Indo-Pacific Bottlenose Dolphin
- Females – 40 years
- Males – 30 -35 years
- An average size adult is 2.4 m long and weighs 155 kg.
- Common in their range
- Protected by the Wildlife Conservation Act 1950
- 12 months gestation
- Females have one calf about once every 4 years
- Females can have 8 calves in her lifetime
- Calf stays with the mother for 3-5 years
- Females may first calf at around age 10-12
- Males may not mate successfully until much later because of intense competition for access to females
- Females have a network of female friends
- Males usually bond closely to one other and form a long-term partnership known as an ‘alliance’
- After weaning, juvenile dolphins spend several years learning about their environment and the dolphin society they inhabit. During these years, they learn important social and feeding skills that they will need to survive as adults.
Home range in the Swan Canning Riverpark
- The ‘Swan’ dolphins split their time between the estuary and coastal areas such as Owen Anchorage.
- They are often seen in the Canning River and some will occasionally travel into the upper reaches of the Swan River.
- Dolphin Watch volunteers can help us determine how far they travel upstream.
- The dolphins most commonly seen in the Riverpark use the year-round and are thought to be long-term residents. It is likely that their mothers were also ‘river’ dolphins.
- In Shark Bay bottlenose dolphins use a feeding technique called “sponging”. To “sponge’, dolphins take a marine sponges off the sea floor and wear it on their beak (rostrum). The sponge provides protection while they probe around on the bottom for fish hidden in sand or under rocks.
- Until recently, all bottlenose dolphins were considered members of one species. Now, scientists recognize two species: the Common Bottlenose Dolphin (Tursiops truncatus) and the Indo-Pacific Bottlenose Dolphin (Tursiops aduncus). In southwestern WA, Common Bottlenose Dolphins are generally found well offshore, while Indo-Pacific Bottlenose Dolphin occur in coastal and estuarine areas.
- In coastal and estuarine areas, bottlenose dolphins are generally observed in small groups of less than ten dolphins. In the open ocean, groups may number to the hundreds.
- Scientists identify dolphins by permanent marks on their dorsal fins. These markings are scars and allow for dolphins to be monitored across their life-times.
- River Guardians’ members can become Dolphin Watch volunteers learn how to monitor dolphins in the rivers.
- Murdoch and Curtin universities work together with the Swan River Trust to monitor dolphins in the rivers.
- River Guardians’ members can become Dolphin Watch volunteers and learn how to monitor dolphins in the rivers www.riverguardians.com
Threats to dolphins
- Dolphins live stressful lives. And adult needs to find more than 12-15kg of a fish a day and they are on constant look-out for sharks. A female also has to look after a dependent calf for 3-5 years.
- Human add to the stress that dolphins experience and so the best thing we can do is leave them alone and let them do what they need to do.
Threats to dolphins include:
- entanglement in discarded fishing line
- health effects from some contaminants
- loss of habitat and declines in food species
- poor water quality from nutrient contamination
- toxic algal blooms
- disturbance from boat traffic
- excessive underwater noise
- people illegally feeding dolphins which can lead to boat strike and entanglement
Image Delphine Chabanne