Ex situ and in situ in the conservation of the European Mink (Mustela lutreola)
BY TIIT MARAN, 1996


Introduction

The European mink, Mustela lutreola, is a semi-aquatic small carnivore belonging to the family Mustelidae. Although it has an astonishing resemblance to the American mink, Mustela vison, its actual closest relatives are the Siberian polecat, Mustela sibirica and European polecat, Mustela putorius. The similarity with the American mink is just an amazing example of adaptive convergence to semi-aquatic lifestyle.

The historical range of the European mink covered almost the whole continental Europe: from Ural mountains to eastern Spain and from central Finland to the Black Sea. Only in Sweden, Norway, Denmark, Belgium, Italy and Portugal the occurrence of the European mink has never been confirmed. Since the mid- nineteenth century its range has dwindled with an accelerating rate (Maran & Henttonen 1995) until its recent inclusion as endangered species in the IUCN Red Data Book (Groombridge, 1993). In the European Union the European mink is listed in Annex II (species whose conservation requires the designation of special areas) and in Annex IV (species of community interest in need of strict protection) of the Directive on the Conservation of Natural Habitats and of Wild Fauna and Flora. The IUCN Action Plan for the Conservation of Mustelids and Viverrids (Schreiber et al. 1989) nominates the European mink as a priority.

Process of the decline

In the mid-nineteenth century the demise of the European mink was noticed in Germany(Youngman, 1982), then in Switzerland(Gautchi, 1983) and, in the 1890s, in Austria (Novikov, 1939). This process resulted in an isolated enclave of the European mink in western Europe. It originally persisted between Brittany in France and Galicia in Spain. Recently the species has suffered from a widespread decline in the French range resulting in total disappearance of the species in its northern part and decrease of number elsewhere (Maizaret, pers.comm. 1994, Moutou 1994). The available data about the European mink in Spain are intriguing as the species was first discovered there only in 1951 and is reported to be spreading southwards at present (Ruiz-Olmo & Palazon, 1990).

In eastern Europe the European mink disappeared from Poland, Hungary, the Czech and Slovak republics and probably also from Bulgaria between the 1930s - 1950s (Romanowski 1990, Szunyoghy 1974, Barta 1956, Schreiber et al. 1989). In other countries the species is at present balancing on the very brink of extinction, or has fallen already over it. Last wild individuals were recorded in 1992 for Finland (Henttonen, 1992), in 1984, 1991, 1993 for Latvia (Ozolins & Pilats, 1995), in 1979 for Lithuania (Bluzma, 1990). Although unlikely, some remnant populations may still survive in the Ukraine (Turjanin, 1986, Tumanov, 1992) and Georgia(Kudatkin in lit. 1991). During the last decades the European mink have plummeted in Russia (Tumanov & Zverjev, 1986, Sidorovich & Kozhulin, 1994, Sidorovich et al. 1995), Belarus (Sidorovich, 1992), Estonia and Romania(H.Almasan, D. Muriaru and O.Ionescu, pers. comm.). Although in severe decline, fragmentary populations of the European mink are still extant in these countries. (for full review of the process see Maran & Henttonen, 1995). Most recent data suggest that the incredibly rapid decline continues and at least during the last five years the status of the European mink in reserves of ex-USSR has reached to a level where there are no vial populations left in any protected areas (Maran et al. in press).


Agents of the decline

This precipitous decline everywhere has prompted the researchers to look for explanations. Yet until recently all the attempts have remained to the level of just pushing forward the hypotheses, without proper testing. The discussion over the hypotheses has been provided in Maran & Henttonen, 1995; some of them have been at least partially tested in Maran et al (in press) and Sidorovich et al. (in press). Loose historical correlative evidences(Maran et al. in press; Maran & Henttonen, 1995) suggest that habitat loss, excessive hunting and impact of the American mink play a crucial role in the extinction. It is also evident that these agents act in concert with the impact of the agents varying in time and place.


