World Whale Day 2025
Humpback whale (Megaptera novaeangliae) captured from one of the midwater BRUVS in Niue (2024).
To begin, Cetacea is the scientific group name for whales, dolphins, and porpoises. All dolphins are whales (in fact, toothed whales) and there are 90 different species of whales that are divided into two categories, baleen and toothed whales. There are 40 dolphin species grouped into 6 families, including species commonly mistaken as whales, such as the killer and pilot whale according to the International Fund for Animal Welfare (IFAW).
Dolphins inhabit a global wide range of habitats: oceans, seas, freshwater rivers and lakes. They can be found in tropical coral reefs to temperate waters, kelp forests, and icy arctic waters. Since dolphins can’t breathe underwater, they must come up for air at least every 10-15 minutes, though they surface on average every 2-3 minutes. Living in complex social groups known as pods, dolphins engage in cooperative hunting, communicate through vocalizations and body language, and form strong social bonds within their pods. Dolphins primarily feed on fish, squid, and occasionally crustaceans while using echolocation to locate and hunt their prey. Their feeding habits help maintain ecological balance within the ocean’s ecosystem and regulate prey populations, preventing the overabundance of certain species. Dolphin’s conservation status ranges from least concern to critically endangered.
Indo-Pacific Bottlenose Dolphins (Tursiops aduncus) are the most common dolphin species around Perth and are present year-round from the Shoalwater Islands to Monkey Mia. Their distribution has also been confirmed in estuarine and coastal waters of eastern, northern, and southern Australia as well as inhabiting the greater Indo-Pacific region. Even by the Swan River, dolphins tend to gather where the water is deep, and they can easily herd schools of fish. Other types of dolphins seen in WA include the Australian Humpback Dolphin (Sousa sahulensis), Snubfin Dolphin (Orcaella heinsohni), Short-beaked Common Dolphin (Dephinus delphis), Striped Dolphin (Stenella coeruleoalba), and the largest member of the dolphin family, the killer whale or also known as the Orca (Orcinus orca). Several threats facing dolphins include entanglements in fishing gear (including gillnets, trawls, and longlines) from commercial fishing practices, habitat loss, pollution, bycatch, and climate change. Research suggests over 300,000 whales and dolphins are killed by industrial fishing each year as dolphins struggle to free themselves which lead to injuries, stress, or suffocation. Ocean pollution in the form of plastic debris, chemical pollutants, pesticides, and oil spills can have detrimental and fatal effects leading to internal injuries, blockages, malnutrition, and lowered health and reproductive success. As dolphins heavily rely on echolocation and vocalization for communication, navigation, and hunting, increasing levels of non-natural noises coming from ship traffic, commercial fishing, and sonar operations, can interfere and disrupt their behavior. Additionally, dolphins’ habitats (coastal areas, estuaries, rivers, lakes, and open ocean) are all threatened by human activities through coastal development, dredging, and dam construction, leading to fragmentation and degradation of their habitats. Ultimately, climate change poses significant challenges to all marine wildlife through rising sea temperatures affecting distribution and behavior, changes in sea level and storm patterns exacerbating coastal erosion and habitat loss, and large tidal fluctuations leading to an increase in strandings.
According to the Australian Government’s Department of Climate Change, Energy, the Environment and Water, Australian waters are home to 45 species of whales, dolphins, and porpoises. While some of these species are permanent residents in Australian waters, others are occasional visitors, migrating from their summer feeding grounds in the Antarctic to the warmer waters of Australia in the winter to raise their calves. For whale watching in Perth, the two main species of whales sighted off Perth’s coastline are the Blue Whale and Humpback Whale. From April to May, you can see the endangered blue whale in the Perth Canyon and from August to December, you can see the humpback migration off the sheltered Perth coastline which provide a resting and socializing ground for the visiting humpbacks. Blue whales are the largest mammal known, including of any known dinosaurs, and rely heavily on the feeding grounds located in the Perth Canyon. Humpback whales are known for their energetic and acrobatic displays as they breach as well as their beautiful vocalizations which travel vast distances. In fact, researchers detected word-like elements from humpback whale recordings in New Caledonia, showing how humpback whale song shares the same structure of making human languages learnable through shorter sounds rather than complex. Seen in Exmouth, Broome, and up to the Kimberley, humpback whales will rest and nurse there, and overall, the WA coastline is a well-established annual migration route for the WA humpback whale population.
Other species that have been sighted in WA include the Southern Right Whales, Sperm Whales, Beaked Whales, and Minke Whales. Unlike toothed whales, baleen whales (humpbacks, minkes, and right whales), have bristles and are known to engage in filter feeding. Baleen whales primarily consume krill, plankton, and small fish (include herring, salmon, and mackerel) whereas toothed whales like the sperm whale generally consumes squid, sharks, rays, and skates.
Concluding with the largest member of the dolphin family and an exceptionally successful predator, the Orca will generally occupy the same home range year-round and can be spotted from as far north as the Arctic Ocean to as far south as the Antarctic Ocean. On the IUCN Red List of Threatened species, Orcas are considered Data Deficient as they cover so many different habitats, their population status is difficult to assess.
Although the Orca prefers colder waters, they’ve been observed in tropical waters and will move to other areas when food becomes scarce. Additionally, the Orca is known to prey at depths of 20 to 60 meters (m) but will also visit shallow waters along coastlines and can dive down to 300 m in search of food. During the nursing period, Orca mothers teach their calves to hunt and show their offspring how to socialize within their pods, so the calf relies on its mother for nutrition and support before claiming their independence. Similarly to wolves and lions, the Orca is a social hunter.
Orcas are highly social, travelling in pods containing as many as 50 individuals which generally stem from multiple generations. Within the pod, they could share prey and rarely leave the pod for more than a few hours. Moving on to Orca’s vocalizations for communication and navigation, there are 3 categories: whistles, discrete calls, and clicks. Whistles and discrete calls are used for communicating within and among pods and each pod is distinct from sounding slightly different from that of other pods. An Orca pod has a distinct dialect that can stay constant in a pod for up to six generations. Meanwhile, clicks are used only for echolocation. Like other toothed whales, the Orca uses sonar to navigate within their aquatic environment. The Orca’s diet includes a wide variety of large preys: seals, sea lions, whales and dolphins, fish, sharks, squid, octopi, sea turtles, sea birds, otters, and more. According to the Whale and Dolphin Conservation (WDC), a significant threat affecting Orcas are whaling, as seen by several countries like Greenland, Japan, and Indonesia which hunt and kill Orcas. Another threat is the capture of Orcas for human entertainment by taking Orcas away from their family pods and being sent to marine parks.
Pollution and entanglement and bycatch in fishing gear, as mentioned previously, are additional pertinent threats. Toxic chemicals from plastics, litter, and oil spills harm health and reproductive success and when Orcas along with other cetaceans accidentally get caught in fishing nets and lines, they not only get injured but can die in the nets. Anthropogenic marine noise also causes stress and interferes with whale and dolphin communication, such as with seismic surveys.
Through marine protected areas (MPAs) we can stop commercial whaling, minimum use and disposal of fishing gear responsibility, prevent marine pollution, slower vessel speeds, less anthropogenic noise in the oceans, stronger regulations distancing people from marine wildlife, which will all ultimately create healthy seas for all the dolphins, whales, and marine wildlife to survive and thrive in.
Written by Scarlett Blydenburgh (MFL MSc student)