experience the initial phase of social housing as stressful.

Do different competition strategies affect social preference and behaviour in silver fox vixens ( Vulpes vulpes)?

Among mammals, social ranking is generally thought to affect the outcome of disputes over preferred, limited or future resources. Therefore, we should expect individuals’ preference for conspecifics to be affected by their own and other individuals’ competition capacity. Here, we investigated the social preference and behavioural response in farmed silver fox vixens ( Vulpes vulpes) towards unfamiliar vixens of different competition capacities, measured by their ability to compete for and defend a limited food resource, in a choice test. We found that low competition capacity vixens spent significantly less time in front of the high competition capacity vixens (2647 ± 600 s) compared to the time they spent in front of the low competition capacity vixens (6041 ± 877 s, P < 0.05). In addition, the low competition capacity vixens spent significantly less time in front of the high competition capacity vixens (2647 ± 600 s) compared to what the high competition capacity vixens did (4215 ± 657 s, P = 0.03). This suggests that low competition capacity vixens perceive high competition capacity vixens as a greater potential threat than high competition capacity vixens do. Time spent in social exploration, resting, sitting and performing aggressive behaviours in front of a stimulus animal were also affected by competition capacity of the foxes. The vixens were also retreating significantly more from the high competition capacity vixens (2 ± 0.8 times) than from the low competition capacity vixens (0.4 ± 0.4 times, P = 0.03), possibly reflecting that the high competition capacity vixens were more offensive than the low competition capacity vixens. Our results contribute to the knowledge of social behaviour in this species, and may have implications for the social housing environment of the farm foxes.

The effects of resource distribution on behaviour in pair housed silver fox vixens ( Vulpes vulpes) subsequent to mixing

In nature, the way essential resources are distributed is recognized as a potentially important factor influencing the frequency of aggressive interactions between animals. This knowledge is rarely taken into consideration when designing housing environments for social groups of farm animals. Adult farmed silver foxes ( Vulpes vulpes) are often housed singly, but previous studies have demonstrated that vixens show a motivation for social contact in particular periods of the year and housing in social groups may therefore act as an alternative housing procedure for foxes. However, grouping unfamiliar animals may result in elevated levels of aggression due to competition for resources and thus affect welfare negatively. In the present study we investigated how housing environments with the same space and resources, but with different resource distributions affected the behaviour of adult vixens housed in pairs. A total of 40 vixens were housed in pairs in two coupled cages (2.00 m × 1.10 m × 0.75 m) with either two nest boxes and two food trays (treatment 1) or one nest box and one food tray (treatment 2) from 18 months of age. The occurrence of aggressive behaviour, play behaviour and synchronous resting was recorded throughout the day (i.e. every third hour for 15 min during 24 h) on day 1, day 5, day 19 and day 33 after mixing. In addition, the frequency of physical aggression was recorded for 75 min around feeding time. Body weight gain and wounds were also recorded on day 25 after mixing. The results showed that there had been more severe aggression in treatment 2 during the days after mixing due to higher frequency of physical aggression around feeding time (treatment 1: 0.6 ± 0.21 times, treatment 2: 2.9 ± 0.99 times, P = 0.06), more wounds (treatment 1: 3 of 10 pairs, treatment 2: 8 of 10 pairs, P = 0.03) and less body weight gain ( P = 0.03) compared to treatment 1. The observed aggression levels throughout the day decreased with subsequent observations days for both aggressive displays ( P < 0.01) and chase behaviour ( P = 0.04), indicating that it takes between 5 and 19 days to establish a stabile social relationship within a vixen pair. There was an increase in social ( P = 0.09) and locomotor play ( P = 0.03) as well as synchronous resting ( P < 0.001) with subsequent days after mixing, suggesting that the stress by being mixed with an unfamiliar conspecific is decreasing with time. In both treatments, there was a decrease in object play ( P < 0.001) with subsequent days after mixing, however vixens in treatment 2 showed in general more object play than vixens in treatment 1 (4.3 ± 0.60 scores vs. 2.5 ± 0.47 scores respectively). To conclude, we found that different resource distributions affected wounds, body weight gain and physical aggression during feeding in pair housed silver fox vixens. The elevated aggression levels the first days after mixing may affect vixens’ welfare negatively, however, the increase of social play after mixing suggests that social housing also have positive effects on welfare. The resource distribution of highly valued resources should be taken into account when designing the future social housing system for farmed foxes.

