The end of radio-trapping operation: troublemakers and haunting questions.

Saturday (16.11.2013) the release and radio-tracking of the European mink in Hiiumaa Island was completed. 15 captive young mink from Tallinn Zoo Conservation Lab were released in the island and radiotracked for more than one and half month. The results of the release were interesting and evidenced remarkably increased release survival. However, the end of the release was a story by itself.
The collars may cause a lot of injuries when animals gain weight in late autumn, so the mink have to be caught and the collars removed. It might seem an easy job – the signal emitted by the transmitters help to locate the very spot of mink. Just set up live-traps in proper way and place along the bank on both sides of the mink location, equip traps with bait and …. voilà – the mink is in trap.
The real process was not so simple – here is the story of retrapping the mink in Hiiumaa Island in 2013.

At the end of the trapping session only 7 mink with collars remained under observations. Our task was to re-trap these 7 mink to remove the collars. The re-trapping was started on 23. of October, when the first collar was removed within one trap-night. On 26th of October the operation was continued and for five mink two traps for each were set up and the remaining one was hoped to get with three traps. The next day was the happy one – four mink in the traps and for the afternoon the collars were removed. Then the luck turned – to get the remaining two mink required notably more traps, nights and efforts. These two mink were simply not going to the traps, despite of all the efforts and long experience in trapping.

The knowledge of exact location of mink helped to set the traps up in the best available positions – real “do not go by” locations; and then the smelly oily smoked sardines as baits – usually very attractive to mink.

These two mink were simply not collaborating. Despite of all the efforts they just passed the traps as if these were non-existent. Even more, they were teasing us…. once it was possible to have a lengthy observation of the swimming mink in near vicinity of the trap.

Other obstacles became evident. In one trapping site close to farm nice black and white domestic cats caught the smell of oily sardines and after that it was impossible to friendly owner to keep the cats away from river bank and from our traps. We have to remove them. Actually, here the mink collaborated and moved upstream, so we followed it with our trapping effort. Then the Norway rats got an idea that the traps were just perfect for nests and they brought leaves and debris into traps till the door of the trap closed. Interestingly, the Norway rats close to water become real semiaquatic mammals. Looking as they jump into water, while escaping from trap, and dive, leaves no doubt – they are very skillful in water.

The time passed and then after some two weeks finally one of the trouble-makers went into trap and were freed from collar. The last one was a real “nuisance” – it just passed the traps – some ten of them in her homerange. We tried salmon instead of sardine as bait with no result. Then we took European mink scats and urine-moistured sand from the zoo to attract the animal – no results again. Finally, we left most of the live-traps empty – without bait. No result.

As a last hope we thought to make use live chick in box inside of livetrap to attract the animal. It was expected that the sound of chick is stimulus for mink strong enough to force her to go into the trap. The take care of the chick we decided to stay in visual distance from the trap, so it would be possible to get to the trap in time.

Then, when we arrived with chicks and equipment, the last troublemaker was in live-trap, without a bait at all in it. It took for us three weeks to get this bugger.

If you look on the graph, it is clear that there are differences in the behavior. Majority behaved like typical nice mink and got to traps as expected, but two .. who were these? Aliens? They were outliers, statistically speaking.. and outliers are important.



A number of speculative questions are rising from this experience:

1. A bit less than third of mink was very complicated to catch despite of their captive origin and ideal situation – we knew exactly the location of the animal. What it means if we use live-trapping as monitoring technique – that is when we even do not know where the animal exactly is? So far we have assumed that every animal have the same likelihood of getting trapped, or, at least, the variation has normal distribution. It is not. So how reliable are our monitoring data if the results depend upon the animals willing or not willing to go to trap? Does this proportion changes with years or with some other variable? We do not know.
2. What it all means in terms of conservation breeding and release operations? Is this around 1/3 ratio typical both for captive population and for wild population? Or it is higher in wild population and the natural selection in captivity actually favors trap-happy mink? Does the ratio  changes with time and duration release operation? What variables are having impact to the ratio? What means trap-happy versus -unhappy type in terms of survival in the wild, are the trap-unhappy type more likely to survive in the wild? Does it mean that if we conduct years-long release operation, we actually provide captive-biased animals for natural selection during release operation to select animals more trap-unhappy? Way more questions than replies.
3. Then, conservation breeding operations starts with founder animals trapped from the wild. Is the ratio of trap-happy and trap-unhappy mink among founder animals is strongly biased towards trap-happy animals? If yes, does it mean that the issue of founder effect in conservation breeding is way more complicated and perhaps overlooked. Again more questions than replies.

