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Small mustelids are an understudied group partly due to the challenges in detecting and monitoring their populations. Despite the classification as Least Concern for several small mustelid species, some studies indicate a population decline in parts of their range. Therefore, efficient and group-specific methods are essential to support monitoring efforts. Camera traps are widely used, particularly to monitor cryptic and nocturnal species such as most carnivores. However, they tend to miss small-sized and fast-moving species due to the sensitivity of the passive infrared sensor. The Mostela is a device which consists of a camera trap and a tracking tunnel inside a wooden box, designed specifically to detect small mustelids. Here, we propose testing the performance of this device and comparing it to a tree-mounted camera trap, using the least weasel (M. nivalis) as a case study. We used multi-scale occupancy models to estimate differences in the detection probability between devices. Although both methods detected the least weasel, the detection probability was higher with the Mostela (0.8, BCI: 0.52–0.97 vs 0.2, BCI: 0.03–0.48). Furthermore, we obtained a higher trapping rate when using a shorter distance between sampling stations (∼350 m). Although the Mostela performed better at detecting the weasel, the number of independent events was low (N = 11). Therefore, we present recommendations in terms of deployment and future research since the development and testing of new methods are essential for the conservation efforts of small mustelids.

• Monitoring small carnivores requires new approaches to the available methodologies. • The mostela is a camera-based method to monitor small mustelids that we tested in a mediterranean agroforestry landscape. • Trapping rate inside the mostela box was of 0.95 individuals per 100 trap nights. • Detection probability by the mostela was, on average, four times higher than by camera traps set on trees. Small mustelids are an understudied group partly due to the challenges in detecting and monitoring their populations. Despite the classification as Least Concern for several small mustelid species, some studies indicate a population decline in parts of their range. Therefore, efficient and group-specific methods are essential to support monitoring efforts. Camera traps are widely used, particularly to monitor cryptic and nocturnal species such as most carnivores. However, they tend to miss small-sized and fast-moving species due to the sensitivity of the passive infrared sensor. The Mostela is a device which consists of a camera trap and a tracking tunnel inside a wooden box, designed specifically to detect small mustelids. Here, we propose testing the performance of this device and comparing it to a tree-mounted camera trap, using the least weasel (M. nivalis) as a case study. We used multi-scale occupancy models to estimate differences in the detection probability between devices. Although both methods detected the least weasel, the detection probability was higher with the Mostela (0.8, BCI: 0.52–0.97 vs 0.2, BCI: 0.03–0.48). Furthermore, we obtained a higher trapping rate when using a shorter distance between sampling stations (∼350 m). Although the Mostela performed better at detecting the weasel, the number of independent events was low (N = 11). Therefore, we present recommendations in terms of deployment and future research since the development and testing of new methods are essential for the conservation efforts of small mustelids. [ABSTRACT FROM AUTHOR]

The lacked‐teeth pygmy weasel, Mustela aistoodonnivalis Wu & Kao, 1991, was originally described as being from Taibai Mountain and Zhashui county, Shaanxi, China. Subsequently, it was considered a subspecies or synonym of Mustela nivalis. In a faunal survey of northwestern Sichuan, eight specimens of M. aistoodonnivalis were collected. A molecular phylogenetic analysis of one mitochondrial and six nuclear genes clustered the specimens as a distinct clade and not with M. nivalis. Morphologically, the lack of the second lower molar differentiated them from M. nivalis, and genetic distances were typical of discrete species. These analyses confirmed that M. aistoodonnivalis is an independent species in the genus Mustela. [ABSTRACT FROM AUTHOR]

Conservation programmes in New Zealand often suppress populations of a single invasive predator for the benefit of threatened avifauna. However, the establishment of whole guilds of invasive species has created complex competitor and predator-prey relationships, including some well-described trophic cascades. Trap networks designed to target stoats (Mustela erminea) are poorly optimised to supress a population of weasels (M. nivalis), and may contribute to periodic spikes in weasel numbers due to decreased interspecific competition and aggression. The consequences of stoat removal and possible weasel release have received little attention. In this small-scale pilot study, we used C13 and N15 stable isotopes to examine diet and relative trophic position of eight weasels and 20 stoats caught in an alpine ecosystem. We explored three dietary models as a framework with which to examine trophic patterns in feeding behaviour of the two mustelid species and potential impacts on native species. The models suggest that, in this specific scenario, weasels preyed at a higher trophic position than stoats and consumed a greater proportion (per capita) of vulnerable taxa like lizards and passerines. We cautiously highlight the potential for negative outcomes for some native taxa in scenarios in which weasels are released from competition with stoats. [ABSTRACT FROM AUTHOR]

Dissecting the link between genetic variation and adaptive phenotypes provides outstanding opportunities to understand fundamental evolutionary processes. Here, we use a museomics approach to investigate the genetic basis and evolution of winter coat coloration morphs in least weasels (Mustela nivalis), a repeated adaptation for camouflage in mammals with seasonal pelage color moults across regions with varying winter snow. Whole-genome sequence data were obtained from biological collections and mapped onto a newly assembled reference genome for the species. Sampling represented two replicate transition zones between nivalis and vulgaris coloration morphs in Europe, which typically develop white or brown winter coats, respectively. Population analyses showed that the morph distribution across transition zones is not a by-product of historical structure. Association scans linked a 200-kb genomic region to coloration morph, which was validated by genotyping museum specimens from intermorph experimental crosses. Genotyping the wild populations narrowed down the association to pigmentation gene MC1R and pinpointed a candidate amino acid change cosegregating with coloration morph. This polymorphism replaces an ancestral leucine residue by lysine at the start of the first extracellular loop of the protein in the vulgaris morph. A selective sweep signature overlapped the association region in vulgaris , suggesting that past adaptation favored winter-brown morphs and can anchor future adaptive responses to decreasing winter snow. Using biological collections as valuable resources to study natural adaptations, our study showed a new evolutionary route generating winter color variation in mammals and that seasonal camouflage can be modulated by changes at single key genes. [ABSTRACT FROM AUTHOR]

