Activities

1. Objectives
2. Completed activities
3. Ongoing

2. Completed activities

   2.1 Island reserve for the European mink in Hiiumaa Island

Feasibility study on the American mink in Hiiumaa in 1997. pdf file, 136 KB.

   2.2 Removal of the American mink

Removal of American mink, mustela vison, from Hiiumaa. Report
November 1998 - March 2000. Tiit Maran pdf file, 6 pps, 161 KB

   2.3 Releases of European mink - 2000

Preparation of European mink for the release
Selecting animals from the captive population of the Endangered Species Centre, the following considerations were taken into account:

• A captive population is the basis of the whole mink conservation work, being also a guarantee that the species can be restored when it has entirely disappeared from the wild. In conservation management the requirements of the captive population are considered of primary importance and for the release only such animals are selected who, with regard to their genetic or other qualities, are not needed for the captive population.
• Specimens least related to each other should be selected.
• As the reproductive lifespan of the females is short, possibly young animals should be chosen for the release - one or two year old specimens would be the best.
• The sex ratio should be equal.

As the majority of the European mink in The Endangered Species Centre are of the first, second or third captive generations, there is no doubt that their behaviour is greatly different from that of the animals living in the wild.

Investigations at Tallinn Zoo have shown that animals living in captivity:

• almost entirely lack the ability of human avoidance (Foto 8);
• are not so agile and successful hunters of prey (frogs, crayfish, fish, small rodents, etc.) as animals living in the wild;
• in some cases (with no pool in the enclosure) have lost the swimming ability and cannot cope in aquatic environment (some are afraid of water, some can swim but cannot dive and are unable to catch fish);
• are not afraid of greater carnivores.

To increase the survival chances of the released animals during the period of adaptation to natural evironment, all the animals were trained before the release.

Release of European mink in 2000
Reintroduction of mink into the wild is a unique undertaking with very little previous experience available. The only source we could use as an example was the elaborate Black-footed Ferret Recovery Plan in the USA (http://www.ngpc.state.ne.us/wildlife/ferret.html). But as there is a great difference between the mink and black-footed ferret biologies, we could only partly use the experience gained with the latter species.

To get some preliminary experience, in 2000 we conducted two experimental releases of mink into the wild. We expected to obtain answers to the following questions:

• What is the approximate survival rate of the animals?
• What are the causes of mortality?
• Which would be the best time for release: early or late summer?
• How long will it take for the mink to adapt to natural environment?
• How will the adaptation take place?
• How much time and energy will radio-tracking of the animals take?
• What kind of conflicts with local people may arise?

Early summer release of mink
During 28-30 June, 9 mink (4 males and 5 females) were released (two or three at a time) to habitats suitable for mink. All the animals were radio-tagged and on the first days after the release they were radiolocated twice a day, then until the end of the first month, once a day, during the second month every other day, during the third month every third day, and up to the end of the observations once a week.

Late summer release of mink
From 4 to 5 September, 8 mink (4 males and 4 females) were released (two or three at a time). The radio-tracking procedure was the same as in the early summer.

Results

• General behaviour of the animals. The released mink usually followed the same behavioural pattern: for the first few days after the release the animal stays in the releasing site but then starts to move long distances, covering tens of kilometres a day. It is noteworthy that in that period the released mink do not necessarily keep near to running waters (as done by their wild conspecifics who seldom go away from water more than a hundred metres), but often wander areas very far away from water and totally unsuitable for them as habitat. But then, usually after a month has passed, the stay on the banks of a river or a stream and establish their home range there. Here you can see the movements of one of the animals after the release. (Map)
• The duration of adapting: according to provisional data it takes approximately a month for an animal to adapt itself to natural environment. After that period no deaths were recorded and the mink had established a more or less settled home range for themselves.
• Causes of death: of 7 recorded deaths 5 (+1?) were caused by other predators (probably martens or feral cats) and 1 by man (the animal was shot dead). (Foto 9)
• Survival: as the transmitters of part of the animals proved to be of low quality, we cannot precisely say how many animals had survived by the end of observation (Nov. 2000). The approximate overall estimation is 24%-60%, while the early summer survival was 33%-77% and the late summer survival much lower: 22%-37%. The three mink livetrapped at the beginning of 2001 were in a very good state and they had gained in weight, which showed that they had been coping well in nature.
• Comparing the early and late summer releases, we could make a conclusion that the early summer release was more successful.
• Conflicts with humans were induced mainly by two animals who going into village killed hens and even kittens. These mink were captured and re-released to their natural environment. In other mink we did not observe any particular inclination to visit village households.

   2.4 Supporters

• UK Government Foundation "Darwinian Initiative for Biodiversity"
• Bernhardine Foundation (Rotterdam, Holland)