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For the ability to control an invasive species and to protect an ecologically similar native species it is essential to map the exact distributions of both species. This is difficult if the species are so morphologically similar that their identification in the field is almost impossible. In Finland, the invasive North American beaver Castor canadensis is spreading towards the range of the native Eurasian beaver Castor fiber and at present, these species are partly sympatric. Effective management of these morphologically similar species requires an efficient method for species identification, ideally one that is non-invasive. Non-invasive genetic methods are used in a wide variety of wildlife species, for example in the research of large carnivores. Feces are a good source of DNA for terrestrial animals, but for the semi-aquatic animals like beavers, feces are not the best option. However, environmental DNA (eDNA) has been successfully used to detect species non-invasively in aquatic and terrestrial environments. We developed a non-invasive, eDNA-based method to map the distribution of the beaver species in Finland and to investigate within-species genetic diversity. The eDNA was obtained from the feed remains (wood chips) from beaver forage sites. With the help of Citizen science, wood chip samples were collected from different parts of Finland. We used our eDNA method to identify the ranges of both beaver species. Additionally, the presence of Eurasian beavers in south-east Finland was proven for the first time. Our non-invasive eDNA method is an effective way to accurately identify the ranges of both beaver species and will allow for the control of the invasive North American beaver and conservation of the native Eurasian beaver in Finland.

Muskrats Ondatra zibethicus are semiaquatic herbivores experiencing long-term and widespread population declines across North America. Translocation may be a viable tool to bolster or reestablish local populations; however, subsequent effects of translocation on muskrats are unknown. We live-trapped and translocated radiomarked muskrats (n = 65) during the summers of 2018–2019 in Voyageurs National Park, MN, USA and assessed post-translocation effects on weekly survival probabilities and space-use patterns. We did not observe homing behavior, though individuals moved an average of 2.2 km (SE = 0.30 km) from release sites and established home ranges within ∼8 days (SE = 1.16 days) post-translocation. Weekly post-translocation survival probabilities (0.95, SE = 0.001) and average home-range sizes (2.52 ha, SE = 0.44 ha) were similar to other studies of non-translocated muskrats. Our most-supported known-fate survival model revealed muskrats using beaver Castor canadensis lodges had greater weekly survival probabilities. Additionally, weekly muskrat survival varied between years suggesting a positive response to a novel soft-release technique applied in 2019. Our study provides the first empirical assessment of translocation effects on muskrats and suggests translocation may be effective for establishing or enhancing local muskrat populations. Additionally, our study suggests beaver lodges may confer fitness benefits to sympatric muskrats particularly during dispersal.

Provision of artificial surface water has been suggested as a management practice that can benefit wildlife in arid and semi-arid regions. With unprecedented droughts predicted for many of these areas in North America in coming decades, understanding species response to the provision of artificial surface water should be evaluated. Moreover, a dearth of knowledge exists in the understanding of avian response to artificial surface water during the non-breeding season. To address this lack of knowledge, we sampled the avian community at varying distances from water sources in Beaver County, Oklahoma, USA from February–March 2013–2014. A total of 20 species were detected. We found no relationship to avian species richness and distance to water. Likewise, pooled data of detections across all species indicated no relationship in relation to artificial surface water. Analysis on individual species indicated that western meadowlarks Sturnella neglecta did not respond to water. However, American tree sparrows Spi...

Tail-mounted transmitters have been used successfully in temperate regions of North America and Europe but have not been tested in more northern parts of American beaver Castor canadensis range. We deployed 63 tail-mounted transmitters on adult beavers in Voyageurs National Park, Minnesota (USA; 48°30′N, 92°50′W), at the southern edge of the boreal forest. Mean transmitter retention time was 133 days (range = 18–401, SD = 101), with only 7% retained > 12 months. Males and females did not differ in retention times. Retention time was similar for transmitters deployed in fall (n = 38, = 135 days) and spring (n = 21, = 130 days). In 24 cases where we confirmed beavers lost transmitters, 63% tore through the side of the tail, 25% pulled out through a widened attachment hole, and 13% had the lock-nut unscrew. Beavers chewed off or pulled out whip antennas on 50% of transmitters before they were detached from the tail, which reduced VHF signal strength and detection distance. The likelihood that an antenna woul...