To achieve long-term suppression of pest populations, devices capable of continued control over extended timeframes are needed. Creating new pest management tools to achieve this goal requires the integration of animal ecology, toxicology, and design engineering. This research outlines the development and testing of a long-life, resetting, toxin delivery system for vertebrate pest control, coupled with advances in novel species recognition systems. Such devices have the potential to offer advantages over current labor-intensive control techniques. Resetting systems have been developed to target several of the most destructive vertebrate pest species in New Zealand, including stoats and weasels. Results of enclosure trials for these two species showed similar responses after a paste containing 40% para-aminopropiophenone was delivered onto the chest and stomach, following triggering by a treadle operated system. Both species groomed the paste off shortly after application and death occurred after an average of 42 minutes for stoats and 57 minutes for weasels. The applications of these resetting devices are now being extended for the control of brushtail possums, another major vertebrate pest in New Zealand. Coupled with this, developments in species identification systems are ensuring that risks to non-targets are substantially minimized. Resetting, long-life toxin delivery systems could be deployed to control a variety of pest species, and further enhancement of these tools are ensuring their use for widespread field applications in a cost-effective, safe and reliable manner.

Abstract Risk recognition by prey is of paramount importance within the evolutionary arms race between predator and prey. Prey species are able to detect direct predator cues like odors and adjust their behavior appropriately. The question arises whether an indirect predation cue, such as the odor of scared individuals, can be detected by conspecifics and subsequently affects recipient behavior. Parents may also transfer their experience with predators to their offspring. In two experiments, we assessed how direct and indirect predation cues affect bank vole (Myodes glareolus) foraging behavior, reproduction, and pup fitness. Weasel (Mustela nivalis) odor served as the direct cue, whereas the odor of weasel‐scared conspecifics, alarm pheromones, was used as an indirect cue and both of those were compared to a control odor, clean wood shavings. Alarm pheromones attracted female voles, measured as time in proximity to the treatment and foraging. Both predator odor and alarm pheromones enhanced reproduction compared to the control odor. Females treated with alarm pheromone had significantly higher pregnancy rates, and pups from predator‐treated mothers were significantly heavier at birth. Our study provides two novel ideas. First, the impact of a predator can be socially transmitted. Second, predation risk likely triggers terminal investment in reproduction.

The least weasel (Mustela nivalis) is one of the most widely distributed carnivorans. While previous studies have identified distinct western and eastern mitochondrial DNA (mtDNA) lineages of the species in the western Palearctic, their broader distributions across the Palearctic have remained unknown. To address the broad‐scale phylogeographical structure, we expanded the sampling to populations in Eastern Europe, the Urals, the Russian Far East, and Japan, and analyzed the mtDNA control region and cytochrome b, the final intron of the zinc finger protein on Y chromosome (ZFY), and the autosomal agouti signaling protein gene (ASIP). The mtDNA data analysis exposed the previous western lineage (Clade I) but poorly supported assemblage extending across Palearctic, whereas the previous eastern lineage (Clade II) was reconfirmed and limited in the south western part of the Palearctic. The ZFY phylogeny showed a distinctive split that corresponding to the mtDNA lineage split, although less phylogeographical structure was seen in the ASIP variation. Our data concur with the previous inference of the Black Sea–Caspian Sea area having an ancestral character. The Urals region harbored high mitochondrial diversity, with an estimated coalescent time of around 100,000 years, suggesting this could have been a cryptic refugium. Based on the coalescent‐based demographic reconstructions, the expansion of Clade I across the Palearctic was remarkably rapid, while Clade II was relatively stable for a longer time. It seems that Clade II has maintained a constant population size in the temperate region, and the expansive Clade I represents adaptation to the cold regions. [ABSTRACT FROM AUTHOR]

There is a significant level of variability of the weasel’s coat coloration in Ukraine. The coloration is continuous from the southern forms of type “vulgaris” (white fur only on the belly and chest with no winter phase) to the northern and eastern forms of group “nivalis” (narrowed brown zone not extended to the legs and lips and expressive white fur coloration in winter). The analysis of distribution of different color phases in space and different seasons suggests the presence of a certain number of transitional forms between these types of coloration. It was found that the variability’s direction conforms to formerly accepted ranges of color phases only in general terms. The color phases have the largest match with biographical (= climatic) zones. The expansion of the range of the southern form (the same as the subspecies nikolskii from the group “vulgaris”) and a significant shift of the limits of its records are shown. The expansion of the southern form’s range is considered as the change of coloration type of the same local forms but not as the distribution of the southern form to north.

Five mustelid species were found in the Ciemna Cave, in layers 13-1 dated at MIS 5-1: Gulo gulo, Meles meles, Martes martes, Mustela erminea and Mustela nivalis, with the remains of M. martes being the most abundant. They were represented almost exclusively by cranial material, mandibles and isolated teeth. Metrically and morphologically most of the remains corresponded to the modern European forms. Only few isolated teeth of M. martes belonged to a great, robust form which was characteristic of cooler phases of the Late Pleistocene and beginning of the Holocene. Another cold-adapted mustelid, represented by a single, damaged calcaneus, was G. gulo. Few bones showed traces of carnivore activity, which can be regarded as one of the accumulation factors, other possible factors being water and accidents. [ABSTRACT FROM AUTHOR]

