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World\'s Oldest Larder

Researchers find 17 million year old hamster burrow

Palaeontologists of the University of Bonn have made an unusual find in the open-cast mining area around Garzweiler. In the path cleared by an excavator they discovered strange accumulations of fossil nuts. Their theory is that a hamster had hoarded food in its burrow and the passages leading to it so as to have something to nibble on in the cold season - more than 17 million years ago. This makes the find the oldest larder ever to be discovered.

At some point the busy little hoarder left its burrow and never came back. Perhaps it became the victim of some prehistoric murder, perhaps some natural catastrophe blocked the entrance to its burrow. Whatever happened, the Bonn palaeontologist Dr. Carole Gee was unable to find any fossil remains of a hamster when she investigated the accumulations of nuts more carefully. Despite this she is fairly confident of her theory, since the location of the roughly 1,800 nuts permits precise conclusions to be drawn about the size of the burrow and the shape of its passages. 'The burrow is definitely that of a rodent, most probably a large hamster or possibly a squirrel,' she concludes in an article in the journal Palaeontology written in conjunction with her fellow authors Dr. Martin Sander and Dr. Bianka Petzelberger.

At the time, in the early Miocene period, the sea lapped the area near Cologne, The rodent's burrow was in the dunes, which were covered in bushes and low-growing plants - at least, a large number of fossil roots have been found in the place where the find was made. The nuts are from an unusual species of tree which nowadays only survives on the North American Pacific coast and in East Asia and is related to the Southern European sweet chestnut. 'We got the University Clinics to examine the fossil plants using a computer tomograph,' Dr. Gee explains. 'They were so well preserved that the two parts of the nut could be clearly discerned in the shell.'

The climate during the Miocene epoch was much warmer than today. Crocodiles lived in the Rhineland, there were apes in the jungles, and palm trees grew far to the north. However, most of today's rodents only hoard large amounts of food when they have to prepare for periods where there is not much food around - for example in regions with severe winters or droughts. 'Perhaps the larders filled to capacity are an indication that the change to a more inequitable climate was already underway,' the paleobotanist Dr. Gee says.

Plant taphonomy is the name given to the attempt to reconstruct the conditions which eventually led to today's fossil finds as comprehensively as possible. 'At some locations, for example, we only find fossil fruits or types of wood, but not leaves,' Dr. Gee explains. However, from this it should not be concluded, of course, that plants did not have leaves in the past. There have to be a lot of coincidences occurring for a branch or twig, a beechnut or an oak leaf to be buried in sediment at a specific place and turn up in a fossilised state millions of years later. 'The factors involved are completely different in the case of a leaf, which is lightweight and soon rots, compared with a more robust twig or nuts which have been buried by a rodent.'

Some mysteries can simply be solved by a talent for accurate observation. For example, when analysing why fossil fruits and wood remnants are often to be found in lens-shaped accumulations together with coarse sand. 'My husband and I frequently go with our children to the River Sieg to examine the remains of plants which have been washed up ashore,' Dr. Gee adds. On one of these trips, shortly after there had been flooding, she noticed that parts of plants such as twigs and woody fruits had become saturated with water and were rolling along with the grains of sand on the bottom of the river. 'As soon as the floodwaters recede, all these are left on the shore in lens-shaped accumulations. Lighter parts of plants such as leaves and blades of grass float on the surface of the water and later accumulate in lines on the riverside meadows, where they soon rot.'

Contact person:
Dr. Carole Gee
Institute of Palaeontology
University of Bonn
Tel.: ++49-228-733063 or ++49-228-691558
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All photos: Georg Oleschinski/Uni Bonn

Fossil nut (black) with leaves, burs, and nuts of the recent golden-leaved chinquapin, Castanopsis chrysophylla, from Oregon for comparison in Dr. Gee\'s hand.
Fossil nut (black) with leaves, burs, and nuts of the recent golden-leaved chinquapin, Castanopsis chrysophylla, from Oregon for comparison, on a green background.
Dr. Gee is holding a sediment peel made from the vertical face at the quarry site:
left, cross section through a gallery; right, cross section through a chamber; scattered are longitudinal sections through fossil roots originating from the fossil soil horizon above.
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