Chemical immobilization of free-ranging Fallow deer in Northers Italy: a retrospective observational study

Induction time is the most important factor when considering wildlife immobilization, and it can widely depend on breed, sex, age class, anaesthesiologic protocol and needle length. The goal of every conservation-veterinary intervention, with a remote drug-delivery system, is to balance the depth and quickness of the anaesthetic protocol, to allow a concise and immediate recovery of the animal to minimize stress, risk of injury and to ensure clinical monitoring as soon as possible. A retrospective observational study was conducted in order to describe the relationship between the upon cited parameters and induction time in 64 free-ranging fallow deer (Dama dama; 32 males and 32 females) in Northern Italy, while captured for management purposes from 30 hectares fenced area, from December 2021 to May 2022. Two Daninject 11 mm dart guns were used with 3ml dart syringes and 2.0 mm x 40 mm or 2.0 mm x 30 mm needles, depending on animals and seasonality. A Wiener Mischung protocol was administered based on an estimation of the animals’ weight (3 mg/kg tiletamine-zolazepam and 3 mg/kg xylazine). The dosage used for adult males was 1.5 ml, for subadult males 1 ml, for adult females 1.1 ml and for subadult females 0.9 ml. Induction time varied between age classes and sex, averaging (minutes) for adult males as 7.6±3.2, subadults males 11.1±3.2, adult females 9.5±1.4 and subadult females 12.3±0.3. No issues with induction, transport and awakening are to be reported. Although the small number of animals per group does not allow us to statistically evaluate the relationship between induction time and sex or age group, we can hypothesize their influence. Moreover, an appropriate experimental design is needed to investigate the relationship between induction time and sex or age group, in order to permit for a better use of the anaesthetic protocol itself and a smoother and safe immobilization procedure.