This paper describes one of the world's first large-scale experiments in biological control of a major vertebrate pest of agriculture, which was tried in New Zealand during the second half of the nineteenth century. Starting from the late 1860s, pasture damage in Southland and Otago by European rabbits was causing serious reductions in productivity of sheep (wool clip and lambing percentages) associated with malnutrition of the breeding ewes, and a consequent decline in the value of pastoral land. In response, and despite repeated local and international warnings, ferrets, stoats and weasels ( Mustela furo, M. erminea and M. nivalis) were liberated on the worst of the rabbit-infested pastures. They were perceived as the 'natural enemies of the rabbit' but (unlike foxes) too small to threaten lambs. Over the 50 years after 1870, upwards of 75,000 ferrets, most imported from Australia or locally bred, were released in the South Island. Over the decade 1883-1892, at least 7838 stoats and weasels arrived from Britain. At least 25 shipments are known, with an average of only 10% mortality per shipment. Of the 3585 animals listed by species, 73% were weasels. The total cost of the ferret programme cannot now be estimated; that of stoats and weasels alone was at least £5441, probably twice that, or >$NZ 1-2 million in today's money. Mustelids (and cats) killed many young rabbits, which was helpful because rates of change in rabbit populations are sensitive to variations in juvenile mortality, but in the most rabbit-prone semi-arid lands, mustelids could not remove enough rabbits to prevent the continuing damage to sheep pastures. The era of deliberate introductions of mustelids to control rabbits in New Zealand was short, expensive, and unsuccessful. [ABSTRACT FROM AUTHOR]

Mustela nivalis, the smallest member of the family Mustelidae, is widely distributed in the Holarctic region and shows high geographical variation. To further understand the molecular evolution of major histocompatibility complex (MHC), we sequenced part of MHC class II DRB gene exon 2, including codons encoding the antigen binding site (ABS), from 35 individuals from Finland, Bulgaria, Russia, and Japan. We detected 27 species-specific alleles (Muni- DRBs), some of which were broadly distributed and others geographically restricted. The ratio of nonsynonymous to synonymous substitution rates for predicted ABS codons exceeded 1, though not statistically significant. In addition, the single break point recombination (SBP) and mixed-effects model evolution (MEME) analyses demonstrated a recombination site and positive selection sites that could be committed to maintain the diversity of Muni-DRBs. In a Bayesian phylogenetic tree, all Muni-DRBs grouped within a Mustelidae clade. The Muni-DRBs showed transspecies polymorphism in related Mustela species that could have appeared to be evolved under long-lasting balancing selection. However, the sister-group patterns suggested that Mustela itatsi and Mustela sibirica alleles are much more closely related to one another than either are to M. nivalis alleles. This result correlates with the large genetic distance separating M. nivalis from M. itatsi or M. sibirica, data for which we have previously reported. [ABSTRACT FROM AUTHOR]

The complete mitogenome (MF459691) of Mustela nivalis contains total 16,502 bp in length and consists of a control region and a conserved set of 37 genes. The phylogenetic tree of the family Mustelidae constructed using 18 mitogenome sequences from 16 mustelid species of 6 genera shows that the mustelid species are separated into two main groups. All the members of the genus Martes form a monophyletic group, which has the genus Melogale as sister clade, and the clade of the two genera is sister to that of the genera Enhydra and Lutra. Among species of the genus Mustela, with the exclusion of M. frenata with Neovison vison as sister species, all the other species of the genus Mustela are well grouped. All members of M. nivalis are well placed within the species M. nivalis clade with the clade of M. itatsi and M. sibirica as sister group.

In this study we investigated the allometry and variation in the baculum of the weasel Mustela nivalis and compared it with head-and-body length, which is not involved in reproduction. The females of many mammalian species select mates in part during intromission and evaluate attributes of the penis that are informative in regard to a male’s size or other characteristics. If females benefit by mating with large males by estimation of the size of the male's penis, then positive allometry between penile size relative to body size is realized. Small residuals in the allometric regression may evolve. In species with pre-copulatory selection (manifested as male-biased sexual size dimorphism) baculum allometry may be isometric or exhibit negative allometry. Weasels exhibit a sexual-size dimorphism, with males being larger, and as a result we predicted that baculum size would exhibit negative allometry or isometry. We also tested the hypothesis that baculum size is positively correlated with adult body size and may be used as a reliable indicator of good genes for female mates during breeding. Negative allometry and a relative weak relationship between baculum size and head-and-body length suggest that the baculum is under stabilizing selection for optimal baculum size. We assumed that penile width as related to bacular thickness could be a reliable indicator of quality during copulation. [ABSTRACT FROM AUTHOR]

Background: Stoat (Mustela erminea) and weasel (Mustela nivalis) populations in south-west England are declining whilst polecats (Mustela putorius), absent for over a century, are increasing. Little is known about the health status of these species nationally. This study aimed at investigating respiratory disease in specimens found dead in south-west England. Results: Trauma caused by road traffic, predator attack or being trapped was the predominant cause of death in 42 stoats, 31 weasels and 20 polecats; most were in good physical condition. Skrjabingylus nasicola was present in all species (weasels 37 %, polecats 39 %, stoats 41 %) and infected animals showed no evidence of loss of body condition. Even in carcases stored frozen L1 larvae were frequently alive and highly motile. Angiostrongylus vasorum infection was diagnosed in two stoats and one weasel: in stoats infections were patent and the lung lesions were likely of clinical significance. These are believed to be the first records of A. vasorum in small mustelids. Pleuritis and pyothorax was seen in two polecats, in one case due to a migrating grass awn. Histological examination of lungs showed granulomata in stoats (38 %), weasels (52 %) and polecats (50 %). Spherules consistent with Emmonsia spp. adiaspores were present in the granulomata of stoats (60 %), weasels (36 %) and polecats (29 %). Adiaspore diameter in all three species was similar (means: stoats 39 μm, weasels 30 μm, polecats 36 μm); these are markedly smaller than that normally recorded for E. crescens. Although they lie within the accepted range for spores of Emmonsia parva this arid-zone species is not found in Britain, thus raising a question over the identity of the fungus. Cases showing numerous granulomata but few or no adiaspores were Ziehl-Neelsen-stain negative for acid-fast bacilli and IHC negative for Mycobacterium spp. However, in some cases PCR analyses revealed mycobacteria, including Mycobacterium kumamotonense and Mycobacterium avium Complex. One stoat had numerous unidentified small organisms present centrally within granulomata. Conclusions: Stoats, weasels and polecats in south-west England share several respiratory diseases, often of high prevalence, but the pathology would appear insufficient to impact on the health status of the populations and other ultimate causes of death should be investigated when examining these species. [ABSTRACT FROM AUTHOR]

