Surgical transfer of in vivo produced farmed European polecat (Mustela putorius) embryos

Surgical embryo transfer of farmed European polecat (Mustela putorius) was investigated as part of an ex situ preservation project. The long-term objective of the project is to develop effective technology for ex situ conservation of the European mink (Mustela lutreola), which is a highly endangered aboriginal European species. Twenty European polecat females, which served as a model species for the European mink, were humanely killed 4-9 days after first mating and embryos were recovered from oviducts and uteri. Donor-recipient pairs (n = 16) were generated by mating the donors (n = 20) once a day for 2 consecutive days with fertile males and by mating the corresponding recipients (n = 16) on the same days with vasectomized males. An embryo recovery rate of 70% (200 recovered embryos/284 corpora lutea) was achieved from 20 donors. Morulae and blastocysts were recovered between Days 5 and 9 after first mating and were regarded as the best developmental stages for uterine embryo transfer. A total of 172 embryos were transferred surgically under general anaesthesia into the ovarian third of the left uterine horn of 16 recipients with a thin glass capillary. Eleven recipients (69%) produced 72 pups equivalent to an average success rate of 42% (72 pups/172 transferred embryos). The average litter size was 4.5 (range 0-9). These results with this model species, farmed European polecat, demonstrate the potential of embryo transfer as an effective method for the preservation of the endangered European mink (M. lutreola). These species are closely related and have a similar reproductive physiology. However, success of applying embryo transfer in conserving European mink is still dependent on further studies both into its reproductive physiology and developing of improved flushing techniques for anaesthetized donors and the successful transfer of frozen-thawed embryos.     

Live cubs born after transfer of OPS vitrified-warmed embryos in the farmed European polecat (Mustela putorius)

The Open Pulled Straw (OPS) method of vitrification has been used successfully for cryopreserving embryos of most domestic animal species. However, there is no report of a successful delivery of offspring after transfer of vitrified embryos in carnivores, even though vitrification has been a successful freezing method for species like swine whose embryos are known to be susceptible to chilling injury. Morulae and blastocysts of farmed European polecat (Mustela putorius) were vitrified and warmed before in vitro culture in modified synthetic oviductal fluid (SOF) for a period from a few hours up to 3 days before being transferred to recipients. Survival rate after vitrification, warming and in vitro culture was 51% (50/98). A total of 50 embryos were transferred surgically into the uteri of four anesthetized recipients. Two recipients delivered a total of eight offspring (2 and 6 each) for an overall survival rate of 16% (eight live cubs/50 transferred embryos). According to our knowledge, these offspring are the first carnivores produced by transfer of in vivo embryos after vitrification by OPS. Based on the present results, we suggest that OPS vitrification can be used as an alternative cryopreservation method for mustelid embryos with pup results comparable to conventional slow freezing.     

Early embryonic development and in vitro culture of in vivo produced embryos in the farmed European polecat (Mustela putorius)

Early embryonic development and in vitro culture of in vivo produced embryos in the farmed European polecat (Mustela putorius) was investigated as a part of an ex situ conservation program of the endangered European mink (Mustela lutreola), using the European polecat as a model species. The oestrus cycles of 34 yearling polecat females were monitored by visual examination of the vulval swelling and, to induce ovulation, the females were mated once daily on two consecutive days. Sixteen yearling males were used for mating. The females were humanely killed 3-14 days after the first mating and the uteri and oviducts were collected for embryo recovery. Uterine and oviductal flushings yielded a total number of 295 embryos, representing developmental stages from the 1-cell stage to large expanded and hatched blastocysts. On Day 3 after the first mating, only 1-16-cell stage embryos were recovered. Between Days 4 and 6 after the first mating, 1-16-cell stage embryos and morulae were found. The first blastocysts were recovered on Day 7 after the first mating. The first implanted blastocysts were detected on Day 11 after the first mating. A total number of 85 embryos were in vitro cultured after recovery. Blastocyst production rates for in vitro cultured 1-16-cell stage embryos and for morulae/compact morulae were 68 and 84%, respectively. For all cultured embryos, the hatching rate was 15%. The in vitro culture requirements for the preimplantation embryos of the farmed European polecat remain to be determined before further utilization of the technique.     

