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PubMed | University of Stirling, Denis Island, University of Sheffield, University of Groningen and 5 more.
Type: Journal Article | Journal: Pest management science | Year: 2016

In Seychelles, the common myna has been shown to have a negative impact on endangered endemic birds on Denis Island, interfering with breeding attempts and attacking adult endemic birds at their nests. This stimulated an attempt to eradicate the islands mynas.The eradication was undertaken in three phases, overall killing 1186 mynas and lasting 5 years. Decoy trapping was the most effective method for catching mynas, but the last birds were shot. Decoy trapping was compromised by catches of non-target species. Data collection from killed birds indicated that trapping did not favour either sex, and that most breeding occurred during the wetter season, November to March.Eradication of mynas from small tropical islands is feasible. The Denis Island eradication was prolonged by difficulties in management and staffing. Using volunteers, the cost of the eradication was similar to that of eradicating rodents from the island. In future eradication attempts in Seychelles, possible food stress during the drier season (May to September) might facilitate trapping at this time. Habitat management, especially the removal of short mown grass, could enhance eradication progress. Continued monitoring is needed to confirm eradication and detect any immigration, and also to record responses in the endemic birds. 2016 Society of Chemical Industry.


Carlsson N.O.L.,The County Administrative Board | Carlsson N.O.L.,Cary Institute of Ecosystem Studies | Jeschke J.M.,Cary Institute of Ecosystem Studies | Jeschke J.M.,Ludwig Maximilians University of Munich | And 3 more authors.
Biological Invasions | Year: 2010

Studies of the effects and population dynamics of invasive species typically cover only short time periods. However, populations of invasive species interact with native species, and these interactions may have strong effects on invaders' populations and effects over time. We present and analyze long-term data on invasive American mink (Neovison vison), native red fox (Vulpes vulpes), and mountain hare (Lepus timidus) in Sweden. The mink's population dynamics followed a pattern of logistic growth from the late 1930s to the late 1970s. In the early 1980s, however, the population tripled, then declined sharply. We suggest that the mink's population tripling was caused by a drastic decline in red fox populations, which caused terrestrial prey to increase. Later recovery of the fox population reversed the trend and caused the mink population's recent decline. Our study shows that species interactions between native and invasive species, and therefore biotic resistance, can change dramatically over time. © 2009 Springer Science+Business Media B.V.


Herfindal I.,Norwegian University of Science and Technology | Melis C.,Norwegian University of Science and Technology | Ahlen P.-A.,Swedish Association for Hunting and Wildlife Management | Dahl F.,Swedish Association for Hunting and Wildlife Management | Dahl F.,Swedish University of Agricultural Sciences
Ecology and Evolution | Year: 2016

Efficient targeting of actions to reduce the spread of invasive alien species relies on understanding the spatial, temporal, and individual variation of movement, in particular related to dispersal. Such patterns may differ between individuals at the invasion front compared to individuals in established and dense populations due to differences in environmental and ecological conditions such as abundance of conspecifics or sex-specific dispersal affecting the encounter rate of potential mates. We assessed seasonal and diurnal variation in movement pattern (step length and turning angle) of adult male and female raccoon dog at their invasion front in northern Sweden using data from Global Positioning System (GPS)-marked adult individuals and assessed whether male and female raccoon dog differed in their movement behavior. There were few consistent sex differences in movement. The rate of dispersal was rather similar over the months, suggesting that both male and female raccoon dog disperse during most of the year, but with higher speed during spring and summer. There were diurnal movement patterns in both sexes with more directional and faster movement during the dark hours. However, the short summer nights may limit such movement patterns, and long-distance displacement was best explained by fine-scale movement patterns from 18:00 to 05:00, rather than by movement patterns only from twilight and night. Simulation of dispersing raccoon dogs suggested a higher frequency of male–female encounters that were further away from the source population for the empirical data compared to a scenario with sex differences in movement pattern. The lack of sex differences in movement pattern at the invasion front results in an increased likelihood for reproductive events far from the source population. Animals outside the source population should be considered potential reproducing individuals, and a high effort to capture such individuals is needed throughout the year to prevent further spread. © 2016 The Authors. Ecology and Evolution published by John Wiley & Sons Ltd.