The nature and strength of social motivations in young farmed silver fox vixens ( Vulpes vulpes)

To investigate the strength of social motivation and the motives underlying social contact in farmed silver foxes ( Vulpes vulpes), we housed six young vixens continuously in a closed economy operant apparatus and measured their ‘maximum price paid’ when required to perform a task to obtain unrestricted social contact or food (a ‘yardstick’ resource). In the former trials, vixens of the same-age and origin acted as stimulus animals ( N = 6), and both test and stimulus foxes could decide their own visit durations to a shared compartment. Their motives for visiting this ‘social compartment’ were examined by recording their behaviour during social contact. When access was almost free (a baseline fixed ratio schedule of 1) the test vixens visited the stimulus fox 30.3 ± 4.3 times and spent 45% of the time together per 24 h. The stimulus foxes spent on average 80% per 24 h in the shared compartment and visited this cage 40.7 ± 9.6 times per 24 h. When higher costs were imposed, the test vixens proved willing to pay to access the stimulus vixens and the average maximum price paid for contact was 38.3 ± 8.3% of the price paid for food when hungry. During the time spent together, the stimulus foxes made use of their opportunity to leave the cage, on average 1.43 ± 0.20 times per visit. The behaviour recordings showed that during initial encounters the vixens would fight to establish dominance, and in four of the pairs the test subject emerged as the dominant individual. However, during subsequent interactions, no serious aggression was recorded and social behaviour was characterised by higher levels of sniffing and grooming (23.7 ± 4.3 times/h), play signals (10.5 ± 4.1 times/h) and agonistic displays (5.5 ± 2.5 times/h). Not all of the time together was used for social interaction and during the observation period, the vixens allocated 33.1 ± 6.9% of the time to synchronous resting. We conclude that young silver fox vixens were motivated for social contact, and that this contact was beneficial for welfare due to the low level of aggression and the occurrence of grooming and play.

Responses of farmed silver foxes (Vulpes vulpes) to excessive food availability: Implications for using food as a yardstick resource in motivation tests

Food is frequently used as a ‘yardstick’ in operant experiments. However, previous work on silver foxes had suggested that how food is presented can affect how they respond to it, with excess food leading to variable consumption rates, and cages containing food being avoided over control cages except while eating. Our first experiment therefore examined foxes’ consumption of excess food in more detail by comparing their daily intakes with foxes fed a control diet for 4 weeks. Eighteen silver fox vixens were assigned to one of two groups in which the experimental group (N=9) was feed 2.5 times that of control (N=9). Although appetite, measured as the amount of food consumed, tended to fluctuate none of the overly fed foxes stopped eating during the experimental period. On average, the excessive fed group consumed more food (317±18g/day) compared to the controls (273±12g/day).In Experiment 2 we aimed to test whether the presence of excess food affected the foxes’ use of the cage. Five silver fox males were housed in separate multi-compartment apparatuses and the position of a food bowl was randomly switched between two cages for 18 days. The subjects had to perform one operant response to enter each cage and time inside the compartments was calculated. The foxes spent significantly less time in the food compartment (4h 13min), compared to the empty cage (12h 12min) and as expected by random (8h) (P<0.05). These results confirm that ad libitum fed silver foxes have a more fluctuating intake rate than animals fed just below maintenance, and that placing food in a cage reduces the time spent there. The day-to-day use of food, and perhaps even its value, can therefore be shaped by how it is presented. Implications for using food as a yardstick resource for silver foxes is that the ration should be held at maintenance. Also, to control for a motivation to leave food positioned in the operant test cage a free control cage distant from food could be provided.

