Lack of sex-specific movement patterns in an alien species at its invasion front - consequences for invasion speed

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

Individual and temporal variation in habitat association of an alien carnivore at its invasion front

Gathering information on how invasive species utilize the habitat is important, in order to better aim actions to reduce their negative impact. We studied habitat use and selection of 55 GPS-marked raccoon dogs (30 males, 25 females) at their invasion front in Northern Sweden, with particular focus on differences between males and females, between movement states, and between seasons and times of the day. Daily movement pattern was used to classify GPS-locations into dispersing and settled. We focused on both anthropogenic and natural landscape characteristics. Since we did not have any a priori knowledge about the spatial scale of raccoon dog habitat selection, we first assessed how landscape characteristics of random points changed with distance from the GPS-location they were paired to. Because changes in habitat use became less pronounced at approximately 5 km for all variables, we focused on habitat use at two spatial scales: fine (500 m) and coarse (5 km). Habitat selection was strongest at the coarse scale, and reflected the results found for habitat use. Raccoon dogs selected agricultural areas and wetlands, lower altitudes, and shallow slopes, and avoided forests, open natural areas, and areas close to water and roads. There were no differences in habitat selection between males and females, or between movement states. This lack of sexual segregation increases the probability of encountering potential mates during dispersal, and therefore the likelihood for reproduction in new areas. The seasonal and diurnal pattern of habitat use may provide guidance for where and when to aim management efforts

Data from: Individual and temporal variation in habitat association of an alien carnivore at its invasion front

Gathering information on how invasive species utilize the habitat is important, in order to better aim actions to reduce their negative impact. We studied habitat use and selection of 55 GPS-marked raccoon dogs (30 males, 25 females) at their invasion front in Northern Sweden, with particular focus on differences between males and females, between movement states, and between seasons and times of the day. Daily movement pattern was used to classify GPS-locations into dispersing and settled. We focused on both anthropogenic and natural landscape characteristics. Since we did not have any a priori knowledge about the spatial scale of raccoon dog habitat selection, we first assessed how landscape characteristics of random points changed with distance from the GPS-location they were paired to. Because changes in habitat use became less pronounced at approximately 5 km for all variables, we focused on habitat use at two spatial scales: fine (500 m) and coarse (5 km). Habitat selection was strongest at the coarse scale, and reflected the results found for habitat use. Raccoon dogs selected agricultural areas and wetlands, lower altitudes, and shallow slopes, and avoided forests, open natural areas, and areas close to water and roads. There were no differences in habitat selection between males and females, or between movement states. This lack of sexual segregation increases the probability of encountering potential mates during dispersal, and therefore the likelihood for reproduction in new areas. The seasonal and diurnal pattern of habitat use may provide guidance for where and when to aim management efforts

Individual and temporal variation in habitat association of an alien carnivore at its invasion front.

Gathering information on how invasive species utilize the habitat is important, in order to better aim actions to reduce their negative impact. We studied habitat use and selection of 55 GPS-marked raccoon dogs (30 males, 25 females) at their invasion front in Northern Sweden, with particular focus on differences between males and females, between movement states, and between seasons and times of the day. Daily movement pattern was used to classify GPS-locations into dispersing and settled. We focused on both anthropogenic and natural landscape characteristics. Since we did not have any a priori knowledge about the spatial scale of raccoon dog habitat selection, we first assessed how landscape characteristics of random points changed with distance from the GPS-location they were paired to. Because changes in habitat use became less pronounced at approximately 5 km for all variables, we focused on habitat use at two spatial scales: fine (500 m) and coarse (5 km). Habitat selection was strongest at the coarse scale, and reflected the results found for habitat use. Raccoon dogs selected agricultural areas and wetlands, lower altitudes, and shallow slopes, and avoided forests, open natural areas, and areas close to water and roads. There were no differences in habitat selection between males and females, or between movement states. This lack of sexual segregation increases the probability of encountering potential mates during dispersal, and therefore the likelihood for reproduction in new areas. The seasonal and diurnal pattern of habitat use may provide guidance for where and when to aim management efforts

Habitat characteristics of raccoon dog observations at multiple spatial scales

Habitat characteristics (habitat type, distance to roads and water, elevation, slope, and length of growing season) for raccoon dog GPS-locations (Scale = 0) and paired random points located within a given distance (Scale > 0 m). Data is aggregated per individual trajectory, season, and light period (day, night, twilight). For further details, see the article

Parameter estimates on habitat use with respect to sex, movement state, season, and light regime in raccoon dogs in northern Sweden.

<p>Bars represent 95% credible interval based on 10 000 MCMC resampling of the posterior distribution of the parameter estimates. Grey symbols and bars indicate no significant (<i>P</i> > 0.05) difference between the groups, i.e. adding the covariate (sex, movement state, season, or light period) did not improve a null model (including only intercept). Black symbols and bars indicate a significant improvement of the model by adding the covariate.</p

Habitat selection at two spatial scales for raccoon dogs in northern Sweden.

<p>Bars represent 95% credible interval based on 10 000 MCMC resampling of the posterior distribution of the parameter estimates. Filled symbols represent habitat selection at the 500 m spatial scale, whereas open symbols represent habitat selection at the 5000 m spatial scale. A positive value indicates that the probability of use is higher for high values of the explanatory variable whereas a negative value indicates that the probability of use decreased with increasing value of the explanatory variable. The first column is the overall habitat selection for all individuals, where black symbols and bars indicate a significant selection (i.e. the 95% CI does not include zero). In the next three columns, interactions between the landscape variable and movement state, season and light period are shown, where black symbols indicate significant difference in habitat selection between the groups at a given spatial scale.</p

Daily location for 55 GPS-marked raccoon dogs in Northern Sweden.

<p>The long-distance trajectories north and west are dispersal events from separate individuals.</p

Overall use of habitat types and landscape characteristics by raccoon dogs in Sweden.

<p>"Obs" refers to GPS-locations, whereas the spatial scales are points (1 random point per GPS-location) randomly located within a given distance from the GPS-location. Grey symbols indicate that the value at the spatial scale was not significantly different from the values at the GPS-locations whereas black symbols indicate significant differences. Significance was obtained by 95% credible intervals from 10 000 MCMC resamplings of a mixed model with raccoon dog identity and treatment number as random factors. Bars represent standard error of the parameter estimate from the mixed model.</p