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Frank Rosell - One of the best experts on this subject based on the ideXlab platform.
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Beaver (Castor Fiber) activity and spatial movement in response to light and weather conditions
Mammalian Biology, 2020Co-Authors: Laura Bartra Cabré, Martin Mayer, Sam Steyaert, Frank RosellAbstract:Animal behaviour can affect individual fitness and is influenced by exogenous and endogenous factors. Here, we investigated how light (daylight length and moonlight), weather (precipitation and temperature), age, sex and social status affected activity and movement of a semiaquatic mammal, the Eurasian beaver ( Castor Fiber ), using GPS relocation data from 47 individuals in south-eastern Norway. Independent of daylight length, beavers had a mean daily activity time of 9:42 h and reduced their activity periods when they were older, most likely due to senescence. In line with this, older individuals also spent less time in water and moved shorter distances. Furthermore, beavers reduced their activity periods in drier weather conditions and spent less time on land during brighter nights and drier conditions, indicating a predation risk avoidance strategy. Individuals spent less time in the water during the colder parts of the year and moved shorter distances with decreasing temperature, suggesting thermal constraints. Our study adds to the increasing amount of evidence that animal behaviour is modulated by various endogenous and exogenous factors, and that weather conditions can affect their behaviour. It remains to be tested, however, how climate variability together with hunting and predation pressure affect space use and demography in species such as the Eurasian beaver.
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Outcomes of a ‘One Health’ Monitoring Approach to a Five-Year Beaver (Castor Fiber) Reintroduction Trial in Scotland
EcoHealth, 2017Co-Authors: Gidona Goodman, Frank Rosell, Simon Girling, Anna Meredith, Roisin Campbell-palmerAbstract:The Scottish Beaver Trial, involving the translocation and release of 16 wild Norwegian beavers ( Castor Fiber ) to Scotland, provides a good example of a ‘One Health’ scientific monitoring approach, with independent monitoring partners on ecology and public health feeding into veterinary health surveillance. Pathogen detection did not prohibit beaver release, although eight beavers were seropositive for Leptospira spp. Six deaths (37.5%) occurred during Rabies quarantine, followed by the death of two animals shortly after release and two wild-born kits due to suspected predation. Two host-specific parasites, the beaver fluke ( Stichorchis subtriquetrus ) and beaver beetle ( Platypsyllus Castoris ) were also reintroduced.
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Outcomes of a 'One Health' Monitoring Approach to a Five-Year Beaver (Castor Fiber) Reintroduction Trial in Scotland.
Ecohealth, 2016Co-Authors: Gidona Goodman, Frank Rosell, Simon Girling, Anna Meredith, Roisin Campbell-palmerAbstract:The Scottish Beaver Trial, involving the translocation and release of 16 wild Norwegian beavers (Castor Fiber) to Scotland, provides a good example of a 'One Health' scientific monitoring approach, with independent monitoring partners on ecology and public health feeding into veterinary health surveillance. Pathogen detection did not prohibit beaver release, although eight beavers were seropositive for Leptospira spp. Six deaths (37.5%) occurred during Rabies quarantine, followed by the death of two animals shortly after release and two wild-born kits due to suspected predation. Two host-specific parasites, the beaver fluke (Stichorchis subtriquetrus) and beaver beetle (Platypsyllus Castoris) were also reintroduced.
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Haematology and Serum Biochemistry Parameters and Variations in the Eurasian Beaver (Castor Fiber).
PloS one, 2015Co-Authors: Simon Girling, Roisin Campbell-palmer, Romain Pizzi, Mary Fraser, Jonathan Cracknell, Jon M. Arnemo, Frank RosellAbstract:Haematology parameters (N = 24) and serum biochemistry parameters (N = 35) were determined for wild Eurasian beavers (Castor Fiber), between 6 months – 12 years old. Of the population tested in this study, N = 18 Eurasian beavers were from Norway and N = 17 originating from Bavaria but now living extensively in a reserve in England. All blood samples were collected from beavers via the ventral tail vein. All beavers were chemically restrained using inhalant isoflurane in 100% oxygen prior to blood sampling. Results were determined for haematological and serum biochemical parameters for the species and were compared between the two different populations with differences in means estimated and significant differences being noted. Standard blood parameters for the Eurasian beaver were determined and their ranges characterised using percentiles. Whilst the majority of blood parameters between the two populations showed no significant variation, haemoglobin, packed cell volume, mean cell haemoglobin and white blood cell counts showed significantly greater values (p
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Rapid rebound in colony number of an over-hunted population of Eurasian beaver Castor Fiber
Wildlife Biology, 2014Co-Authors: Howard Parker, Frank RosellAbstract: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...