Immobilization of free-ranging European mink (Mustela lutreola) an polecat (Mustela putorius) with medetomidine-ketamine and reversal by atipamezole

From March 1996 to August 1999, 24 free-ranging European mink (Mustela lutreola) and 25 free-ranging polecats (Mustela putorius) were immobilized for clinical procedures and to place radio transmitters. Data were recorded during 14 and 12 trials, respectively. Animals received intramuscularly 10 mg/kg ketamine (KET) combined with 0.20 mg/kg medetomidine (MED), antagonized by 1.00 mg/kg atipamezole (ATI). Anesthesia times were similar between species. Induction was smooth and rapid (0.7-3.9 min); the degree of anesthesia and muscle relaxation was satisfactory in most animals. Two individuals showed signs of spontaneous recovery before injection of ATI. In other individuals, ATI was injected 28.1-54.0 min after the MED-KET injection and rapidly reversed the effects of the MED. Rectal temperature and heart and respiratory rates decreased significantly 5-25 min post MED-KET injection in both species. Rectal temperature successfully remained stable by placing animals on a warmed plastic table (37 C) during anesthesia. According to these results, this anesthetic protocol produces a safe and rapid immobilization in free-ranging European mink and polecats and is recommended for surgical procedures such as radio transmitter implantation. However caution is required as hypothermia can be severe. Body temperature must be monitored and means provided to maintain stability.     

Diets of European polecat Mustela putorius in Great Britain during fifty years of population recovery

Following nineteenth-century declines, polecats Mustela putorius are recolonising Great Britain. Polecat diet relates to two potential risks to recovery. First, rabbits Oryctolagus cuniculus, which are important prey for polecats, have experienced extreme population fluctuations, with near extirpation due to myxomatosis in the 1950s, recovery in 1960s–1990s and declines in 1990s–2010s. Second, polecats are secondarily exposed to anticoagulant rodenticides by eating contaminated rodents, and the frequency of polecat exposure to rodenticides is increasing. We analysed stomach contents from 99 polecats collected in 2012–2016 and compared results with earlier studies. Lagomorphs were the most abundant prey (66% frequency of occurrence, 95% confidence interval 53–74%), followed by other mammals (12%, 4–18%), amphibians (10%, 3–16%) and birds (7%, 1–13%). Diet varied seasonally; lagomorph occurrence was highest in spring and summer and lowest in autumn. Dietary niche breadth was greater in the 1960s, when rabbits were scarce, than in other decades, but did not differ between the 1990s and 2010s, indicating that diets have not diversified with recent rabbit declines. This may be because rabbit abundance is not yet low enough to cause dietary diversification or because polecats were collected in areas where rabbits were still abundant. Rodents did not increase in diet between the 1990s and 2010s and still occur with < 10% frequency, indicating that rodents need not contribute much to diet to expose polecats to rodenticides. This potentially limits the effectiveness of management actions designed to minimise polecat exposure to contaminated rodent prey.     

Kin recognition versus familiarity in a solitary mustelid, the European polecat Mustela putorius

The aim of this experimental study was to investigate kin discrimination in the polecat and to analyse the ontogeny of interactions. Juvenile polecats (ten males and nine females) had been raised under four distinct experimental conditions: 1, kin, familiar; 2, kin, unfamiliar; 3, non-kin, familiar; 4, non-kin, unfamiliar. During dyadic encounters between polecats in neutral enclosures, the number of positive (tolerance), negative (aggression), intermediate (intimidation), and neutral interactions (no direct interactions) were recorded at two different ages of the animals (50 and 70 days old). Male-male encounters were characterised by more aggressive behaviour than female-female ones. The proportion of these negative interactions increased with age, while the proportion of positive interactions decreased. Although aggressive behaviours varied among groups, the reaction did never differ with the kinship. Kin selection theory provides successful explanations for a wide range of phenomena, but our results suggest that multiple mechanisms running simultaneously might be involved in social behaviours. Familiarity clearly influenced the social behaviour of polecats and might be involved in a kin facilitation effect favouring interactions. Animals raised together demonstrated more positive and less negative interactions, so that, despite the individualistic way of life of the polecat, familiarisation may result in more tolerance, emphasising that solitary species may provide significant information on social life. Anyway, familiarisation in polecat may be regarded as a cognitive form of recognition.     