Planning of the recovery

The recovery planning is restricted by two circumstances:

1. The process of te decline has been sped up during the last decade and almost all the still extant wild populations are highly endangered. Thus, there is NO TIME for detailed research and surveys to found scientifically solid base for the recovery plan. The research must by conducted simultaneously with the conservation efforts including those ones securing physical survival of the species.
2. The agents responsible for the decline have not been clearly distinguished. In spite of a relatively clear indication that the extinction of the European mink can be attributed to the habitat loss, excessive hunting and impact of the American mink, the possibility still remains that some other unknown agents are contributing to the demise.

With no time for further studies to clearly identify the responsible agents, the only, although somewhat arbitrary decision must be to regard the habitat loss, contest with the introduced American mink and excessive hunting as the main factors leading to the extinction. While the habitat loss and excessive hunting are the factors whose impact can be reduced by in situ actions, the spread of the American mink in Europe seems to be irreversible and leave at present stage little hope to recover the autothon in the wild. Therefore, although coordinated captive breeding is the most expensive conservation tool, it is still the only adequate option with the prospect of the survival of the European mink.

The goal of the recovery plan must be the following:

· Long-term aim - recovery of the species in the wild

· Short-term aim -

ex situ - achieve the physical survival of the species;

- advocating for the species in zoos and other breeding facilities

in situ - studies on testing the proposed explanations of the decline;

- further screening of the change in wild populations;

- getting new founders for captive stock;

- seeking for the suitable sites and methods for restoration of the species in the wild populations;

- informing the local inhabitants about the critical status of the European mink and the ways of preserving this species.

The ex situ actions have a priority here, but cannot be successful without the in situ component.

The standard aim usually recommended for the captive breeding programs is to preserve 90% of the genetic diversity of the wild populations for the next 100 - 200 years (Soule et al. 1986). If it is to be taken as an aim for the European mink breeding program and if data deriving from the captive breeding (Maran, 1994a) are used, the genetic calculations (Capacity v. 2.11 by J. Ballou) reveale that 30 - 40 founders are needed and the size of the target population must be 400 - 850 animals for effective preservation of the species in situ. Two critical aspects arise from these figures. There are not enough founders in the present captive stock and the perspective to get so many additional founders is not good. However, even much smaller founders contribution may still be enough at least to initiate a project. For instance, the relatively successful Black-footed ferret(Mustela nigripes) recovery project in North-America can rely only on the contribution of 5 founders(Thorne & Russel,1991) .

Another complication which can be foreseen in long term is the lack of space for the target population. If every participating breeding facility would keep 8 breeding animals, at least 50 - 100 facilities must participate in the program. Even if the European mink would be a "good zoo animal" it is still not likely that 17- 30 % of the 300 European zoos(IUDZG/CBSG, 1993) are willing to cooperate.

Although is the ex situ suggested to be the priority among short-term aims, it is evident that the preservation of the species cannot be achieved without concurrent efforts also in situ. The field activities help to understand the severity of the problem; they also reveal fresh biological data urgently needed for properly tuning the conservation project; and hopefully will finally help to find the solution for how to restore the European mink in the field. Also, in the conservation efforts carried through to date the in situ and ex situ components are so interwoven that it is easier to review them together instead of describing separately.


Conservation process

The project for protecting the European mink initiated by Tallinn Zoo is not the only and the first one. Preceding Russian projects, though not successful, have been analyzed in detail elsewhere (Maran, 1994b, Shvarts & Vaisfeld, 1993.).