Effects of behaviour selection on litter size, fetal development and plasma progesterone concentrations during pregnancy in silver fox vixens

Animal domestication is a natural selection experiment the important result of which is a great increase in the rate of appearance of new forms and in the wild range of variation of organisms. Analysing different aspects of this problem, D.K. Belyaev has came to a hypothesis that the morphological and physiological reorganisation of domestic animals has been going by the way of unconscious selection of animals on their behaviour, carried out by person at the very first stages of domestication (Belyaev, 1979). To testify this hypothesis, a population of tame silver foxes has been produced in long-term selection for lack of aggression and fear towards humans (domestic behaviour) at the Institute of Cytology and Genetics in Novosibirsk, Russia. In the process of selection the genetic transformation of behaviour and morphology, and physiological functions has been observed (Trut, 1999). In particular, selected animals show no aggressiveness to man, behave amicably towards humans and have some changes in the coat colour and body constitution (Trut, 1999). The important part of Belyaev’s hypothesis was the assumption that selection for domestic behaviour could affect the reproductive function, in particular the pituitary-gonadal axis controlling reproduction and fertility. The aim of this study was to obtain information about possible changes in reproduction between control (C) and domesticated (D) vixens. Reproductive performance, potential fertility, embryonic mortality and fetal viability were analysed for vixens from domesticated and control population. In addition, plasma progesterone concentrations were determined in selected and control females during pregnancy.

Control of red fox (Vulpes vulpes) fertility with cabergoline: dose response and timing of intervention

Cabergoline, a potent dopamine agonist and inhibitor of prolactin secretion, was investigated as a potential fertility control agent in the red fox ( Vulpes vulpes). Sixty silver fox vixens were selected randomly and artificially inseminated. Cabergoline was fed to groups of 12 vixens in a minced beef ration either as a single dose of 25, 50 or 100 microg kg(-1), or a dose of 50 microg kg(-1) that was repeated 2 days later (2 x 50 microg kg(-1)). Four foxes from each group of 12 were given cabergoline at day 28, day 35 or day 48 after artificial insemination, and a control group of four foxes was used as a comparison for each dose day. In a separate trial, two groups of five foxes were selected randomly from the farm population and fed 100 microg kg(-1) of either cabergoline or a placebo each day from day 42 to day 46 of pregnancy. Foxes that received single doses of cabergoline of 100 microg kg(-1) or 2 x 50 microg kg(-1) aborted at day 28, but the same doses did not result in abortions when administered on days 35 and 48. Although lactation was not terminated in groups that received a single or double dose of cabergoline, increased post-natal cub mortality was associated with cabergoline administration. Growth of cubs between 4 and 8 weeks of age was not inhibited in vixens that received cabergoline. Doses of 100 microg cabergoline kg(-1) administered each day from day 42 to day 46 resulted in abortions and terminated lactation. The capacity of single doses of cabergoline to cause abortions in the red fox during mid- rather than late pregnancy is contrary to reported observations for the domestic dog. This finding indicates that luteotrophic support of the corpus luteum by prolactin may be more important at mid-pregnancy in the red fox. The results of this study support previous field observations that cabergoline delivered in bait affects the reproductive success of vixens and may be a practical adjunct to the lethal control of wild red foxes in Australia.