Wallgren M.,Forestry Research Institute of Sweden | Bergstrom R.,Forestry Research Institute of Sweden | Bergqvist G.,Swedish Association for Hunting and Wildlife Management | Olsson M.,Forestry Research Institute of Sweden | Olsson M.,Swedish University of Agricultural Sciences
Forest Ecology and Management | Year: 2013

We investigated the spatial distribution of browsing and damage by moose (Alces alces) in young Scots pine (Pinus sylvestris) stands of central Sweden. The study involved four spatial scales from landscape to individual trees and aimed at evaluating the possibilities of using selective thinning of damaged pine stands as a tool for reducing the economic losses for forestry. As expected, we found that damage on pine main stems is unevenly distributed between young pine forest stands in the landscape, but without any spatial autocorrelation at this scale. On stand scale however, there was a positive spatial autocorrelation of survey plots including pine trees damaged by moose. This relationship was strongest at short distances and ceased at around 350. m between plots. Both percent recent and previous damage on pine main stems were negatively correlated with the number of pine stems per plot, suggesting that keeping a higher pine stem density may reduce the damage levels. However, an increasing density of birch instead increased the probability of recent damage to the pines. The most important explanatory variable for recent damage on pine main stems on plot level was previous damage on the same. Therefore damaged pines that are spared during pre-commercial thinning may continue to be eaten by moose and possibly lighten the browsing pressure on previously undamaged trees. We also found that both recent damage and browsing on a particular pine enhances the risk of recent damage and browsing, respectively, also on the nearest neighboring pine. Removing damaged trees while thinning may therefore create undesired gaps within the stands. On tree level browsing of lateral shoots increased the chances of stem damages on individual trees and vice versa, suggesting that individual trees may simultaneously be affected by moose foraging in more than one way, i.e. damage may cause permanent change in stem structure, while browsing of lateral shoots may retard stem growth. In conclusion, we argue that there are means of reducing damage levels in pine stands while performing pre-commercial and commercial thinning, but that the actions have to be evaluated in relation to additional factors on the relevant spatial scale. © 2013 Elsevier B.V.


Bergqvist G.,Swedish Association for Hunting and Wildlife Management | Bergstrom R.,Forestry Research Institute of Sweden | Wallgren M.,Forestry Research Institute of Sweden
Silva Fennica | Year: 2014

Moose browsing damage from the winter preceding the study (recent damage) on Scots pine, birch and aspen was examined in relation to forage availability, an index of moose population density and site productivity in young forests in the hemiboreal zone. Recent damage was observed for 4.1 ± 0.54% (mean ± SE; Scots pine), 16.8 ± 1.89% (birch) and 67.6 ± 13.76% (aspen) of the trees. A multiple regression with five independent variables explained 19% (Scots pine) 14% (birch) and 33% (aspen) of the variation in recent damage. Cover of Scots pine browse was the most important variable for predicting damage to Scots pine and accounted for 44% of the explained variation. When birch was overtopping pine there was a significant increase in damage to pine. Moose index was the only significant variable to explain recent damage to birch, and accounted for 64% of the explained variation. For aspen, damage was negatively correlated to coverage of Scots pine and birch browse, each variable accounting for 38% of the explained variation. For Scots pine, increasing the number of pines ha-1 and performing pre-commercial thinning in such a way that pines are not overtopped may be efficient ways of reducing damage proportions, whereas birch needs to be protected from moose (by a reduction of the moose population or otherwise) in order to escape damage. Increased amounts of Scots pine browse and birch browse may also reduce damage levels to aspen, according to this study.


Bergqvist G.,Swedish Association for Hunting and Wildlife Management | Bergstrom R.,Forestry Research Institute of Sweden | Wallgren M.,Forestry Research Institute of Sweden
Scandinavian Journal of Forest Research | Year: 2013