Seven North American beavers Castor canadensis (Cc) were introduced into Finland in 1937 to supplement an ongoing reintroduction of the nearly extinct Eurasian beaver C. fiber (Cf). At that time, many zoologists recognised only one species. However, in 1973, chromosome counts (Cf¼48, Cc¼40) acknowledged two species, and Cc became an invasive alien. Recently, expanding populations of both species have converged on two fronts in Finland and northwestern Russia. According to Gause’s competitive exclusion principle, two species with identical niches cannot coexist indefinitely . The imminent question is whether coexistence or competitive exclusion will ultimately result, with the possible regional extirpation or eventual extinction of Cf. We reviewed published cases of interspecies contact and compared their life history, ecology and behaviour. The few published incidences of contact were inconclusive with respect to competitive advantage. Body size is similar, but Cc litter size is slightly greater. Only minor differences in life history, ecology and behaviour were found to exist, suggesting nearly complete niche overlap. Though competitive exclusion resulting in the extinction of a native mammal by an alien congener at the continental landscape scale has been rare, the process may be difficult to detect due to potential time lags of centuries. Thus, there is a distinct risk that Cc may eventually competitively exclude Cf at all landscape scales. As no country in Eurasia obviously wants an invasion of Cc, and as most national conservation laws and international treaties forbid the spread of alien species, we advocate that the precautionary principle be adhered to and an attempt to eradicate Cc from Eurasia be seriously considered. Successful eradication is still possible if the will to do so exists. Here, we outline an eradication strategy.

Several metrics of biodiversity are used to assess the variability and abundance of multiple species across various ecological levels. Previous research suggests that biodiversity in agricultural areas is diminished due to habitat fragmentation and alterations to natural vegetation. Contrary to the effects of agriculture, the American beaver Castor canadensis has been shown to have a significant contribution to increased biodiversity. Our study focuses on the biodiversity of mammals in wetland areas of the southern mixed-wood boreal forest natural region of east-central Alberta, Canada. We compared various measures of biodiversity levels of mammals in the winter months between wetlands on agricultural land and wetlands in Miquelon Lake Provincial Park (MLPP). Similarly, we compared wetlands with active and inactive beaver colonies to determine differences in winter biodiversity of mammals and the amount of water coverage within a pond. We collected data using winter tracking surveys and analyzed ...

The current reestablishment and growth of beaver Castor fiber populations throughout Eurasia has created a need for methods to control population size. While lethal-trapping has been the most common harvest and control method for beaver world-wide for centuries, in recent decades spring hunting has developed as the main lethal method in Norway, Sweden and Finland. An experimental hunt where hunters annually removed 22–26% (mean = 24%) of the estimated spring population of beavers on 242 km2 in southeast Norway led to an unanticipated 46% decline in colony number after only three years. We monitored the population response in colony number throughout the ensuing four years of no hunting during which time the number of colonies rebounded by 93%. The rapid increase in colony number suggested a high rate of dispersal to vacated colony sites by animals from unexploited colonies within the study area (approximately half were unexploited each year) and from bordering townships where harvest was light at the time...

Dispersal and long-term monitoring of beaver Castor canadensis and C. fiber populations has been hampered by the inability to retain external transmitters on the animals and the limited range of internal transmitters. We tested several transmitter designs to develop an effective and reliable external transmitter for beavers. A modified ear-tag transmitter fitted with a plastic sleeve and attached to the tail was found efficacious in pen trials. We captured and tagged 31 beavers in Phoenix, Arizona, USA, to further test these modified ear-tag transmitters in the field. Retention of the sleeve transmitter averaged 343.5 days±44.2 (SE), more than triple the time previously reported. The addition of neoprene washers to the underside of the tail increased retention to 89%. Long-term monitoring of beaver populations may now be possible with increased retention of transmitters with the addition of neoprene washers.

We examined the seasonal food habits of wolverine Gulo gulo in subboreal and interior wet-belt montane environments in British Columbia by analyzing scats collected during the course of two concurrent wolverine studies. Understanding foraging ecology for a wide-ranging carnivore such as the wolverine is important, particularly because reproduction has been demonstrated to be closely linked to food abundance. Wolverine diet was shown to vary regionally and seasonally. Regional variation was related to differences in prey availability between study areas. Moose Alces alces, caribou Rangifer tarandus, and hoary marmots Marmota caligata were abundant and common prey items within both study areas. Mountain goats Oreamnos americanus and porcupine Erithizon dorsatum were more abundant and more frequent prey items in the Columbia Mountains, while snowshoe hare Lepus americanus and beaver Castor canadensis were more abundant and more frequent prey items in the Omineca Mountains. Within the winter season, ...