Control of red fox (Vulpes vulpes) fertility with cabergoline: dose response and timing of intervention

Cabergoline, a potent dopamine agonist and inhibitor of prolactin secretion, was investigated as a potential fertility control agent in the red fox ( Vulpes vulpes). Sixty silver fox vixens were selected randomly and artificially inseminated. Cabergoline was fed to groups of 12 vixens in a minced beef ration either as a single dose of 25, 50 or 100 microg kg(-1), or a dose of 50 microg kg(-1) that was repeated 2 days later (2 x 50 microg kg(-1)). Four foxes from each group of 12 were given cabergoline at day 28, day 35 or day 48 after artificial insemination, and a control group of four foxes was used as a comparison for each dose day. In a separate trial, two groups of five foxes were selected randomly from the farm population and fed 100 microg kg(-1) of either cabergoline or a placebo each day from day 42 to day 46 of pregnancy. Foxes that received single doses of cabergoline of 100 microg kg(-1) or 2 x 50 microg kg(-1) aborted at day 28, but the same doses did not result in abortions when administered on days 35 and 48. Although lactation was not terminated in groups that received a single or double dose of cabergoline, increased post-natal cub mortality was associated with cabergoline administration. Growth of cubs between 4 and 8 weeks of age was not inhibited in vixens that received cabergoline. Doses of 100 microg cabergoline kg(-1) administered each day from day 42 to day 46 resulted in abortions and terminated lactation. The capacity of single doses of cabergoline to cause abortions in the red fox during mid- rather than late pregnancy is contrary to reported observations for the domestic dog. This finding indicates that luteotrophic support of the corpus luteum by prolactin may be more important at mid-pregnancy in the red fox. The results of this study support previous field observations that cabergoline delivered in bait affects the reproductive success of vixens and may be a practical adjunct to the lethal control of wild red foxes in Australia.

Preference for various nest box designs in farmed silver foxes ( Vulpes vulpes) and blue foxes ( Alopex lagopus)

Nest box choice experiments were carried out outside the breeding season on adult silver and blue fox vixens with no previous permanent nest box experience. Nest boxes were varied in height of placement, number of rooms, presence of entrance room or platform and light conditions. Only one parameter was varied in any one experiment. Both fox species clearly preferred an elevated multi-room nest box; while silver foxes showed preference for boxes supplied with a platform, blue foxes preferred boxes with an entrance room. There was no significant box preference with respect to light conditions. The possible welfare implications of the preferences are discussed.

Effects of environmental stressors on deep body temperature and activity levels in silver fox vixens ( Vulpes vulpes)

The present study was performed to investigate the effects of 14 different environmental stimuli on stress-induced hyperthermia (SIH) and levels of locomotor activity in six (three infanticidal, three non-infanticidal) 2.5-year-old silver fox vixens. The effects of contact with humans (six experiments; handling for 5 min, handling of neighbouring animal for 5 min, presence of one person for 20 s, 5 and 90 min, presence of a group of humans for 5 min), exposure to unfamiliar foxes (four experiments; presence of an unfamiliar cagemate [female, male] and an unfamiliar neighbouring animal [female, male] for 90 min), and various recorded noise stimuli (four experiments; aircraft noise [duration 15 s, 100 dB], machine noise [duration 15 s, 90 dB], firing a shotgun [duration 1 s, 90 dB], human conversation [duration 15 s, 95 dB]) played back and repeated at 20 s intervals during 5 min were tested. Deep body temperature and activity levels were monitored with surgically implanted radio telemetry devices. All registrations were made during the 90-min period after stimulus presentation. The presence of humans and other silver foxes, but not exposure to loud recorded noise, resulted in a SIH. Comparison of the SIH between the normally reproducing vixens and the previously infanticidal vixens revealed significant differences. The SIH response was most pronounced in the previously infanticidal vixens, whereas the levels of physical activity were lowest in this group. The present study indicated that important means to improve animal welfare in silver foxes should include an improvement of the general human–animal relationship and emphasises the importance of a stable social environment.