Bayesian analysis of hybridization and introgression between the endangered european mink (Mustela lutreola) and the polecat (Mustela putorius)

Human-mediated global change will probably increase the rates of natural hybridization and genetic introgression between closely related species, and this will have major implications for conservation of the taxa involved. In this study, we analyse both mitochondrial and nuclear data to characterize ongoing hybridization and genetic introgression between two sympatric sister species of mustelids, the endangered European mink (Mustela lutreola) and the more abundant polecat (M. putorius). A total of 317 European mink, 114 polecats and 15 putative hybrid individuals were collected from different localities in Europe and genotyped with 13 microsatellite nuclear markers. Recently developed Bayesian methods for assigning individuals to populations and identifying admixture proportions were applied to the genetic data. To identify the direction of hybridization, we additionally sequenced mtDNA and Y chromosomes from 78 individuals and 29 males respectively. We found that both hybridization and genetic introgression occurred at low levels (3% and 0.9% respectively) and indicated that hybridization is asymmetric, as only pure polecat males mate with pure European mink females. Furthermore, backcrossing and genetic introgression was detected only from female first-generation (F1) hybrids of European mink to polecats. This latter result implies that Haldane's rule may apply. Our results suggest that hybridization and genetic introgression between the two species should be considered a rather uncommon event. However, the current low densities of European mink might be changing this trend.     

The distribution and status of the polecat Mustela putorius in Luxembourg

1. The presence and distribution of the polecat Mustela putorius in Luxembourg was studied for the first time. Postal surveys were conducted among all the tenants of the hunting areas and all the farmers in the country. 2. Except for the otter Lutra lutra, the polecat appears to be the least common mustelid in Luxembourg. Farmers and hunters perceived the polecat differently according to their interests. Farmers had a more tolerant attitude towards the species but 17% still considered it a pest. 3. Live trapping of polecats was carried out for 3 years: 16 individuals were caught. This suggests a very low population density. Hunting records of this mustelid were examined for the period 1955–2000. There has been a very strong decrease in the number of polecats killed, giving rise to concerns that its population may be dramatically declining. Moreover, hunting data from neighbouring Germany confirm that this is a regional situation.     

Growth and development of the European ferret (Mustela putorius)

Body weight, body length, and other developmental parameters were studied in the European ferret, Mustela putorius, from birth to 26 weeks of age. Males and females did not differ in weight until the seventh week of live, and they did not differ in length until the ninth week of life, when the males began to grow faster. Adult males (1400--1500 g) were heavier than adult females (800--900 g), but females reached adult size faster than males.     

The fever reaction of the polecat Mustela putorius x Mustela putorius furo to a bacterial pyrogen: the hypo- and hyperthermic phases]

It has been demonstrated that the ferret (Mustela putorius x Mustela putorius furo) responds to intramuscular injection of Salmonella typhi lipopolysaccharide (30 ng/kg-100 micrograms/kg) by biphasic change in the body temperature (Tb): the initial decrease in the latter is followed by hyperthermia. Maximum rise in Tb (1.6 +/- 0.1 degrees C) was observed after the injection of lipopolysaccharide in the highest dose. Rabbit leucocytic pyrogen/interleukin-1 (1 ml from 3.5 x 10(7) peritoneal phagocytes, 3 ml/kg) induces a pronounced (1.1 +/- 0.3 degrees C) decrease in Tb. Mechanisms of hypothermic effects of pyrogens are discussed. The described pattern (hypothermia-hyperthermia) of Tb response to lipopolysaccharide in the ferret presumably reflects the central thermoregulatory process which is the same for different changes in Tb during fever.     

