Wolf Depredation
4. Verifying Wolf Kills
A verified wolf kill means that the death of an animal was investigated by an agency independent of livestock producers and confirmed as killed by a wolf. Verified kills are the most reliable objective gauge of depredation. However, although verified losses are likely to be true, they are criticised as recording only minimum losses. Some field research suggests that unconfirmed (non-verified) wolf kills might be six times the number of verified kills (Bjorge et al 1985). Until this issue is clarified the number of verified versus unconfirmed wolf kills will remain a controversial issue.
Why should verified losses only record minimum losses? Because depredation is rarely seen when it happens. It is not always possible to confirm livestock animals are depredated when they go missing because usually the only evidence comes from the kill site and...
- The site may not be found - rugged or forested terrain may be too difficult to search
- Carcasses inevitably break up and scatter - so the evidence is destroyed.
- Carcasses may be totally eaten - so ditto.
- Carcasses may be too decomposed - so ditto.
Furthermore, verified totals do not necessarily take into account other important factors, such as injured livestock or stress-induced abortions, which are harmful to livestock interests.
The rest of this page briefly touches on an important issue of verification, specifically, how can you know an animal was killed by a wolf.
Verifying A Wolf Kill
How do you know a wolf killed an animal? You do not know - unless you find a wolf with a smoking gun bending over the corpse. So you have to build up evidence bit by bit and make a judgement. The more knowledge and experience you have, the more likely you may be right.
Examine The Surroundings:
Search the ground for paw marks and hairs. You can distinguish wolf prints from those of other predators but not from large dog prints. Examine hairs under a microscope for the species they belong to.
Distinguish Depredation From Scavenging:
Animals scavenged by wolves are already dead, having died from other causes, such as ill health, accident or other predators. So look for indications that a struggle took place: that the prey animal was grappled alive. Haemorrhages beneath the skin - on the neck, throat, back or hindquarters - indicate a struggle, because only live animals bleed when bitten.
Identify Signs Of Different Predators:
Distinguish depredation by wolves from other predators. The combination of certain wounds suggest a wolf:
- Bites and large jagged wounds on flanks, hindquarters and upper shoulders of large livestock, like cattle and horses
- Bites on head, neck, throat, back and hindquarters of small livestock, like sheep and calves
- Size and spacing of puncture wounds on the carcass matching the diameter and spacing of wolf canines
- Signs of feeding on viscera and hindquarters
- Broken and chewed limb bones
- Carcass almost totally consumed or torn apart and scatted by successive feedings
- Large prey eaten on site and smaller ones dragged a short distance from the kill site.
Handling & Feeding Patterns:
Each predator species has to some extent a distinctive method for tackling prey and feeding on them. Judiciously use these differences as clues:
May leave claw marks causing bleeding below the skin. They often drag their prey away to eat and then cover the carcass with earth and vegetation.
Tend to go for the throat of sheep and lambs, clamping down on the windpipe or severing the jugular vein. Often leave multiple tooth marks on the throat, whereas wolves tend to clamp only once and hold on. Coyotes sometimes drag their prey away to feed on them.
Typically attack several sheep in a flock. They bite the back, flanks, rear and hind legs of sheep, causing abundant multiple wounds. Unless the dogs are feral they often leave their quarry uneaten.
Leave their distinctive paw marks and faeces. They may peel back the skin of their prey, tend to go for muscle rather than organs, and may eat the udder.
Bite and break poultry bones but not the heavier sheep bones. May bite lambs and kids on the throat and sometimes bite the neck and back several times.
Leave distinctive talon puncture marks - not to be mistaken for teeth marks. Eagles tend to skin carcasses, eat the brains and leave the skeletons of large prey intact. They may also leave feathers and droppings at the site.
What about theft?
Weigh Up The Evidence:
Finally, marshal your inferences and make a judgement. Experts cannot always establish the cause of death and you may have to come to a decision with whatever clues you have.
© Wolf Trust 2004. All rights reserved.