Danish free-ranging mink populations consist mainly of farm animals: Evidence from microsatellite and stable isotope analyses

Two methods were used to separate free-ranging mink Mustela vison into wild mink and escaped farm mink. Analysis of stable carbon isotopes was performed on teeth and claws of 226 free-ranging mink from two areas in Denmark. A classification based on empirical data resulted in three groups (n=213); 47% were newly escaped farm mink and another 31% had been born in farms and lived in nature for more than ca. 2 months. The remaining 21% may or may not have been born in nature, but they had been free ranging for more than a year and were thus considered wild. A genetic analysis by means of microsatellites was performed on a subsample of the trapped mink (86 individuals) and on 70 farm mink, in order to assess the proportion of escaped farm mink in the free-ranging population. Strong genetic evidence for a high percentage of escaped farm mink in the free-ranging population (86%) was found, in agreement with the carbon isotope results. Both methods can be used to distinguish between farm and wild mink, but whereas microsatellites can only say whether a given mink originated from a farm or not, carbon isotopes can give some more detail on the period of time that a farm mink has been living in natural habitats. The high proportion of escaped farm mink in the Danish nature could have serious implications for the preservation of other vulnerable species and should be carefully considered when designing conservation strategies.     

The genetic legacy of the 19th‐century decline of the British polecat: evidence for extensive introgression from feral ferrets

In the 19th century, the British polecat suffered a demographic contraction, as a consequence of direct persecution, reaching its lowest population in the years that preceded the First World War. The polecat is now recovering and expanding throughout Britain, but introgressive hybridization with feral ferrets has been reported, which could be masking the true range of the polecat and introducing domestic genes into the species. We used a fragment of the mitochondrial DNA control region and 11 microsatellite loci to characterize the frequency and extent of hybridization and introgression between the two species and assess whether the 19th‐century decline corresponded to a genetic bottleneck in the polecat. The proportion of admixture detected in the wild was high (31%) and hybrids were more frequently found outside Wales, suggesting that hybridization is more likely to occur along the eastern edge of the polecat's range expansion. The patterns observed in the mitochondrial and nuclear DNA data show that introgression was mediated by crosses between male polecats and female ferrets, whose offspring backcrossed with polecats. No first‐generation (F₁) hybrids were identified, and the broad range of observed admixture proportions agrees with a scenario of past extensive hybridization between the two species. Using several different methods to investigate demographic history, we did not find consistent evidence for a genetic bottleneck in the British polecat, a result that could be interpreted as a consequence of hybridization with ferrets. Our results highlight the importance of the Welsh polecat population for the conservation and restoration of the genetic identity of the British polecat.     

Evaluation of a black-footed ferret resource utilization function model

Resource utilization function (RUF) models permit evaluation of potential habitat for endangered species; ideally such models should be evaluated before use in management decision-making. We evaluated the predictive capabilities of a previously developed black-footed ferret (Mustela nigripes) RUF. Using the population-level RUF, generated from ferret observations at an adjacent yet distinct colony, we predicted the distribution of ferrets within a black-tailed prairie dog (Cynomys ludovicianus) colony in the Conata Basin, South Dakota, USA. We evaluated model performance, using data collected during post-breeding spotlight surveys (2007–2008) by assessing model agreement via weighted compositional analysis and count-metrics. Compositional analysis of home range use and colony-level availability, and core area use and home range availability, demonstrated ferret selection of the predicted Very high and High occurrence categories in 2007 and 2008. Simple count-metrics corroborated these findings and suggested selection of the Very high category in 2007 and the Very high and High categories in 2008. Collectively, these results suggested that the RUF was useful in predicting occurrence and intensity of space use of ferrets at our study site, the 2 objectives of the RUF. Application of this validated RUF would increase the resolution of habitat evaluations, permitting prediction of the distribution of ferrets within distinct colonies. Additional model evaluation at other sites, on other black-tailed prairie dog colonies of varying resource configuration and size, would increase understanding of influences upon model performance and the general utility of the RUF. © 2011 The Wildlife Society.     

月光及光照对艾虎活动的影响

采用野外研究与室内研究相结合的方法研究了月光周期和光照对夜行性动物艾虎活动的影响。野外无线电遥测结果表明,艾虎的日活动时间不受月光周期的影响,雌雄艾虎在不同的季节及繁殖期和非繁殖期都有相对稳定的活动时间,其开始活动和结束活动的时间与月光周期和日出、日落都没有明显的相关性。室内模拟研究结果也表明,由于环境条件的变化,艾虎增加了白天的活动时间,但仍然以夜间活动为主,光照强弱对艾虎的活动格局和活动时间没有明显的影响。以上结果表明昼夜变换使艾虎形成了相对稳定的生物种节律,艾虎在取食过程中可能利用洞道等隐蔽场所降低明亮月光期的高捕食风险。     

Evaluation of iophenoxic acid and rhodamine B for marking feral ferrets (Mustela furo)

Abstract

The blood marker iophenoxic acid, and the fluorescent dye rhodamine B, were evaluated as means of assessing bait consumption in the ferret, Mustela furo. Iophenoxic acid was elevated above baseline concentrations for a minimum of 28 days after dosing, indicating that it is a suitable medium‐term marker. Rhodamine B marked ferrets for a maximum of 7 days, and would therefore have limited operational use with feral ferrets. Iophenoxic acid was used in a field trial to assess the effectiveness of a newly developed baiting strategy for control of wild ferrets. All 21 ferrets captured after field baiting with iophenoxic acid had elevated levels of serum iodine, indicating that the newly developed baiting strategy is highly effective for marking ferrets.     

