The feasibility of the translocation and introduction of red squirrels (Sciurus vulgaris) as a population reinforcement tactic is being investigated in a series of five release studies in a 1700-ha Red Squirrel Reserve in Thetford Forest, East Anglia, UK. A soft-release method using a 1-ha pre-release pen is being used. The protocols developed and the results of the first four studies have been described.1 This paper describes the health of the squirrels involved in two of the studies, number three (the experimental study) and number four (the follow-up study). In the third study, 23 red squirrels were translocated from two sites in the north of England to Thetford. The health of each squirrel was examined under inhalational anaesthesia using isoflurane (IsoFlo, Mallinckrodt Veterinary, Uxbridge, UK) prior to release. Lactated Ringers’ solution was administered subcutaneously, and tick infestations were treated with ivermectin (MSD AgVet, Hoddesdon, UK) diluted in propylene glycol at approximately 200 µg/kg body weight in 18 animals. One juvenile male died prior to the induction of anaesthesia but no pathologic lesions were found on postmortem examination. Nine squirrels were recaptured 18 days after release for a health examination; they were in good physical condition and had maintained body weight (±20 g). After 33 days in the pre-release pen, one female was found dead, and a postmortem examination did not reveal the cause of death. Four squirrels escaped from the pre-release pen after three days due to vandalism, but the remaining 17 squirrels were successfully released into the Reserve. In the follow-up study (number four), which took place 24 days after the third study, eight animals from different sources were placed in the pre-release pen but all died over the following 28 days from a disease associated with parapoxvirus infection before release into the Reserve. Parapoxvirus infection may cause significant mortality in red squirrel populations and the translocation of squirrels may increase the likelihood of epidemics of infection. Proposals for translocations and the reinforcement of populations must take account of the risk of parapoxvirus infection.
1. Venning, T., A.W. Sainsbury, and J. Gurnell. 1997. Red squirrel translocation and population reinforcement as a conservation tactic. In: Gurnell, J., and P.W.W. Lurz, eds. The Conservation of Red Squirrels, Sciurus vulgaris L. Peoples Trust for Endangered Species. London. Pp 133–143.