Un interessante documento pubblicato nel 2009 dal periodico Biological conservation che illustra con dovizia di dati una ricerca durata ben otto anni su un piccolo gruppo di Visoni europei (Mustela lutreola) nati in cattività e reintrodotti in natura dopo essere stati muniti di radio-collare.
L’abstract del documento recita:
As part of a conservation initiative, captive-bred individuals of the endangered European mink Mustela lutreola were released to a Baltic island ‘sanctuary’, Hiiumaa Island (Estonia), and their survival was monitored over eight years. Altogether, 54 released mink were equipped with radio-collars between 2000 and 2003 and their survival and causes of death were studied as a function of sex, age, housing conditions before release and number of generations in captivity. Mortality was greatest ( 50%) during 1–1.5 months following release. The survival of males was significantly higher than that of females (25% decline in 21 days, and 10 days, for males and females, respectively). Releasing pregnant females appeared to be an unsuccessful strategy. There was no evidence that the number of generations for which the lineage of the released individuals had been bred in captivity had any effect on survival. The main cause of death was other carnivores and raptors, although this broad categorization may conceal a diversity of fatal scenarios.
We recommend for the future that the European mink being prepared for release should be maintained in large naturalistic enclosures beforehand, that a preponderance of females should be released, and that the indications that younger animals make better candidates for release should be investigated.
Di seguito un grafico interessante riportato nel documento che rappresenta la percentuale di Visoni sopravvissuti in natura dopo il rilascio (più del 50%):
The survival of captive-born animals in restoration programmes – Case study of the endangered European mink Mustela lutreola
Tiit Maran a,b,*, Madis Põdra b, Merje Põlma a, David W. Macdonald c
a Species Conservation Lab, Tallinn Zoological Gardens, Paldiski Road 145, 13522 Tallinn, Estonia
b Institute of Mathematics and Natural Sciences, Tallinn University, Narva Road 25, Tallinn 10120, Estonia
c Wildlife Conservation Research Unit, Department of Zoology, University of Oxford, Tubney House, Abingdon Road, Tubney, Oxon OX13 5QL, UK
Il documento (in lingua inglese) è disponibile in formato PDF (720 Kb)