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Providing evidence to improve practice

Individual study: Survivorship of captive-bred and wild-caught reintroduced European otters Lutra lutra in Sweden

Published source details

Sjöåsen T. (1996) Survivorship of captive-bred and wild-caught reintroduced European otters Lutra lutra in Sweden. Biological Conservation, 76, 161-165


This study is summarised as evidence for the intervention(s) shown on the right. The icon shows which synopsis it is relevant to.

Release captive-bred individuals to re-establish or boost populations in native range Terrestrial Mammal Conservation

A replicated, controlled study in 1989–1993 in two rivers in southern Sweden (Sjöåsen 1996; same experimental set-up as Sjöåsen 1997) found that captive-bred European otters Lutra lutra released into the wild had a lower survival rate than did wild-born translocated otters. One year after release, the survival rate of captive-bred otters (42%) was lower than that of wild-born translocated otters (79%). Additionally, captive-bred otters with a shorter (5–48 day) period between separation from their mother and release to the wild had a higher survival rate (80%) than individuals with a longer (49–98 day) period (13%). Between 1989 and 1992, twenty-five captive-bred and 11 wild-born otters were released into two rivers. Thirty-four otters were released in one river catchment and two in the other. Captive-bred otters were descendants of two captive females. Wild-born otters were live-trapped along the Norwegian coast. All otters were around one year old when released. All except one were released between February and June. All were fitted with an implanted radio-transmitter and monitored for one year on 64% of days.

(Summarised by Ricardo Rocha)

Translocate to re-establish or boost populations in native range Terrestrial Mammal Conservation

A replicated, controlled study in 1989–1993 in two rivers in southern Sweden (Sjöåsen 1996; same experimental set-up as Sjöåsen 1997) found that wild-born translocated European otters Lutra lutra had a higher survival rate than did released captive-bred otters. One year after release, the survival rate of wild-born translocated otters (79%) was higher than that of released captive-bred otters (42%). Between 1989 and 1992, eleven wild-born otters and 25 captive-bred otters were released into two rivers in south-central Sweden. Thirty-four otters were released in one river catchment and two in the other. Wild-born otters were live-trapped along the Norwegian coast. Captive-bred otters were descendants of two captive females. All otters were around one year old when released. All except one were released between February and June. All were fitted with an implanted radio-transmitter and monitored for one year on 64% of days.

(Summarised by Ricardo Rocha)