What do migrating humpback whales get up to at resting points on their long journey? Australian researchers have shone some light on this by analysing the animals’ behaviours at two key stopovers on the country’s east coast.
Resting and socialising appeared to be important, but there were also differences in how the whales (Megaptera novaeangliae) used the areas.
“Overall, our results suggest that the Gold Coast bay provides habitat for a wide range of critical humpback whale activities,” says senior researcher Olaf Meynecke from Griffith University, “in particular for resting mother-calf pairs, mature whales seeking copulation and socialising immature whales.”
In line with previous reports, it seemed Hervey Bay is most important for resting, nursing and courtship, with more mother-calf pair sightings and shallower waters not as conducive to competition between males.
The observations, reported in the journal Marine and Freshwater Research by lead author Sarah McCulloch and colleagues, confirm the zones serve important functions and should be considered whale protection areas.
This is vital in light of myriad challenges facing the magnanimous marine animals.
“Global environmental changes, including increases in water temperature and decreases in sea ice cover, and anthropogenic threats, such as water and noise pollution, entanglements and ship strikes, are affecting cetacean species worldwide,” the team writes.
As migratory species, the whales are particularly vulnerable, heightening the need to understand their use of safe havens along the way for rest, feeding, reproduction, breeding and calving.
“What behaviours are they performing there, what forms of socialisation are they engaging in, and how important are these behaviours for their fitness and survival?” asks McCulloch.
It’s estimated that around 30,000 humpback whales migrate along Australia’s east coast each year from high-latitude feeding habitats to low-latitude breeding areas.
To explore their use of this coastline, the researchers analysed 5400 records devotedly collected by researchers, citizen scientists, and whale watchers between 2011 and 2018 – representing 1432 hours’ work over 672 days – to understand what the animals were doing.
Behaviours such as breaching and flippering suggest communication between individual whales or pods, for instance, as well as lobtailing, fluke slapping and pectoral fin slapping. Head lunges, peduncle slaps and tail thrashing can reflect competition and other agonistic intentions, while social behaviours include rolling over, belly up and pectoral fin wave.
Resting is particularly important for lactating mothers, who spend more than a third of their time conserving energy to maintain body composition and feed their calves.
This is the first time humpback whale behaviour has been used to compare habitat use of two resting areas, according to Meynecke.
“The work demonstrates that long-term citizen science data can make significant contributions to better understand the species habitat preferences,” he says. “Our study also shows that humpback whales need a variety of stopovers during their annual migration to socialise, rest and mate.”
The study has particular relevance for disruptive human activities in those regions, such as whale-watching tours, increased tourism, commercial fisheries and shark nets, which the authors say should be factored into management and conservation strategies.