The effect of an improved man–animal relationship on sex ratio in litters and on growth and behaviour in cubs among farmed silver fox ( Vulpes vulpes)

Earlier experiments indicate that silver foxes' fear of humans can be reduced by humans offering them food titbits. Sex ratio, cub growth and behaviour were examined in litters produced by multiparous silver fox vixens that had been given a titbit twice a week during pregnancy (G1, N=14) or received the same amount of human contact without any titbit (G2, N=14). The cubs were tested in an open field (1.15×1.15 m square area divided into a 5×5 square grid) at 30 days of age, when they were in the early stages of primary socialisation. Cub activity was recorded (number of grid lines crossed [Lc] during 3 min). There was no treatment-related difference in number of cubs born or cubs weaned at 49 days (4.9±0.3 and 4.1±0.4 vs. 4.8±0.5 and 3.8±0.4 for G1 and G2, respectively; NS). However, G1 vixens delivered a significantly higher proportion of male cubs than G2 vixens (64% vs. 51%, p<0.05; G1:3.1±0.4 male cubs, 1.8±0.3 female cubs; G2:2.5±0.4 male cubs, 2.3±0.3 female cubs). Female cubs from G1 vixens were more active in the open field (G1:51.4±4.8 Lc, G2:34.2±4.7 Lc, p<0.05) and heavier (49 days old, G1:1660±42 g, G2:1491±40 g, p<0.01) than the female G2 cubs. No significant differences in activity or live weight were found for male cubs (activity: G1:46.4±3.4 Lc, G2:37.1±4.3 LC, NS; weight 49 days old: G1:1716±29 g, G2:1729±37 g, NS). Reduced fear of humans during pregnancy affected the sex ratio in the litter as well as the growth and activity of female cubs in the silver fox.

Effects of Handling and Physical Restraint on Rectal Temperature, Cortisol, Glucose and Leucocyte Counts in the Silver Fox (Vulpes vulpes)

The present paper describes the effects of handling and one hour of physical restraint on rectal temperature (Trec), plasma cortisol, plasma glucose and leucocyte counts in six 8-months old silver fox vixens (Vulpes vulpes). Mean Trec in silver foxes 5 min after capture was 40.1 degrees C and increased during restraint, showing a maximum of 40.8 degrees C at 30 min thereafter. Supplementary, deep body temperature (Tb) was recorded with surgically implanted biotelemetry devices in 6 adult silver fox vixens kept isolated from environmental disturbances in a barn. Mean Tb in these foxes ranged between 38.0-38.4 degrees C, showing a diurnal variation and being at the lowest between 0700-1600 hour. When a person approached a fox and was present for 5 min, Tb increased rapidly. The results indicated that a stress-induced hyperthermia (SIH) was evoked rapidly within the first registration at 5 min after capture, and that this response continued during one hour of physical restraint. Plasma glucose and plasma cortisol levels increased during one hour of physical restraint, whereas numbers of lymphocytes, total white blood cell counts, and total granulocytes decreased. Furthermore, previously reported base levels of plasma cortisol and plasma glucose were exceeded. The results indicate that the hypothalamic-pituitary-adrenal (HPA) axis and the sympathoadrenal medullary (SAM) system were activated within 5 min of handling and restraint. Furthermore, hyperthermia is a promising indicator of acute stress in silver foxes.

Effect of Repeated Blood Sampling on Plasma Concentrations of Cortisol and Testosterone and on Leucocyte Number in Silver Fox Vixens (Vulpes Vulpes)

Abstract It is of great importance to be able quantitatively to evaluate the stress to which captive fur animals are subjected to by various forms of management. A range of haematological and hormonal parameters have been shown to be good indicators of stress. However, blood sampling, which entails the presence of humans and handling of the animals, can itself be a stressor that influences the results of an experiment. The present study shows that a group of silver foxes (n = 7) that had been regularly blood sampled (RBS-group) for a year had higher plasma concentrations of cortisol and lower concentrations of testosterone compared with an earlier non-blood-sampled group (NBS-group) (n = 7). The RBS-group also tended to have a lower number of lymphocytes. In addition, during a series of five blood samples taken at 30 min intervals, both groups showed an increase in plasma concentrations of cortisol, whereas numbers of lymphocytes and eosinophil leucocytes decreased. Plasma testosterone concentrations decr...

