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

Abstract

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 wildcaught 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.

KEY WORDS:

• Behaviour
• brushtail possum
• humaneness
• pathology
• phosphorus paste
• vertebrate poison
• welfare

Acknowledgements

This work was funded by a Foundation for Research, Science and Technology grant. We thank Bruce Warburton, Penny Fisher, and Christine Bezar for helpful comments on the draft manuscript.