Strategic animal welfare issues: ethical and animal welfare issues arising from the killing of wildlife for disease control and environmental reasons.

Ethical and animal welfare concerns about the destruction of free-living wildlife for disease control and environmental reasons have historically received little attention from animal welfare scientists, legislators or the public. Nevertheless, all vertebrates can experience pain and distress, regardless of whether they are unwanted pests or not. A wide range of methods is used to kill or otherwise control unwanted wildlife. The animal welfare impacts of most of these methods are not known. The extremely high number of animals being controlled and the potential impacts of this control on their welfare suggest that this is a significant strategic issue that should be considered by the World Organisation for Animal Health (OIE). This is particularly important, given the focus of the OIE on disease control and the requirement for pest control as a part of this process.

Behavioural, biochemical, and pathological responses of possums (Trichosurus vulpecula) poisoned with phosphorus paste.

AIM: To investigate the behavioural, biochemical and pathological responses of possums following poisoning with phosphorus paste, in order to assess the implications for the welfare of possums. METHODS: After ingestion of phosphorus paste by wild-caught possums (18 high dose, nine low dose, and 12 non-poisoned controls), behavioural observations were made at 15-min intervals for 24 h or until death. Serum biochemistry, and gross and microscopic pathology were assessed at 3-hourly intervals in a further 21 possums. RESULTS: Possums that ingested phosphorus paste developed an abnormal posture (high incidence of crouching after 4-8 h), mild congestion of the gastric mucosa, and elevated levels of creatine kinase (CK) in serum after 3-6 h. Retching was observed in 67% possums, and 44% vomited at least once. Possums were prostrate from about 18 h after eating the poison, and the response to handling, an indicator of consciousness, was lost at about 24 h, followed by death at 25 h. CONCLUSION: The main welfare concern was the possibility of discomfort or pain caused by the congestion of the gastric mucosa, as indicated by the crouched posture adopted by poisoned possums. Retching and vomiting may also have caused pain and distress. The degree of pain or discomfort would depend on the degree of congestion of the gastric mucosa, which was typically mild, and on the duration and severity of retching and vomiting, which were typically short and mild. Possums remained conscious until 1 h before death, implying that they were able to experience pain and distress from the effects of ingestion of phosphorus for almost the entire period of illness, which lasted for approximately one day.

Individual variation in corticosterone secretion in laying hens.

1. Plasma corticosterone responses to a handling and isolation stressor were measured in laying hens once, before two groups were mixed into a single larger group, and again after the groups were mixed. Hens were bled before the stressor was applied and within 3 min of removal from groups (0 min sample), and again 15 and 45 min later 2. Social interactions were recorded throughout the experiment using continuous, all-occurrences sampling during group observations and the social rank index of each hen was calculated. 3. Plasma corticosterone was low immediately after birds were first picked up and sampled on each occasion, and rose to a peak after repeated handling, 15 min later. It then declined and was almost back to basal levels 40 min after first handling. 4. Corticosterone responses were greater 6 d before mixing (first day of sampling) than they were 1, 7 or 21 d after mixing. Corticosterone concentrations and responses were not elevated 1 d after the two groups of hens were mixed. 5. Variation in corticosterone concentrations and responses within and between hens was quantified by calculating coefficients of variation of corticosterone concentrations and areas under corticosterone response curves. Variation tended to be less within than between hens. 6. There was a transient increase in aggressive interactions immediately after mixing. One bird was clearly dominant in each observed dyadic interaction and hierarchies tended to strong linearity in all groups. Social rank was not related to corticosterone concentrations or responses. 7. Area under the corticosterone response curve can be used to compare differences between and within laying hens in their responsiveness to a handling and isolation stressor.

Animal welfare and ethical issues relevant to the humane control of vertebrate pests.

Vertebrate pests and pest control impact on people, animals and the environment, so any ethical consideration of vertebrate pest control must incorporate the interests of all three. The necessity of intervention, whether it involves killing animals or not, must be properly evaluated. Justification for pest control is only tenable if all of the negative impacts (harms) on people, animals and the environment are minimised and all of the positive impacts (benefits) are maximised as far as can be feasibly achieved. In all cases, the most humane control methods possible must be used; we must actively seek ways to improve the humaneness of existing methods and to find new methods that are more humane. There are six major principles that guide the design and execution of ethically sound vertebrate pest control programmes. (1) The aims or benefits and the harms of each control programme must be clear. (2) Control must only be undertaken if the aims can be achieved. (3) The methods that most effectively achieve the aims of the control programme must be used. (4) The methods must be applied in the best possible way. (5) Whether or not each control programme actually achieved its precise aim must be assessed. (6) Once the desired aims or benefits have been achieved, steps must be taken to maintain the beneficial state. An ideal pest control method would be effective and easy to use, affordable, safe for human users and for people exposed to it, humane, specific to the target species or individuals, and safe for the environment. Although such a gold standard is difficult to achieve, we can only retain ethical credibility if we conscientiously strive to make incremental improvements towards that gold standard.

Effect of potassium cyanide on behaviour and time to death in possums.

AIM: To assess the sickness behaviours of possums after eating a lethal dose of potassium cyanide. METHOD: Spontaneous behaviour and the time to loss of physical responses were examined. RESULTS: Cyanide ingestion caused a short-lasting period of mild respiratory stimulation. There was no salivation, retching or vomiting. Convulsions occurred in 73% of the possums. After the ingestion of cyanide, the average time to onset of ataxia was 3 minutes, the average time to overall loss of consciousness was 6.5 minutes, and the time to cessation of breathing was 18 minutes. CONCLUSION: Cyanide is a rapid-acting toxin with few undesirable signs from the welfare perspective.