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The distribution of the European mink (M us tela lutreola) in France : towards a short term extinction?

by C. MAIZERET 1 ""d~ , P. MIGOT

2, R. ROSOUX \ J.-P. CHUSSEAU \

T. GATELIER S, H. MAURIN 6 and C. FOURNIER-CHAMBRILLON'

' GREGE, Route de Prechac, 33730 Villandraut

2 ONC, Saint-Benoist, 78610 Auffargis

.! SFEPM, Museum d 'histoire naturelle, Pare Saint-Paul, 18000 Bourges 4 Federation departementale des chasseurs de la Gironde, BP 231, 33028 Bordeaux Cedex

5 Conseil general des Landes, 40025 Mont-de-Marsan Cedex

6 SPN, Museum National d ' Histoire Naturelle, 75231 Paris Cedex 05

Summary. -From I 991 to 1999, standardised prospecting of all hydrographic systems in the area where European minks could reasonably be expected in France (276 ten-consecutives­nights trapping operations) resulted in the capture of 53 animals. During the same period, 91 specimens accidentally trapped, captured as part of another study or found dead were also recorded.

All data but one were collected in the south of the study area and it is most likely that, apart from possible exceptions, the European mink is only present in Aquitaine and south of Poi­tou-Charentes. These results evidence a drastic decline of the species, as half of its former range has been lost over the last 20 years. Remaining populations reach low densities and some of them are probably on the verge of extinction.

Resume. - De 1991 a 1999 une prospection systematique de tous les reseaux hydrogra­phiques ou le Vison d' Europe etait susceptible d' etre present (276 operations de piegeage de dix nuits consecutives) a permis de capturer 53 animaux. Dans le meme temps i1 a ete recueilli 91 specimens qui avaient ete trouves morts, pieges accidentellement ou captures dans le cadre d'un autre programme d'etude.

Toutes ces donnees, sauf une, proviennent de la partie sud de la zone d'etude et il est pro­bable que, sauf exception, le Vison d'Europe ne soit plus represente a l' heure actuelle qu ' en Aquitaine et dans le sud de la region Poitou-Charentes. Ces resultats indiquent un declin impor­tant de l'espece puisque son aire de repartition a ete reduite de moitie en une vingtaine d'annees. Les resultats du piegeage semblent par ailleurs indiquer que les noyaux de population qui subsistent sont en densites faibles . Plusieurs d'entre eux sont probablement au bord de I' extinction.

KEY WORDS: European mink, Mustela lutreola, France, distribution, regression, conser­vation.

Mammalia, t. 66, n° 4, 2002 : 525-532.

526 MAMMALIA

' INTRODUCTION

The European mink (Mustela lutreola) is one of the 15 species of carnivores listed by the U.I.C.N. as threatened with extinction (Baillie and Croombridge 1996). This species disappeared from most of its range in the last century (Y oungman 1982 ; Saint Girons 1991; Rozhnov 1993; Maran and Henttonen 1995; Maran et al. 1998), and its distribution is still dramatically reducing. It remains relatively abundant only in Russia, with an estimated population of about 40,000 animals, but is quickly declining (Tuma­nov 1992; Maran 1992). In Belarus, Estonia and Romania, the European mink is on the verge of extinction (Maran 1991; Sidorovich 1991; Rosier 1991).

In Western Europe, only a small population survives in Southwestern France and Northern Spain. In the Atlas of French mammals, Broyer and Erome (1984) reported that the species was only present in about a quarter of France, while a century ago it ranged over half of the country (V an Bree and Saint Girons 1966; Y oungman 1982; Camby 1990; De Bellefroid and Rosoux 1998).

However, the recent surveys were based on hearsay (Broyer and Erome 1984; Braun 1990, Lode 2001 ), and many informers probably misidentified M us tela lutreola and M. vison. Moreover, Lode (1995) showed that small and very dark polecats (Mus­tela putorius) can be found in the French population (about 5% of aJl specimens), and these look closely like European minks. So, at the turn of the nineties, available data were unreliable. The objective of our study was to census all the catchment basins cur­rently inhabited by the species and accurately map its present distribution before laun­ching a conservation program.