Does fear of humans by silver fox affect reproductive performance and cub behaviour?

Earlier experiments indicate that the silver foxes’ fear of humans is reduced with use of food titbits. Sex ratio, growth and behaviour were examined in cubs from multiparous silver fox vixens, which either received a titbit twice a week during pregnancy (Gl, n = 14), or received the same amount of human contact without any titbit (G2, n = 14). The cubs were tested in an open field ( 1.15 m X 1.15 m area divided into a 5 x 5 square grid) at 30 days of age, in the early stages of primary socialisation. Cub activity was recorded (number of grid lines crossed (Lc) during 3 min). There was no difference due to treatment in the number of cubs born or cubs weaned at 49 days (4.9 f 0.3 and 4.1 f 0.4 vs. 4.8 f0.5 and 3.8* 0.4 for Gl and G2, respectively; NS). However, the Gl vixens delivered a significantly higher proportion of male cubs than G2 (64% 6 vs. 5 1% 0, P < 0.05; Gl , 3.1 k 0.48, 1.8 k 0.3 0 ; G2, 2.5 f 0.48, 2.3 + 0.3 P ). Female cubs from Gl were more active in the open field (Gl, 51.4k4.8Lc; G2,34.2*4.7Lc; P<O.O5), and heavier at 49 days of age (Gl, 1660*42 g; G2, 149 1 rt 40 g; P < 0.01) than female G2 cubs. No significant differences in activity or liveweight were found for male cubs (activity: Gl, 46.4& 3.4Lc, G2, 37.1 f4.3Lc; NS; weight at 49 days; Gl CT, 17 16 f 29 g; G2 0, 1729 f 37 g, NS). Reduced fear of humans during pregnancy affected the sex ratio in the litter, and growth and activity of female cubs in the silver fox. 0168-1591/95/$09.50

Long-term effects of different handling procedures on behavioural, physiological, and production-related parameters in silver foxes

Fifty-one silver fox vixens, subjected to three different handling treatments as cubs (no-handling, gentle or forced handling), were studied for long-term effects on behavioural, physiological and production-related parameters in a one and a half year period following the last handling session. As juveniles, the animals were exposed to three different behavioural tests at 18, 22, 28, and 32 weeks of age. Both forcibly and gently handled animals showed reduced fear responses compared with nonhandled controls in test situations involving close contact with humans ( P < 0.05). The foxes were tested again as adults at 10, 13, 15, and 18 months of age with the same behavioural tests. It was revealed that forcibly handled animals persistently showed reduced fear responses compared with control animals, both in close contact with humans and when exposed to a novel object, whereas gently handled animals only differed from control animals in one of the tests involving some human contact and when exposed to a novel object ( P < 0.05). Significant differences between adult gently handled and forcibly handled animals were found in the “confront’ test involving close human contact. In this test more flight responses were observed in the gently handled group than in the forcibly handled group ( P < 0.01). Control animals had significantly larger adrenal weights compared with both forcibly handled animals and gently handled animals at 22 months of age (total mean adrenal weight: controls, 0.62 g; gentle, 0.54 g; forced, 0.54 g, P < 0.05, general linear models). Other physiological measures and production-related parameters such as body weight, body size, gastric ulceration and pelt qualities did not differ between treatments ( P > 0.05). Early post-weaning handling made foxes less fearful towards humans. Forced handling seemed somewhat superior to gentle handling as a means to produce animals which, in the long term, adapted better to the farm environment both behaviourally and physiologically. Non-handled control animals suffered from long-term stress as reflected by high levels of fear responses and enlarged adrenals. Thus post-weaning handling may be beneficial in the long term for the wellbeing of farmed foxes. When applied as a management routine, handling had no significant influence on later production-related parameters and was not considered an economic risk.

