|“||The giant whales have arrived! Forget the gentle filter feeders of the 21st century. These days, every whale is a killer.||”|
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The Beasts Within
Whale Killer is the second episode of Walking with Beasts series. It takes place at the end of the Eocene-start of the Oligocene epochs. This is a time of an extinction event so unlike the previous episode, which was featured on the beginning of mammal evolution in general, the episode shows extinction of many first (archaic) mammal families instead.
This episode introduces Basilosaurus, an ancient type of whale (Archaeoceti). Basilosaurus became the new king of the ocean after the giant Marine Reptiles of the Mesozoic died out (see Cruel Sea). It was much bigger than the sharks it shared the ocean with, and it regularly ate the sharks. However, Basilosaurus was still less advanced than the modern species of whale; it still had rear flippers (that helped it during the mating) and lacked the blubber and the 'melon' organ of the modern cetaceans, so it couldn't "sing" - instead it emitted high-pitched sounds.
At the same time, this program depicted the beginning of 'climate chaos' - a relatively minor extinction event between Eocene and Oligocene, also known as "The Great Cut".
On land mammals too have become big and huge. This episode featured brontotheres (Embolotherium) and Andrewsarchus, a mammal that was considered to be a Mesonychid when Whale Killer was aired, but now is considered to be a closer relative to the Entelodonts. Both were much bigger than the land mammals featured in New Dawn episode, but their brains were still small and their behavior - primitive. They were the first true mammal rulers of the land and most of them would die out during "The Great Cut".
As the El Nino continues and the extinction event is beginning, the female Basilosaurus is forced to change her hunting ground from open seas to mangrove swamps (the future Sahara desert). There she encounters small sharks, Apidium, and Moeritherium. A shark eats an Apidium but is too small to attack Moeritherium. The female Basilosaurus attack a Moeritherium but she miscalculates the tides' height and runs aground. Eventually, she manages to escape, but the Moeritherium is long gone.
Embolotherium continue to strive, but a high percentage of their calves is being still-born. Two Andrewsarchus steal such a calf, but begin to fight over it in order to determine which of them gets to eat it first. The calf's mother decides that the calf is alive and fights off the Andrewsarchus - for a time. (Note that in book version the Andrewsarchus managed to steal the calf and eat it instead.)
The female Basilosaurus discovers a lagoon where a smaller species of ancient whale called Dorudon are beginning to calf. At first the smaller whales use their numbers' advantage to chase away the giant, but the female Basilosaurus eventually returns and begins to hunt and devour Dorudon calves - and this time the adults can't stop her.
Several months later Basilosaurus gives birth to her own calf, but the episode ends saying that both the mother and child are doomed to perish - but whales as a group will survive.
Both Basilosaurus and Dorudon are Archaeoceti, an ancient group of whales that are not direct of ancestors of the modern cetaceans. They are descendants of Ambulocetus from the previous episode, but only distant ones. Archaeoceti could only live in shallow tropical seas of the Paleogene and when they began to disappear, so did those ancient whales as narrated in the episode.
Both Embolotherium and Andrewsarchus represented ancient terrestrial mammal lineages that evolved directly from the Paleocene Epoch. These mammals were often large and strong (in fact, they were Earth's first mammal megafauna), but their brains were primitive as was their behavior - and so they died out when the climate conditions of Earth changed and they could not adapt: they needed too much of a too specific sort of food, for example.
Apidium represented the next stage in primate evolution. They were flat-nosed monkeys, and though they lived millions of years ago before their modern cousins they were very similar to them: they were diurnal, social animals with family bonds that lived in groups and could adjust their behavior to changing conditions (like the rising tide), which means that they were able to adapt and evolve into new species, unlike Embolotherium, Andrewsarchus and Moeritherium.
Moeretherium was featured in this episode as an early species of elephant; in reality, it was more of a side branch on the elephants' evolutionary tree. In many ways it was more like a modern tapir or hippopotamus and was no relation to the modern elephants. They probably evolved from a mammal such as Paleomastodon, which lived alongside Moeritherium in late Eocene Africa, but on land.