METHODS

1. Study area and distribution of trapping operations

In order to obtain an extensive mapping of the distribution, a standardized survey was carried out from 1991 to 1999 in the 17 departments of Western France where the European mink was likely to be found according to the available data (Broyer and Erome 1984 ).

The maps of the Water Agencies depicting the boundaries of the hydrographic systems were used to define the prospecting plan. These maps show the division of the catchment areas of the main rivers into hydrographic sectors and sub-sectors. At least three trapping campaigns were organised in each sector. As soon as an European mink was captured in one sector, the same trapping effort was carried on in each sub-sector to improve the accuracy of the species distribution inside the hydrographic system.

2. Trapping network and techniques

To avoid misidentifications we organised a network of trained trappers able to identify an European mink with certainty. This network gathered up 171 persons over the whole study area. They were all working for agencies in charge of nature conserva­tion or hunting (see the list in the acknowledgements). Selected according to their skills and motivation, they were teached the protocols of the study and the handling tech-

MUSTEIA LUTREOIA IN FRANCE 527

niques. The French Ministry of the Environment provided them with special licences to trap the protected European mink for scientific purposes.

Trapping and handling techniques have been extensively reported by Maizeret et al. (1996 and 1998).

Animals were caught in 60 x 15 x 15 cm live-traps, fresh or tinned sardines being used as bait. For each trapping operation 10 traps were installed for 10 consecutive nights in an hydrographic sector. Each trapper was free to choose the exact place of traps provided they were at least I 00 m apart.

The animals were handled inside cages generally used for farming American mink. They were weighed, sexed and marked by cutting off a tuft of hair in some conspicuous place in order to identify the captures.

All specimens were then released on the same day at the place where they had been captured. A total of 276 trapping operations were carried out (27 600 trap nights).

3. Other mink records

Members of the network were also asked to collect information on animals found dead or accidentally captured during pest destruction operations. They had to collect the same types of data as those collected on trapped animals during the standardized campaign. Moreover, from 1996 to 1999 we captured animals for a study of spacing behaviour by radiotracking (Maizeret et al., 200la.) and these data were also included in this paper.

All the data used in this study have been collected by members of the network trained for identification of the European mink.

RESULTS

During the trapping campaigns 53 different animals were captured, 7 of them being caught twice. The average trapping success of the whole program is 0.19 indivi­duals per I 00 trap nights (TN).

Ninety one other data were collected apart from the trapping program: 29 animals were captured by trappers apart from standardized trapping operations, 25 were killed by cars, 6 were hunted by dogs or other predators, 18 were captured during the radio­tracking study and 13 other ones were found dead, the circumstance of death being unknown.

All but one of these 144 data were located in 7 departments of the southern half of the study area (Fig. 1). Most data came from Gironde (n = 59) and Landes (n = 37), the other ones from Charente-Maritime (n = 15), southern Charente (n = 12), Pyrenees­Atlantiques (n = 10), Lot et Garonne (n = 6) and western Dordogne (n = 4).

In these 7 southern departments, the trapping success was 0.32 animals captured per 100 TN.

In the northern half of the study area, no European mink was recorded in Basse­Normandie and Bretagne and only one dead animal was found in 1992 in Pays de la Loire region. This record was not confirmed by several trapping campaigns concentra­ted in the sector. The absence of capture does not mean that the species is totally absent throughout the Northern part of the study area but it is reasonable to assume that, at best, only a very small isolated populations could survive in this sector.

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To summarize, the present range of the European mink in France mainly extends from the departments of Charente and Charente-Maritime (46° 15'N) in the North to the Spanish border in the South, and eastwards to Dordogne and Lot-et-Garonne (1 o 4'E) (Fig. 2).

Pays de la Loire

0 100 200 km ---===--===

e Data collected during standardized trapping operations 0 Unsuccessful trapping operations A Reliable data collected apart standardized trapping operations

- Limits of the regions

Aquitaine

Midi-Pyrenees

- Limits of the departments (I : Charente-Maritime, 2: Charente, 3: Gironde, 4: Dordogne, 5 : Lot-et-Garonne, 6: Landes, 7 : Pyn!nees-Atlantiques).

Fig. 1. - Data collected on European mink distribution in France during an extensive survey from 1991 to 1999.