Roisin Campbell-palmer - One of the best experts on this subject based on the ideXlab platform.
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Reintroducing beavers Castor Fiber to Britain: a disease risk analysis
Mammal Review, 2019Co-Authors: Simon Girling, Mary Fraser, Adam D. Naylor, Roisin Campbell-palmerAbstract:Eurasian beavers Castor Fiber are potential hosts for a range of infectious diseases and parasites, including those typical of common European rodents. A number of infectious organisms are potentially zoonotic and may be notifiable under animal health legislation. The official trial beaver reintroductions to Scotland, the retrospectively licensed releases in England, and the increasingly obvious presence of large numbers of unlicensed illegally released animals have highlighted potential disease risks. We aimed to conduct a disease risk analysis, based on peer reviewed publications, for selection and health screening of Eurasian beavers prior to release into the wild in Britain. Adapted from the International Union for the Conservation of Nature’s ‘Guidelines for Disease Risk Analysis’, a four‐step process was used to formulate a disease risk analysis: 1) problem description; 2) hazard identification based on literature review; 3) risk assessment, which resulted in categorisation of pathogens into low, medium, and high risk; and 4) risk management: identification of mitigating measures, followed by risk re‐evaluation in light of the reported effectiveness of the mitigation measures. The highest‐risk pathogens identified in the literature review process included: parasites, specifically Cryptosporidium parvum, Echinococcus multilocularis, Eimeria spp., Fasciola hepatica, Giardia spp., Trichinella britovi; bacteria, specifically Escherichia coli, Franciscella tularensis, Mycobacterium avium, Salmonella spp., Yersinia spp.; a fungus Chrysosporium parvum (Emmonsia parva); and terrestrial rabies virus. Most could be mitigated by sourcing beavers from Britain. The rest could be mitigated by pre‐release testing procedures that are already established. The risk of introducing significant disease to humans, domestic animals, or wildlife by releasing into the wild in Britain a beaver that was captive‐bred in Britain or a wild beaver from Scotland, based on the current evidence of disease incidence, and assuming the use of robust, peer reviewed, pre‐release health screening techniques, can be viewed as low.
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Outcomes of a ‘One Health’ Monitoring Approach to a Five-Year Beaver (Castor Fiber) Reintroduction Trial in Scotland
EcoHealth, 2017Co-Authors: Gidona Goodman, Frank Rosell, Simon Girling, Anna Meredith, Roisin Campbell-palmerAbstract:The Scottish Beaver Trial, involving the translocation and release of 16 wild Norwegian beavers ( Castor Fiber ) to Scotland, provides a good example of a ‘One Health’ scientific monitoring approach, with independent monitoring partners on ecology and public health feeding into veterinary health surveillance. Pathogen detection did not prohibit beaver release, although eight beavers were seropositive for Leptospira spp. Six deaths (37.5%) occurred during Rabies quarantine, followed by the death of two animals shortly after release and two wild-born kits due to suspected predation. Two host-specific parasites, the beaver fluke ( Stichorchis subtriquetrus ) and beaver beetle ( Platypsyllus Castoris ) were also reintroduced.
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Outcomes of a 'One Health' Monitoring Approach to a Five-Year Beaver (Castor Fiber) Reintroduction Trial in Scotland.