Wolf Canis lupus relationships with wild ungulates, domestic animals and humans were studied in an area of ca 800 km2 at the head of the Lovat River in northeastern Belarus during 1990–2000. The region was dominated by natural habitats (78%) consisting mainly of forests and bogs, but also lakes and rivers. The abundance of wild ungulates, such as moose Alces alces, wild boar Sus scrofa, and roe deer Capreolus capreolus, as censused by snow tracking and assessed by game wardens, declined 5 to 6-fold between 1990 and 1996, most probably due to uncontrolled exploitation and poaching. During 1997–2000, the numbers of ungulates began to recover. Wolves responded to the shortage of wild ungulates by a strong shift in feeding habits. When wild ungulates were numerous, wolf diet as studied by scat analysis was composed of wild ungulates (80–88% of consumed biomass), with small additions of medium- and small-sized wild animals (7–13%), mainly beaver Castor fiber and hare Lepus sp., and domestic animals (4–6%), mai...

Hunting Eurasian beaver Castor fiber with firearms during late spring is the dominating harvest form in Norway but may violate the Norwegian wildlife management principle of not hunting during the breeding season. In particular, shooting mothers from newborn young would be considered cruel. As beaver cannot be sexed or effectively aged under spring hunting conditions, selective harvesting at this time is impossible. We examined 32 pregnant beaver shot between 27 March and 12 May 1997–1999 in southeast Norway. No post-parturition females were shot, despite a 15-day extension of the normal hunting season to 15 May. A regression model predicted a mean birth date for the population of 13 May, with most births between 7 and 18 May and few before 30 April. Post-parturition females were not shot primarily because most births occur after hunting has ceased. Additionally, reduced activity of mothers outside the lodge may limit exposure to hunters. Terminating hunting a month earlier would eliminate the shooting of pregnant females with well-developed foetuses. However, as few watersheds in Norway are ice-free before mid-April, and most beaver are presently bagged in late April, this would likely result in a major reduction in beaver harvests and an increase in damage complaints.

The ability of Eurasian beavers Castor fiber to recognise different predator odours has received little research, nor has the use of predator odours to deter Eurasian beavers from damaging agricultural crops, fruit and forest trees. Recognition of and response to predator odours by prey is of adaptive significance because it reduces predation risk. We tested the hypothesis that predator odours decrease foraging and predicted that: human and wolf Canis lupus odour would decrease foraging more effectively than other predator odours. Our results showed that all tested predator odours (red fox Vulpes vulpes, river otter Lutra lutra, lynx Lynx lynx, wolf and brown bear Ursus arctos), except those from human and dog Canis familaris, significantly decreased foraging during summer. River otter, red fox, lynx, wolf and brown bear odours had the strongest effects during summer. During autumn, river otter odour was significantly more effective than the other predator odours, except those from lynx, human and red fox, in decreasing foraging. Only odour from river otter, human, lynx and red fox had a significantly stronger effect than the three controls during autumn. Overall, the river otter odour was most effective in decreasing foraging. Odours from predators sympatric with the Eurasian beaver did not have a larger effect than those of originally sympatric, but now absent species. Beavers ate more sticks with predator odour in autumn than in summer. Our results have clear practical implications, and several are suggested.

Introduced mammals and birds have had a high rate of success in the Nordic countries. Out of 18 species new to the area, 14 (78%) have established a population in at least one country. American mink Mustela vison, raccoon dog Nyctereutes procyonoides, muskrat Ondatra zibethicus, white-tailed deer Odocoileus virginianus, Canada goose Branta canadensis and pheasant Phasianus colchicus have been the most successful exotics. Ecological effects caused by the newcomers include: displacement of European mink Mustela lutreola and beaver Castor fiber by American counterparts, changes in aquatic vegetation patterns caused by muskrat grazing, and locally heavy predation pressure on colonial waterbirds by the American mink. From now on, introductions of new species should be avoided, at least until proven harmless.

On the basis of questionnaires to moose hunters the colonisation pattern of reintroduced beaver in the province of Varmland was mapped. The beaver spread rapidly within water drainage systems resulting initially in scattered colonisation and very low population densities in relation to range. Spread was slowed by watershed divides. Illustrating the shape of the expansion wave front by plotting the relative increase of the population and range against time, shows a very flat front characterised by long dispersal distances.