Mustela nivalis (Least Weasel) reaches the southernmost portion of its North American range in the Appalachian Mountains. Throughout its southern range, the Least Weasel is considered rare or uncommon. We suggest that the current designation might underestimate the population due to a lack of records and limited knowledge of its distribution. We compiled Least Weasel records from the 7 southern-most states (Georgia, Kentucky, Maryland, North Carolina, Tennessee, Virginia, and West Virginia) in the Appalachian region. We searched museum/university collections, state agency databases, and contacted small colleges to locate specimens in teaching collections. Additionally, we implemented a citizen-science project to alert cat owners of the potential for cat-killed Least Weasel specimens and explained how to report these specimens. For all specimens, we attempted to determine the method of capture. The Least Weasel appears to be more abundant and widely distributed than previously documented. We identified 133 Least Weasel specimens; the greatest number (30) from Tennessee. For many states, we more than doubled the number of previous records. We determined a collection method for 83 specimens, the most common of which were cat and dog captures/kills (37% of specimens) and trapping (30%). Citizen scientists contributed 7 new records from eastern Tennessee and southwestern Virginia. We feel this approach has the potential to discover many future specimens. [ABSTRACT FROM AUTHOR]

The dorsal surface structure of the lingual papillae in the least weasel was compared with that of other carnivorous mammalian species. Two types of mechanical papillae (filiform and conical) and two types of gustatory papillae (fungiform and vallate) were observed. The filiform papillae had secondary processes. Rarely conical papillae were observed. A few taste buds were seen on the surfaces of the fungiform papillae. The four vallate papillae were located on both sides of the posterior end of the lingual body. In conclusion, morphological characteristics of the lingual papillae and their distribution in the least weasel were similar to those of the Japanese marten and ferret. The conical papillae in the lingual apex of the Japanese marten and ferret were not observed, but the conical papillae were seen in the lingual apex of the least weasel. [ABSTRACT FROM AUTHOR]

Competition, habitat structure and predation risk may alter mobility and activity of animals. In particular, small predators need to weigh the positive and negative impacts of the presence of competing larger predator species. Other predators present a risk but may also enhance the predation efficiency of smaller predators if avoiding one predator species increases prey exposure to the other. We studied how habitat structure and the presence of avian predators affected the activity patterns of radio-collared least weasels Mustela nivalis nivalis, small-bodied predators highly specialized on hunting small rodents and subject to intraguild predation. Least weasels appeared to schedule their mobility according to the peak activity of the avian predator present in large outdoor enclosures. In the presence of diurnal European kestrels Falco tinnunculus, least weasels moved less during night compared with evening and day, whereas in the presence of nocturnal Tengmalm's owls Aegolius funereus, least weasels moved more during night than during other time periods. Least weasels almost exclusively used the tall grass habitat in all treatments, whereas owls used the short grass habitat most and kestrels used both habitats equally. Our results suggest that beneficial interactions play an important role in the interaction between least weasels, kestrels and owls, and that the avoidance of risky habitats by least weasels minimizes the risk of intraguild predation. [ABSTRACT FROM AUTHOR]

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Carnivore victims of road accidents can be seen often on the road network in Bulgaria. The weasel Mustela nivalis is the smallest carnivore in this country. It is a strictly protected species under the Biological Diversity Act, Annex 3 (2002) and the Bern Convention, Annex III (1979). The effect of some characteristics of the habitat through which the road network passes on mortality has been studied: vegetation, distance to town/village, distance to animal farm and farm buildings, and the influence of season. The most common casualties were observed at a distance of 500-2000 m from the town/village and 500 m from farms, feed storage places or farmyards, which relates to the connection of the weasel to anthropogenic landscape. Higher is the percentage of casualties in open areas with low grass vegetation or farm crops compared to places with forest or shrub vegetation. [ABSTRACT FROM AUTHOR]

The relationship between predators and prey is thought to change due to habitat loss and fragmentation, but patterns regarding the direction of the effect are lacking. The common prediction is that specialized predators, often more dependent on a certain habitat type, should be more vulnerable to habitat loss compared to generalist predators, but actual fragmentation effects are unknown. If a predator is small and vulnerable to predation by other larger predators through intra-guild predation, habitat fragmentation will similarly affect both the prey and the small predator. In this case, the predator is predicted to behave similarly to the prey and avoid open and risky areas. We studied a specialist predator’s, the least weasel, Mustela nivalis nivalis, spacing behavior and hunting efficiency on bank voles, Myodes glareolus, in an experimentally fragmented habitat. The habitat consisted of either one large habitat patch (non-fragmented) or four small habitat patches (fragmented) with the same total area. The study was replicated in summer and autumn during a year with high avian predation risk for both voles and weasels. As predicted, weasels under radio-surveillance killed more voles in the non-fragmented habitat which also provided cover from avian predators during their prey search. However, this was only during autumn, when the killing rate was also generally high due to cold weather. The movement areas were the same for both sexes and both fragmentation treatments, but weasels of both sexes were more prone to take risks in crossing the open matrix in the fragmented treatment. Our results support the hypothesis that habitat fragmentation may increase the persistence of specialist predator and prey populations if predators are limited in the same habitat as their prey and they share the same risk from avian predation. [ABSTRACT FROM AUTHOR]