Ecohealth, 2016Co-Authors: Gidona Goodman, Frank Rosell, Simon Girling, Anna Meredith, Roisin Campbell-palmerAbstract:The Scottish Beaver Trial, involving the translocation and release of 16 wild Norwegian beavers (Castor Fiber) to Scotland, provides a good example of a 'One Health' scientific monitoring approach, with independent monitoring partners on ecology and public health feeding into veterinary health surveillance. Pathogen detection did not prohibit beaver release, although eight beavers were seropositive for Leptospira spp. Six deaths (37.5%) occurred during Rabies quarantine, followed by the death of two animals shortly after release and two wild-born kits due to suspected predation. Two host-specific parasites, the beaver fluke (Stichorchis subtriquetrus) and beaver beetle (Platypsyllus Castoris) were also reintroduced.
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Haematology and Serum Biochemistry Parameters and Variations in the Eurasian Beaver (Castor Fiber).
PloS one, 2015Co-Authors: Simon Girling, Roisin Campbell-palmer, Romain Pizzi, Mary Fraser, Jonathan Cracknell, Jon M. Arnemo, Frank RosellAbstract:Haematology parameters (N = 24) and serum biochemistry parameters (N = 35) were determined for wild Eurasian beavers (Castor Fiber), between 6 months – 12 years old. Of the population tested in this study, N = 18 Eurasian beavers were from Norway and N = 17 originating from Bavaria but now living extensively in a reserve in England. All blood samples were collected from beavers via the ventral tail vein. All beavers were chemically restrained using inhalant isoflurane in 100% oxygen prior to blood sampling. Results were determined for haematological and serum biochemical parameters for the species and were compared between the two different populations with differences in means estimated and significant differences being noted. Standard blood parameters for the Eurasian beaver were determined and their ranges characterised using percentiles. Whilst the majority of blood parameters between the two populations showed no significant variation, haemoglobin, packed cell volume, mean cell haemoglobin and white blood cell counts showed significantly greater values (p
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The Eurasian beaver (Castor Fiber) is apparently not a host to blood parasites in Norway.
Veterinary Parasitology, 2012Co-Authors: Hannah B. Cross, Roisin Campbell-palmer, Simon Girling, Frank RosellAbstract:Parasites can alter the physiology and behaviour of host species and negatively impact on their fitness thus affecting population densities. This is the first investigation into the presence of blood parasites in the Eurasian beaver (Castor Fiber); a species that has been the subject of many translocation and reintroduction programmes. Two hundred and seventy blood slides prepared from the blood of 27 beavers from southern Norway were microscopically analysed for the presence of blood parasites. This study reports an absence of blood parasites in the Norwegian Eurasian beavers sampled.
Simon Girling - One of the best experts on this subject based on the ideXlab platform.
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Reintroducing beavers Castor Fiber to Britain: a disease risk analysis
Mammal Review, 2019Co-Authors: Simon Girling, Mary Fraser, Adam D. Naylor, Roisin Campbell-palmerAbstract:Eurasian beavers Castor Fiber are potential hosts for a range of infectious diseases and parasites, including those typical of common European rodents. A number of infectious organisms are potentially zoonotic and may be notifiable under animal health legislation. The official trial beaver reintroductions to Scotland, the retrospectively licensed releases in England, and the increasingly obvious presence of large numbers of unlicensed illegally released animals have highlighted potential disease risks. We aimed to conduct a disease risk analysis, based on peer reviewed publications, for selection and health screening of Eurasian beavers prior to release into the wild in Britain. Adapted from the International Union for the Conservation of Nature’s ‘Guidelines for Disease Risk Analysis’, a four‐step process was used to formulate a disease risk analysis: 1) problem description; 2) hazard identification based on literature review; 3) risk assessment, which resulted in categorisation of pathogens into low, medium, and high risk; and 4) risk management: identification of mitigating measures, followed by risk re‐evaluation in light of the reported effectiveness of the mitigation measures. The highest‐risk pathogens identified in the literature review process included: parasites, specifically Cryptosporidium parvum, Echinococcus multilocularis, Eimeria spp., Fasciola hepatica, Giardia spp., Trichinella britovi; bacteria, specifically Escherichia coli, Franciscella tularensis, Mycobacterium avium, Salmonella spp., Yersinia spp.; a fungus Chrysosporium parvum (Emmonsia parva); and terrestrial rabies virus. Most could be mitigated by sourcing beavers from Britain. The rest could be mitigated by pre‐release testing procedures that are already established. The risk of introducing significant disease to humans, domestic animals, or wildlife by releasing into the wild in Britain a beaver that was captive‐bred in Britain or a wild beaver from Scotland, based on the current evidence of disease incidence, and assuming the use of robust, peer reviewed, pre‐release health screening techniques, can be viewed as low.