Field work with mink is good time after all. You have opportunity to be outside and see nice areas. Have a look at the photos.



The last troublemaker is in this photo. After removal of the collar it swiftly disappeared from opened trap like a shadow. Nice and good animals – good luck to her in streams of Day Island.





In summary, the mink, like all animals, are not simple pre-programmed biorobotes with easily predictable behaviours. They have their personalities, they learn, they change their behavior, and therefore, they are like us, humans, very different from each other. What holds for one person might not be fully correct for other … so lets be careful with our thinking models.


Russian field ecologist visiting Species Conservation Research Lab at Tallinn Zoo and Hiiumaa Island release site.

11. -12. of July leading Russian field-ecologist Alexander Saveljev, the Head of the Department of Animal Ecology at Russian Research Institute of Game Management and Fur Farming of Russian Academy of Agricultural Sciences. The researchers (esp. Dr. Dmitri Skumatov) in his team have conducted the most comprehensive studies on the status and distribution of the European mink in Russia.

Dr. Saveljev visited the European mink breeding facility in the Lab and was given review about the European mink research and conservation actions in Estonia. The second day of his visit was devoted to Hiiumaa Island and the release operation there.

Hopefully this visit has established a good ground for future collaboration on European mink conservation and research between the Russian and Estonian experts.

European mink day in Calviac Zoo, France

A week ago, on 24th of June, Calviac Zoo hold a special event for European mink conservation.  This was a highpoint of series of events devoted to European mink conservation in this cosy zoo. This final event was attended by number local people, authorities and member of French Parliament.  Local radio broadcasts and newspapers reflectyed this event.

Emmanuel Mouton, the director of the Calviac Zoo and the organizer of all these events, considered the even as great success. For this event zoo prepared new information posters about the European mink and its conservation.

The main funding organization Fondation EDF made short video about the European mink and the event.

Thank you Calviac team for this nice work for conservation of this world most critically endagered small carnivore.

Litter with 7 young is fine in breeding facility

In the last blog I wrote that one of our European mink females, Kelly, had 7 pups and it was likely that the female might not have enough milk to feed all seven young mink. So, we were afraid that we have to crossfoster some pups to another female.

The check revealed a good news, all seven pups are doing fine, are well-fed and happy, so no need to crossforster. Here’s a photo of how they looked.

The size of first three litters of the European mink born this year checked for sex and number

10 days after birth we count the mink babies. That is how many are born, what sex etc. That is a time for different moods. Not always things work out as planned before breeding season.

A female called Rulla had only one female pup, another female Kelly seven pups (four males and three females).

Today we checked the next female and she has 6 pups (one male and five females). Well, it feels good to see so many young pups, but also brings along worries. Do female have enough milk to raise up such a number of pups. Very ofter poor mom is not able to this and then in one day, all of a suddenly we find less young in the nest. This time we have a worry with Kelly, she is nervous and the pups are unquiet. It is likely that we have to move some of her pups to another female, probably Kelly. That is, of course, after marking the young with chips.

Next week we hope to film the first check of litter. So keep your eyes on the blog.

Construction of European mink breeding facility started in France

According to the mass media, on 3rd of May the construction of special breeding facility for European mink was started in France. It is claimed to be the very first in Europe. Surprising, that people involved in this project do not know anything about on-going activities in Spain, in Germany and in Estonia, not to speak about the earlier actions in Russia adn EAZA invovlement in conservation breeding of the European mink.

The facility will be built at zoo called Zoodyssee in Chizee. The budget for the construction is 2,4 mln Euro.

Good news to European mink conservation. It is only to be hoped that it will not remain an isolated “island-action” in Europe, but will become a part of all-european effort for conservaiton of this globally most critically endagenered small carnivore.

