Papers by Tomas Willebrand
European Journal of Wildlife Research, Oct 11, 2018
Dispersal is a fundamental process that facilitates population and range expansion by providing a... more Dispersal is a fundamental process that facilitates population and range expansion by providing a mechanism for colonization and metapopulation linkages. Yet quantifying the dispersal process, particularly long-distance dispersal events, has been inherently difficult due to technological and observational limitations. Additionally, dispersal distance calculated as the straight-line distance between initiation and settlement fails to account for the actual movement path of the animal during dispersal. Here, we highlight six long-distance dispersal events, representing some of the longest dispersal distances recorded for red foxes. Cumulative dispersal movements ranged from 132 to 1036 km and occurred within both sexes (1 female, 5 males). With one exception, dispersal events ranged from 7 to 22 days and tended to be directed north-northwest. Importantly, cumulative movements were up to five times longer than straight-line distances, with two foxes traveling an additional 114 and 256 km before returning to, and settling in, areas previously encountered during dispersal. This suggests a role of habitat assessment and homing behavior during dispersal and indicates that the capacity and potential for dispersal are not limiting factors to either sex in a red fox population. Dispersal capacity should thus be considered regarding transboundary management and disease control of red fox populations.
Landscape characteristics explain large-scale variation in demographic traits in forest grouse
Landscape Ecology, Nov 21, 2013
ABSTRACT The effects of landscape composition on species and populations have become increasingly... more ABSTRACT The effects of landscape composition on species and populations have become increasingly important due to large and rapid habitat changes worldwide. In particular, concern is raised for several forest-dwelling species such as capercaillie and black grouse, because their habitats are continuously changing and deteriorating from human development. Conservation of these species is linked to sustainable forest management that seeks to benefit multiple species, which demands knowledge about demographic rates in relation to forest composition and structure. We related the spatial variation in adult density and chick production of capercaillie and black grouse to landscape characteristics from 13 areas within the boreal forest of Norway. Linear mixed effects models showed that black grouse and capercaillie had similar associations to landscape characteristics. Adult density of both species was positively related to the proportion of old forest (>80 years), but only if the area had large proportions of mid to high productive forests. Chick production was negatively related to the proportion of old forest, but positively to habitat diversity and more so for black grouse compared to capercaillie. However, the result for chick production suggest that other forest types also are important, and that forest grouse needs a variety of habitats during their life history stages. Management that seeks to simultaneously conserve populations of black grouse and capercaillie needs to ensure a matrix of various forest types. A special focus must be on the critical life history of local populations to successfully preserve viable populations, for black grouse and capercaillie this implies protection of old and mid to high productive forest while keeping a heterogeneous landscape.
The Mountain Mistra Programme: Options for Managing Land Use in the Swedish Mountains
... This potentially could aid the Sami community in developing the commercial base to support re... more ... This potentially could aid the Sami community in developing the commercial base to support reindeer herding and in preserving their ... induced resource polymorphism on performance in arctic char (Salvelinus alpinus)', Evolutionary Ecology, vol 5, pp231228 Baskin, LM and ...
Acta pharmacologica et toxicologica, Mar 13, 2009
The solubility of 2,2',4,4',5,5'-hexachlorobiphenyl (HCB) in heparinized blood from guinea-pig, h... more The solubility of 2,2',4,4',5,5'-hexachlorobiphenyl (HCB) in heparinized blood from guinea-pig, heparinized plasma from mouse and in solutions of Intralipidm, bovine serum albumin (BSA) and in gammaglobulin was examined by studying the equilibrium between HCB adsorbed to a test tube wall and HCB in the aqueous phase. After 24 hours of incubation at 37" the highest concentration of HCB was found in the Intralipidm solution, the lowest one in the gammaglobulin solution. Blood and plasma were able to dissolve equivalent concentration of HCB. One conclusion of these experiments is that the largest part of HCB in blood is bound to albumin. The explanation of different patterns of uptake to solutions of Intralipid and BSA is discussed.