Metabolic rates and body mass of mammals vary seasonally along with ambient temperatures and food availability. At the population level, seasonal changes in metabolic rate and mass can be due to selective mortality or emigration of individuals whose metabolic rate or mass differs from the average for the population. Alternatively, the metabolic rates of individuals can change seasonally, such that the population average increases or decreases due to shifts in the physiology of the overall population. The latter implies that individuals respond in a similar manner to changing seasonal conditions. We studied seasonal changes in body mass (BM) and resting metabolic rate (RMR) in free-ranging male weasels (Mustela nivalis) to test the consistency of these traits in individuals caught in different seasons of the year. At the population level, BM was remarkably stable across the seasons (F3, 124 = 0.25, P = 0.9). In contrast, BM-corrected RMR varied significantly between seasons and was the lowest in winter (F3,135 = 9.13, P< 0.0001). We demonstrated that individual weasels were consistent in how their BM and RMR deviated from the seasonal means for the population (intraclass correlation, τ = 0.78 and 0.33, respectively). This variation among individuals explained ~76% and 27% of the total variation of BM and basal metabolic rate, respectively. Hence, the relatively constant BM at the population level across seasons is due to a relative constancy of BM in individuals. Our study is one of relatively few research projects that demonstrate that seasonal changes in RMR observed in the wild population are in part due to a consistency in individual responses to changing environmental conditions. [ABSTRACT FROM AUTHOR]

Predation risk is an environmental stressor that can induce changes in prey behavior and physiology. Perception of predation risk may indirectly affect offspring traits and future fitness prospects via impacts on the condition of parents. Females may influence the survival of their offspring via maternal effects, especially when breeding in stressful conditions. We investigated the effects of continuous predation risk perceived by mothers on the maternal allocation of immune factors and carotenoids in eggs of the pied flycatcher Ficedula hypoleuca. We collected eggs from wild pied flycatchers that bred in the vicinity of a predator nest (pygmy owl Glaucidium passerinum), were exposed to cues of a mammalian nest predator (urine of least weasel Mustela nivalis), or received appropriate controls for these two groups. Pied flycatchers transferred more immunoglobulin in eggs under high predation risk in both owl and mammalian predator treatments. The presence of owl nests also lowered the level of lysozyme transferred in the eggs in one of the two study years. Predation risk did not modify egg size or overall carotenoid levels. Our results show that continuous predation risk perceived by females during egg-laying affects egg composition. This different allocation of maternal immune factors may be an adaptive response evolved to increase the probability of offspring survival. [ABSTRACT FROM AUTHOR]

We present radiocarbon evidence for the presence of the weasel ( Mustela nivalis) on Mallorca prior to the Roman colonization of the Balearics. Bone collagen from a single specimen recovered at Cova del Ninot, Mallorca rendered two radiocarbon ages, independently obtained at two laboratories (2σ interval: 386-206 cal BC). These dates indicate that the translocation of the weasel to Mallorca occurred in Late Prehistory. The inhabitants of Mallorca at that time were the Talaiotic people (Iron Age settlers of the Balearics). The weasel appears to have been introduced by Talaiotic mercenaries returning to the island on Carthaginian ships. This is the first documented case of the translocation of a wild carnivorous mammal to the Gymnesic Islands (i.e., Mallorca and Menorca) in prehistoric times. Some ecological consequences of this invasion are outlined. [ABSTRACT FROM AUTHOR]

In general, landscape genetic studies have ignored the potential role that the phenotype of individuals plays in determining fine-scale genetic structure in species. This potential over-simplification ignores an important component that dispersal is both condition- and phenotype-dependent. In order to investigate the relationship between potential dispersal, habitat selection and phenotype, we examined the spatial ecology, body mass and fine-scale genetic structure of weasels ( Mustela nivalis) in Białowieża Forest in Poland. Our study population is characterized by an almost three-fold phenotypic variation in adult body mass and weasels were segregated in certain habitats according to size. We detected significant genetic structuring associated with habitat within the studied area and analyses of radio-tracking and re-capture data showed that the maximum extent of movement was achieved by weasels of medium body size, whereas the smallest and largest individuals exhibited higher site fidelity. With the unrestricted movement of the medium-sized individuals across optimal habitat, genetic admixture does occur. However, the presence of a barrier leads to unidirectional gene flow, with larger individuals outcompeting smaller individuals and therefore maintaining the genetic break in the study area. This highlights the importance of considering both intrinsic (phenotype) and extrinsic (environmental) factors in understanding dispersal patterns and ultimately, gene flow in complex landscapes. [ABSTRACT FROM AUTHOR]

We attempted to live trap lemmings under the snow in their preferred winter habitat at two sites in the Canadian Arctic using chimney-like boxes. Lemmings used the boxes during winter, but we had very low trapping success in April and May. During spring trapping, in contrast to most of the winter, subnivean temperatures became colder than ambient air temperatures. We hypothesize that our low success in spring resulted from lemmings' leaving the deeper snow areas where our boxes were located and moving to shallower snow or exposed tundra. We suggest that the trapping boxes could be successful if trapping occurred earlier during winter. [ABSTRACT FROM AUTHOR]