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Outcomes of a ‘One Health’ Monitoring Approach to a Five-Year Beaver (Castor Fiber) Reintroduction Trial in Scotland
EcoHealth, 2017Co-Authors: Gidona Goodman, Frank Rosell, Simon Girling, Anna Meredith, Roisin Campbell-palmerAbstract:The Scottish Beaver Trial, involving the translocation and release of 16 wild Norwegian beavers ( Castor Fiber ) to Scotland, provides a good example of a ‘One Health’ scientific monitoring approach, with independent monitoring partners on ecology and public health feeding into veterinary health surveillance. Pathogen detection did not prohibit beaver release, although eight beavers were seropositive for Leptospira spp. Six deaths (37.5%) occurred during Rabies quarantine, followed by the death of two animals shortly after release and two wild-born kits due to suspected predation. Two host-specific parasites, the beaver fluke ( Stichorchis subtriquetrus ) and beaver beetle ( Platypsyllus Castoris ) were also reintroduced.
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Outcomes of a 'One Health' Monitoring Approach to a Five-Year Beaver (Castor Fiber) Reintroduction Trial in Scotland.
Ecohealth, 2016Co-Authors: Gidona Goodman, Frank Rosell, Simon Girling, Anna Meredith, Roisin Campbell-palmerAbstract:The Scottish Beaver Trial, involving the translocation and release of 16 wild Norwegian beavers (Castor Fiber) to Scotland, provides a good example of a 'One Health' scientific monitoring approach, with independent monitoring partners on ecology and public health feeding into veterinary health surveillance. Pathogen detection did not prohibit beaver release, although eight beavers were seropositive for Leptospira spp. Six deaths (37.5%) occurred during Rabies quarantine, followed by the death of two animals shortly after release and two wild-born kits due to suspected predation. Two host-specific parasites, the beaver fluke (Stichorchis subtriquetrus) and beaver beetle (Platypsyllus Castoris) were also reintroduced.
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Haematology and Serum Biochemistry Parameters and Variations in the Eurasian Beaver (Castor Fiber).
PloS one, 2015Co-Authors: Simon Girling, Roisin Campbell-palmer, Romain Pizzi, Mary Fraser, Jonathan Cracknell, Jon M. Arnemo, Frank RosellAbstract:Haematology parameters (N = 24) and serum biochemistry parameters (N = 35) were determined for wild Eurasian beavers (Castor Fiber), between 6 months – 12 years old. Of the population tested in this study, N = 18 Eurasian beavers were from Norway and N = 17 originating from Bavaria but now living extensively in a reserve in England. All blood samples were collected from beavers via the ventral tail vein. All beavers were chemically restrained using inhalant isoflurane in 100% oxygen prior to blood sampling. Results were determined for haematological and serum biochemical parameters for the species and were compared between the two different populations with differences in means estimated and significant differences being noted. Standard blood parameters for the Eurasian beaver were determined and their ranges characterised using percentiles. Whilst the majority of blood parameters between the two populations showed no significant variation, haemoglobin, packed cell volume, mean cell haemoglobin and white blood cell counts showed significantly greater values (p
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The Eurasian beaver (Castor Fiber) is apparently not a host to blood parasites in Norway.
Veterinary Parasitology, 2012Co-Authors: Hannah B. Cross, Roisin Campbell-palmer, Simon Girling, Frank RosellAbstract:Parasites can alter the physiology and behaviour of host species and negatively impact on their fitness thus affecting population densities. This is the first investigation into the presence of blood parasites in the Eurasian beaver (Castor Fiber); a species that has been the subject of many translocation and reintroduction programmes. Two hundred and seventy blood slides prepared from the blood of 27 beavers from southern Norway were microscopically analysed for the presence of blood parasites. This study reports an absence of blood parasites in the Norwegian Eurasian beavers sampled.
