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Providing evidence to improve practice

Action: Sterilize predators Terrestrial Mammal Conservation

Key messages

Read our guidance on Key messages before continuing

  • One study evaluated the effects on potential prey mammals of sterilizing predators. This study was in the USA and Canada.



  • Survival (1 study): A before-and-after study in the USA and Canada found that sterilising some wolves (combined with trapping and removing others) did not increase caribou survival.


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.

Referenced papers

Please cite as:

Littlewood, N.A., Rocha, R., Smith, R.K., Martin, P.A., Lockhart, S.L., Schoonover, R.F., Wilman, E., Bladon, A.J., Sainsbury, K.A., Pimm S. and Sutherland, W.J. (2020) Terrestrial Mammal Conservation: Global Evidence for the Effects of Interventions for terrestrial mammals excluding bats and primates. Synopses of Conservation Evidence Series. University of Cambridge, Cambridge, UK.