黄鼬(Mustela sibirica)体型大小的性二型及地理变异

本文报道黄鼬体型大小的性二型及其与地理变异的关系。个体大小的性二型现象很可能与繁殖行为有关,许多在繁殖季节有争偶行为的一雄多雌兽类,雄性都有较大的个体。     

Sex- and concentration-dependent effects of predator feces on seasonal regulation of body mass in the bank vole Clethrionomys glareolus

Increased perception of predation risk can cause changes in activity, feeding and reproductive behavior in a wide range of taxa. Many small mammals in the temperate zone exhibit fluctuations in body mass in response to changing photoperiod. Bank voles lose body mass in winter which they regain when photoperiod increases in the spring. To determine if predation risk affects seasonal changes in body mass (BM), bank voles were exposed to two concentrations (low: LC and high: HC) of weasel feces. Food intake (FI) and daily energy expenditure (DEE) were measured to establish if differences in body mass were due to adjustment in energy intake or expenditure. Fecal corticosterone (CORT) was measured to assess whether the voles had detected and responded to predator feces as a physiological stressor. Voles of both sexes had higher levels of fecal CORT in the groups exposed to weasel feces compared to controls. Voles responded to the predator feces in a sex- and concentration-dependent manner. Males responded to LC feces by gaining less mass following the change in photoperiod. This was mediated by reduced FI and higher DEE. Female voles also gained less BM in response to HC feces, but increased both FI and DEE. We hypothesize that males may gain a short-term advantage by lowering BM in response to predation risk, which may be regained without affecting reproductive success. The consequences of mass loss in females may be more significant as this may delay the onset of breeding or reduce the size or number of young, thereby negatively affecting breeding success.     

The suprachiasmatic nucleus of the mink (Mustela vison): apparent absence of vasopressin-immunoreactive neurons

The hypothalamic suprachiasmatic nucleus is centrally involved in generation of several circadian rhythms. Neurons of the mammalian suprachiasmatic nucleus express a number of neuropeptides including vasopressin. The suprachiasmatic nucleus of the mink (Mustela vison) is easily distinguished from neighbouring hypothalamic areas and the underlying optic chiasm as a small nucleus containing densely packed parvocellular neurons. A dorsal and ventral subdivision were clearly recognized within the midportion and caudal part of the nuclcus. Using immunohistochemistry, we have identified vasopressin-, neurophysin-, and vasoactive intestinal peptide-immunoreactive neuronal elements in the hypothalamus of the mink. Vasoactive intestinal peptide-immunoreactive neurons can be observed in the ventral aspect of the suprachiasmatic nucleus, but to our surprise, no vasopressin immunoreactive perikarya are found within the suprachiasmatic nucleus, this absence being independent of the experienced annual cycle. The hypothalamic paraventricular and supraoptic nuclei contain large numbers of vasopressin-, neurophysin-and vasoactive intestinal peptide-immunoreactive magnocellular neurons with extensive projections towards the infundibulum and neurohypophysis. A comparative analysis of the distribution of vasopressin-immunoreactive elements in a number of conventional laboratory animals has demonstrated that, in contrast to the rat, golden hamster and Mongolian gerbil, neither vasopressin-containing perikarya in the suprachiasmatic nucleus nor fine calibered immunoreactive fibres entering the adjacent subparaventricular zone are present in the mink. The mink is a photodependent seasonal breeder, and thus vasopressin-immunoreactive neurons in the suprachiasmatic nuclei may not be essential for the photoperiodic regulation of reproduction and seasonal events experienced by this species.     

Identification of a tyrosinase (TYR) exon 4 deletion in albino ferrets (Mustela putorius furo)

Albinism is due to a lack of pigmentation in hair, skin and eye, and has been shown to occur in several animal species. Mutations of the tyrosinase (TYR) gene account for albinism in domestic cats, rabbits, cattle, mice and rats. In this study, we demonstrate that a TYR mutation accounts for albinism in the ferret (Mustela putorius furo). The coding sequence of the five exons of TYR was determined in genomic DNA from wild-type pigmented 'sable' coloured and albino ferrets. It was not possible to amplify TYR exon 4 in albino ferrets originating from different breeds. The deletion of exon 4 in albino ferrets was confirmed by Southern blot hybridization of genomic DNA from albino and pigmented ferrets. This is the first report of a deletion of a TYR exon in a non-human mammal.