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

Abstract

SummaryEfficient 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.

Nest predation by raccoon dog Nyctereutes procyonoides in the archipelago of northern Sweden

“…We even find it likely that raccoon dogs actively search for nests during such explorations because birds often nest in these habitats. Our raccoon dogs did not have partners, which does affect the size of their activity areas (Herfindal et al 2016). Pairs utilize smaller areas, although this, if anything, should intensify their search for food even more within that area.…”

“…Raccoon dog data from the management project Norrbotten County is the invasion front of the raccoon dog from Finland into Sweden (Herfindal et al 2016). More than 140 wild raccoon dogs have been sterilized (to prevent reproduction) and collared with GPS units (Tellus Ultra Light, Followit AB) in northern Sweden from 2010 until 2018 as part of a management project (Dahl et al 2010;MIRDINEC 2014).…”

“…One purpose of the collared animals is to use them as Judas animals to find and cull new animals (Dahl et al 2010;MIRDINEC 2014). Another purpose is to learn more about where, when, and how the raccoon dogs move, and which types of habitats they utilize in the dispersal front, to improve management efficiency (Herfindal et al 2016;Melis et al 2015). To date, well over 500,000 positions have been gathered from these animals.…”

Ovulation, fertilization and preimplantation embryonic development in raccoon dogs ( Nyctereutes procyonoides )

“…While it is a native to Eastern Asia, about 9000 individuals were purposely introduced to different parts of European Russia and Western Asia between 1927 and 1957. Today, the raccoon dog is widespread in Asia, Northern and Eastern Europe and still spreading in Central Europe (Norodd et al, 1988;Drygala et al, 2016;Herfindal et al, 2016).…”