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Fig. 2. - Rivers where the European mink is currently present in Southwestern France (dark lines).

DISCUSSION

At the turn of the twentieth century, the European mink was recorded in 38 French departments and only 13 were still occupied by 1980 (De BellPfroid and

:y Rosoux 1998). The present study confirms the regular occurrence of the species in only 7 departments of the southern part of the previous range and a small isolated popula-

530 MAMMALIA

tion could subsist in the northern part. This means that nearly half of the range of the species has been lost during the last 20 years.

Moreover, the trapping success suggests that the densities are quite low in the pre­sent distribution area. In Spain, with the same method, Palaz6n and Ruiz-Olmo ( 1998) obtained a better trapping success (3.2 captures per 100 TN vs. 0.32 in the southern area of the present study). Related studies on American mink also provided better results: 16.7 captures per lOO TN in Canada (Ritcey and Edwards 1956), 7.4 in Swe­den (Gerell 1971), 1.8 in Scotland (Dunstone and Birks 1983), from 2 to 10 in England (Halliwell and MacDonald 1996), 3.2 in Argentina (Previtali et al. 1998).

At the moment, the French population spreads continuously from Charente and Charente-Maritime to the Spanish border. The presence of European minks in Northern Spain on the upper Bidassoa river (Palaz6n et al. 2002) could even suggests a contact between French and Spanish populations. However, the western part of the Basque country is an heavily urbanized area and exchanges of individuals between the French coastal rivers and the catchment of the Ebro river must be very difficult.

The future of the European mink in France is very dark, a short term extinction is likely, so the conservation of the species must be a priority. Consequently the Euro­pean mink is one of the first mammal species to have been proposed for a «national action plan» by the French Ministry in charge of Environment (Maizeret et al., 2001b). This plan, introduced in 1999, still needs fundamental biological data to direct actual measures of recovery. Studies on causes of mortality (Fournier et al. 200lb), spatial behaviour (Foumier et al., in prep.), habitat use (Maizeret et al. 200la), diet (Libois et al. in prep.), pathology (Fournier et al., 2001a) and genetics (Libois et al. in prep.) are in progress but it seems too Jate to wait for the answers to all the questions before implementing conservation measures. So, the Ministry in charge of Environment is now engaging the second stage of the plan which deals with putative measures of habi­tat conservation, reduction of various causes of mortality, control of the extension of American mink and promotion of public awareness.

ACKNOWLEDGEMENTS

This study was funded by the French Ministry of the Environment. It was carried out by the working group on the distribution of the European mink which comprises the following orga­nizations: Association des piegeurs agrees de Charente, Association pour la Defense de l'Envi­ronnement en Vendee, Conseils generaux de la Gironde et des Landes, Conseil Superieur de la Peche, Federations departementales des chasseurs de la Charente, de la Charente-Maritime, des Cotes d' Armor, des Deux Sevres, du Finistere, du Gers, de la Gironde, des Hautes Pyn!nees, de l' llle et Vilaine, des Landes, de la Loire Atlantique, du Lot-et-Garonne, du Morbihan, des Pyre­nees Atlantiques et de la Vendee, Jalle riviere propre, Groupe Mammalogique Breton, Groupe Mammalogique Nmmand, Groupe de Recherche et d'Etude pour la Gestion de l'Environnement, Erminea, Ligue pour la Protection des Oiseaux, Observatoire du Patrimoine Nature] des Pyrenees Atlantiques, Office National de la Chasse et de la Faune Sauvage (Direction de la recherche et du developpement et services departementaux de garderie), Organbidexka-col-libre, Pares natu­rels regionaux d' Armorique, de la Brenne, du Cc-•entin, des Landes de Gascogne et du Marais Poitevin, Pare National des Pyrenees Occidentales, Museum National d'Histoire Naturelle, Pro Lutra, Societe Fran~aise pour l'Etude et la Protection des Mammireres, Societe pour l'Etude la Protection et l' Amenagement de la Nature dans le Sud-Ouest. J.-F. Brulard drew the map. Thanks to S. Aulagnier for his helpful comments and to E. Taran for the English corrections.

MUSTELA LUTREOLA IN FRANCE 531

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