The small size and elongate shape of weasels (Mustela nivalis) probably evolved to facilitate movement within the burrow systems of prey species, but result in high energy costs of thermoregulation. In this study we measured metabolic rates of weasels during voluntary locomotion to determine whether energy costs of transport are also high in these unusually shaped mammals. In addition, we measured the lower and upper limits of aerobic metabolism [resting metabolic rate (RMR) and maximal oxygen consumption in forced exercise (Vo2,max)], and used the wide size range of adult weasels to investigate the intraspecific scaling of energy metabolism. Finally, we combined measurements of energy use during running with radiotracking and doubly labeled water data from free-living weasels to estimate the importance of locomotor costs in daily energy budgets. We found that weasels have higher than predicted costs of running, largely because of an elevated intercept of the speed versus metabolic rate relationship. Running costs were strongly affected by the approximately fourfold range of body size in adults. As reported in other studies, the RMR of weasels was considerably higher than predicted from body mass. Maximal oxygen consumption was also higher than predicted, but factorial aerobic scope (Vo2,max/RMR) was within the normal range for mammals. Intraspecific mass scaling of RMR and Vo2,max did not differ from typical interspecific mammalian allometries. In wild weasels, locomotor costs comprised roughly 5% of daily energy expenditures; this low value was primarily a result of short travel times and distances. [ABSTRACT FROM AUTHOR]

Least weasels are highly specialized small-rodent predators. Despite the fact that they are hypothesized to play an important role in generating the lemming cycles, a key process for the functioning of the terrestrial tundra ecosystem, very little is known about the biology of these miniature carnivores in the Arctic. At Mys Vostochny in western Taimyr, Russia, least weasels were observed for the first time during a lemming peak in 2005, but not in two subsequent years with low lemming densities. Here we report observations about weasel signs in lemming winter nests, body condition, habitat use, and diet in summer 2008, a year when lemmings had been numerous under the snow but populations crashed before the summer, and least weasels were abundant. Stable isotope analyses revealed that weasel diet was dominated by Siberian lemmings during spring. As expected, given lower resource availability when the lemming population crashed, weight (taking into account body length) was somewhat lower in 2008 than in 2005. Tracking tunnels and trapping showed that in summer least weasels mostly used sheltered habitats such as rocky outcrops and driftwood. Together with surveys of lemming winter nests, tracking tunnels appeared to be a promising method for monitoring least weasels in the Arctic tundra. [ABSTRACT FROM AUTHOR]

Overarching trends can be seen in European mammalian phylogeography, yet it is clear that species responded differently depending on adaptations to past environments. We built upon previous work on the phylogeography of weasels ( Mustela nivalis) in Europe by using well-preserved museum specimens from a proposed phylogeographic suture zone. The complete cytochrome b gene was amplified from 49 individuals from present-day Poland and analyzed with previously published data on a European scale to identify glacial refugia and infer recolonization processes. Bayesian coalescent analysis revealed the importance of the Last Glacial Maximum and the Younger Dryas in the diversification of, and demographic changes in, identified mitochondrial lineages. Our analysis, in conjunction with the available fossil data, strongly points to a Carpathian origin for one of the lineages, and further highlights the importance of this region as a refugium for European mammals. Mustela nivalis originating from this refugium appear to have a selective advantage over M. nivalis from other lineages in certain environments in the suture zone in central Europe, with climate clearly influencing the distribution of mitochondrial DNA lineages. This has important implications not only for our understanding of how past climatic events shaped the genetic architecture of species, but also how they will respond to current and future climatic changes. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 106, 57-69. [ABSTRACT FROM AUTHOR]

This study reports the first set of microsatellite markers for the weasel (Mustela nivalis). We chose to isolate loci with tetranucleotide repeat motifs because they can be scored less ambiguously than the more commonly used dinucleotide loci. All 11 loci showed considerable variation within a population sample of 28 individuals from Portugal, with number of alleles ranging from four to nine per locus and observed and expected heterozygosities ranging from 0.21 to 0.86 and from 0.40 to 0.84, respectively. No linkage disequilibrium was detected between pairs of loci, and only one locus (Mn 1.30) deviated from Hardy-Weinberg equilibrium expectations in the analyzed population sample. Among the 11 loci, Mn 1.30 was the only one for which all known males were homozygous. Analysis of an additional population sample of 23 individuals (14 males and 9 females) from Denmark revealed that all males, but only four females, were homozygous for Mn 1.30, supporting the idea that the locus is X-linked. These novel polymorphic microsatellite markers should be useful in studies of population genetics and molecular ecology of the weasel. [ABSTRACT FROM AUTHOR]

Body mass (BM) and resting metabolic rates (RMR) are two inexorably linked traits strongly related to mammalian life histories. Yet, there have been no studies attempting to estimate heritable variation and covariation of BM and RMR in natural populations. We used a marker-based approach to construct a pedigree and then the 'animal model' to estimate narrow sense heritability ( h2) of these traits in a free-living population of weasels Mustela nivalis-a small carnivore characterised by a wide range of BM and extremely high RMR. The most important factors affecting BM of weasels were sex and habitat type, whereas RMR was significantly affected only by seasonal variation of this trait. All environmental factors had only small effect on estimates of additive genetic variance of both BM and RMR. The amount of additive genetic variance associated with BM and estimates of heritability were high and significant in males ( h2 = 0.61), but low and not significant in females ( h2 = 0.32), probably due to small sample size for the latter sex. The results from the two-trait model revealed significant phenotypic (r P = 0.62) and genetic correlation (r A = 0.89) between BM and whole body RMR. The estimate of heritability of whole body RMR (0.54) and BM corrected RMR (0.45) were lower than estimates of heritability for BM. Both phenotypic and genetic correlations between BM corrected RMR and BM had negative signals (r P = −0.42 and r A = −0.58). Our results indicate that total energy expenditures of individuals can quickly evolve through concerted changes in BM and RMR. [ABSTRACT FROM AUTHOR]