European mink ex situ conservation training course in France

In 16. – 17. of March training the courses on European mink ex situ conservation were held in Calviac Zoo in France. The training course consisted of six lectures during one and half day followed by practical demonstration of European mink handling in captivity. The course was organised by Calviac Zoo and attended by zoo specialists in France interested in conservation of this species.


The training course consisted of the following workshop lectures:

1. European mink, Mustela lutreola, conservation breeding – introduction to the course.

2. European mink, Musteal lutreola, the species and its conservation.

3. European mink, Mustela lutreola, captive breeding – sophisticated conservation tool.

4. European mink, Mustela lutreola, conservation breeding program.

5. European mink, Mustela lutreola, conservation breeding – practical issues.

6. Reintroduction, complicated conservation tool.


This was the second course of its kind. The first one was hold in Spain in March 2011.

Article about low breeding efficiency of European mink in captivity: what causes it?

New research article is just published on-line in Zoo Biology. It is about the problems behind low breeding success in European mink conservation breeding program.

This is the first time the problem of aggressive and passive males has been properly mapped. It is a good starting point for attempts to solve this mystery.

The abstract of the article (click here to download it):

The Causes of the Low Breeding Success of European Mink (Mustela lutreola) in Captivity

Kairi Kiik,1*

Tiit Maran,2,3

Astrid Nagl,4

Kadri Ashford,2

and Toomas Tammaru1

1Department of Zoology, Institute of Ecology and Earth Sciences, University of Tartu, Tartu, Estonia
2Species Conservation Lab, Tallinn Zoological Gardens, Tallinn, Estonia
3Institute of Mathematics and Natural Sciences, Tallinn University, Tallinn, Estonia
4Department of Biomedical Sciences and Biochemistry, University of Veterinary Medicine, Vienna, Austria

High among‐individual variation in mating success often causes problems in conservation breeding programs. This is also the case for critically endangered European mink and may jeopardize the long‐term maintenance of the species’ genetic diversity under the European mink EEP Program. In this study, breeding success of wild and captive born European minks at Tallinn Zoological Garden are compared, and the mating behavior of the males is analyzed. Results show that wild born males successfully mate significantly more often than captive born males (89% and 35%, respectively). On the basis of an extensive record of mating attempts, both male aggressiveness and passivity are identified as primary causes of the observed mating failures. All other potential determinants have only a minor role. Mating success as well as a male’s aggressiveness and passivity are shown to depend more strongly on the male than the female partner. Wedid not find any evidence that the behavior of an individual is dependent on the identity of its partner. We suggest that aggressiveness and passivity are two expressions of abnormal behavior brought about by growing up in captivity: the same individuals are likely to display both aggressive and passive behavior. The results point to the need to study and modify maintenance conditions and management procedures of mink to reduce the negative impact of the captive environment on the long‐term goals of the program.

Zoo Biol. XX:XX–XX,
2013. © 2013 Wiley Periodicals Inc.

European mink map in IUCN Redlist is misleading

IUCN Redlist is definitely a very good source of information about the status of species.

That holds also for the European mink. Since the recent update, which shifted Euroean mink to the category ofCritically Endangered Species, it contains the most updated information currently available about its status.

In this light it is dissapointing that the map provided in IUCN Redlist site (cklick here) is flawed.  The problem is that the definition of yellow-color areas, “extant populations”, is incorrect.

For Russia, the original legend for yellow areas was – MAY STILL SURVIVE. The latter  meaning is completely different to “extant”, as it stand now. The yellow areas in Russia does not mean that there are healthy populations, far from this. It means that it is likely something may still exists in this areas in contrast ot the red color “Possibly extinct” , which mean that the species is most likely extinct.

I wrote respective note to IUCN Redlist authorities, but have not received any feedback. Usually to have anything changed in Redlist site is very time-consuming and cumbersome task – do not expect rapid corrections.

So keep in mind that this map is very misleading and tust more the text.


Last, but not least. The map does not highlight the establishing population in Hiiumaa Island in Estonia that is our own work during last ten years.