Moose (Alces alces L.) browse Scots pine (Pinus sylvestris L.) mainly during the winter. There is a growing concern also regarding summer browsing by moose on Scots pine. We studied summer browsing on Scots pine during two consecutive years. In a survey of 47 stands in 2003, current summer browsing was found for 20.4% of the Scots pine main stems, and on almost half of them (9.8%) the top shoot was browsed. This indicates that the pine damage causing reduced wood quality was as serious during summer as during the preceding winter. There was significantly more summer browsing on previously browsed pines, compared to a random use, both at tree and stand level, and summer browsing was also spatially clumped within stands. Browsing on top shoots occurred up to a height of 2.8 m, whereas side shoot browsing was recorded for pines with a height up to 4.8 m. In 2004, 11 of the 47 stands were randomly selected for a more detailed study of pines browsed during that summer. The summer browsed trees contained, on average, 114 current shoots tree-1, and 10.5 shoots tree-1 (9.2%) were browsed. In this area, summer browsing may explain a considerable part of the moose-related forest damage recorded. The proportion of pines subjected to summer browsing did not change with availability of pines. Hence, increasing the number of Scots pine trees in young stands may be a way to increase the number of unbrowsed pine trees at a given moose population density. © 2013 Copyright Taylor and Francis Group, LLC.


Bergqvist G.,Swedish Association for Hunting and Wildlife Management | Bergstrom R.,Forestry Research Institute of Sweden | Wallgren M.,Forestry Research Institute of Sweden
Scandinavian Journal of Forest Research | Year: 2012

Food selection by large herbivores occurs at a hierarchy of scales, for example landscape, patch or plant. Several hypotheses regarding food plant selection on patch or plant level have been developed. In this cafeteria-type design field experiment, conducted during one winter immediately after planting, we tested the effect of species mixture on browsing by large herbivores (mainly roe deer) on Scots pine seedlings in mixture with seedlings of ash (highly preferred) or silver birch (less preferred). Browsing on Scots pine was not affected by species mixture, neither in terms of the number of browsed pines nor browsing intensity. Instead, browsed biomass was positively and significantly correlated to the total biomass available for browsing. Also, there were differences due to species, with ash being most browsed (44.6%), followed by Scots pine (18.9%) and silver birch (11.6%). Browsed biomass per browsed seedling, however, was largest for Scots pine. In addition, browsed seedlings were initially taller compared to unbrowsed seedlings for all species. The main management implication in this study is that the species mixture did not influence large herbivore browsing on Scots pine seedlings. Hence, removing or discouraging more (or less) attractive browse species in early stages of pine regeneration activities seems unnecessary from the point of large herbivore browsing. © 2012 Copyright Taylor and Francis Group, LLC.


Elmhagen B.,University of Stockholm | Hellstrom P.,University of Stockholm | Angerbjorn A.,University of Stockholm | Kindberg J.,Swedish Association for Hunting and Wildlife Management
Annales Zoologici Fennici | Year: 2011

Cyclic dynamics with extensive spatial synchrony has long been regarded as characteristic of key herbivores at high latitudes. This contrasts to recent reports of fading cycles in arvicoline rodents in boreal and alpine Fennoscandia. We investigate the spatiotemporal dynamics of boreal red fox and alpine arctic fox in Sweden as a proxy for the dynamics of their main prey, voles and Norwegian lemming, respectively. We analyse data from five decades, 1960-2008, with wavelets and autocorrelation approaches. Cyclic dynamics were identified with at least one method in all populations (arctic fox n = 3, red fox n = 6). The dynamics were synchronous between populations, or coupled with a 1-yr lag, in 8 of 13 pairwise comparisons. Importantly though, the dynamics were heterogeneous in space and time. All analytical approaches identified fading cycles in the three arctic fox populations and two northern red fox populations. At least one method identified similar patterns in three southern red fox populations. Red fox dynamics were cyclic in the 1970s primarily, while arctic fox dynamics was cyclic until the late 1980s or early 1990s. When cyclic, 4-yr cycles dominated in arctic fox and northern red fox, whilst 3-4-yr cycles was found in southern red foxes. Significant cyclic regimes reappeared in the 1990s or 2000s in two red fox populations and one arctic fox population. Cycles and regionally coupled dynamics appeared associated in northern arctic and red foxes. This study supports accumulating evidence which suggests that cyclic and synchronous patterns in the dynamics of lemmings and voles are nonstationary in space and time. Furthermore, the similar patterns of change in both fox species indicate that persistence of cycles is governed by similar mechanisms in lemmings and voles. © Finnish Zoological and Botanical Publishing Board 2011.

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