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No. 161: Methods of assessing the status and monitoring of ferret and pine marten acc. Habitats Directive

Elmeros, M., Asferg, T. & Søgaard, B. 2015. Metoder til vurdering af status og overvågning af ilder og skovmår iht. Habitatdirektivet. Aarhus Universitet, DCE – Nationalt Center for Miljø og Energi, 50 s. - Videnskabelig rapport fra DCE - Nationalt Center for Miljø og Energi nr. 161.


EU member states must report on the conservation status of species and habitats listed on all the annexes in the Habitats Directive to the EU Commission every six years.  In Denmark, the assessments are based on the survey results from the monitoring programme NOVANA. The programme does not include species listed only on Annex V, e.g. pine marten (Martes martes) and polecat (Mustela putorius). Previous assessments of pine marten and polecat conservation status were based on experts’ opinions.

An evidence based assessment of a species’ conservation status implies that empirical information is available on the species range, population size and trend, habitat area and quality as well as an assessment of future prospects, i.e. pressures and threats for the species. The spatial units for the assessments are 10x10km squares.

The latest survey of pine marten and polecat distribution was collected for the Danish Mammal Atlas. Records from 1985-2006 showed a scattered distribution of pine marten in Jutland south of Limfjorden and on Zealand. A single specimen was recorded on Funen. The polecat was widely distributed throughout the country apart from Lolland-Falster and smaller islands. None of the species has ever been recorded on Bornholm.

This report describes the present distribution and population trends of pine marten and polecat in Denmark from recent systematic and incidental observations. We evaluate the suitability of this information as basis for evidence based assessment of the two species’ conservation status, and outline operational monitoring methods for the two species.

We collected information on pine marten and polecat distribution and population from game bag statistics, questionnaires, citizen science web platforms, and zoological taxidermists, museums and research institutions. None of the two species has an open season in Denmark, but it is legal to cull polecat in and around buildings and poultry pens.

Culled polecats are recorded on municipality level by hunters in the game bag statistics. The present range is consistent with previous mappings. To collect more precise distribution data (to10x10km squares) we distributed a questionnaire to hunters who had reported polecats in the 2013/2014 season. This method is assessed as a suitable method for future monitoring of the polecat range.

6000 polecats were reported during the hunting seasons 2009/2010-2013/2014. The annual polecat game bag numbers show a significant decline over the past 10 hunting seasons, but not across the past 20 or 5 hunting seasons. However, without correction for variations in annual culling effort the hunting bag is not a reliable method to monitor population trends.

A request for information on pine martens observation was distributed to game managers and nature guides in the Nature Agency, members of the Danish Society for the Conservation of Nature, polecat and stone marten hunters and general naturalists. Only 60 observations were reported from 2009-2014, resulting in a very incomplete and fragmented range map.

The precision on the provenance of pine martens and polecats submitted to taxidermists’ etc. in the period 2004-2014 only allowed assessment of range and occurrence on municipality level. The ranges seemed biased as to the distribution of the sampling points, especially for the pine marten.

The distribution of pine marten from citizen science sources is flawed by misidentifications. For the polecat the citizen science observations seemed biased towards observer distribution, e.g. higher density near bird observation sites.

The annual numbers of pine martens and polecats submitted to taxidermists and observations from citizen science sources were low, and the temporal trends in the different sources were not correlated.

Overall, the evaluated information is only assessed as suitable to form an empiric basis for an assessment of conservation status for polecat range (assessed as ‘favourable’). Thus, polecat population and habitat status is assessed as ‘unknown’. For the pine marten none of the available information is suitable for an evidence based assessment of the conservation status of any parameters, i.e. range, population and habitat is ‘unknown’. Assessment of future prospects will be assessed by the Nature Agency.

Suitable methods to monitor pine marten and polecat distribution range and occurrence, population trends and habitat area and quality, as well as some of the potentially major pressures and threats, are presented.