Howard Parker - One of the best experts on this subject based on the ideXlab platform.
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Rapid rebound in colony number of an over-hunted population of Eurasian beaver Castor Fiber
Wildlife Biology, 2014Co-Authors: Howard Parker, Frank RosellAbstract: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...
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more genetic data are needed before populations are mixed response to sourcing eurasian beaver Castor Fiber stock for reintroductions in great britain and western europe
Mammal Review, 2012Co-Authors: Frank Rosell, Roisin Campbellpalmer, Howard ParkerAbstract:Halley described three options for sourcing Eurasian beavers Castor Fiber for reintroduction in Britain and Western Europe: (i) use animals from populations within a single western evolutionarily significant unit (ESU); (ii) mix animals from two or three western ESUs; and (iii) mix animals from eastern and western ESUs. Option three contravenes International Union for Conservation of Nature guidelines, so debate should focus on options one and two. We believe there is a need for further genetic analysis, before a final decision can be made. This decision should not be heavily influenced by cost or be determined by the genotypes of existing captive or escaped populations.
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More genetic data are needed before populations are mixed: response to ‘Sourcing Eurasian beaver Castor Fiber stock for reintroductions in Great Britain and Western Europe’
Mammal Review, 2011Co-Authors: Frank Rosell, Roisin Campbell-palmer, Howard ParkerAbstract:Halley described three options for sourcing Eurasian beavers Castor Fiber for reintroduction in Britain and Western Europe: (i) use animals from populations within a single western evolutionarily significant unit (ESU); (ii) mix animals from two or three western ESUs; and (iii) mix animals from eastern and western ESUs. Option three contravenes International Union for Conservation of Nature guidelines, so debate should focus on options one and two. We believe there is a need for further genetic analysis, before a final decision can be made. This decision should not be heavily influenced by cost or be determined by the genotypes of existing captive or escaped populations.
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Parturition dates for Eurasian beavers Castor Fiber: when should spring hunting cease?
Wildlife Biology, 2001Co-Authors: Howard Parker, Frank RosellAbstract: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.
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Eurasian beavers (Castor Fiber) behavioral response to simulated territorial intruders
Canadian Journal of Zoology, 2000Co-Authors: Frank Rosell, Geir Johansen, Howard ParkerAbstract:Eurasian beavers (Castor Fiber) live in family groups that defend territories against other conspecifics. Part of this territorial defence involves constructing scent mounds near the stream bank within territories and marking them with Castoreum, a urine-based fluid from the Castor sacs, and (or) anal-gland secretion. The aim of this study was to test the hypothesis that Eurasian beavers show one or more forms of territorial behavior when an intruder, simulated in the form of experimental scent mounds (ESMs), has scent-marked inside the territory. We predicted that beavers would show a stronger response to ESMs with Castoreum than to those without. Results showed that 85% of all beaver families (N = 20) made one or more behavioral responses to ESMs marked with Castoreum from foreign adult males, whereas no ESMs presented without Castoreum received a response. We therefore conclude that a main function of territorial marking by beavers is to advertise spatially related dominance status, thereby providing opportunities for intruders to assess the presence of the owner and reducing the cost and risks of agonistic conflict for both the owner and intruders. Additionally, it appears to be the scent emitted from an ESM and not the sight of it to which beavers respond.
Bart A. Nolet - One of the best experts on this subject based on the ideXlab platform.
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Territory and group sizes in Eurasian beavers ( Castor Fiber ): echoes of settlement and reproduction?
