Abstract
Apex predators live at the top of an ecological pyramid, preying on animals in the pyramid below and normally immune from predation themselves. Apex predators are often, but not always, the largest animals of their kind. The living killer whale Orcinus orca is an apex predator in modern world oceans. Here we focus on an earlier apex predator, the late Eocene archaeocete Basilosaurus isis from Wadi Al Hitan in Egypt, and show from stomach contents that it fed on smaller whales (juvenile Dorudon atrox) and large fishes (Pycnodus mokattamensis). Our observations, the first direct evidence of diet in Basilosaurus isis, confirm a predator-prey relationship of the two most frequently found fossil whales in Wadi Al-Hitan, B. isis and D. atrox. This extends our understanding of their paleoecology. Late Eocene Basilosaurus isis, late Miocene Livyatan melvillei, and modern Orcinus orca are three marine apex predators known from relatively short intervals of time. Little is known about whales as apex predators through much of the Cenozoic era, and whales as apex predators deserve more attention than they have received.
Highlights
The modern killer whale Orcinus orca has a global distribution in the world’s oceans
During excavation we found the remains of sharks, a nice prearticular dentition of the large bony fish Pycnodus mokattamensis, and numerous subadult remains of the smaller basilosaurid archaeocete Dorudon atrox, all mixed with bones of the skeleton of the larger Basilosaurus isis
The WH 10001 Basilosaurus excavation preserves evidence of four large vertebrate species found together: (1) a single adult skeleton of the large archaeocete Basilosaurus isis (Figs 3 and 4), with no duplication of parts indicating more than one individual; (2) thirteen skeletal elements of the medium-sized archaeocete Dorudon atrox (Fig 6), with duplicated supraorbital portions of right frontals indicating that a minimum of two juvenile skeletons are present; (3) the prearticular dentition of at least one pycnodontid bony fish Pycnodus mokattamensis; and (4) one tooth of the large lamnid shark Carcharocles sokolowi
Summary
The modern killer whale Orcinus orca has a global distribution in the world’s oceans. 6 to 8 meters in length, are apex (top) predators in the world’s oceans. They feed on a variety of invertebrate and vertebrate animals including squids, sharks, bony fishes, turtles, seabirds, and other marine mammals. Orcas are known to attack, kill, and eat the largest of the toothed whales, the sperm whale Physeter macrocephalus [5], though sperm whales outweigh orcas by a factor of 10 (15 vs 1.5 metric tonnes). To do this orcas cooperate and attack in groups [5, 6, 7]. Orcas are known to attack and kill a variety of sharks, including the great white shark
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