Island Weirdness #31 – Tiny Elephants On Parade Part 2: Flores

Much like Japan, ancient Flores had a succession of dwarf stegodontids – close relatives of modern elephants that were capable of island-hopping through Indonesia by swimming.

A stylized illustration of an extinct dwarf elephant. It has curved tusks, small ears, and very proportionaly short stumpy legs.
Stegodon sondaari

Stegodon sondaari lived on Flores during the Early Pleistocene, about 900,000 years ago, and was the size of a small water buffalo at just 1.2m (3′11″) tall at the shoulder. It was probably descended from the larger Stegodon trigonocephalus, known from Java, and it had proportionally short legs which may have been an adaptation to clambering over rough terrain and steep inclines.

Around 850,000 years ago Stegodon sondaari disappeared from Flores, probably due to a large volcanic eruption, but a new wave of stegodontids quickly recolonized the island. The mid-sized Stegodon florensis probably originated from either Java to the west or Sulawesi to the north, and eventually evolved into a new dwarfed subspecies.

A stylized illustration of an extinct dwarf elephant. It has long gently curving tusks and small ears.
Stegodon florensis insularis

Stegodon florensis insularis wasn’t quite as small as its predecessor, standing around 1.8m tall (5′10″). It probably didn’t shrink quite so much due to the existing presence of various predators on Flores, since it was likely the main prey of large Komodo dragons, it was hunted by Homo floresiensis, and it may also have been occasionally targeted by giant storks.

It seems to have disappeared around the same time as several other unique endemic species, between 50,000 and 20,000 years ago, due to either climate change, another volcanic eruption, or the arrival of modern humans – or perhaps a combination of all of those factors.

And that’s all for this month… but Island Weirdness will be back later for part 2, with more giants, more dwarfs, and so many elephants.

Island Weirdness #30 – Homo floresiensis

The most surprising resident of ancient Flores would have to be Homo floresiensis, a species of archaic humans nicknamed “hobbits” due to their unusually small stature.

Standing at an adult height of about 1.1m tall (3′7″), they were smaller than any population of modern humans and are thought to represent an unusual case of insular dwarfism.

They also had much smaller brains than would be expected for their size, similarly to the miniature hippos of Madagascar, which was probably an energy-saving adaptation in an island environment with limited resources, since brains are metabolically expensive organs. An area of their brains associated with higher cognition was about the same size as in modern humans, however, so they weren’t necessarily less intelligent – stone tools and butchery marks on dwarf elephant bones suggest they were cooperatively hunting, and there’s also possible evidence of fire use for cooking.

It’s not clear exactly where they belong on the human family tree, and attempts at extracting DNA from the known remains have so far failed. They might be descendants of a population of Homo erectus who arrived on Flores about 1 million years ago, or they may even have been part of a much older unknown lineage that dispersed from Africa over 2 million years ago.

Although they were initially thought to have lived on Flores from 190,000 years ago up to about 12,000 years ago, more accurate dating of the cave where their skeletal remains were discovered suggests they actually disappeared about 50,000 years ago – about the same time that modern humans arrived on the island.

Island Weirdness #29 – Leptoptilos robustus

Indonesia is located at the junction between several tectonic plates, and as a result a large number of volcanic islands make up the region. While some of these islands have had land connections to Asia or Australia in the past, others are separated by deep ocean trenches and have been isolated with little movement of species between them.

The island of Flores in the southeastern Lesser Sunda archipelago was formed fairly recently – sometime in the last 15 million years – and has been home to some highly unusual endemic species, including dwarf elephants, giant rats, Komodo dragons, and diminutive “hobbits”.

Leptoptilos robustus was a huge stork, closely related to the living marabou and adjutants but estimated to have been at least 20% larger. It would have stood around 1.8m tall (5′10″) and had a chunkier build with unusually heavy thick-walled bones, suggesting it may have become functionally flightless. Only fragmentary arm bones were found, however, so its unknown whether its wings were reduced in size or not.

There were few large carnivorous mammals on Flores (possibly none), and Leptoptilos robustus would have had little competition for carrion and prey. It may even have filled an ecological niche similar to the giant Hatzegopteryx of Cretaceous Hațeg Island – a large terrestrial stalking predator eating any smaller animals unfortunate enough to fit into its mouth.

The known remains date to the Late Pleistocene, around 50,000 to 20,000 years ago, and this giant bird seems to have gone extinct sometime during that date range. It’s unclear what killed it off, but possible factors include a changing climate on the island, a major volcanic eruption, and the arrival of modern humans.