Conservation Genetics, Feb 3, 2021
The genetic structure of a population can provide important insights into animal movements at var... more The genetic structure of a population can provide important insights into animal movements at varying geographical scales. Individual and social behaviors, such as philopatry and dispersal, affect patterns of relatedness, age and sex structure, shaping the local genetic structure of populations. However, these fine scale patterns may not be detected within broader population genetic structure. Using SNP genotyping for pairwise relatedness estimates, we investigated the spatial and genetic structuring of 141 red foxes within south-central Sweden at two scales. First, we looked at broad scale population structuring among red foxes at the regional level. We then estimated pairwise relatedness values to evaluate the spatial and genetic structure of male, female and mixed sex pairs for patterns of philopatry and dispersal at a more localized scale. We found limited genetic differentiation at the regional scale. However, local investigations revealed patterns of female philopatry and male biased dispersal. There were significant differences in pairwise geographic distances between highly related same sex pairs with the average distance between related males, 37.8 km, being six times farther than that of related females, averaging 6.3 km. In summary, the low levels of genetic differentiation found in this study illustrates the mobility and dispersal ability of red foxes across scales. However, relatedness plays a strong role in the spatial organization of red foxes locally, ultimately contributing to male biased dispersal patterns.
BMC Ecology, Jun 15, 2017
Background: Human food subsidies can provide predictable food sources in large quantities for wil... more Background: Human food subsidies can provide predictable food sources in large quantities for wildlife species worldwide. In the boreal forest of Fennoscandia, gut piles from moose (Alces alces) harvest provide a potentially important food source for a range of opportunistically scavenging predators. Increased populations of predators can negatively affect threatened or important game species. As a response to this, restrictions on field dressing of moose are under consideration in parts of Norway. However, there is a lack of research to how this resource is utilized. In this study, we used camera-trap data from 50 gut piles during 1043 monitoring days. We estimated depletion of gut piles separately for parts with high and low energy content, and used these results to scale up gut pile density in the study area. We identified scavenger species and analyzed the influences of gut pile quality and density on scavenging behavior of mammals and corvids (family Corvidae). Results: Main scavengers were corvids and red fox (Vulpes vulpes). Parts with high energy content were rapidly consumed, mainly by corvids that were present at all gut piles shortly after the remains were left at the kill site. Corvid presence declined with days since harvest, reflecting reduction in gut pile quality over time independent of gut pile density. Mammals arrived 7-8 days later at the gut piles than corvids, and their presence depended only on gut pile density with a peak at intermediate densities. The decline at high gut pile densities suggest a saturation effect, which could explain accumulation of gut pile parts with low energy content. Conclusions: This study shows that remains from moose harvest can potentially be an important food resource for scavengers, as it was utilized to a high degree by many species. This study gives novel insight into how energy content and density of resources affect scavenging patterns among functional groups of scavengers.
Animal Biology, 2016
Declines in populations of capercaillie (Tetrao urogallus) and black grouse (Lyrurus tetrix) have... more Declines in populations of capercaillie (Tetrao urogallus) and black grouse (Lyrurus tetrix) have been reported from both Central Europe and the continuous boreal forests of Fennoscandia. While intensified land-use is assumed to be the underlying cause of these declines, the mechanisms are not yet understood. Predation is the proximate cause of mortality of eggs, chicks and adults throughout capercaillie and black grouse ranges, but the link between predation and habitat and/or climate change remains unclear. To investigate temporal trends in reproductive output of woodland grouse, we collated previously published and unpublished data of reproduction in capercaillie and black grouse throughout their ranges from 1930 to 2012. We show that, overall, reproductive success has decreased and stabilized at low levels in most regions whilst capercaillie reproductive output in Scotland is still declining. With today's net reproduction, capercaillie and black grouse adult survival is too low to compensate for reproduction declines. Consequently, populations are expected to further decline unless reproductive performances improve. We put our findings in the context of changes in land use, climate and generalist predator numbers. By critically reviewing how these factors limit reproductive success in capercaillie and black grouse, we hope to shed light on the underlying mechanisms causing the decline. Our results imply that measures should be undertaken to reduce mortality of capercaillie and black grouse chicks and eggs. We suggest that future studies should aim to better understand which predators limit capercaillie and black grouse populations and how predation rates are mediated by continuously changing habitat and climate.
The Auk, Apr 1, 1988
perate bird/fruit interactions: phenological strategies. Evolution 33: 973-982. WHEELWRIGHT, N. T... more perate bird/fruit interactions: phenological strategies. Evolution 33: 973-982. WHEELWRIGHT, N. T. 1986. The diet of American Robins: an analysis of U.S. Biological Survey records. Auk 103: 710-725. ß & G. •I. ORIANS. 1982. Seed dispersal by animals: contrasts with pollen dispersal, problems of terminology, and constraints on coevolution. Am. Nat. 119: 402-413.
