Mammals of the Great Barrier Reef | Cairns Tours

Mammals of the Great Barrier Reef

By James Dixon | 27th February 2015

Of the hundreds of marine species that inhabit the warm tropical waters of the Great Barrier Reef, some of the most spectacular are the marine mammals, who use the Reef to engage in beautiful courtship rituals before mating, and where they give birth to and raise their calves. While whales and dolphins may have some physical characteristics similar to fish, whales and dolphins are warm-blooded mammals that breathe air with their lungs, and suckle their young.


Entering the sheltered waters of the Great Barrier Reef from June, regular sightings of a range of stunning mammals can be seen until late October. Bottlenose, Irrawaddy, and Spinner dolphins frolic in the crystal clear waters of the Reef, alongside Humpback, Minke, and Shortfinned Pilot whales. Offshore, in the deeper waters of the Reef, is where you will encounter Orcas, Striped dolphins, Sperm whales, Fraser’s dolphins, Pygmy Sperm and Killer whales.

The observation vessels, which are in abundance during the season, are operated by well-trained instructors, who closely heed the distance restrictions put in place for the care and protection of these giants of the sea. While these intelligent and fascinating creatures are easily observed from these distances, the inquisitive mammals have been known to gently approach boats and divers with open curiosity. Those fortunate enough to experience this wonderful phenomenon have described it as a truly spiritual encounter.

Environmental Concerns

The greatest threats to our giant mammals are a combination of being netted and killed by tuna anglers, swallowing or becoming entangled in discarded plastic waste, and chemical pollution. While more than half a million dolphins were killed in 1974 – primarily through being caught in the nets of tuna fishermen – dolphin mortalities have decreased in more recent times with the advent of smaller nets with adaptations allowing dolphins to escape. Of great concern however is the estimated 100,000 tonnes of plastic fishing material that is lost or discarded at sea per annum worldwide. Add to that the estimated figure of 450,000 plastic containers that are dumped at sea every day and the ocean becomes a death trap for our giant mammals. Toxic chemical pollution from sewerage run off – as well as waste from ships and industrial facilities – continues to cause great harm to the reproductive cycles of our ocean mammals, as well as compromised immune systems, and direct mortalities.

Restrictions on whaling and stringent rules regarding the netting of dolphins have helped conserve these beautiful creatures, but continued diligence is required to ensure our giant mammals of the sea avoid extinction