The conservation efforts on the European mink in Tallinn Zoo can be divided into two periods. The first started in 1984, when the conservation-oriented actions for breeding of the European mink were initiated. The rationale of the programme was to build up a captive population with the final aim to create a reserve for the European mink in one of the Estonian islands (Hiiumaa). Thus, in its very beginning this project was designed to act only on national scale. Cooperation between zoos and other breeding facilities as a possible conservation tool was not seriously acknowledged because the modern zoo ideology and ideas of the conservation biology had not yet gone through the "iron curtain". The program foresaw in addition to the ex situ component also in situ actions: survey on the status of the European mink in Estonia and ecological screening of the Estonian islands to identify the most suitable one for the reserve. Founders were trapped in Estonia and some were obtained from Russia(Tver Region); also enclosures were built. In 1986, with three females producing litters, the first success was achieved in breeding. Thereafter until 1991 more or less regular breeding was achieved. Unfortunately, demographic stochasticity and relatively small population size resulted in uneven sex balance highly favoring females. In 1991, 8 European mink died with obvious signs of digestion disorders. The health problems were probably caused by inadequate food quality as a result of the critical economic situation in 1990 - 1991 in Estonia. Ironically, most of the died animals were males, which increased the negative impact of uneven sex balance to such an extent that the further persistence of the captive stock became questionable. The prospects of improving the ex situ actions by adding new founders were also obscured by a rapid negative change in the status of the wild European mink in Estonia.

At the same time, with Estonia opening to the western conservation communities, the inevitable necessity for international cooperation became more and more apparent. In 1992 the European mink Conservation & Breeding Committee was found as an international body to coordinate and promote the conservation efforts of the European mink.

Tallinn Zoo gave all the European mink in its collection to the EMCC. This may be considered as the start of the next stage in the efforts to preserve the species. The following tasks were foreseen for the EMCC:

• build up a long-term self-sustaining captive population
• establish an studbook guaranteed by IUCN/IUDZG
• integrate the species into the EEP breeding programme
• assist to initiate field work on the species
• present the European mink conservation problems to the public
• negotiate funds from participating zoos and institutions.

One of the principles to follow was to connect the in situ and ex situ components in the conservation of the mink. It was decided that the zoos willing to cooperate in the captive breeding and to get animals for a loan must fund also the in situ actions. The mutual obligations were fixed in the Memorandum of Participation(MOP). The first zoos attending the project were Helsinki Zoo and Ähtari Zoo in Finland. It was decided that the funds received from them should be used for acquiring urgently needed new founders for the captive stock. Actually the future of the whole breeding program depended upon that.

However, due to the incredibly quick decline of the wild population and the delay in receiving the funds, only one European mink was trapped in Estonia during 1.5 years of intensive field work. In 1994 during the first biannual meeting of the EMCC it was decided that the field activities should be switched over to Russia, with the aim to get new founders as well as to support the in situ activities there. Following the decisions of the EMCC several visits were made to Russia and contacts with people working in the field were made. In the same year a contract was concluded with the Central Forest Biosphere Reserve (Tver Region, Russia) to support the mink research there and to receive European mink for ex situ programme. At the same time two other unwritten agreements were made to obtain mink from elsewhere in Russia. Although all these agreements were designed to get new founders before the breeding season in 1994, none of these gave any timely results and only in late 1995, 6 (4.2) of initially planned 10 European mink arrived in Tallinn. All agreements have been prolonged to achieve better results in 1996. At present the captive stock consists of 30 mink and 8 institutions are participating in the EEP.

As the observed decline of the European mink in Estonia (Maran, 1991) and the recent demise in Belarus (Sidorovic 1990) had been incredibly quick and the latest available information on the status of the species in central Russia dated back to the early 1980s, there was enough ground to worry about the actual status of the species in Russia. Keeping this in mind, EMCC supported and initiated with available but unfortunately relatively modest funds a preliminary survey in the central districts of Russia. It resulted in reports (Sidorovich et al., 1994, 1995) revealing a drastic change in these areas: almost everywhere the European mink has declined rapidly and in several districts contrary to the prevailing beliefs the species has disappeared entirely. The reports were extremely important for understanding the grave status of this species and they wiped off the illusion in Europe as well as in Russia itself that the central regions of Russia are safe strongholds of the European mink. The most recent information (Maran et. al. in press, V.Katchanovski pers. comm. 1996) reveals that the decline continues with accelerating rate leaving thus less and less hope for resultful actions in situ.