Spatial and temporal variation in the distribution and abundance of red foxes in the tundra and taiga of northern Sweden
European Journal of Wildlife Research, Feb 19, 2016
Variation in the distribution and abundance of animals in space and time are key concepts of popu... more Variation in the distribution and abundance of animals in space and time are key concepts of population ecology. We studied these variations in a population of red foxes (Vulpes vulpes) in the tundra and taiga of northern Sweden. We analysed 12 years (1974–1985) of snow tracking data from a large area of 65,375 km2. Specifically, we evaluated to what extent the distribution of red foxes was explained by the presence of prey and how this interacted with snow depth and altitude. We also tested for temporal linear trends in the distribution and abundance of red foxes during the study period. The distribution of red foxes was explained by the presence of rodents, hares, tetraonid species, and ungulates (i.e. carcasses). Snow depth had a negative effect on the impact of small prey on the distribution of the red foxes, whereas it had a positive effect on the impact of ungulates. The influence of hares increased with altitude. Neither distribution nor abundance of red foxes showed a positive or negative linear trend, suggesting a stable population in northern Sweden during our study. This study showed that the distribution of red foxes was not only influenced by the presence of their main prey (rodents), but also by interactions between alternative prey, altitude, and snow depth. This study also emphasizes the importance of ungulate carcasses for red foxes and for wildlife management.
Breeding and Age in Female Black Grouse Tetrao tetrix
Ornis scandinavica, 1992
This study evaluates breeding success of 78 (25 yearling and 53 adult) Black Grouse females in ce... more This study evaluates breeding success of 78 (25 yearling and 53 adult) Black Grouse females in central Sweden. Black Grouse females were captured and radiomarked in late winter or early spring. Females were monitored from egglaying until late July/ early August when broods were flushed. Yearlings were significantly smaller (body weight and wing length) than adult females captured at leks. All yearlings made breeding attempts. Yearlings laid significantly smaller first clutches and eggs than adult females. Nest predation was similar for both age classes but yearlings had a lower tendency to renest. More yearlings than adult females lost their entire brood during the 5 weeks after hatching, 82% vs 35%, respectively. Only 2 of 25 (8%) yearlings raised chicks to 5 weeks of age compared with 20 of 50 adult females (40%). Adult birds raised on average 1.72 chicks per female compared with 0.16 for yearlings. Mechanisms that can explain the age-specific breeding success, such as maternal condition and territorial behaviour are discussed. It is suggested that the large difference in age-specific breeding success observed in this study was a result of the overall habitat structure in the area.
Wildlife Biology, Dec 24, 2021
Rapid declines in red fox Vulpes vulpes populations have followed outbreaks of epizootic mange ca... more Rapid declines in red fox Vulpes vulpes populations have followed outbreaks of epizootic mange caused by the mite Sarcoptes scabiei. In Sweden, the first outbreak of sarcoptic mange started in 1977/1978 and affected the whole country by 1984. Here we used data on the number of harvested red foxes (51 480) from Gävleborg county (18 199 km 2) in Sweden between 1970 and 1994. We used data on the prevalence of sarcoptic mange in a sample of harvested red foxes (2694) from 1974 to 1982. A rapid decline in harvested foxes occurred two to three years after the prevalence of sarcoptic mange first became evident. In the same period, mark-recovery data were used to estimate changes in survival rates, and the best model included an effect of age (young or adult) and period (annual) on the survival and recapture probabilities. The analysis was based on data from 701 young foxes of which 523 were recovered, and 133 adults of which 131 were recovered. Average annual survival was 0.55 (range = 0.53-0.58) for adults and 0.36 (range = 0.32-0.39) for young foxes in the three years preceding the outbreak. During the outbreak and the remaining six years of the study, the average survival was reduced to 0.41 (range = 0.30-0.48) for adults and to 0.25 (range = 0.17-0.30) for young foxes. A population model, based on results on our survival analysis and literature data on fecundity, was developed to project the decline of the fox population. The rate and magnitude of the reduction in projected population and harvested foxes were similar, with both reduced by almost ninety percent. Harvest statistics indicate the fox population recovered to pre-mange densities in less than 10 years after the first detection of mange indicating a rapid development of resistance in the host. This study shows the importance of long-term population monitoring in combination with largescale field-experiments to devise alternative management options.
Workshop Summary: Management Implications of Nest and Brood Predation in Grouse
Ornis scandinavica, Jul 1, 1991
Applied sciences, Dec 4, 2019
By using microsatellite markers, we were able to evaluate the genetic structuring and gene flow i... more By using microsatellite markers, we were able to evaluate the genetic structuring and gene flow in red foxes in part of Scandinavia. This allowed us to delineate movement patterns of red foxes, which is important for wildlife management authorities regarding the spread of parasites and disease. The application of microsatellite markers illustrated a detailed time-and cost-effective method to investigate the gene flow and movement patterns compared to traditional tracking and GPS methodology.
