APPROACH TO THE STRANDED DUGONG

Orphaned, injured, entangled or diseased dugongs may be found washed ashore or in shallow water. There are four potential options for dealing with these animals (Woods et al. 2008).

5.1 Treatment and release

Straightforward entanglements in netting or other debris that can be easily removed allow the animal to be released immediately. Minor wounds can be cleaned and debrided. If infected or contaminated, a single dose of a long-acting antibiotic may be considered. If there is any doubt about the overall health of the animal advice should be sought from an experienced marine mammal veterinarian regarding additional assessment and a course of action.

5.2 Rescue and rehabilitation

Rescue for the purposes of rehabilitation requires very careful consideration. Specialised facilities, expertise and a reliable food supply are essential, and rehabilitation is likely to be prolonged and costly. The welfare of the indi­vidual and the ultimate goal of return to the wild must be the highest priorities. If welfare is likely to be compro­mised and the prognosis for release is poor, euthanasia is indicated (see section 5.4.1). Dependent, orphaned calves that need hand-rearing are difficult to rehabilitate and their return to the wild is generally unsuccessful. If a decision is made to take an orphaned calf into care, a permanent care option must be available. Geraci and Lounsbury (1993) suggest that manatee calves captured as dependent young should not be released, as they have not learned important behaviours for avoiding boats or finding refuges during cold weather. There has only been one reported attempt at returning a hand-reared dugong to the wild. After a period of 3 mo in a large natural sea­water lagoon, the animal was released, but 2 mo later it was found in poor body condition and lethargic, with significant tusk rake marks on its back from male dugongs.

Independent, sick or injured animals may be consid­ered for short-term treatment and rehabilitation, provid­ing suitable facilities and expertise are available.

Once fully recovered and fit, dugongs should be screened for infectious diseases before release, to ensure they do not pose a disease risk to free-ranging popula­tions. Recommended screening includes: serologically negative for important contagious diseases such as mor- billivirus, leptospirosis and brucellosis; blood, faecal and nasal cultures to exclude Salmonella, Shigella, Yersinia and Campylobacter spp.; and negative faecal PCR results for Cryptosporidium spp., Campylobacter spp., Salmo­nella spp., Blastocystis hominis, Giardia spp., Dienta­moeba fragilis and Trichomonas spp. Animals should be in ideal body condition and physically and behaviourally capable of surviving in the wild. They must always be released where a free-ranging dugong population exists and ideally the population from which they originated if it is known.

5.3 Relocation

It may be possible to relocate healthy, geographically iso­lated or trapped dugongs (Blyde and Mackie 2017). Occa­sionally, dugongs strand well south of their normal range when water temperatures are too cold and seagrass beds are inadequate or they may become trapped in tidal waterways. Animals that strand when water temperatures are too low may have a better chance of survival if relo­cated to warmer waters. Proposals for relocation should be assessed on a case-by-case basis. Approval to relocate is required from relevant authorities.

5.4 Euthanasia

Given the challenges of rescue, rehabilitation and release of dugongs, euthanasia of stranded animals is a realistic and important consideration to ensure appropriate wel­fare outcomes for individuals.

5.4.1 Criteria for euthanasia

• Disabling injury (deep penetrating wounds, dislocated or broken tailstock or limbs)

• Substantial haemorrhage or discharge from the mouth, genital opening or rectum

• Rectal temperature >42°C

• Blistering and sloughing of >30% of the skin surface

• Loss of major reflexes, loss of tongue withdrawal and jaw tone

• Dependent calf with no mother in sight and no option for permanent care

• Rescue and rehabilitation is not a viable option: no suitable transport options, facilities and expertise una­vailable; or the animal is geographically isolated or difficult to access

5.4.2 Methods for euthanasia

a.

Where practical and safe, shooting into the brain is an effective method of euthanasia. The firearm must possess a high muzzle velocity and jacketed projectiles should be used. Either a dorsal shot or a lateral shot are effective, depending on the position of the animal (Fig. 47.4).

b. Lethal injection

This is the preferred method and should always be per­formed by a veterinarian. The animal should be sedated before euthanasia. Drugs of choice for sedation include tiletamine/zolazepam (5 mg/kg IM), medetomidine (30 μg∕kg IM), diazepam (1 mg/kg IM), xylazine (1 mg/kg

Fig. 47.4. Shooting into the brain is an effective method of euthanasia of dugongs (Dugong dugon). The trajectory required for a dorsal shot is illustrated. Credit: Mark Blyde

IM) or midazolam (0.1 mg/kg IM). They can be used alone or in combination with an analgesic such as butor­phanol (0.1 mg/kg IM). This is particularly important if IP administration of barbiturates is required. These drugs and dose rates should not be used in animals not destined for euthanasia as they may produce profound sedation and respiratory depression. IM injection into the caudal epaxial muscles is the preferred site. The needles must be long enough to pass through the blubber layer and pene­trate the musculature. Venous access is very difficult and has been described above (see section 3.1.1). Pentobarbi­tone can be administered IC or IP following sedation. Needles that are long enough to penetrate the abdominal or thoracic wall are required.

6.