Behavioral Ecology and Sociobiology, 2005Co-Authors: Ruairidh D. Campbell, Frank Rosell, Bart A. Nolet, Vilmar A. A. DijkstraAbstract:According to current theories of territoriality, an animal is expected to defend the smallest area that can provide resources for maximisation of reproduction, known as the ‘economically defendable’ area. In group territorial species however, the strategies behind resource defence are likely to be more complex with corporate territoriality, cooperative breeding, delayed dispersal and intra-group competition all potentially playing a role. Here we examined group territoriality in a social herbivorous rodent, the Eurasian beaver Castor Fiber. Beavers in our study do not inhabit economically defendable territories. Instead the sequence of arrival of pairs into unoccupied areas seems to play a more important role in determining the size of the territory, whereas group size is determined by past reproductive success. We argue that the settlement pattern and reproductive history have a lasting impact in the territorial system of beavers due to a combination of the low adult mortality, high dispersal costs, and avoidance of resource depletion.
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Comeback of the beaver Castor Fiber : an overview of old and new conservation problems
Biological Conservation, 1998Co-Authors: Bart A. Nolet, Frank RosellAbstract:Abstract Due to over-hunting c. 1200 Eurasian beavers Castor Fiber survived in eight relict populations in Europe and Asia at the beginning of the 20th century. Following hunting restrictions and translocation programmes in 15 countries, the Eurasian beaver became re-established over much of its former range, and presently numbers c. 430 000. The translocated populations often consist of a mixture of geographical forms. Preservation of the original, unmixed populations has therefore top priority: all five in Europe have reached the assumed minimum viable population size of c. 1880 animals each, but the three in Asia are still endangered. Their protection should be carried out at the level of river catchments. Nowadays the main threats for beavers are habitat destruction and introduced North American beavers Castor canadensis. On the other hand, growing beaver populations cause increasing conflicts with man, and population and/or damage control may therefore be required. In view of these two very different problems, we conclude that the conservation of beavers is best served by preservation and restoration of riparian woods with intact natural water regimes.
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Factors affecting scent-marking behavior in Eurasian beaver (Castor Fiber)
Journal of Chemical Ecology, 1997Co-Authors: Frank Rosell, Bart A. NoletAbstract:We tested the hypothesis that a main function of territory marking in Eurasian beaver (Castor Fiber) is defense of the territory. The results showed that: (1) beaver colonies with close neighbors scent-mark more often than isolated ones; (2) the number of scent markings increased significantly with the number of neighboring territories and individuals, the mean distance to all other territories, duration of territory occupancy and length of wooded banks within the territory; (3) the number of scent markings by a colony was not related to the number of animals in the colony, the distance to nearest neighbors' main resting-site, or age of beaver; (4) the number of scent mounds or scent markings in territories with breeding and nonbreeding beaver did not differ; (5) there was no significant difference in the number of scent markings during the season (16 April–31 August); and (6) some of the scent mounds were concentrated at feeding sites, resting sites, and near trails, but most had no apparent relationship to any of these sites. Therefore we concluded that scent marking apparently plays an important role in territory defense of the Eurasian beaver.
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Development and viability of a translocated beaver Castor Fiber population in The Netherlands
Biological Conservation, 1996Co-Authors: Bart A. Nolet, J.m. BavecoAbstract:We monitored survival, reproduction and emigration of a translocated beaver Castor Fiber population in the Netherlands for five years and used a stochastic model to assess its viability. Between 1988 and 1991, 42 beavers were released in the Biesbosch National Park. The mortality was initially high but gradually fell to normal rates. However, the breeding success was low, and we hypothesized that this was either a temporary phenomenon (the translocation hypothesis) or a permanent feature (the poor habitat hypothesis). According to the computer simulations, the isolated population was viable under the first but not under the second hypothesis. In the latter case, the prospects generally improved by the foundation of another population in the Gelderse Poort (100 km from the Biesbosch), However, this second habitat should be optimal for beavers in order to reduce the extinction probability of the Biesbosch population to below 10% in 100 years,' the loss of genetic variability (1-2% per generation) was just above the applied tolerable risk (1%), but the effects of inbreeding are unknown in beavers. We conclude that the beaver population in the Biesbosch is not viable unless the reproductive success increases, either in the Biesbosch itself or in a nearby population. We recommend applying such viability analyses to evaluate the likely success of any translocation. [KEYWORDS: population viability analysis; reintroduction;translocation; simulation model; Castor Fiber Species conservation; extinction]