Background information and definitions
Predators can limit population sizes of prey species. Changes in habitat or land management can lead to increases in predator populations which might negatively affect prey. Removing or controlling predators, especially native predators, for the benefit of their wild prey species can be a controversial management strategy. Nonetheless, there is potential for such management to lead to increases in the abundance, survival or reproduction success of prey species. Sterilization of predators may be proposed as an alternative strategy that may be regarded as being more acceptable than removal or lethal control.
Supporting evidence from individual studies
A before-and-after study in 1994–2002 in a large forest and shrubland area in Alaska, USA and Yukon, Canada (Boertje et al. 2017) found that sterilising some wolves Canis lupus (and trapping and removing others) did not reduce caribou Rangifer tarandus mortality. The annual mortality of caribou calves (≤1 year old) did not differ after wolf sterilization and removal commenced (50–67%) compared to before (39–65%). Adult female (≥1 year old) annual mortality was also similar after wolf sterilization and removal commenced (9–10%) compared to before (9%). In a 50,000-km2 study area, 52–78 newborn caribou calves/year were radio-collared in May 1994–2002. In fifteen wolf packs, the dominant pair was sterilized in November 1997 and remaining wolves in those packs were translocated, mainly in April 1998. Eight additional packs were similarly treated over the following two winters. Caribou mortality was measured over four years before and five after wolf control commenced during ≥3 aerial surveys/year.Study and other actions tested