Baleen whales: Rewriting the evolutionary history of the largest animals ever

A new discovery from the Museums Victoria Research Institute has fundamentally altered our understanding of the evolution of the largest creatures to have ever roamed the seas – the baleen whales.

This research, led by Dr. James Rule (Monash University and Natural History Museum, London) and Dr. Erich Fitzgerald (Museums Victoria Research Institute), is detailed in their paper, “Giant baleen whales emerged from a cold southern cradle.”

Challenging the narrative of baleen whale evolution

Contrary to the long-held belief that the Ice Age in the Northern Hemisphere, approximately 3 million years ago, was the catalyst for the evolution of massive baleen whales, this new study proposes a different timeline and location.

The researchers discovered that this significant evolutionary step occurred as early as 20 million years ago in the Southern Hemisphere.

This revelation stems from the analysis of a fossil housed in the Museums Victoria collection. This fossil, part of a whale’s lower jaw and dating between 21 to 16 million years old, was discovered in 1921 on the bank of the Murray River in South Australia.

Its significance was realized by Dr. Fitzgerald about a decade ago when he identified it as the largest baleen whale of its time.

Crucial region for whale evolution

Dr. Rule and Dr. Fitzgerald, in collaboration with teams from Australia and New Zealand, demonstrate that whales first evolved into gigantic sizes in the Southern Hemisphere. This region has been home to larger whales throughout their evolutionary history, spanning 20-30 million years.

The research emphasizes the critical role of the Southern Hemisphere, particularly Australia, in understanding whale evolution. Previously, theories were predominantly based on Northern Hemisphere fossils. However, findings like the Murray River whale fossil challenge these notions and contribute to a more globally inclusive understanding of whale evolution.

Dr. Fitzgerald highlights the significance of the Southern Hemisphere and Australia in whale fossil discoveries, stating that such findings are reshaping our comprehension of whale evolution into a more accurate and global perspective.

“The Southern Hemisphere, and Australia in particular, have always been over-looked frontiers for fossil whale discovery,” explains Dr Fitzgerald. “Fossil whale finds in the South, like the Murray River whale, are shaking up the evolution of whales into a more accurate, truly global picture of what was going on in the oceans long ago.”

Extraordinary size of baleen whale evolution

The study also uncovered that the size of a baleen whale’s jaw tip is indicative of its overall body size. The Murray River whale, estimated to be about 9 meters long, was already a significant size 19 million years ago.

Dr. Rule notes that this size was already a third of the length of modern blue whales, which can reach the length of a basketball court.

“The largest whales alive today, such as the blue whale, reach the length of a basketball court,’ says Dr Rule.  “Around 19 million years ago the Murray River whale, at 9 meters long, was already a third of this length. So, baleen whales were well on their way to evolving into ocean giants.”

Several factors contributed to the early evolution of colossal whales in the Southern Hemisphere, including the freezing of Antarctica, changes in ocean currents, and a surge in plankton biomass. This occurred long before these creatures reached similar sizes in the Northern Hemisphere.

Exploring the Australian fossil collection

Museums Victoria Research Institute, home to Australia’s most extensive whale fossil collection, is a leader in whale evolution research. Plans are underway for further research on other whale fossils in the collection.

A key project, “Raising Leviathan,” focuses on whale evolution and involves the local community and citizen scientists in unearthing the largest ever whale fossil found in Melbourne, an unidentified species from Beaumaris.

Lynley Crosswell, CEO of Museums Victoria, comments on the significance of this discovery. She said, “Today’s revelation from Museums Victoria Research Institute and our partners reshapes whale evolution history, affirming our commitment to world-leading research. The Murray River fossil highlights our institute’s role in solving real-world problems, contributing new knowledge, and leading in whale evolution research.”

Implications and future study

Visitors to the Melbourne Museum, the only venue in Australia showcasing the comprehensive story of whale evolution, can view an articulated skeleton of a Blue Whale. This exhibit, part of the museum’s general entry, invites guests to delve into the fascinating chronicle of whale evolution.

In summary, this research from the Museums Victoria Research Institute has challenged our previous understanding of baleen whale evolution. Through the discovery of a fossilized lower jaw and meticulous analysis, scientists have revealed that these colossal creatures began their evolution into ocean giants as early as 20 million years ago in the Southern Hemisphere.

This study highlights the importance of considering the Southern Hemisphere fossil record for a more accurate understanding of whale evolution. The findings have shed new light on the factors driving the evolution of giant baleen whales and have paved the way for further research and exploration in this exciting field.

More about baleen whales

As discussed above, baleen whales, known for their immense size and unique feeding mechanism, are some of the most fascinating creatures inhabiting our oceans. These gentle giants play a vital role in the marine ecosystem.

Characteristics of baleen whales

Baleen whales possess a distinctive feature: baleen plates. These plates, made of keratin, hang from the upper jaw and act as a filter for small prey like krill and plankton. Unlike their toothed whale counterparts, baleen whales do not have teeth.

Among baleen whales, the blue whale holds the title of the largest animal on Earth, measuring up to 100 feet. Other notable species include the humpback whale, known for its acrobatic breaches, and the gray whale, famous for its long migrations.

Baleen whale behavior

Baleen whales employ various feeding strategies. The blue whale uses a method called lunge feeding, where it swiftly swims towards a swarm of krill with its mouth open wide. The humpback whale, on the other hand, uses bubble net feeding, creating a circle of bubbles to trap its prey.

These whales often undertake extensive migrations, traveling thousands of miles between feeding and breeding grounds. For instance, gray whales embark on one of the longest migrations, journeying between the Arctic and Mexican waters.

Communication and social structure

Baleen whales are known for their vocalizations, which serve as communication and, in some species, as a tool for echolocation. The songs of the humpback whale are particularly complex and can last for hours.

While some baleen whales like blue whales are often solitary, others, like the humpback whales, exhibit more social behavior. They can be seen in small groups, especially during breeding seasons.

Conservation status and threats

Many baleen whale species face threats from human activities. Commercial whaling, though significantly reduced, has had a lasting impact on their populations. Today, they also face threats from entanglement in fishing gear, ship strikes, and climate change.

International efforts, such as those by the International Whaling Commission, aim to protect baleen whales. Marine protected areas and regulations on shipping and fishing also contribute to their conservation.

Role of baleen whales in the ecosystem

Baleen whales play a crucial role in the marine ecosystem. Their feeding habits help regulate the populations of krill and small fish. Additionally, their excrement is a significant source of nutrients for marine life, contributing to the ocean’s health.

In summary, baleen whales, with their immense size and unique characteristics, are a marvel of the natural world. Understanding their behavior, threats they face, and their ecological importance helps us appreciate and protect these majestic creatures of the ocean.

The full study was published in the journal Proceedings of the Royal Society B Biological Sciences.

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