- The polecat project (original) (raw)
The European Polecat Project
Mustela putorius
Brown to dark brown in fur, the European polecat Mustela putorius L. 1758 has generally a yellowish patch on the face giving the impression of a bandit's mask. Polecats are bigger than weasels but exhibit an important sexual dimorphism ( = 1.75). Adult sizes vary from 350 to 450 mm (body length) and in weight 0.7 kg for females to 1.7 kg for males.
Related to the Mustelidae family (stoats , otters, badgers, skunks…) polecats are mainly nocturnal and individual animals with a home range of about 1 km 2 . They shelter in cavities in stream banks or under tree roots. Formerly spread throughout the Western Palearctic, polecats are mainly found in woodlands, farmlands and wetlands.
The species may breed once a year in May-June and after a gestation of 42 days, three or four pups are cared for by the female. Feeding mainly upon frogs, toads and bank voles, the polecats are also rat destroyers in the wild. Polecats seldom hybridise with the Steppe polecat ( M. eversmanni) or the European mink (M. lutreola). The Ferret M. furo often largely albino, is a domestic form deriving from the extinct subspecies, the Berber polecat ( M. putorius berberii = furo) as attested by ancient roman texts and genetics.
The aim of studies is to characterise sexual behaviour variations and environmental constraints affecting polecat populations.
1. Sexual behaviour
Natural populations of the European polecat show an important polyphenotypism concerning the colour of the fur and the size, traits often associated in mustelid genomes. Besides animals presenting the typical phenotype with a characteristic "mask", some polecats are smaller and darker (dark phenotype). Although these two phenotypes are sympatric, dark polecats have been found to exploit mainly forest brooks, emphasizing that dark phenotype resulted from character displacement and lead to sympatric divergence and possible speciation.
The predisposition of females in preferring males of their own phenotype supports the hypothesis of a trend towards intra phenotype endogam y. Nevertheless, a strong inbreeding avoidance strategy characterized polecat mating as revealed by the low genetic relatedness between reproductive males and females.
Dark phenotype in wild polecat, Brittany 1992 and in captive polecat
Polecats hybridized with the rare European mink ( Mustela lutreola) in some part of their range and have fertile descendants. Polecats were also found to develop numerous homosexual interactions, forming alliances between two males or two females, despite they ordinary lived a very solitary life. Such homosexual behaviour was unique among solitary carnivores and has no evolutionary explication.
Influencing the sex ratio and alternative behaviours within frog populations, polecat predation reduced the polyandry and may balance sexual divergence of interest. This result supports that polyandry emergence may stem from female mate choice when female benefits from gifts or parental care improving their fitness while polyandry mainly results from sexual conflict and only profits to males when no material advantages were conferred to females. Anyway, by affecting the variance of reproductive behaviors, polecat predation influences the changes in traits linked to reproductive isolation and may reduce the divergence.
2. Feeding tactics
The polecats' diet remained flexible and the predator could integrate a great variety of resources, such as birds or carrion, into its diet. The trophic status of the species corresponded to a generalist feeder . But, and despite its dietary eclecticism, the polecat could concentrate its predation upon frogs or rodents. The dietary patterns are characterised by the alternation of rodent and anuran prey. Terrestrial and nocturnal amphibians such as Common frogs, Agile frogs or Common toads were preyed upon and their occurrence in the diet coincided with the anuran breeding season.
Polecats stored anurans and exhibited a clear selective predation upon anuran males probably more easily detected because of their chorus. Furthermore, the storage of prey showed the remarkable cognitive aptitude .
Predation by polecats should have implications for anuran population genetics because exchange in frogs and toads mainly resulted from the migration of some males. Common toad (and predated one)
Agile Frog and common toad remains
Toa
3. Home range
The utilisation of different habitats was directly correlated with different prey availability. Bank vole occurrences in the diet were associated with the use of woods and anuran occurrences were correlated with the exploitation of marshes or ponds. The exploitation of different habitats is directly influenced by trophic factors and emphasises the opportunism of feeding strategies . Changes in movements correlated with anuran dispersion and the response was sigmoidal (polynomial regression) revealing an area-restricted search. This response may be regarded as an “aggregative response”. The successive utilisation of different habitats discloses the importance of the heterogeneity of landscapes for the mustelids.
