Main Club –2 August 2024
Dr Holly Raudino is a senior research scientist in the Department of Biodiversity, Conservation and Attractions (DBCA) Marine Science program. Her interests are whales and dolphins off the coast of Western Australia (WA). Her PhD, through Murdoch University, was on the Bunbury Bottlenose Dolphins. She talked about how marine mammals are faring in a changing world.
Holly covered eight species in her talk: the Australian Snubfin Dolphin, the Australian Humpback Dolphin, the Bottlenose Dolphin, the Dugong, the Australian Sea Lion, the Humpback Whale, the Pygmy Blue Whale, and the Long-finned Pilot Whale.
Snubfin Dolphins and Humpback Dolphins are nominated to be listed as vulnerable on the Environment Protection and Biodiversity Conservation (EPBC) threatened species list. As distinct from the familiar and more common Bottlenose Dolphins, these two species are found in more northerly, tropical waters.
We have heard of mass strandings of Long-finned Pilot Whales. The possible causes of this phenomenon have been investigated by testing for a range of diseases. It is possible that Salmonella may have contributed to the strandings. New research is planned on wild, free-ranging, Long-finned Pilot Whales by taking “blow samples”, in which samples of condensation and DNA are taken from the air exhaled from the blowholes, using either poles or drones. The Bremer Canyon is the only place these whales have been found in big concentrations. They form maternal groups, staying with a matriarch, and only mate when different pods meet.
Australian Sea Lions have an unusual 18-month reproductive cycle, and only one pup is born at a time. About 40 to 60 pups are born each breeding season at the largest colonies near Jurien Bay. Their range is only from the Abrolhos to the Recherche Archipelago and part of the SA coast. Research is helped by Aboriginal sea rangers counting pups (Pups don’t move until after they moult) and by tagging. Population growth is limited by entanglement in fishing gear, disease, parasites, human disturbance and Climate Change.
The tourist activity of swimming with Humpback Whales may help people identify with the natural world, but is it disturbing them? Current studies on the distribution of this species and changes over time may help to answer this question.
Dugongs occur from the east coast of Africa to the Red Sea, Southeast Asia, New Guinea and northern Australia. In aerial surveys in Shark Bay, where they graze on sea grasses, dugongs are visible even when they are underwater. Surveys every five years show a relatively stable population despite the seagrasses not having quite recovered from the marine heatwave around 2010-11. Dugongs can suppress reproduction when food is scarce.
Holly gave us an idea of the diversity of marine mammals in Australian waters, some of which were unfamiliar to us, and an idea of the range of ingenious techniques that have been developed to help research the biology of these wonderful animals.
Mike Gregson