The Fascinating Upside-Down Resting Behavior of Southern Right Whales

Along the southern shorelines of Australia, a remarkable sight can be witnessed during this time of the year - southern right whales (Eubalaena australis) swimming in the shallow waters. These ocean giants have migrated from the Southern Ocean and Antarctica to breed, give birth, and rest. One intriguing behavior observed in these whales is their tendency to rest upside-down, a phenomenon not reported in other large whales.

Initially, this behavior may seem perplexing, leading one to assume that the animal is sick or injured. However, research suggests that this behavior is actually an indicator of a healthy mother carefully managing her energy reserves during one of the most energetically demanding periods of her life. Southern right whales migrate long distances, exceeding 6,000 kilometers, and do not feed when they are on the calving grounds in Australia, relying on stored energy in their blubber.

To better understand this behavior, researchers employed drones to film the behaviors of whales along the Great Australian Bight. Hundreds of drone flights captured hours of footage of the whales nursing and resting, revealing that mothers with newborns require the largest amount of energy. The observed upside-down resting behavior sparked interest, as it was only exhibited by mothers with newborn calves and one mother in the late stages of pregnancy.

Approximately 25% of the observed mothers rested upside-down, suggesting a link to the energetic demands of reproduction. When these mothers rested in this position, they did so for roughly 19% of the time they were followed. Two possible reasons for this behavior are that it helps mothers regulate milk production and prevent overheating. By lying upside-down at the surface and exposing their belly and pectoral fins to the sea breeze, they may be increasing the surface area of skin in contact with the cool air, helping to regulate their body temperature.

However, this behavior also places southern right whales in a vulnerable position, as rotating the right way up is a challenging task, especially for an animal weighing over 40 tonnes. Understanding unique behaviors such as upside-down resting is crucial, particularly as southern right whale populations stall and are yet to recover from historical whaling. Conservation efforts and further research are necessary to protect these magnificent creatures and their habitats.

The history of southern right whales is marked by intense hunting, with populations severely depleted by the early 20th century. Although commercial whaling is no longer a significant threat, other human activities, such as ship strikes and entanglement in fishing gear, continue to impact these whales. As we strive to protect and conserve southern right whales, it is essential to recognize the importance of preserving their habitats and migration routes, ensuring the long-term survival of these incredible animals.