Early calving of East Australian humpback whales (Megaptera novaeangliae) outside of historic calving grounds

Humpback whales (Megaptera novaeangliae) undertake an annual migration from polar feeding areas to tropical and subtropical areas to calve and breed. It is believed that the purpose of this migration is to increase the... [ view full abstract ]

Humpback whales (Megaptera novaeangliae) undertake an annual migration from polar feeding areas to tropical and subtropical areas to calve and breed. It is believed that the purpose of this migration is to increase the survival and growth of calves by relieving them from the energetic demands of thermoregulation in a polar environment. Calving grounds of humpback whale populations around the world share similar characteristics. Warm water appears to be an important factor determining suitable calving areas, with consistent temperatures of at least 21°C. Shallow, sheltered inshore waters are also desirable traits of a calving area, to provide the calves with protection from predators and rough conditions through their most vulnerable period of development.
Significant shifts have been recorded in ocean circulation patterns in recent years, with changes observed in the strength and location of currents and other hydrodynamic features, and these trends are predicted to continue. It is likely that these altered environmental conditions will result in a shift in the distribution of humpback whale habitats, as they move to areas with more desirable conditions for feeding and calving. The locations of Southern Ocean fronts, where dense concentrations of krill can be found, are predicted to shift poleward as a result of climate change, forcing cetaceans to migrate further to reach these important feeding grounds. However, impacts on energy budgets could be avoided if warming subtropical waters allow for calving at higher latitudes.
This presentation documents the observations of a number of young calves (neonates) off the Gold Coast, Australia, born while on the northern migration, prior to arriving on the traditional calving grounds (located in the Great Barrier Reef region and further to the north). Identification photos were taken onboard commercial whale watching vessels in July and August 2013 and 2014, with a total of 30 neonates observed travelling north in over these periods. Surveys will be repeated in 2015. It is predicted that the number of calves born in the Gold Coast bay and to the south will increase as waters continue to warm, resulting in the expansion of the calving grounds of this population.