Along the vast southern ribs, the humpback whales further punctuate the seasons cycle by their spectacular migrations. Known to give birth in the hot northern waters, they nevertheless seem to upset the established rules. In recent years, the birth of humpback whales has been documented much further south than expected, even in the temperate waters of Tasmania. This discovery raises questions about the influence of the climate, but also on what we thought of knowing the habits of these seas giants.
These discoveries, from a patient collection of data by researchers, Whale-Watching operators and government agencies, include births up to 43 ° southern latitude, as in Port Arthur in Tasmania. These observations question the rule that reproduction is confined to tropical waters. Vanessa Pirotta, biologist at Macquarie University and co -author of the study, advances several hypotheses. Perhaps this phenomenon already existed without anyone noting it, or the waters of the South are now hot enough to allow births.
Since 1900, the surface temperatures of the seas around Australia have increased on average by 1.08 ° C, with a more marked warming in the southeast of the country and in Tasmania, according to the Australian agency CSIRO. This warming could make these temperate areas more welcoming for females ready to put low, pushing the limits of the “tropical cradle” historically accepted.
The birth of humpback whales in temperate waters exposes newborns to new risks
Giving birth earlier on the migratory journey is potentially to spare part of the mother's trip. But for the whale, this can also mean a longer journey in a period of great vulnerability. Humans frequent more temperate regions, often more agitated and potentially more dangerous than the relative sweetness of tropical areas.
Young whales are due to face a series of threats: collisions with ships, tangle in fishing nets, intense sound pollution, not to mention natural predators. Angus Henderson, a researcher at the University of Tasmania, recalls that the demographic resumption of whales since the end of industrial hunting has increased the probability of conflicts with human activities. And as the Guardian points out, the multiplication of births in the south increases the vigilance area necessary to protect these little ones, already fragile by nature.
A whale born in Tasmania must travel up to 2,300 km to reach the large coral barrier. This extended journey increases exposure to human disturbances. Certain photos collected for the study also show injuries of indeterminate origin on newborns observed in the open sea.
The current protection framework is no longer enough to follow this shift towards the south
If these births in the temperate zone are no longer exceptions, the management of their protection must evolve. However, as the authors of the study recall, most of the Australian and New Zealand jurisdictions still do not recognize temperate regions such as putting down habitats. As a result, maritime regulations (speed of ships, approach distance, net surveillance) remain calibrated for tropical areas.
This legislative discrepancy creates a void that weakens young cetaceans. Especially since the majority of these observations come from players in the field, such as photographers, sea guides or tourist boats passengers. These citizens, often better placed than institutions to identify rapid developments, have become precious allies for science.
Global warming may not explain everything, but it acts as a revealer of the inadequacy between old models and new realities. The time has come to fully integrate these new areas into the conservation devices. Baby whales will not wait until the cards are updated to be born where they can.
