Hoarding is a common animal behaviour. Lots of creatures cache food for times of scarcity.
You probably know that squirrels hide nuts and wood mice store seeds, but did you know that fire ants stockpile excess food in the warmest part of their nests to create ‘insect jerky’? You do now.
Other animals hoard items for their homes. Decorator crabs collect seaweed, anemones and sponges to camouflage their shells, while bone-house wasps collect ant corpses, which they use to seal the entrance to their nest.
But all these trinkets pale into insignificance when compared with the hoarding of the bearded vulture (Gypaetus barbatus).
With wingspans of up to 3m (10ft), they are some of Europe’s largest birds of prey, or raptors. They typically pair for life and return to the same cliffside nest sites every year.
Each breeding season, they add new material to their nests, which builds up into layers. In addition, the same sites are often reused across generations, turning some of these nests into time capsules.
In 2025, scientists reported what they found when they peered into 12 ancient, abandoned bearded vulture nests in southern Spain.
Alongside nesting material, such as sticks and feathers, they discovered 2,483 “abundant and well-preserved” artefacts. Most of these were bits of undigested prey, such as hooves, bone fragments and pieces of eggshell, but around 10 per cent of the objects were items made by humans.
These included 72 pieces of leather, 129 pieces of cloth, odd bits of basket, a crossbow bolt and part of a slingshot.
There was also one complete, and several incomplete, old-fashioned sandals. Known as agobías, this sort of footwear was woven from fibrous esparto grass. They typically lasted for a few days and had to be regularly repaired and replaced by the wearer.
Many of these artefacts, including the sandals, were dated to the Middle Ages – the medieval period that lasted from the 5th to the late 15th century.
Exactly why the birds carried the items to their nests is unclear. One theory is that they were looking for material to bulk up their nests. Another is that they were interested in local history and thought their chicks might be too.
Once widespread in southern Spain, numbers of bearded vultures fell drastically in the 19th and 20th centuries, when they were widely persecuted. Today, things have picked up a little thanks to conservation efforts and the birds are classified as ‘Near Threatened’.
Thanks to the locations of these historical nests, the artefacts were remarkably well-preserved from the ravages of time.
In the paper describing their findings, the authors said that due to “the solidity of bearded vulture nest structures and their locations in the western Mediterranean, generally in protected places such as caves and rock shelters with relatively stable temperature and low humidity conditions, they’ve acted as natural museums.”
This makes bearded vultures not only one of nature’s weirdest hoarders, but also the curators of one of the most eclectic collections of historical artefacts in the world.
This article is an answer to the question (asked by Jackie Bryce, Chichester) 'Do any animals hoard treasure?'
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