Eagle involvement in accumulation of the Taung child fauna

1. What they did

The Taung child, found in 1924 at a lime quarry near Taung, South Africa, was the first ape-man fossil ever discovered. The bones found with it are unusual: almost all are of small animals, and many skulls are damaged. Early scientists, including Raymond Dart, believed the ape-men themselves had hunted these animals and smashed their skulls. Later researchers suggested a leopard, other carnivores or water had brought the bones together.

Berger and Clarke tested a different idea: that a large eagle collected the Taung bones, including the child. They reviewed the history of the Taung fauna and the hunting and feeding habits of three large African eagles: the crowned, martial and black eagles. They compared the Taung bones with bone collections from beneath modern eagle nests, and with published lists from hyena and leopard lairs. Then they looked for eagle feeding damage on the fossil skulls.

2. What they found

Size of the animals

• The Taung fauna is dominated by small species of under 2 kg. Every animal over 20 kg is known only from isolated fragments, which could have been carried in already dismembered, as eagles do with large prey.
• The other South African ape-man sites (Sterkfontein, Makapansgat, Swartkrans) are dominated by large species, like modern leopard and hyena lairs.
• At four South African crowned eagle nest sites, small mammals made up over 40% of species, and over 50% at three of them. That pattern matches Taung.
• Of 87 antelope bones from crowned eagle nests, 91% were from young animals.

Condition of the skulls

• Many Taung skulls are fairly complete, and some, including the Taung child, still have the lower jaw attached.
• There are no carnivore tooth marks, no porcupine gnaw marks and no “eaten out” antelope carcasses.
• Leopards and hyenas almost always chew skulls, and leopards usually separate the lower jaw. Articulated skulls with jaws are often found beneath eagle nests.

Eagle-type damage on the fossils

• Several fossil baboon skulls have holes punched through the braincase, depressed flaps of bone about 1 cm wide, removed skull bases, and v-shaped nicks along broken edges.
• These match talon and beak damage on modern monkey, baboon and hyrax skulls from beneath eagle nests.
• On the Taung child’s skull, fragments of the braincase appear to be pushed into the natural brain cast, a depression like those eagles make.
• The damage could not have come from rockfall, because the caverns formed in tufa with no rock falls.

Other clues

• Tortoise shells without carnivore damage: black and martial eagles take tortoises, and a pair of golden eagles took 84 in 119 days, dropping them from 30–60 m.
• Large bird eggshells, described as “the size of a goose egg”, suggest large birds nested nearby.
• In over 70 years of searching, including nearly 6 years of intensive excavation, no other hominin has been found at Taung, unlike the other ape-man sites.
• The bones are in pristine condition and there are no rounded stream cobbles, which argues against water carrying them far.

The eagles

• Crowned eagle: wingspan often over 1.9 m. Takes antelope up to 30 kg (bushbuck), and primates are favoured prey. It can lift prey heavier than itself, and dismembers and caches heavy prey. One attacked a 7-year-old child of about 20 kg in Zambia, and part of a child’s skull was found in a nest in Zimbabwe. Usually nests in tall trees (12–30 m), sometimes on cliffs.
• Martial eagle: Africa’s largest eagle, wingspan over 2.5 m. Takes monitor lizards, game birds, hares, mongooses and small antelope. Has nested in potholes in cliffs in Angola.
• Black eagle: wingspan about 2 m. Hyraxes can make up as much as 98% of its prey, but it also takes vervet monkeys, young baboons, bushbabies, small antelope up to about 15 kg, and tortoises. It nests on rock ledges and in small caves, sometimes for over 30 years. At Gladysvale in 1992, about 50 scientists watched a pair feed on a blesbok ram that had apparently been killed by a leopard, showing how scavenging can add large-animal bones to an eagle collection.
• Black eagle feeding: it eats from the head and breaks through the palate to the brain. For large hyraxes, often only the skull, a few vertebrae and the pelvis remain.

3. What they concluded

• The size of the animals and the damage to the Taung bones fit a large eagle, not any known mammal bone collector.
• The authors suggest a large eagle killed and collected the Taung child and much of the fauna. The crowned eagle is a likely candidate: nyala in the fauna suggest a wetter, more wooded past at Taung that could have suited a forest eagle. An extinct eagle species is also possible.
• Not every Taung fossil need come from eagles; other agents may have contributed.
• The authors expect that no adult ape-man will ever be found in these deposits, and that the collection of the Taung child was most likely a one-off event.
• Studying the fossil eggshells might identify the eagle.

4. How tracking was or was not used

The study rests on reading feeding signs on bones. No tracks or trailing were involved. The authors compared the damage on the fossils with feeding damage on bones from beneath modern eagle nests and with published descriptions of leopard, hyena and porcupine damage. The signs they used:

• Eagle signs: holes and depressed fractures in the braincase from talons; skull bases removed to reach the brain; crushed skulls and distorted jaws; v-shaped nicks from the beak along broken edges; skulls left whole with the lower jaw still attached.
• Signs ruled out: carnivore tooth scars and punctures, chewed ends of long bones, chewed jaws, “eaten out” antelope carcasses (leopard and hyena); chisel-shaped gnaw marks (porcupine).
• Damage from other causes: blasting at the quarry and the chipping of the rock around the fossils by tools during preparation.
• Other signs: tortoise shells without carnivore damage; large eggshells; one field observation of eagles scavenging a leopard kill.

5. Tracker or observer certification

Not reported. The authors are palaeoanthropologists, and no qualification in tracks and signs interpretation is described. The conclusions rest on their reading of bone damage.

7. Implications for conservation (from the paper)

None stated. The paper is about the fossil record, and it shows how large eagles act as major predators of primates and small antelope, a role similar to that of medium-sized carnivores.