A long tunnel cave — about 1.5 kilometres in length — filled with hundreds of thousands of animal bones. No, this is not the opening scene of an Indiana Jones movie. The Umm Jirsan lava tube situated in Saudi Arabia has a collection of bones of wolves, camels, foxes, horses, hyenas, bats, cattle, and even three human cranial or skull remains. A new study published last month notes that these bones were collected by striped hyenas over a period of about 7,000 years.
The site was first investigated in 2007 and extensive studies on 1,917 bones and teeth showed that there were about 40 individuals representing 14 taxa. Radiocarbon dating revealed that the animals lived about 439 to 6,839 years ago.
But how do we know striped hyenas brought it?
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Wolves, striped hyenas, and foxes have similar dietary preferences, but their feeding behaviours are different. Wolves usually eat their prey at kill sites and feed their pups by regurgitating the previously ingested meat. But striped hyenas and red foxes are avid hoarders of bones. Striped hyenas are also known to loot human gravesites, and several human cranial remains have been found near their dens. They keep these bones to be eaten during times of food scarcity or even to feed their young.
The assemblage includes a variety of animals, including cattle, caprids, horses, camels, rodents, and even humans! (3/n) pic.twitter.com/S7LF434psF
“There are other similar sites reported from the Middle East and Africa. However, there have been very few detailed studies of these assemblages,” explains first author Mathew Stewart from Max Planck Institute for the Science of Human History in Germany in an email to indianexpress.com. The findings were published in Archaeological and Anthropological Sciences.
Striped hyenas also have powerful neck and jaw muscles that help them transport large carcasses over long distances. The presence of hyena skeletal remains, and coprolites, or fossilised faeces, suggested that these bones were primarily accumulated by striped hyena (Hyaena hyaena).
The Umm Jirsan lava tube system is currently the longest reported lava tube in Arabia with a horizontal passage length of 1481 m and typical height of 8–12 m (PALAEODESERTS PROJECT)
The study team has planned to survey and investigate other similar sites in the region. “Impressively, the thousands of bones reported in the paper represent only a tiny fraction of the material preserved in the Umm Jirsan lava tube,” adds Dr. Stewart.
The bone assemblage from the Umm Jirsan lava tube in the Harrat Khaybar region, Saudi Arabia. (PALAEODESERTS PROJECT) 
The Umm Jirsan lava tube system is currently the longest reported lava tube in Arabia with a horizontal passage length of 1481 m and typical height of 8–12 m (PALAEODESERTS PROJECT)
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