Small Mustelid Foundation

Small Mustelid Foundation

Who we are in a nutshell

Since 2010 the Dutch Small Mustelid Foundation (SKM) has been delving into the ecology and conservation status of Small Mustelids (Common weasel Mustela nivalis, Stoat M. erminae and Polecat M. putorius) in the Netherlands, with a particular focus on the development of reliable techniques and means to study these elusive animals in the field. The SKM is a small non-profit organisation with a team of dedicated researchers.

We have been successful with the development of the so-called Mostela method. Mostela is a convenient acronym for Mos (the surname of its inventor Jeroen Mos) and the genus name of small Mustelids Mustela.  The ‘prototype’ Mostela is a durably built plywood box with a PVC tube as entrance and exit for small mammals up to the size of a female polecat. The walkthrough tube is a modified tracking tube, with a window allowing the recording of a passing small mammal using a quality or high speed cameratrap or wildcam, placed at the other end of the box. More information of the working principle of the Mostela can be found →here.

→ A building plan for the Mostela in English (PDF).

Open PVC tube allowing the walk-through of members of the Small Mustelid family, allowing track and video recording. (©E. van Maanen)

The Mostela with the standard 80 mm diameter tube has been well demonstrated to allow the cameratrap detection of the ‘weasel spectrum’. That is to say, weasels from the size of the smallest female weasel up to the biggest male stoat can enter the box and be recorded recognizably. The prototype Mostela has been used successfully in field trials by the SKM with the survey of habitats harboring Common weasel and stoat populations with a reasonably high density.

The Common weasel has been predominantly recorded, being much more ubiquitous in the Netherlands than the seemingly rare and more habitat critical stoat (with more affinity for wetland or riparian habitats), believed to be in decline in the Netherlands. There are certainly areas where weasels are scarce, whereas in other areas they are more common and encountered more. Moreover, the local to regional abundance of ‘weasels’ is dependent on vole densities and has been found to peak during vole outbursts (every 4-6 years), with densities declining again afterwards.

The SKM looking into the habits and habitat (macro to micro) of Small Mustelids with field research. (©E. van Maanen)

The Mostela-trapping of weasels for inventory or longer term monitoring in the Dutch modern cultural landscapes is an intensive endeavour, requiring and at the same time providing more insight into their complex population ecology and conservation needs; a reiterative process. So far, the method has shown considerable potential for more rigorous field research and standardized surveys. For instance, mark-and-recapture is possible with individual recognition for the Common weasel, using variation in the demarcation line (the lateral line dividing the brown of the back and the white belly); this is however not possible in stoats with a smooth unvaried line.

Recording of a male weasel in a Mostela, showing a distinctive pattern in the lateral demarcation line of the dual coloration. (©E. van Maanen)

Polecats are also believed to be in decline in the Netherlands and also follow the vole cycle to a certain degree, although probably less independently than its smaller cousins. Even though a female polecat could easily enter the Mostela in comparison to a sizeable male, we have not yet been able to make such capture. We have been reasonably successful in recording polecats using the so-called Jiggler-method. This is simply a sturdy metal wire bent like a rod with a tea egg attached to the end of it, allowing filling with lure of choice; hence a versatile lure station placed in front of a cameratrap. The method has been particularly successful in attracting and recording pine martens (Martes martes) and Stone or Beech martens (M. foina), as well as other mesocarnivores like badger, genet, wild cat and raccoon.

Martens like this pine marten can be lured to a Jiggler, allowing the throat or ‘bib’ pattern to be recorded for mark-and-recapture and individual recognition. (©E. van Maanen)

Our activities are currently focussed on improving the methodology for recording Small Mustelids in the field, following on more cost-effectivene and ‘smart’ technology (for instance downsizing and modulation of cameratraps) and through gaining more insight into the presence-absence conditions of these animals in relation to habitat qualities. Habitat qualities include first of all a reliable foodbase in space and time, together with the availability of favourable macrohabitat and microhabitat characteristics; respectively low-intensive use natural landscapes and small-scale habitat requirements such as cover and resting and nesting places. The presence of predators (including raptors) and larger mammalian carnivores as competititve ‘enemies’ (through trophic top-down regulation), may be a determinant as well.

Through international collaboration we also seek to share knowledge and exchange experience with ecological studies into Small Mustelids in other parts of Europe. Hence we have started collaboration with other research groups in the United Kingdom, Germany, Poland and in Switzerland.

International collaboration, here with Swiss researchers.

At the conservation level we are concerned at underpinning:

  • reliable indications of population trends in certain areas of the Netherlands;
  • the habitat management needed for more stable populations and fecundity of small mustelids, and;
  • issues like the ecotoxicology of second-generation anticoagulant rodenticides (SGARs), already studied abroad with growing evidence of detrimental effects in raptors and predatory mammals.

At the same time we endeavour further to expose Small Mustelids in the public mainstream as a relatively unknown and ‘forgotten’ species group fulfilling key ecological roles at the lower throphic level, gaining more appreciation and better protection.

Seminar for students by the SKM on Small Mustelids at the University of Cumbria (UK), January 2017.

→ Organisational and contact info

The stoat – having evolved in cool boreal regions – is probably a species sensitive to environmental changes, including the forcing effects of climate change. (©E. van Maanen)