Kumimanu is an extinct genus of giant penguin that lived roughly 60 million years ago and just a few million years after the extinction of the non-avian dinosaurs.
How big Kumimanu penguins?
The genus Kumimanu includes two different species. The largest, Kumimanu fordycei, was described as recently as 2023. This particularly large species is known from parts of a spine, shoulder blade, knee, and leg, and an almost complete right arm.
From these fossils, researchers (which included researchers from the University of Cambridge) have estimated that Kumimanu fordycei weighed nearly 160kg and may have stood taller than an average human (>1.7m).
The other known species of Kumimanu, Kumimanu biceae, wasn’t quite as heavy as its close cousin, though it may have been taller. Some estimate its height at around 1.77m, meaning it would have stood shoulder-to-shoulder with Hollywood hardman Jason Statham.
Where did Kumimanu live?
Both species of Kumimanu are known from fossils discovered on the South Island of New Zealand, specifically from the southern region of Otago.
By the time that Kumimanu appeared in the Paleocene, New Zealand had drifted away from Australia and, like today, was its own, independent island ecosystem. However, unlike today, it lay a lot further south and most of it was covered by shallow seas, swamps, and low-lying land.
These kinds of habitats, along with a subtropical environment, provided the perfect conditions for some of the earliest penguins, including giant forms like Kumimanu.
Kumimanu lived on the beaches of New Zealand’s South Island and swam along its shores. It likely lived alongside several other early penguins, including another large species known as Petradyptes stonehousei.
This species was described in the same 2023 study that described Kumimanu fordycei and while it may be 100kg lighter than this particular giant, it’s still estimated to have stood taller than an emperor penguin - the largest penguin alive today.
What did Kumimanu eat?
Like today’s penguins, Kumimanu was flightless and hunted exclusively underwater.
However, a close inspection of the bones that make up Kumimanu’s arms revealed that it may have retained some ancestral features that were once necessary for flight, but were suboptimal for swimming. This means that it may not have been quite as agile underwater as its living descendants.
Nevertheless, researchers think Kumimanu had a very similar diet to today’s penguins and was also capable of hunting fast and slippery prey, such as fish and squid. Kumimanu’s long, pointed beak - an adaptation shared by many extinct and extant penguins - would have helped it in its pursuit of this kind of prey.
Based on its large size, some think Kumimanu may have been capable of hunting larger prey than today’s penguins.
Some of the largest fish preyed upon by penguins today are cod, which grow to an average length of 1m. This in mind, Kumimanu may have hunted fish that were closer to 1.5m in length, or even bigger.
How did giant penguins evolve?
Not long after penguins evolved in New Zealand and Antarctica 62 million years ago, they achieved giant body sizes. It’s thought this happened a few million years after their ancestors, who likely swam on the water’s surface before diving, lost their ability to fly and swapped their wings for flippers.
While losing their ability to fly meant that early penguins could no longer hunt from the air, it did mean they could start to experiment with larger body sizes, as they no longer needed to support their own weight during take off and flight.
There are a number of advantages to being big, particularly in the environments where early penguins lived, and it’s these advantages that likely set them on the evolutionary path towards gigantism.
By carrying a few extra pounds, these giant penguins were able to hunt larger prey than other, smaller penguins, save energy when diving, and better insulate themselves in cold water. This particular advantage may have helped early penguins spread from warmer environments in New Zealand to colder environments further south and closer to Antarctica.
Kumimanu wasn’t the only giant penguin from prehistory; Palaeeudyptes klekowskii, the aptly-named ‘Mega Penguin’, may have been even taller, standing 2m tall according to some estimates. While Palaeeudyptes klekowskii may own the title of ‘tallest penguin ever’, it was nowhere near as heavy as Kumimanu, weighing in at just 116kg.
Palaeeudyptes klekowskii lived a few million years after Kumimanu in the Late Eocene (around 35 million years ago) and is known from an extensive collection of fossils discovered on Seymour Island, a tiny island near the northernmost tip of Antarctica.
Why did Kumimanu and other giant penguins become extinct?
For more than 40 million years, giant penguins thrived on the coasts of New Zealand, Antarctica, and even Peru, but by 20 million years ago they had disappeared.
It’s unclear exactly what caused the extinction of these giants, though researchers think it may have had something to do with the arrival of some new predators.
Around the same time that giant penguins faced extinction, seals started spreading across the southern hemisphere. As a group, seals (or pinnipeds) evolved in the Late Oligocene (~24 million years ago) in Arctic Canada, but they quickly made their way south and into the lands of the giant penguins.
These travelling seals would have directly competed with giant penguins, not just for food but territory too. It’s thought they may have also preyed on giant penguins, particularly their chicks.
The disappearance of giant penguins also coincides with the dispersal of squalodontids, or shark-toothed dolphins, and other primitive, fish-eating toothed whales.
The smaller species of penguins that lived alongside their larger cousins would have no doubt faced similar pressures from these new ecological competitors, but they ultimately weathered this particular storm and gave rise to modern penguins, roughly 14 million years ago.
What’s the largest penguin alive today?
The largest penguin alive today, the emperor penguin (Aptenodytes forsteri), can grow up to 1.3m tall and weigh up to 45kg.
While this places them sixth on the list of largest living birds - dwarfed only by the emu, the cassowary (northern and southern), and the ostrich (Somali and common) - they’re dwarfs compared to the likes of Kumimanu and other giant penguins from prehistory.
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Still, Kumimanu is far from the largest bird of all time. That particular title goes to Aepyornis maximus, a species of elephant bird that lived in Madagascar during the last ice age and only faced extinction in 1000 AD. This giant reached heights of 3m and weighed nearly a ton.
Illustration of the giant extinct penguin Kumimanu fordycei towering over other extinct penguins that were the same size as modern-day emperor penguins. Image credit: Dr Simone Giovanardi.