Scottish Animal Welfare Commission - trapping of terrestrial wild mammals using snares: position paper

Animal welfare impacts of snares

The WAWC review refers to the most widely recognised method of assessing the welfare of individual animals - the Five Domains model (1) (2). 

This model provides a framework for organising scientifically derived information to assess what it might be like to be a certain animal in a particular situation or condition. According to this characterisation of welfare, physical wellbeing and mental or psychological wellbeing are not separable, but are inherently and inextricably linked.

The model consists of four physical (or functional or ‘fitness’) domains, where scientific information, such as behaviour indicators, physiological indicators, clinical signs, biological indicators and patho-physiology, is collated to try and understand the mental experiences and, therefore, the welfare state of the animal.

The physical domains are:

• domain 1: information about the animal’s nutritional and hydration status
• domain 2: information about its physical environment, such as substrate, air quality or temperature
• domain 3: the animal’s health or functional status, including disease or injury or other functional impairment
• domain 4: the animal’s behavioural interaction with components of its environment. This includes interactions with and perceptions of other animals, including human beings

The body of information, collated in domains 1 to 4, is used in domain 5 to infer the mental experiences that the animal might be having and that matter to it, as these are the experiences most relevant to the animal’s welfare state. This process of inference is a cautious one, but is supported by existing knowledge about how mental experiences are generated by the animal’s nervous system. 

Based on the Five Domains model, welfare harms associated with snaring may include:

• domain 1 (nutritional impacts): being caught in a snare prevents the animal eating and drinking normally. This may lead to dehydration and starvation
• domain 2 (environmental impacts): depending on where the snare is positioned and the weather conditions, the trapped animal may experience exposure to the elements
• domain 3 (physical impacts): trapped animals suffer a variety of external and internal injuries (3). Struggling to escape the snare may result in exertional or capture myopathy (4) (5) (6) and there are numerous references to capture myopathy in the latest edition of the international guide to mammal trapping (7). Escape behaviour may also include self-mutilation and, in rabbits, tonic immobility (8). Oral and dental injuries may arise as a result of trying to chew free from the snare (9). Predation or injury of the trapped animal may occur (10). Death may result from exhaustion or from asphyxiation as a result of strangulation (11). The size and conformation of non-target species caught in a snare can influence the injuries sustained (12), which includes target species trapped in the wrong size of snare (for example a fox caught in a rabbit snare and vice versa)
• domain 4 (behavioural impacts): normal behaviours are restricted or cannot be performed. These may include feeding, moving, lying down, caring for dependent young, escaping from predators. Attempts to escape can lead to self-trauma. Sites where animals have been caught in snares may show signs of extreme disturbance to the surrounding ground and vegetation (a ‘doughnut’), where the animal has tried to run, jump or scrabble its way out of the trap, often for several hours or more (13). The behaviour of different species caught in a snare can be varied and influence the range of injuries sustained
• domain 5 (mental impacts): these can include fear and distress (14), anxiety, pain, hunger and thirst, breathlessness and stress associated with trying to escape from the snare

The speed at which welfare begins to be impacted is rapid (seconds from the moment of restraint) and suffering can be prolonged due to the lengthy intervals between inspections. Some animals die in snares, but the expectation is that animals remain alive until the snare is inspected, at which point they should be humanely killed, or released unharmed, if a non-target species.

At present, the law in Scotland (section 11B of the Wildlife and Countryside Act 1981) only requires that snares be inspected at least once every day at intervals of no more than 24 hours.

The use of stops on snares is intended to reduce the severity of injuries and prevent snared animals from being strangled. Snare loops vary in minimum size, depending on the species targeted, and in some instances the stop can prove ineffective (15), depending on the size and body conformation of the trapped animal, resulting in increased injury and possible death by strangulation. In both target and non-target animals the snare may ‘hold’ and significantly injure the animal around body parts other than the neck, resulting in a range of traumatic injuries (16). A free-running snare may also easily become self-locking due to rusting or twisting, causing injury or death by strangulation before the trap is inspected. Where injuries were caused to badgers caught in stopped restraints, 62% of restraints had some degree of twisting, unravelling or fraying after use, and that damage was associated with an increased risk of injury (17).

Although a swivel is thought to mitigate the risk of twisting and locking, in practice swivels near the anchor can become tangled with vegetation and so allow the snare to lock. The Game and Wildlife Conservation Trust recommends the inclusion of another ‘in-line’ swivel fitted midway along the snare, thus ensuring the snare always includes at least one functional swivel and the cable does not unravel or become over-wound (18).