Predation on two vole species by a shared predator: antipredatory response and prey preference

In prey communities with shared predators, variation in prey vulnerability is a key factor in shaping community dynamics. Conversely, the hunting efficiency of a predator depends on the prey community structure, preferences of the predator and antipredatory behavioural traits of the prey. We studied experimentally, under seminatural field conditions, the preferences of a predator and the antipredatory responses of prey in a system consisting of two Myodes species of voles, the grey-sided vole (M. rufocanus Sund.) and the bank vole (M. glareolus Schreb.), and their specialist predator, the least weasel (Mustela nivalis nivalis L.). To quantify the preference of the weasels, we developed a new modelling framework that can be used for unbalanced data. The two vole species were hypothesised to have different habitat-dependent vulnerabilities. We created two habitats, open and forest, to provide different escape possibilities for the voles. We found a weak general preference of the weasels for the grey-sided voles over the bank voles, and a somewhat stronger preference specifically in open habitats. The weasels clearly preferred male grey-sided voles over females, whereas in bank voles, there was no difference. The activity of voles changed over time, so that voles increased their movements immediately after weasel introduction, but later adjusted their movements to times of lowered predation risk. Females that were more active had an elevated mortality risk, whereas in the case of males, the result was the opposite. We conclude that, in vulnerability to predation, the species- or habitat-specific characteristics of these prey species are playing a minor role compared to sex-specific characteristics.     

Amplification of DNA markers from scat samples of the least weasel<Emphasis Type="Italic">Mustela nivalis nivalis</Emphasis>

To test the feasibility of using field-collected scats as a source of DNA in the study of the least weaselMustela nivalis nivalis Linnaeus, 1766, DNA was extracted from scat samples collected from captive weasels using a modified extraction protocol. Using universal primers, the control region of the mitochondrial genome was successfully amplified from scat-extracted DNA. This amplification resulted in two products; one equivalent in size and sequence to the product obtained from tissue-extracted weasel DNA, and the other slightly larger and equivalent in size and sequence to the domestic house mouseMus musculus, the food source of the captive weasels. This demonstrates the reliability of DNA extraction from scats, as well as the possibility, under favourable circumstances, of identifying the prey species from the same samples. In addition, we attempted to amplify microsatellite loci from both tissue and scat-extracted DNA using six primer pairs designed for other mustelids, the American minkMustela vison and the wolverineGulo gulo. While three loci, Mvi57 (American mink), Ggu216 and Ggu234 (wolverine), were found to be polymorphic in the least weasel, amplification of these loci from the scat extracted DNA was only successful for approximately half of the samples. Although further work is needed, the present results suggest that it is possible to use scats as a source of DNA in field studies of the least weasel.     

Endozoochorous seed dispersal by sympatric mustelids, Martes melampus and Mustela itatsi, in western Tokyo, central Japan

We investigated seed dispersal by two sympatric mustelid species, the Japanese marten (Martes melampus) and Japanese weasel (Mustela itatsi), along an intercity forest path in western Tokyo, central Japan, from Jul 2007 to Jul 2008. We aimed to investigate the effect of food/habitat preference of these mustelids (martens are semi-arboreal frugivores while weasels are terrestrial carnivores) on their seed dispersal characteristics, which determine their efficacy as seed dispersers. In total, we analyzed 478 fecal samples collected from the two mustelids (N_marten = 381, N_weasel = 97). The proportions of feces containing seeds for martens and weasels were 81.4% and 55.7%, respectively. The number of plant species whose seeds were found within the feces were 28 and 17, respectively. Almost all seeds within feces of both mustelids were intact. The number of plant species whose seeds were found within a single fecal sample ranged from one to four, but no significant difference was detected between the two mustelids. However, marten feces contained a significantly greater number of seeds of most plant species as well as total number of seeds than did weasel feces. The numbers of plant species and seeds represented in marten feces varied seasonally, but those represented in weasel feces did not. Our findings suggest the possibility that both mustelids act in some ways as seed dispersers, although martens seem to disperse a greater diversity and total amount of seeds.     

黄鼬在吉林环长白山旅游公路路域活动的调查研究

2008年11～12月,采用样线法对环长白山旅游公路改扩建工程全线路域200 m范围内黄鼬活动情况进行了3次调查.调查结果显示:K10～K45路段黄鼬穿越公路较多;黄鼬穿越公路频率与路域植被类型和雪被深度有密切的关系;黄鼬已经开始利用涵洞穿越公路;公路对黄鼬具有吸引效应,影响域范围约为50 m.为此提出了相应的保护对策.     