Advocating for the mink in various international forums has appeared to be a very important part of the EMCC activities as it provides a possibility to find new partnerships. In 1995 partnership with the WildCRU at Oxford University started under the project funded by the English Government Foundation "Darwinian Initiative." This project involves various aspects including the following: collecting information on the change in the European mink population in Russia, testing the proposed hypotheses of decline and contributing to the captive breeding programme. The project involves actions in Belarus, Estonia and Russia and is a good example of integration between ex situ conservation activities and rigid scientific research both in situ and ex situ. This cooperation will remarkably improve the perspectives for solving several complicated problems faced in the attempts to preserve this species.

Until now the European mink is still a legal game in Russia and therefore printed informative materials for the local inhabitants explaining the need of saving the European mink have a major importance. Very little has been done recently in Russia to educate the public in regard of the European mink conservation. To fulfill at least partly this gap the EMCC published in early 1996 a poster in Russian with the financial support from Societa Faunistica la Torbiera (Italy) and Darwinian Initiative Foundation (UK.). This poster is distributed in central regions of Russia. It gives general information about the species, but also calls for assistance in preserving the species.

The second biannual meeting of EMCC at the Tallinn Zoo in May 1996 drew the conclusions of the last two-years activities, but also featured the basic guidelines for the coming years.

As the major problem in conservation of the European mink is the low number of founders, it was decided to intensify the attempts to get founders from the wild. The possibility to hire someone to deal only with monitoring the decline of the mink and with looking for the new founders in Russia was considered as the way to gain better results. However the very low and irregular funding remains the main hampering factor here.

Keeping in mind the possibility that the attempts to get wild founders may not meet a full success it was decided to encourage any attempts to obtain the European mink of unknown origin having become recently available from Novosibirsk. Several zoos have already obtained the animals from there. Although these new animals are valuable for the captive breeding programme in general, their unknown origin creates a lot of complications. These animals are kins, but information about the extent of the kinship is not available. Proper management of captive population is therefore difficult. To tackle this problem the EMCC biannual meeting decided that the DNA study of all the captive mink should be initiated as one of the priorities.

Normally zoos prefer to keep one to two pairs of animals of one species. This has also been the wish of most of the zoos interested in keeping the European mink. The option of keeping small number of mink in a large number of facilities will lead to very complicated management procedures in comparison to a larger number of mink in few facilities. That is because the reproductive life span of the European mink is very short (3 - 4 years) and with having small mink groups in numerous facilities the genetic considerations dictate a very frequent exchange of the animals between zoos. Frequent shipment of the animals is expensive and it also exposes the mink to frequent dangers occurring during shipment, not to mention sophisticated "paperwork" and logistics for transporting the animals from one country to another. Apart from reducing the need of frequent shipment the specialized breeding centers would also enable us to concentrate on various research necessary for the effective preservation of the species. Therefore it was decided that a low number of facilities with higher number of mink should be the preferred strategy for ex situ programme.

While analyzing the attempts to preserve the species, it seems that poor financial support, organizational weakness, inadequate professional performance and under-estimation of the extent of the efforts needed to preserve the species, but also bad luck finally led to the set-back during the first stage in the conservation attempts in Tallinn Zoo. The re-launched project basing on the modern theory of conservation biology might have better perspectives for success although the same shortcomings are likely to continue hampering the project. The progress depends very much on breeding success during the next years and, further on, upon the financial and organizational possibilities to found a solid and continuous base for the project. The moderately positive results gained to date have become possible only due to the concern and assistance of a few conservation-minded persons in Europe. Unfortunately, in spite of the inclusion of the European mink into numerous conservation priority lists in Europe and world-wide, the survival of the European mink in Europe have so far remained on nobody`s responsibility. Without a serious change here the prospects of escaping the final extinction of the European mink in Europe are pretty low.


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