Provide more small artificial breeding sites rather than fewer large sites
Overall effectiveness category Unknown effectiveness (limited evidence)
Number of studies: 1
Background information and definitions
When providing artificial breeding sites for colonial mammals, there may be a trade-off between providing large sites, which may support larger, more-resilient populations at each site, or a greater number of small sites, which may increase the chance of at least some sites surviving threats such as predation or disease. The size of the overall population may also be influenced if the density of animals occupying these sites differs between different sized sites.
Supporting evidence from individual studies
A replicated, controlled study in 2002–2005 of two grassland and scrubland plots at a site in Andalucia, Spain (Rouco et al. 2011) found that providing smaller artificial warrens for wild rabbits Oryctolagus cuniculus supported higher rabbit densities than did larger artificial warrens. Rabbit density was higher in small artificial warrens (4–13 rabbits/12 m2 plot) than it was in large artificial warrens (11–24 rabbits/48 m2 plot). Two plots (4 ha each, 2 km apart) were fenced to exclude terrestrial predators. Each plot had 18 artificial warrens, comprising 12 small and six large warrens. Warrens were skeletons of wooden pallets covered by earth and branches. Large warrens (48 m2) were the size of four small warrens (12 m2). In autumn 2002, five rabbits were released into each small warren, and 20 rabbits were released into each large warren. Rabbits were surveyed by live-trapping, three times, from November 2004 to May 2005.Study and other actions tested