Ask Dr Dazza | Dolphins

Dolphins!!!! Let’s celebrate the announcement of the 17^th NRL team with a discussion about dolphins. Dolphins (along with whales) belong to a group of animals called Cetaceans. They are descendants of hippopotamus-like animals.

There are two species that are residents in the Moreton Bay Region – the Australian humpback dolphin and the bottlenose dolphin. These two species can be distinguished visually by the fact that the former is light grey and has a shorter dorsal fin, while the latter has a much higher dorsal fin and is dark grey in colour. Both species can occur throughout Moreton Bay, but they have different habitat preferences.

Australian humpback dolphins associate with inshore habitats and are common on the western side of Moreton Bay. Bramble Bay is one of their favourite locations. Moreton Bay contains the southernmost population of this species on the Australian east coast. The species was thought to be the same as the one that occurs widely throughout south-east Asia, but it is now known to only occur in Australia. It’s as unique as the koala! The population in Moreton Bay consists of somewhere between 100 and 160 animals. This is small in absolute terms, but large for the species in relative terms. The population of Indo-Pacific humpback dolphins in Moreton Bay is discrete, with limited genetic mixing with populations elsewhere.

Bottlenose dolphins in South East Queensland region prefer the central and eastern side of Moreton Bay and Point Lookout – although they can occur anywhere. The bottlenose dolphins at Point Lookout form large schools and constitute a discrete community with very small home ranges. The bottlenose dolphin population at Point Lookout is the largest resident population of the species in the world and is estimated to number between 700 and 1000 animals.

Dolphins are a sacred totem for the Quandamooka people of Moreton Bay and are called Buangan by them. Prior to European arrival, dolphins and Quandamooka cooperatively hunted together for sea mullet and other species.

Dolphins are a focus of eco-tourism activities in Moreton Bay (and elsewhere). Such activities have been shown to have negative effects on dolphins; in particular, food provisioning can result in increased mortality rates through mothers neglecting their calves, resulting in calf malnourishment and death by disease or shark bite. While regulated feeding activities at Moreton Island have not been implicated in negative impacts, there are concerns that unregulated feeding activities, such as those that occur at Amity Point, may result in negative impacts on dolphins in Moreton Bay, as has been documented elsewhere.

Coastal dolphins are particularly vulnerable to the exposure and accumulation of contaminants as a result of them being resident in an area, long lifespan, position within the food chain and large fat repositories that can serve as deposits for contaminants. The effect of such contamination is not known with certainty, although impacts on health are likely.