Understanding population dynamics of feral horses in the Tuan and Toolara State Forest for successful long-term population management

The study of any wild animal’s home range requires the collection of spatiotemporal data, obtained independently of climatic conditions or time of day. This can be achieved by the attachment of Global Position System (GPS) data loggers, which, in large species, is best achieved by remote immobilisation. Feral horses (Equus caballus) usually occupy remote areas of Australia, however a considerable population increase has been observed in a close proximity to metropolitan areas of the Australian east coast, creating increasing conflict with human interests. The aim of this study was to investigate the efficacy of remote chemical immobilisation of feral horses with medetomidine combined with tiletamine-zolazepam to facilitate placement of satellite GPS collars. Nine feral horses were darted from the ground with 60 mg of medetomidine and 1500 mg of tiletaminezolazepam. The effects of medetomidine were reversed with 50-100 mg of atipamezole 30-40 minutes post induction (IV/IM). Physiological variables monitored during anaesthesia were heart rate, respiratory rate, temperature and oxygen haemoglobin saturation (SpO2). All horses were successfully immobilised with between one and three darts (n = 9). The mean dose of medetomidine was 0.15 ± 0.01 mg kg (SEM) and tiletamine-zolazepam was 3.61 ± 0.16 mg kg. Mean time from darting to lateral recumbency was 13 ± 2.7 min, and mean recumbency time was 54 ± 13 min. Vital signs for all anaesthetised animals remained within normal range during anaesthesia, with the exception of one animal displaying a transient drop in SpO2. No mortalities were encountered. The combination of medetomidine and tiletamine-zolazepam provided