Habitat selection of coexisting competitors: a study of small mustelids in northern Norway

The coexistence of two very similar species, stoat and least weasel, has puzzled many researchers. From their ecology it is expected that they do not coexist, not locally at least, and still they seem to do. We reviewed the specific hypotheses proposed to explain their coexistence and related these to general theories of competitive coexistence. To test these conjectures, we studied the habitat selection of least weasels and stoats on landscape and on local scale. The study was performed during the winters, the most critical season, in years 1986–2001 in northern Norway. Stoats were usually more numerous than least weasels. Stoats showed preference for productive areas both at the landscape and at the habitat scale and appeared stereotypic in their habitat selection. Least weasels were more generalized and flexible in their habitat selection. Contrary to results reported in many studies, least weasel did not react to the presence of stoats and were not excluded from the areas with stoats. We suggest that in the conditions of northernmost Fennoscandia, the two species exhibit a variant of classical competitive coexistence. Both species have a shared preference for rodents, but the access to exclusive alternative prey in stoats allows their coexistence with least weasels, which are more efficient predators on rodents. We suggest that more attention should be paid on survival resources, exploited during times of low resource density, when studying the coexistence between close competitors.     

Movement patterns of a specialist predator,the weasel<Emphasis Type="Italic">Mustela nivalis</Emphasis> exploiting asynchronous cyclic field vole<Emphasis Type="Italic">Microtus agrestis</Emphasis> populations

We investigated habitat selection and movement characteristics of male weaselsMustela nivalis Linnaeus, 1766 during the breeding season through radio-telemetry in Kielder Forest (KF) in order to assess how weasel movement is influenced by prey dynamics, mate searching and predation risk, and whether the scale of weasel movement corresponds to the spatial scale of the asynchronous, multi-annual vole population cycles observed in KF. Weasels used habitats with a high proportion of grass cover to a much larger extend than habitats with less grass cover and moved through the latter habitats faster and / or straighter. Habitats with high amounts of grass cover also had the highest field vole abundance, although total rodent abundance did not differ between habitats. The selection of this habitat by weasels might reflect weasels preferring field voles as prey or avoiding habitats with little grass cover and high intraguild predation risk. Five out of 8 male weasels radio-tracked had low day-to-day site fidelity and moved between different clear cuts. Three other males were resident in a single clear cut. This variation may reflect mate searching by male weasels. The observation that most weasels (5 out of 8) roamed over large areas and the scale of their dispersal potential suggests, that if they regulated vole populations, they should have a greater synchronising effect on the spatial scale of vole population dynamics than what is observed in vole populations in KF.     

No evidence of past bottlenecks in two Danish mustelids: results of craniometric and genetic studies in time and space

A craniometric and molecular genetic investigation was conducted in Danish stoat (Mustela erminea) and weasel (Mustela nivalis) populations. Specimens used were collected over a wide time span (stoat: 1864–2002; weasel: 1863–1990) and from several geographical regions (Jutland peninsula and the two islands of Funen and Zealand). The study was made with a temporal and a spatial perspective, allowing the estimation of differences in genetic diversity and craniometrical trait means between geographical regions and through time with the use of ancient DNA techniques. Univariate statistics of 11 trait lengths did not reveal geographical differentiation in size and shape among the different regions for the stoat, but a geographical differentiation in shape was found for the weasel. There was evidence for reductions in skull size with the year of collection in male stoats, but not in females, which suggests that some selective pressures or environmental factors have affected male stoats to a greater extent than female stoats and the weasel. Relatively high values of heterozygosity were found in both the stoat and weasel, using microsatellite markers. The level of genetic variability of the stoat collected recently was compared with the level of genetic variability in the historical samples, demonstrating that the stoat has not suffered severe loss of genetic variability through the investigated period. A comparison of recent and historical genetic variability of the weasel was not possible because the ancient DNA extracted from the weasels was too degraded. Pairwise F_ST values and assignment tests showed small but significant genetic differentiation between the different geographical regions for both the stoat and weasel. No genetic differentiation between the recent and historical samples of the stoat was found. © 2006 The Linnean Society of London, Biological Journal of the Linnean Society, 2006, 88 , 541–553.     

