Release of Non-Target Species

A document highlighting the details on this page is available to be viewed, downloaded and printed here – Release of Non-Target Species

Other documents – Reducing Non-Target Captures when Mink Trapping: the use of Water Vole Excluders & Water Vole Excluder Fitting Instructions


The purpose of this project and this guidance is to trap and eradicate mink but mink traps will catch other species in addition to the target mink so the mink trapper will need to be prepared to deal with non-target species in the appropriate, legal and safe manner. Likely species that the mink trapper might encounter in their traps include mammals such as otter, stoat, polecat, ferret and other mustelids, rats, water voles finally birds such as moorhen and water rail.


Some species are protected from killing under wildlife legislation whereas for others it is illegal to release them back into the wild.
Species it is illegal to release and thus must be dispatched if caught in the live trap:

  • North American mink – our target species.
  • Grey squirrel.
  • Black rat (all but extinct in England, only found as transient populations in docks and warehouses).

Mink are the target species for this programme but it is possible to catch grey squirrels. These species should be dispatched using humane methods. Note whilst mink can be dispatched without the use of a comb as they will stand still in the trap, this is unlikely to work for grey squirrel. These species are unlikely to settle in a trap and are likely to require combs to restrict their movement to allow a safe dispatch as per the standard GWCT method.
Note in Scotland and Northern Ireland the brown rat is considered as outside its natural range and should also always be dispatched rather than released.

Legally protected species – these should all be released:

  • Otter.
  • Water vole.
  • Most bird species including the species most likely to be caught – moorhen and water rail.
  • Polecat, which from protected against deliberate trapping. Trappers should avoid setting traps in areas where polecat may be. In addition they are difficult to distinguish between polecat and ferret and thus we strongly suggest that all polecat like animals are released.

Note if otter are likely to be in the area traps are being placed for mink then otter guards should be fitted to all active traps/rafts. This is will not guarantee you won’t catch otters however and young otters can fit between otter guards and have on a very small number of occasions been trapped and then released.

Water vole will often use a raft as a latrine and can repeatedly get trapped. Consider moving a raft to a different location if water vole droppings are seen on a raft or if water voles are repeatedly caught in the same location.


Good guides to the species mentioned above can be found here for mammals and here and for birds here

Safe Release

Many of the non-target species have a powerful bite or sharp claws and as with any wild animal care should be taken handling the trap and releasing the animal. Use the carrying handle to pick up the trap when removing it from the raft tunnel. A metal hook can be useful in removing the trap safely from the raft without getting your fingers anywhere near the mesh of the trap. In addition there is the possibility of disease transmission from the animal so wear disposable gloves whilst working with the trap and then hand washing following release should be undertaken.

With many bye-catch mammals they will chew the trap so opening the trap door can be much more difficult following a capture as door opening wires may have been cut. Thus to prevent getting bitten a comb should be used to restrain the animals in the back of the trap whilst the trap door is safely opened. The animal can then be safely released. In the case of water vole and otter release into the nearby ditch. For other animals and birds open the trap towards adjacent vegetation. Finally keep a spare magnet trigger cord with you as this could also have been chewed by the trapped animal.