DUGONG
14.1 Capture and physical restraint
Capture of free-ranging dugongs (Dugong dugon) is difficult because they are entirely aquatic, cryptic and secretive, are often found in murky and remote habitats and have large body size (up to 400 kg).
A variety of methods such as hoop or seine nets, and the ‘dermal hold-fast’ technique (Fuentes et al. 2013) have been used, particularly in remote areas. Most, however have low success and poor welfare outcomes for the animals.A ‘rodeo method’ used to capture free-ranging dugongs in shallow open water has proven more successful with better welfare outcomes (Lanyon et al. 2006) (Fig. 9.14). The method involves close pursuit of a dugong by boat. The dugong is caught around the peduncle region by a catcher leaping off the boat, then restrained at the water surface by several people while data are collected. No ropes or nets are used. For more detailed examination and sampling, dugongs are moved onto a mesh stretcher in the water then craned onto a boat deck. They are placed on a padded open-cell foam mattress to cushion their body mass and reduce pressure on internal organs. There is no need for additional physical restraint as they do not move and remain calm. This capture and handling method does not appear to result in acute capture stress (Lanyon et al. 2010; Lanyon et al. 2012).
Dugongs can be held out of water for several hours. Intermittent spraying with water prevents hyperthermia and the skin drying, although their skin is much more resistant to drying than that of cetaceans. They are prone
Fig. 9.14. A dugong (Dugong dugon) being captured using the 'rodeo method'. Operators prepare to leap onto the animal.
to hypopnoea or apnoea when removed from water and close monitoring of respiratory parameters (rate, ETCO2) are essential.
ETCO2 can be monitored via a face mask placed loosely over the nostrils with a capnometer attached. If hypopnoeic or apnoeic, dousing the head or snout with water or running a slow trickle over the snout will stimulate breathing. If respiration does not improve and ETCO2 remains elevated the animal should be returned to the water (D Blyde pers. comm.).Serum lactate levels in dugongs caught by the ‘rodeo method’ and restrained out of water ranged from 24.2 to
52.3 mmol/L (Lanyon et al. 2015), which are generally higher than in manatees (0.5-37 mmol∕L caught by nets and restrained on land (Wong et al. 2012). This suggests that restrained dugongs may benefit from supplemental oxygen administered via a nasal tube or face mask and maintenance of regular respirations to avoid respiratory acidosis (D Blyde pers. comm.).
14.2 Chemical restraint
The unique anatomy, physiology and aquatic environment of dugongs make sedation and anaesthesia challenging. There are no reports of chemical restraint of dugongs. If required, extrapolation from methods used on manatees may be used (Woods et al. 2008; Nolan and Walsh 2014). However, there are anatomical and physiological differences between dugongs and manatees (Blyde 2023). IM injections are given in the epaxial muscles, shoulder or caudal neck cranial to the shoulders.
15.