Fossils and phylogeny uncover the evolutionary history of a unique antipredator behaviour

Recently, two squirrel species (Spermophilus spp.) were discovered to anoint their bodies with rattlesnake scent as a means of concealing their odour from these chemosensory predators. In this study, we tested multiple species with predator scents (rattlesnake and weasel) to determine the prevalence of scent application across the squirrel phylogeny. We reconstructed the evolutionary history of the behaviour using a phylogenetic analysis and fossil records of historic predator co‐occurrence. Squirrels with historical and current rattlesnake co‐occurrence all applied rattlesnake scent, whereas no relationship existed between weasel scent application and either weasel or rattlesnake co‐occurrence. This was surprising because experimental tests confirmed rattlesnake and weasel scent were both effective at masking prey odour from hunting rattlesnakes (the primary predator of squirrels). Ancestral reconstructions and fossil data suggest predator scent application in squirrels is ancient in origin, arising before co‐occurrences with rattlesnakes or weasels in response to some other, now extinct, chemosensory predator.     

Reproductive investment under fluctuating predation risk: Microtine rodents and small mustelids

Summary We studied the reproductive investment of microtine rodents (bank vole (Clethrionomys glareolus),Microtus epiroticus andMicrotus agrestis) in western Finland under predation risk from small mustelids. During 1984–1992, the yearly mean litter size of overwintered bank voles was smaller at high least weasel and stoat densities than at low densities (close to 3 versus 4–5). In addition, the annual mean litter size of young bank voles was negatively correlated to the least weasel density. In youngM. agrestis voles, the yearly late summer litter size was negatively associated with the autumn density of small mustelids. In the crash phase of the vole cycle (1989 and 1992), we removed small mustelids (mainly least weasels) from four unfenced areas in late April to late May and studied the reproduction of voles in four removal and comparable control areas (each 2–4 km²). Reduction of small mustelids significantly increased the proportion of pregnant bank vole females, but not that of pregnantMicrotus vole females. We conclude that predation risk apparently reduced reproductive investment of free-living bank vole females; these voles appear to trade their current parental investment against future survival and reproductive prospects. Accordingly, the presence of small mustelids (or their scent) may slow down the reproductive rate of voles. As antipredatory behaviours occurred on a large scale, our results add evidence to the hypothesis that crashes in multiannual vole cycles are driven by small mustelid predators.     

Neoplasia in the Siberian weasel (<Emphasis Type="Italic">Mustela sibirica</Emphasis>): two case reports of fibrosarcoma and interstitial cell tumour

Two cases of neoplasia occurred in two adult Siberian weasels (Mustela sibirica) in a game reserve in southern Lower Saxony, Germany. The first case, a male weasel, showed an enlargement of the right testicle, which was surgically removed. The tumour was classified as an interstitial cell tumour. One year after surgery, the male weasel died by accident and revealed tumour lesions of uncertain histogenesis within the abdominal cavity and the spleen at necropsy. The second case, a female animal, became suspicious by a dermal mass in the upper left hind limb, which was also surgically excised. Pathological examinations revealed a fibrosarcoma that recurred twice after removal of the original mass. These two cases of neoplasia in the Siberian weasel are demonstrated with regard to clinical aspects and discussed on the basis of their pathomorphological features.     

The predation risks of interspecific eavesdropping: weasel–vole interactions

Competing species benefit from eavesdropping on each other's signals by learning about shared resources or predators. But conspicuous signals are also open to exploitation by eavesdropping predators and should also pose a threat to other sympatric prey species. In western Finland, sibling voles Microtus rossiameridionalis and field voles M. agrestis compete for food and space, and both species rely upon scent marks for intraspecific communication. Both vole species are prey to a range of terrestrial scent hunting predators such as least weasels, however, the competitively superior sibling voles are taken preferentially. We tested in large out‐door enclosures whether field voles eavesdrop on the signals of its competitor, and whether they behave as though this eavesdropping carries a risk of predation. We presented field voles with scent marks from unknown conspecifics and sibling voles and measured their visitation, activity and scent marking behaviours at these scents under high (weasel present) and low (weasel absent) predation risk. Field voles readily visited both field and sibling vole scents under both high and low predation risk; however their activity at sibling vole scent marks declined significantly under increased predation risk. In contrast, predation risk did not affect field voles’ activity at conspecific scents. Thus, field voles were compelled to maintain eavesdropping on heterospecific scents under an increased risk of predation, however they compensated for this additional risk by reducing their activity at these risky scents. Scent marking rates declined significantly under high predation risk. Our results therefore reveal a hidden complexity in the use of social signals within multi‐species assemblages that is clearly sensitive to the potential for increased predation risk. The predation risks of interspecific eavesdropping demonstrated here represents a significant generalisation of the concept of associational susceptibility.     