Integration of the Romania in the EU is imposing a special attention to hunting animals populations. The aim of the present paper was to study the quantitative evolution of the hunting population for the 13th species, in the period 2007-2011, in the hunting terrain 54 Padureni, from Forest Domain - Lunca Timişului, with a total surface of 11,963ha. The paper shows that form the 13th species studied 5 were not identified on this hunting terrain Red Deer (Cervus elaphus L.), Wildcat (Felis silvestres L), European Pine Marten (Martes martes L.), Least Weasel (Mustela nivolis L.) Muskrat (Ondatra zibethica L.). For the other species identified the individuals number evolution demonstrated that there is a god correlation between the number of individuals and it-s biogenic capacity. Also the paper recommends a special attention to natural selection and the efficient use of artificial selection, especially for the following 3 species: Roe Deer (Capreolus Capreolus L.), Wild hog (Sus scrofa L.) and Common Pheasant (Phasianus colchicus L.). [ABSTRACT FROM AUTHOR]

Phylogenetic relationships among species of the family Mustelidae were examined using the combined nucleotide sequences of the three mitochondrial genetic loci (cytochrome b ( MT-CYB; 1140 bp), NADH dehydrogenase subunit 2 ( MT-ND2; 1044 bp), and displacement loop ( MT-DLOOP; 540 bp)), with special emphasis on the phylogenetic history of four Taiwanese mustelid species: (Boddaert, 1785), (Gray, 1831), L., 1766, and Pallas, 1773. Maximum likelihood phylogenetic analysis of the combined sequences of the mitochondrial genetic loci produced a topology largely congruent with that of previous studies at the species level. Analyses of intraspecific genetic variations revealed two Melogale moschata individuals from Taiwan and Vietnam that showed genetic distances comparable with interspecific variations within the mustelid lineages. Furthermore, Mustela nivalis, recently discovered in Taiwan, was not as genetically differentiated from other continental conspecific individuals as a previous morphological survey suggested. Divergence time estimations for the mustelid lineages of Taiwan and the Eurasian continent by the Bayesian relaxed molecular clock approach suggested multiple colonization of Taiwan by mustelids from the continent during the Pleistocene, creating a hierarchical pattern of endemism based on the differential isolation history of the mustelid species in Taiwan. [ABSTRACT FROM AUTHOR]

Abstract: Anticoagulant rodenticides are widely used to control rodent populations but they also pose a risk of secondary poisoning in non-target predators. Studies on anticoagulant rodenticide exposure of non-target species have mainly reported on frequency of occurrence. They have rarely analyzed variations in residue concentrations. We examine the occurrence and concentrations of five anticoagulant rodenticides in liver tissue from 61 stoats (Mustela erminea) and 69 weasels (Mustela nivalis) from Denmark. Anticoagulant rodenticides were detected in 97% of stoats and 95% of weasels. 79% of the animals had detectable levels of more than one substance. Difenacoum had the highest prevalence (82% in stoats and 88% in weasels) but bromadiolone was detected in the highest concentrations in both stoat (1.290μg/g ww) and weasel (1.610μg/g ww). Anticoagulant rodenticide concentrations were highest during autumn and winter and varied with sampling method. Anticoagulant rodenticide concentrations were higher in stoats and weasels with unknown cause of death than in specimens killed by physical trauma. There was a negative correlation between anticoagulant rodenticide concentrations and body condition. Our results suggest that chemical rodent control in Denmark results in an extensive exposure of non-target species and may adversely affect the fitness of some stoats and weasels. [Copyright &y& Elsevier]

Abstract: In this study we examined temporal and geographical variations in a sample of 124 skulls of the weasel Mustela nivalis and 146 skulls of the stoat M. erminea, collected in Sweden between 1959-1992 and 1913-1990, respectively. We used Principal Component Analysis (PCA) to combine the effects of latitude, longitude, year of collection, mean ambient temperature and Net Primary Productivity (NPP). The first principal component (PC1) contained latitude, ambient temperature and NPP and was significantly and positively related to male (but not female) skull size of both stoats and weasels. None of the other factors or their interactions were significantly related to skull size. We conclude that ambient temperature, either directly through energy savings, or indirectly through improved food availability (increased NPP), had a significant effect on determining body size of male stoats and weasels in Sweden. Our results support the hypothesis that male and female of these species are affected by different selection pressures and thus react differently to changing environmental conditions. [ABSTRACT FROM AUTHOR]

Knowledge of species distribution is fundamental to conservation and management efforts. Unfortunately, distribution of many mammal species in the southeastern United States, including some considered endangered, threatened, or of special concern, has been and remains poorly documented. We queried museums, reviewed the published literature, and searched state Natural Heritage Inventory databases to obtain distributional information for 13 mammal species considered rare (Global Rank G1-G3 or State Rank S1-S3) or of other conservation concern in the Southern Appalachian region. We constructed distribution maps for selected mammal species within the region based on 7 state Natural Heritage Inventory databases and 1539 county records from 26 museums and 57 published sources. Napaeozapus insignis (Woodland Jumping Mouse), Mustela nivalis (Least Weasel), and Tamiasciurus hudsonicus (Red Squirrel) exhibited large (>150 km) geographic differences from currently accepted range maps. Sorer dispar (Rock Shrew), Synaptomys cooperi (Southern Bog Lemming), Neotoma magister (Allegheny Woodrat), and Zapus hudsonius (Meadow Jumping Mouse), exhibited small (<75 km) geographic differences. The remaining 6 species showed little to no range differences from commonly accepted range maps. Because seven of 13 mammals showed substantial differences from known range maps, our updated maps may aide managers and others in focusing surveying and conservation efforts. [ABSTRACT FROM AUTHOR]