Princesse , Female polecat, Grand-lieu, Western France
The activity area averages a monthly surface of 38 hectares for the males and 19 for the females but in western France, the total home range represents about one km2 . The social organisation is characterised by particular individualistic exploitation of the space. Animals regularly show a strategy of spatial avoidance even between males and females and the predation concentrates on zones of strong trophic potentialities.
4. Activity rhythm
Nocturnal activities are predominant and the level of total diel activity is moderate and stable throughout the year (about 30%). Polecats exhibit a bi modal activity rhythm and changes in activity distribution highly correlate with main prey activity rhythm. Seasonal changes in the activity rhythm of polecats appear synchronised with the rhythm of their prey.
5 . Social Behaviour
Polecat s were characterized by an individualistic way of life , often called solitary although the species showed main social interaction through olfactive cues. Although aggressive behaviours varied among groups, the reaction did never differ with the kinship. Kin selection theory provides successful explanations for a wide range of phenomena but our results suggest that multiple mechanisms running simultaneously might be involved in social behaviours. Familiarity clearly influenced the social behaviour of polecats and may be involved in a kin facilitation effect favouring interactions. Animals raised together demonstrated more positive and less negative interactions so that and despite the individualistic way of life of the polecat, familiarisation may result in more tolerance, emphasising that solitary species may provide significant information on social life. Anyway, familiarisation in polecat may be regarded as a cognitive form of recognition.
6 . Biological conservation
Major causes of the loss of biodiversity are the destruction of habitat and the direct persecution. Because of trapping and habitat alterations, Polecats suffered a certain decline all over Europe. In France, Polecats are still destroyed as pest by trappers under the responsibility of hunting companies. In Great Britain and in Italy, populations were restricted to some areas but everywhere polecat populations showed a certain decrease in density. No one can predict how the extinction of one species will affect the natural ecosystems, but the decline gives evidence of the alteration of natural habitats. Mustela putorius conservation in Europe needs a new policy for species protection. Future conservation plans in France should incorporate both a real legal protection status and agricultural practises should be carried out which are respectful of the environment.
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BERZINS R., HELDER R. & LODÉ T. 2002. The influence of odour familiarity on the female polecat (Mustela putorius) mate choice. Adv Ethol, Suppl to Ethology 23:37
LODÉT. 2001. Mating system and genetic variance in a polygynous mustelid, the European polecat. Genes and Genetic systems 76: 221-227
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LODE T. 1998 - Genetic heterozygosity in polecat Mustela putorius populations from western France. Hereditas 129: 259-261
LODE T. 1994 - The polymorphism of the European polecat Mustela putorius in France. Small Carnivore Conservation 11 : 10.
LODE T. 1993 - Stratégies d'utilisation de l'espace chez le Putois européen Mustela putorius L. dans l'ouest de la France. Revue d'Ecologie Terre Vie 48 : 305-322
LODÉ T. 1991 - Evolution annuelle du régime alimentaire du Putois Mustela putorius L. en fonction de la disponibilité des proies. Bulletin d'Ecologie 22 : 337-342.
LODE T. 1991 - Conspecific recognition and mating in Stone marten Martes foina Erxleben 1777. Acta theriologica 36 : 275-283.
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LODE T. 1990 - Le régime alimentaire d'un petit carnivore, le Putois Mustela putorius dans l'ouest de la France. Gibier Faune Sauvage 7 : 193-203.
LODÉ T. 1988 - Territoire et utilisation de l'espace chez le Putois. Bull. Erminea 6 (2): 22-27
LODÉ T. & LE JACQUES D. 1988 - Le régime alimentaire des petits carnivores : contribution à l'identification des proies d'après l'analyse des fèces. Bull. Erminea 6 (1): 1-36.
