Scientists from the Canary Islands have compiled data on wild ferrets in La Palma and the damage they cause in the ecosystem, to confirm that the island is the one with the highest number of naturalised animals in the archipelago. The Canarian government permits rabbit hunting using ferrets, an ancient and common practice that has its disadvantages when the ferrets escape or are released into the wild.
In the Canaries more than 20, 000 ferrets (Mustela furo) are kept in captivity, and the number of hunting licences in 2007 was 9552. La Palma is the island with the lowest number of ferret licences (531) on the archipelago. However, "the number of naturalised animals is much higher than expected", Félix M. Medina, main author of the study and researcher in the Environmental Ministry of the Island Council of La Palma, points out to SINC.
In the study, performed in collaboration with the University of La Laguna and recently published in the journal Oryx, the researchers gathered all the analysis done on the Canary Islands and contributed 45 new observations -carried out between 1998 and 2007- on wild ferrets, alive or dead, in 28 towns on the island of La Palma.
Nowadays, "the species seems to be widely distributed in the north of the island, with a seemingly isolated population in the centre", the scientist describes.
After observing a couple with three babies in 2007, Félix M. Medina now confirms the reproduction of these animals in the natural environment. The investigation also demonstrates that the abundance and distribution of ferrets are "directly related to the availability of these prey, as well as the availability of other kinds of food and shelter which they find in the rural and cultivated areas of La Palma".
The team made the observations in wooded areas of Canarian pine forests or monteverde, and in cultivated rural areas, "which is in line with the general behaviour of ferrets, because in these areas rabbits (Oryctolagus cuniculus) are very abundant", the researcher explains.
Between January and April 2006, scientists carried out a preliminary control of wild ferrets due to the damage they were causing on some farms. They set 36 live capture traps in Las Tricias, to the south-east of La Palma. Between August and November that year, they set traps in other towns and, in total, captured 10 specimens.
Negative effects on the fauna
Although the scientists indicate that "the effect of wild ferrets on the native fauna of the island is currently unknown", it is likely that it could "negatively" affect various species of birds that breed on the ground. This is the case with the laurel pigeon (Columba junoniae) and the Eurasian woodcock (Scolopax rusticola). Ferrets could also hunt subspecies of endemic lizards Gallotia galloti palmae. "There is need for greater awareness of this problem in the public authorities, as well as tightening the law, controlling and penalizing the use of ferrets without a muzzle, in addition to launching information campaigns, especially amongst hunters, to reduce the risk on native species", Medina confirms.
Medina, Félix M.; Martín, Aurelio. "A new invasive species in the Canary Islands: a naturalized population of ferrets Mustela furo in La Palma Biosphere Reserve" Oryx 44(1): 41-44 enero de 2010.