Demography and ecology of a black grouse (Tetrao tetrix L.) population
... Tetrao tetrix L.) population [breeding success]. Willebrand, T. (Uppsala Univ. (Sweden). Zoof... more ... Tetrao tetrix L.) population [breeding success]. Willebrand, T. (Uppsala Univ. (Sweden). Zoofysiologiska Inst.). Record number, SE8820391. Corporate author, Uppsala Univ. Publisher, Uppsala Univ., Uppsala (Sweden). Date of publication, 1988. AGRIS Categories, Animal ecology ...
Wildlife Biology, 2001
BioOne Complete (complete.BioOne.org) is a full-text database of 200 subscribed and open-access t... more BioOne Complete (complete.BioOne.org) is a full-text database of 200 subscribed and open-access titles in the biological, ecological, and environmental sciences published by nonprofit societies, associations, museums, institutions, and presses.
Censusing Spring Population of Willow Grouse and Rock Ptarmigan
Page 1. Censusing Spring Population of Willow Grouse and Rock Ptarmigan Maria Hörnell & Tomas... more Page 1. Censusing Spring Population of Willow Grouse and Rock Ptarmigan Maria Hörnell & Tomas Willebrand ... In the Swedish mountains the willow grouse and the rock ptarmigan are preyed upon by a number of predators, but their importance as prey species varies greatly. ...
Research, publications and knowledge in wildlife research and management
Fish and wildlife in the Swedish mountain region: resources, use and management
International Journal of Biodiversity Science & Management, 2006
ABSTRACT Hunting and fishing are an important part of life for many Swedes. The importance of fis... more ABSTRACT Hunting and fishing are an important part of life for many Swedes. The importance of fish and wildlife is even greater in the northern part of Sweden and especially in the Swedish mountain area, which covers a large geographical area but is sparsely populated. The biological systems in the mountain ecosystems can be characterised as arctic with low productivity and biodiversity. This article addresses two important species typical for this region (willow grouse and Arctic char), provides an up-to-date characterisation of current use and management, and presents a range of management models that frame the mechanisms of population dynamics of fish and game. It is concluded that lack of knowledge of population responses of fish and game in the mountain region to different harvesting options and management strategies is a practical obstacle, as is knowledge and understanding of the costs and benefits associated with different ecological management strategies. However, it is also crucial to integrate other disciplines with ecology for successful management.
Mammal research, Aug 15, 2017
Red fox (Vulpes vulpes) shares similar prey preferences and co-occurs with several other carnivor... more Red fox (Vulpes vulpes) shares similar prey preferences and co-occurs with several other carnivores, and is together with pine marten (Martes martes), the most common mesocarnivore in the northern boreal forest. Voles are important prey for both species, but it is unclear to what extent they compete for the same food resources in winter. Here, we use 2139 km and 533 km of meticulous snow tracking of red foxes and pine martens to evaluate their food niches. We measured hunting and digging behaviour, whether successful or not, and the effect of snow depth and temperature. Pine martens were restricted to forested habitats, whereas red foxes used a wide range of habitats. Red foxes were found to dig more often than pine martens, 0.67 vs. 0.39 digging events per kilometre. Hunting was less common and similar in both species, about 0.1 hunting event per kilometre. Pine martens were more efficient in hunting and finding food remains compared to red foxes. Increasing snow depth reduced hunting success and also reduced dig success of red foxes. Food niche overlap was small. Red foxes used mostly voles and carrion remains of ungulates, whereas pine martens used cached eggs and small birds. We suggest that caching eggs is an important strategy for pine martens to survive winter in northern latitudes. Snow depth was important for capturing voles, and thick snow cover appeared to mask the effect of vole peaks. Intensified land use, as clear-cutting and leaving slaughter remains from harvest, will benefit red foxes on the expense of pine martens. The ongoing climate change with warmer winters and less snow will likely further benefit the red fox.
Utvärdering av Åtgärdsprogrammet för fjällgås 2011–2017 : (Anser erythropus)
Rapporten ar en extern utvardering av det nu gallande atgardsprogrammet forFjallgas (2011–2015, f... more Rapporten ar en extern utvardering av det nu gallande atgardsprogrammet forFjallgas (2011–2015, forlangt t.o.m. 2017) och till delar projekt Fjallgas, utfort pauppdrag av Naturvardsverket. Utvarder ...
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Papers by Tomas Willebrand