REPRODUCTION
Dugongs are long-lived (>70 yr) and females do not reach sexual maturity until aged 10-17 yr. Females are polyovular and polyoestrous and may undergo several sterile cycles before conceiving (Marsh 1989).
Gestation is ~13 mo. Pregnancy can be diagnosed by ultrasound examination, faecal progesterone metabolite concentrations and body morphometrics (Burgess et al. 2012a). Faecal progesterone metabolite concentrations >1000 ng/g, maximum girth >215 cm, anal girth >126 cm and teat length >5 cm are consistent with pregnancy. Serum prolactin levels have proven useful in diagnosing pregnancy in Florida manatees (Trichechus manatus Iati- rostris) (Nau et al. 2017) and may be useful in dugongs. The tusks (upper incisors) of males erupt when body length reaches 240-260 cm at between 6 and 12 yr of age when they become sexually mature (Burgess et al. 2012b). Males fight using their tusks as weapons and can inflict significant injuries to other dugongs when competing for females or food. The GnRH agonist deslorelin (Suprelorin, Virbac, Milpera, NSW) has been used in a male dugong in an attempt to reduce testosterone levels and aggression. Dosages of 9.4 mg and 15.6 mg IM were ineffective in reducing testosterone levels, sperm production and aggression (Burgess et al. 2013).2.
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