Environmental factors influencing habitat exploitation by the polecat Mustela putorius in western France

Variation in habitat use was studied by radiotracking 11 polecats Mustela putorius in two wetlands in western France. Habitat selection showed a clear seasonality. Marshes were the most exploited habitat in spring while woods were mainly used in the coldest months and meadows were frequented in summer and winter. An analysis of scats showed that diet correlated with habitat utilization. The proportions of bank voles Clethrionomys glareolus , and meadow voles Microtus sp. were, respectively, related to the use of woods and meadows, while amphibians (mainly Rana dalmatina and Bufo bufo) were associated with marshes. Availabilities of rodents, assessed monthly by trapline success, were also significantly correlated to their occurrences. In contrast, no correlations were found between larger prey, such as brown rats Rattus norvegicus and rabbits Oryctolagus cuniculus , and any habitats or their abundance in the field. The occurrences of these prey and of some minor resources, such as shrews and birds, were correlated most with meteorological factors. The exploitation of marshes and amphibians increased when small rodents declined. Therefore, in the polecat, habitat selection was mostly influenced by trophic factors. Dietary diversity was greater in spring when food resources decreased, suggesting that polecats were optimal foragers. The study has emphasized that the polecat is a generalist feeder.     

Pregnancy toxemia in the European ferret (Mustela putorius furo).

BACKGROUND AND OBJECTIVE: Pregnancy toxemia may lead to appreciable mortality among jills and their offspring. The objective of this report was to increase awareness of the disease, its likely cause, and practical prevention and treatment measures. METHODS: Ten cases of pregnancy toxemia were evaluated. Jills were in late gestation (mean, 38 days; range, 34 to 42 days) and had large litters (mean, 11.5 kits; range, 7 to 15 kits). RESULTS: The most common clinical signs of disease were lethargy, inappetence, dehydration, and excess shedding. Hematologic and clinical biochemical abnormalities included anemia (4 of 8 jills tested), hypoproteinemia (5 of 7), azotemia (7 of 7), hypocalcemia (5 of 6), hyperbilirubinemia (3 of 3), and high liver enzyme activities (6 of 6). Two jills were found dead; two jills were euthanized, six received supportive treatment, and cesarean section was performed on five. The three jills that survived tended to have less pronounced azotemia, hypoproteinemia, and liver enzyme activity increases and were not anemic. Hepatic lipidosis was observed grossly in all jills that died and was confirmed by histologic examination in four jills. CONCLUSIONS: Pregnancy toxemia in ferrets resembles metabolic diseases in several other animal species and requires aggressive treatment, including supportive care, nutritional supplementation, and cesarean section. Maintaining adequate nutrition and avoiding stress late in gestation may prevent the disease.     

Nonsurgical collection and nonsurgical transfer of preimplantation embryos in the domestic rabbit (Oryctolagus cuniculus) and domestic ferret (Mustela putorius furo)

The objective of this study was to develop nonsurgical methods of embryo collection and transfer in domestic rabbits (Oryctolagus cuniculus) and domestic ferrets (Mustela putorius furo) to serve as models for use in mammals in which surgical procedures are the usual means for applying embryo transfer technology. Specially designed transcervical catheters were used together with a fibre optic endoscope to visualize and then catheterize the rabbit and ferret cervices. Five consecutive transcervical uterine flushes in each of eight superovulated female rabbits 78-89 h after an ovulatory injection of LH resulted in the retrieval of 187 embryos, for an average of 23 embryos per rabbit. A total of 116 embryos were nonsurgically transferred to the uteri of ten recipients, and resulted in 23 young (20%). Eight rabbits (80%) produced young with an average litter size of 2.88 (range 1-7). Ten consecutive transcervical uterine flushes in each of 37 female ferrets 145-178 h after an ovulatory injection of hCG resulted in the retrieval of 324 embryos, an average of 8.76 embryos per ferret. A total of 251 embryos from 27 donors were nonsurgically transferred to the uteri of 31 recipients, and resulted in 65 young (26%). Twenty-eight of the recipients (90%) were initially pregnant, as indicated by postpartum necropsies, and twenty-two ferrets (71%) produced young. The average litter size was 2.95 (range 1-7). This is the first report of live births resulting from the nonsurgical collection of embryos from a donor followed by nonsurgical transfer of those same embryos to a synchronous recipient. The methods reported here can serve as models for use in other mammals in which direct visualization and manipulation of the cervix are not possible, and will be particularly useful in endangered species.     