Notes on the Weasel in Historic Plains Indian Culture

Abstract

One of the smaller mammals of the Creat Plains is the short-legged, slender-bodied, agile and aggressive weasel. The historic Indian tribes of this region did not eat the weasel, but the northern tribes snared these animals in winter to obtain their handsome white pelts. Winter weasel pelts were coveted items in both intratribal and intertribal trade and were used by many tribes to decorate war bonnets, and the finest men’s shirts and leggings. Whole weasels were sometimes tied to shields as war medicine, and some Siouan tribes carv, ed representations of the weasel at the ends of their wooden war clubs. Among the Plains Indians the association of the weasel with warriors’ clothing and weapons appears to have been derived from their recognition of the fighting qualities of the weasel.     

Weasel (<Emphasis Type="Italic">Mustela nivalis</Emphasis>) decline in NE Spain: prey or land use change?

In this note, we reported the decline of weasel populations in NE Spain between the end of the last century and present. Our results suggested a delayed numerical response of weasels to wood mice abundance during the first study period (1995–1998), but no response at all in the second and longer period (2008–2015). Small mammals’ outbreaks triggered weasel’ populations in the first period, but they did not in the second period. Other factors may be invoked to explain the recent lack of numerical responses of weasels to mice. Population declines of small mammals have been noted in the study area in recent years, whereas an increase of casual predation records of weasels by generalist raptors has been documented. Both trends seemed to be related to the effects of the process of natural afforestation experienced by Mediterranean areas due to land abandonment. Top-down increased predation may add to bottom-up decreasing prey availability to explain current weasel declines.     

香鼬的栖息地选择、觅食和育幼行为

香鼬（Ｍｕｓｔｅｌａａｌｔａｉｃａ）喜栖于人类居住区附近的高寒草甸草场,主要以高原鼠兔（Ｏｃｈｏｔｏｎａｃｕｒｚｏｎｉａｅ）为食,其数量分布与高原鼠兔的密度分布成正相关。在高原鼠兔的繁殖盛期,香鼬主要捕食鼠兔幼体,每只成体平均每天捕获鼠兔６．２只,相当于每１００克体重日获取食物重量２７３．５克,在高原鼠兔的繁殖后期和非繁殖期,每只成体平均每天捕获鼠兔２．７５只,相当于每１００克体重日获取食物重量２９６．３克。繁殖期育幼任务全部由雌性成鼬承担,幼鼬从７月初开始地面活动,８月初开始扩散。     

Habitat requirements of weasels <Emphasis Type="Italic">Mustela nivalis</Emphasis> constrain their impact on prey populations in complex ecosystems of the temperate zone

Differences in habitat use by prey and predator may lead to a shift of occupied niches and affect dynamics of their populations. The weasel Mustela nivalis specializes in hunting rodents, therefore habitat preferences of this predator may have important consequences for the population dynamics of its prey. We investigated habitat selection by weasels in the Bia?owie?a Forest in different seasons at the landscape and local scales, and evaluated possible consequences for the population dynamics of their prey. At the landscape scale, weasels preferred open habitats (both dry and wet) and avoided forest. In open areas they selected habitats with higher prey abundance, except during the low-density phase of the vole cycle, when the distribution of these predators was more uniform. Also in winter, the distribution of weasels at the landscape scale was proportional to available resources. In summer, within open dry and wet habitats, weasels preferred areas characterised by dense vegetation, but avoided poor plant cover. In winter, weasels used wet open areas proportionally to availability of habitats when hunting, but in contrast to summer, they rested only in habitats characterized by a lower water level, which offered better thermal conditions. At the local scale, the abundance of voles was a less important factor affecting the distribution of these predators. Although we were not able to provide direct evidence for the existence of refuges for voles, our results show that they may be located within habitat patches, where availability of dense plant cover and physiological constraints limit the activity of weasels. Our results indicate that in complex ecosystems of the temperate zone, characterized by a mosaic pattern of vegetation types and habitat specific dynamics of rodents, impact of weasels on prey populations might be limited.     

