Remove or control competitors
Overall effectiveness category Unknown effectiveness (limited evidence)
Number of studies: 2
Background information and definitions
The range occupied by a species may be limited by the presence of competitors. In many cases, removing native competitors may be a controversial management strategy. However, abundance increases or range expansion of a competitor species, due to habitat or land management changes, may motivate removal or control of this species if its presence negatively impacts on another species that is deemed to be a higher conservation priority.
Supporting evidence from individual studies
A replicated, controlled study in 1999–2011 at 10 tundra sites in Norway and Sweden (Angerbjörn et al. 2013) found that the number of arctic fox Vulpes lagopus litters increased after control of red foxes Vulpes vulpes, along with supplementary winter feeding at arctic fox dens. Where red foxes were intensively controlled, the number of active artic fox dens in winter increased more than at sites where no control or a low level of control was undertaken (data reported as statistical model results). The same response was found in the number of arctic fox litters produced, and with more litters produced when food was provided at den sites (data reported as statistical model results). Three sites were intensive control sites, with an average of 19–92 red foxes culled, and supplementary feeding provided for an average of 11–13.5 arctic fox dens at two of those sites. Three sites had low levels of control, with 1.5–7 red foxes culled and 1–3 dens fed at each of those sites. Four sites had no fox control and only one den was fed at one site. Red foxes were controlled during winter from 1999. The number of arctic fox litters was counted in known arctic fox dens during July and August 1999–2011.Study and other actions tested
Referenced paperAngerbjorn A., Eide N.E., Dalén L., Elmhagen B., Hellström P., Ims R.A., Killengreen S., Landa A., Meijer T., Mela M., Niemimaa J., Norén K., Tannerfeldt M., Yoccoz N.G. & Henttonen H. (2013) Carnivore conservation in practice: replicated management actions on a large spatial scale. Journal of Applied Ecology, 50, 59-67.
A controlled study in 2005–2010 in 25 tundra sites in Finnmark, Norway (Hamel et al. 2013) found that the probability of colonization by arctic fox Vulpes lagopus was higher in sites where red foxes Vulpes vulpes had been controlled. Arctic foxes colonized some sites where red foxes were controlled but their probability of colonizing sites without fox control was zero (reported as statistical model results). Between 2005 and 2010, intensive culling removed 885 red foxes from the Varanger peninsula. Foxes were monitored annually, over a 2-month period in late winter, using automatic digital cameras in front of a frozen block of reindeer remains. Fifteen camera sites were located across the area where red foxes were controlled and 10 areas without control (Nordkynn peninsula and Ifjordfjellet). Each camera took photographs of the carcass and its close surroundings every 10 min.Study and other actions tested