A panel of microsatellite markers for genetic studies of European polecats (Mustela putorius) and ferrets (Mustela furo)

We report a panel of 12 microsatellite markers, including nine novel polymorphic loci isolated in the European polecat and three loci previously developed in closely related species, for genetic studies of polecats and ferrets. We tested the panel at fine geographic scales in polecat and domestic ferret populations of Britain and Portugal and at a broad geographic scale, using 50 polecat samples from across Western Europe. At the fine geographic scales, we recorded one to five alleles per locus and observed and expected heterozygosities ranging from 0 to 0.80 and from 0 to 0.74, respectively. These values increased markedly in the European sample of polecats. No linkage disequilibrium was detected between any pair of loci and all genotypic frequencies complied with Hardy–Weinberg equilibrium expectations. The microsatellite panel allowed the molecular discrimination of polecats and domestic ferrets in Britain, where hybridisation between the two species has been documented. Thus, these loci may be useful not only in genetic studies of polecats and ferrets but also in studies to assess hybridisation between these two mustelid species.     

Reproductive cycle of the steppe polecat (Mustela eversmanni)

In laboratory conditions, in a natural photoperiod, testicular redevelopment began in late December. Maximal testis size was attained by the end of February. Testicular regression began in mid-May and was complete by the end of August. Oestrus was first observed in late March and continued throughout April. Females mated for the first time between 30 March and 8 April. Mating generally coincided with peak concentrations of urinary oestrone conjugates and when vaginal lavages contained greater than 90% cornified epithelial cells. Blastocyst implantation occurred by Day 13 and the post-implantation period was 29 days. Gestation ranged from 39 to 43 days and first parturition occurred in mid-May. Concentrations of urinary oestrone conjugates and free progesterone were elevated during the first half of pregnancy, reaching maximum values at mid-pregnancy, and then gradually declined as parturition neared. Litter size of primiparous females averaged 6.8 young/female. Females that were pseudopregnant or lost their litters shortly after birth, and several with weaned kits, exhibited a second oestrus.     

Functional response and area‐restricted search in a predator: seasonal exploitation of anurans by the European polecat,Mustela putorius

A study of the feeding habits and movements of 11 radiotracked polecats Mustela putorius in western France revealed that seasonal predation upon agile frogs, Rana dalmatina, was directly influenced by prey abundance and distribution. Although dietary structure showed the importance of mammalian prey (71.5%), polecats exploited nocturnal, terrestrial anurans in spring (31.6%). The periodic activity of anurans at spawning sites led both to a maximum density in spring and to a patchy distribution. The monthly variations in anuran dietary occurrences were associated with changes in frog availability. The functional response of polecats to frog density was sigmoidal shaped (type 3 response). Frog consumption rate increased more slowly than prey density but frogs were actively removed at higher density. It is therefore suggested that frog populations were moderately affected by the predator and this density dependent effect tends to stabilise anuran populations. Predation upon anurans was also correlated with a prey dispersion index as revealed by a polynomial regression. Polecats concentrated their predation on spawning congregations of the breeding adult frogs. Movements were smallest in spring and polecats changed their track length by increasing the difference between a succession of small movements and of longer journeys towards profitable sites. Changes in movements correlated with the anuran dispersion index and the response was sigmoidal (polynomial regression) revealing an area‐restricted search. This response may be regarded as an ‘aggregative response’ according to the first part of the definition of Begon et al. (1996) . Functional and area‐restricted search responses to the frog abundance and dispersion constitute an original example of predator‐prey coexistence strategies among vertebrates. I suggest that such predation could be favoured by the individualistic habits of the mustelid.