黄鼬的产仔环境和鼬巢密度调查

长江中下游平原及华北平原是黄鼬(Mustela Sibirica)的主要产区,在黄土高原地区的数量则较为稀少。为了掌握黄鼬对繁殖环境的选择和各地资源状况,达到合理利用黄鼬资源的目的,我们选择长江流域的崇明岛,淮河流域的宿县,黄河流域的衡水县及黄土高原的太原、交城进行调查。调查期间,得到上海市畜产公司、山西省和太原市畜产公司、衡水地区畜产公司及宿县地区畜产站的热情支持。     

Multiple predators induce risk reduction in coexisting vole species

Large predators may affect the hunting efficiency of smaller ones directly by decreasing their numbers, or indirectly by altering their behaviour. Either way this may have positive effects on the density of shared prey. Using large outdoor enclosures, we experimentally studied whether the presence of the Tengmalm's owl Aegolius funereus affects the hunting efficiency of the smallest member of the vole-eating predator guild, the least weasel Mustela nivalis, as measured by population responses of coexisting prey species, the field vole Microtus agrestis and the sibling vole M. levis . We compared the density and survival probability of vole populations exposed to no predation, weasel predation or combined predation by a weasel and an owl. The combined predation of both owl and weasel did not result in obvious changes in the density of sibling and field vole populations compared to the control populations without predators, while predation by least weasel alone decreased the densities of sibling voles and induced a similar trend in field vole densities. Survival of field voles was not affected by predator treatment while sibling vole survival was lower in predator treated populations than in control populations. Our results suggest that weasels are intimidated by avian predators, but without changing the effects of predators on competitive situations between the two vole species. Non-lethal effects of intraguild predation therefore will not necessarily change competitive interactions between shared prey species.     

Functional response of the least weasel, Mustela nivalis nivalis

We investigated the functional response of the least weasel ( Mustela nivalis nivalis ) in a series of experiments conducted in large outdoor enclosures (0.5 ha). Radiocollared Microtus voles were released in the enclosures at different densities (4, 8, 16 and 100/ha) three days before the release of a radiocollared weasel. During the three-day experiment every vole killed was replaced with another one as soon as possible to retain constant prey density. The results demonstrated type II functional response with the predation rate reaching 50% of the asymptotic rate at a vole density of 15 individuals per ha. More voles were killed at the highest densities than would be expected from the known energy demands of weasels. Female and male voles were killed in proportion to their abundances in the enclosures, and no difference in predation risk was detected between voles released in the enclosure before the weasel (residents) and during the experiment (transients).     

The Jeju weasel, Mustela sibilica quelpartis, a new definitive host for Gnathostoma nipponicum Yamaguti, 1941

Adult gnathostomes were discovered in the stomach of the Jeju weasel, Mustela sibilica quelpartis, road-killed in Jeju-do (Province). Their morphological characters were examined to identify the species. Total 50 gnathostome adults were collected from 6 out of 10 weasels examined. In infected weasels, 4-6 worms were grouped and embedded in each granulomatous gastric tumor, except 1 weasel. Male worms were 25.0×1.4 mm in average size, and had a tail with pedunculate papillae, a spicule, and minute tegumental spines. Females were 40.0×2.5 mm in average size, and had a tail without tegumental spines. Pointed and posteriorly curved hooklets were arranged in 8-10 rows on the head bulb. Tegumental spines were distributed from behind the head bulb to the middle portion of the body. The spines were different in size and shape by the distribution level of the body surface. Fertilized eggs were 65.5×38.9 μm in average size, and had a mucoid plug at 1 pole. These gnathostomes from Jeju weasels were identified as Gnathostoma nipponicum Yamaguti, 1941. By the present study, it was confirmed for the first time that G. nipponicum is distributed in Jeju-do, the Republic of Korea, and the Jeju weasel, M. sibilica quelpartis, plays a crucial role for its definitive host.     

A population study of the metastrongylid nematode Skrjabingylus nasicola in the weasel Mustela nivalis

Analyses of adult worms of Skrjabingylus nasicola occurring in the nasal sinuses of the weasel Mustela nivalis from three localities in the British Isles show that the intensity of infestation can be correlated with increasing severity of skull damage, which in turn increases as the weasel ages. It is suggested that, apart from hormonal differences, the smaller sized female skull is likely to be linked with lower levels of infestation in female compared with male weasels. Also a reduction in mean worm length in female skulls and in heavy infestations of S. nasicola is probably the result of a "crowding effect", previously described for other helminth infections in the definitive host. Crowding appears to have no effect on the sex ratio of worm populations, although there is a tendency for the ratio of female: male worms to increase in female weasels. Reasons for this are discussed.