Plant-associated micro-organisms such as mycotoxin-producing endophytes commonly have direct negative effects on herbivores. These effects may be carried over to natural enemies of the herbivores, but this has been rarely explored. We examined how feeding on Neotyphodium endophyte infected (E+) and endophyte free (E2) meadow ryegrass (Scherodonus pratensis) affects body mass, population size and mobility of sibling voles (Microtus levis), and whether the diet mediates the vulnerability of voles to least weasel (Mustela nivalis nivalis) predation. Because least weasels are known to be olfactory hunters, we also examined whether they are able to distinguish olfactory cues of voles fed on E+ and E2 diets. Neither body mass of voles nor population size differed between diets. However, contrary to our prediction, least weasels preyed more often on voles fed with E2 grass than on voles fed with E+ grass. The mobility of voles fed on E+ grass was reduced compared to voles fed on E2 grass, but this effect was unrelated to risk of predation. Least weasels appeared unable to distinguish between excrement odours of voles between the two treatments. Our results suggest that consumption of endophytic grass is not directly deleterious to sibling voles. What's more, consumption of endophytes appears to be advantageous to voles by reducing risk of mammalian predation. Our study is thus the first to demonstrate an effect of plant-associated microbial symbionts on herbivore-predator interactions in vertebrate communities. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

We studied factors influencing daily energy expenditures (DEE) of male least weasels (Mustela nivalis) using the doubly labelled water technique. The relationship between ambient temperature and DEE formed a triangular pattern, characterized by invariance of the maximum DEE and an inverse relationship between minimum DEE and temperature. A simple energetic model relating the DEE of male weasels to activity time (AT) and ambient temperature predicted that, across seasons, less than 10 per cent of measurements approach the upper bound of observed DEE. Male weasels were able to maintain a relatively constant maximum energy output across varying temperatures by adjusting their AT to changes in temperature. They achieved maximum energy expenditures in winter due to high thermoregulatory costs, and in spring and summer due to high levels of physical activity. This pattern exemplifies a ‘metabolic niche’ of a small mammal having extremely high energy expenditures primarily driven by ambient temperature. [ABSTRACT FROM AUTHOR]

1. We reviewed patterns of fruit consumption amongst 10 species of mesocarnivores: red fox Vulpes vulpes, weasel Mustela nivalis, stoat Mustela erminea, polecat Mustela putorius, stone marten Martes foina, pine marten Martes martes, Eurasian badger Meles meles, common genet Genetta genetta, Egyptian mongoose Herpestes ichneumon and wildcat Felis silvestris in Mediterranean Europe. 2. The 65 reviewed studies recorded 79 different fruits eaten by carnivores, 58 of which were identified to species. Most records (63%) were of fleshy fruits with high pulp content. The frequency of occurrence of fruit items varied widely amongst species and regions. Four of the carnivore species (red fox, stone marten, badger and common genet) included more than 30 fruit species in their diet. 3. A longitudinal pattern was detected in the consumption of fruit in the Mediterranean region, with the frequency of occurrence of fruit consumption increasing towards the east. [ABSTRACT FROM AUTHOR]

Indirect interaction between two competing species via a shared predator may be an important determinant of population and community dynamics. We studied the effect of predation risk imposed by the least weasel Mustela nivalis nivalis on space use, foraging and activity of two competing vole species, the grey-sided vole Myodes rufocanus, and the bank vole Myodes glareolus. The experiment was conducted in a large indoor arena, consisting of microhabitat structures providing food, shelter, trees for refuge and separated areas with high and low predation risk. Voles were followed for 5 days: 2 days before, 1 day during and 2 days after the presence of weasel. Our results suggest an effect of weasel presence on the vole community. Voles of both species shifted their activity from risky to less risky areas, climbed trees more often and were less active. Seed consumption was not affected by weasel presence. The time spent in the risky and less risky area did not differ between species, but bank voles spent more time in trees than grey-sided voles. Males of both species were more exposed to predation risk than females, i.e. generally spent more time in the risky area. Proportion of time spent in the risky area, the use of area, trees and food stations were sex dependent. Activity and use of trees were species dependent. We found no evidence for despotic distribution between our two species, although bank voles seemed to be more affected by coexistence, since they lost weight during the experiment. Based on our results we conclude that predator response was largely similar between species, while the sex-specific responses dominated. Besides a stronger escape response in the bank vole, the strongest individual differences were sex specific, i.e. males were more prone to take risks in space use and activity. [ABSTRACT FROM AUTHOR]

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 Białowieża 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. [ABSTRACT FROM AUTHOR]

Dissimilar vulnerabilities of different prey types and preferences of predators are factors likely to contribute to community dynamics. This may happen via differential individual properties of prey animals (e.g. vigilance, escape) or via habitat effects making hunting by a predator easier and more rewarding in some habitats, or both. Furthermore, community dynamics may be influenced by predator mediated apparent competition, in which an increase in one prey type has negative effects on another prey type indirectly via the shared predator. We summarize the current knowledge from the field in a model predator-prey system consisting of sympatric boreal vole species and their common specialist predator and review field studies using predator manipulation and studies on the responses of individuals in the laboratory and in outdoor enclosures. The vole species studied represent different prey types that are thought to have different vulnerabilities. Our observations on the main resident specialist predator, the least weasel ( Mustela nivalis nivalis L.), show that it hunts according to prey availability and suitability of the hunting habitat. Prey voles respond to the presence of the predator behaviorally in various ways to avoid predation. We conclude that even if the least weasel is a specialized predator of small rodents it acts like a generalist predator within the small rodent guild and may facilitate the coexistence of prey species via predator switching. This may lead to interspecific synchrony between prey populations, which has often been observed. We suggest that the processes determining the community impact of predator-prey interactions are driven by the behavioral arms race between the predator and the prey, together with the habitat-dependent density of prey and net gain for the predator. [ABSTRACT FROM AUTHOR]