Editorial — Managing animal movements
Goats moving along a ridge line. Image - Christian Gortazar Schmidt.
In 2008, the Department of Conservation began the eradication of stoats from Resolution Island, Fiordland. Five years later, stoats still persist on the island because of repeated reinvasion from the South Island mainland, only half a kilometre away. In 2011, bovine TB was detected in the Rolleston Range, Canterbury, a long way from the nearest source of infection. One strong possibility is that TB was carried there across the Southern Alps by a dispersing deer. These two examples clearly demonstrate why failure to prevent dispersal and reinvasion is one of the main reasons both eradication and sustained control of pest species are often unsuccessful. However, there are also situations where managers want to promote animal movements into controlled areas. Where pest species have been removed or their numbers drastically reduced, the aim is often to promote the re-establishment of native animals by facilitating their migration and settlement.
Understanding animal movements is fundamental to many aspects of pest management. Animal location data provide essential information on how animals behave and how they interact with each other, their environment, and the baits, traps and devices used to control them. Using such knowledge will help managers improve the efficiency and effectiveness of control and better understand key ecological questions about pest population dynamics, pest-native species interactions and pests as disease vectors. The ability of researchers to collect detailed animal movement data has increased hugely through the growing use of global positioning systems (GPS), telemetry and remote sensing devices such as animal to animal contact loggers and remotely triggered trail cameras. Recognising the growing significance of this area of research for pest management, Landcare Research has recently established an Animal Movements research group which brings together its wildlife biologists, pest researchers, modellers and database experts to maximise the information that can be obtained from animal movement data.
The present issue of Kararehe Kino features examples of the six main areas where research to improve information on animal movements will aid pest management outcomes. First, there are pest species for which better basic information on movements and dispersal behaviour will improve management strategies and tactics (ungulates, wild dogs). Second, there are species with currently limited distributions where the management aim is to prevent range expansion and where movement outside of the current range must be detected as quickly as possible (ungulates, wallabies). Third, more information on triggers for dispersal and dispersal behaviour, including settlement rules, will help manage problems of pest reinvasion after control or eradication (stoats, rats). Fourth, predictive spatial models of pest populations at local and national scales used by managers to plan control will be improved by the inclusion of new information on habitat-related differences in home range size and changes in movement behaviour of survivors of control and of animals in adjacent uncontrolled areas (possums, rats). Fifth, management strategies such as buffer zones to prevent or contain pest dispersal will be enhanced by formal assessment of their effectiveness (buffers). Sixth, strategies to prevent the spread of diseases and parasites carried by pests are critically reliant on good information about pest movements, both of the disease vectors themselves and also of the other potential disease hosts with which they interact (bovine TB).
Much, however, remains to be learned about pest animal movements. Researchers know little, for example, about the detail of how animals use their home ranges – if they did, managers might improve the effectiveness of ground-based control methods. Further, researchers have little knowledge of what triggers animals to disperse from their natal areas and what decision processes they use in choosing a new location in which to settle – if they did, the ability of managers to manage pest animal spread and reinvasion would undoubtedly be improved. But thanks to GPS and contact logger technology and new methods of analysing movement data, researchers should now be able to address questions fundamental to the design of large-scale control operations such as how landscape features in the real world and intra- and inter-specific interactions among pests influence pest animal movements.