Reproduction in Silver-Fox Vixens in Breeding Boxes with and without an Entrance Tunnel

Abstract On nine farms in a joint fur-farm area, reproduction was studied in 834 silver-fox vixens (Vulpes vulpes L.), half of which were primiparous. Two different breeding boxes with a narrow entrance tunnel and two versions of a traditional box were used. The vixens had access to the box after insemination. No effect of box type was found on two farms with a high reproduction. In the remaining seven farms, vixens in tunnel boxes more often bore offspring and had a lower cub mortality 0–3 weeks postpartum than vixens in traditional boxes. The effects were most pronounced for primiparous vixens. It is concluded that breeding boxes with an entrance tunnel may improve the reproduction and the welfare of both vixens and their offspring.

Effects of different post-weaning handling procedures on the later behaviour of silver foxes

Male and female cubs from 52 litters of primiparous silver-fox vixens were in pairs randomly assigned to three groups at the age of 8 weeks. Seventeen pairs were exposed to forced handling and 18 pairs were exposed to gentle and unforced handling twice daily for 3 continous weeks post-weaning. Seventeen pairs of fox cubs served as control animals and were not handled. Behavioural tests performed at the cubs' age of 18, 24, 30 and 32 weeks showed that handling of foxes either forcibly or gently affected the foxes' fear responses towards humans compared with no handling. Handled animals showed less fear responses and more exploration compared with control animals at most ages of testing (0.05< P<0.001, χ 2) The gently handled group showed a marked reduction of fear responses towards people both known and unknown to them and a less evident reduction of fear responses when exposed to novel stimuli. Foxes forcibly handled showed some reduction of fear responses towards people known and unknown to them and they showed more exploration when exposed to novel stimuli compared with both gently handled animals and control animals at most ages of testing. It was concluded that gentle handling of fox cubs was a means to reduce later fear responses towards humans and that forced handling was a means to reduce the general fearfulness of the foxes. Positive human-fox relationships may be achieved by gentle, unforced handling and forced handling may produce less emotional foxes, but further research is needed to conclude if one of the handling procedures is more efficient than the other in making the foxes better adapted to the frequent exposures to humans and the different management routines in the farm environment.

Periparturient behaviour of successfully reproducing farmed silver-fox vixens

As part of a project series aiming at understanding the reproductive behaviour of farmed silver foxes, this paper describes the normal variation in behaviour around parturition shown by successfully reproducing vixens. The behaviour of 19 vixens (eight primiparous, 11 multiparous) kept under traditional management conditions, was video-recorded inside the breeding box day and night, and analyzed in four phases from 24 h before delivery to 72 h after. Births were distributed uniformly around the clock. True litter size at birth was 3.8 (SD = 1.7) for primiparous vixens and 4.7 (SD = 1.5) for multiparous vixens. The period elapsing between individual births was 56 (SD = 29) min. The parturition period lasted 192 (SD = 87) min. The time-budget of behaviour showed a pronounced individual variation in all phases, but with few differences related to parity. During the last 24 h prior to parturition, the vixens stayed in the breeding box 63% of the time. Two-thirds of this time was spent resting or sleeping. All vixens dug vigorously on the box floor, on average for a total of 102 min, mainly during the last hours before parturition. Vixens never lined the nest with fur tangles. The delivery of cubs seemed to be quite easy, except for the first-born cub of some primiparous vixens. About 60% of the parturition phase was spent cleaning, grooming and inspecting cubs. During the 3 postparturient days, vixens rested or slept 70% of the time, though an average sleeping bout lasted only 11 min. Vixens showed active cub-care, mainly consisting of grooming cubs while lying down, for 24% of the time during the first postparturient day and for 18% during the next 2 days. This behaviour showed no relationship to litter size, indicating that an average cub receives more care the smaller the litter size. The vixens were rarely seen to retrieve cubs or to bring them outside the breeding box. Vixens left their boxes for an average total of 50 min per postparturient day. The results showed that not only multiparous, but also primiparous vixens may show completely adequate behaviour around parturition.