Ancient foxes gorged on scraps discarded by humans 42,000 years ago just as they do today, a new scientific study reveals.
The sight of urban foxes rummaging in our rubbish bags and helping themselves to our dinner scraps is common in Britain’s towns and cities today.
But these scavengers have been gorging on our meaty leftovers since the Upper Paleolithic period.
Researchers in Germany studied fox remains found at various archaeological sites throughout the country for carbon and nitrogen isotopes, which indicate diet.
They found that, when Neandethals occupied the areas more than 42,000 years ago, foxes fed mainly on small mammals that they were able to catch themselves.
However, when humans turned up during the upper Paelolithic period, their diet suddenly changed to include more reindeer – an animal that was hunted by humans and that foxes would have been unable to catch and kill on their own.
The researchers claim that, because the diets of ancient foxes were influenced by humans, these small carnivores might be tracers of human activity over time.
‘Dietary reconstructions of ice-age foxes have shown that early modern humans had an influence on the local ecosystem as early as 40,000 years ago,’ said Chris Baumann of the University of Tübingen in Germany.
‘The more humans populated a particular region, the more the foxes adapted to them.’
In the wild, foxes regularly feed on scraps left behind by larger predators like bears and wolves.
But the closer foxes live to human civilisation, the more their diet is made up of foods that humans leave behind.
Today, there are around 430,000 foxes in the UK, according to a Department for Environment, Food and Rural Affairs estimate – one fox for every 150 people.
Foxes exist in what is known as a commensal relationship with humans, meaning they gain food and other benefits from humans without either hurting or helping us.
In this study, Baumann and colleagues hypothesised that if this commensal relationship goes back to ancient times, then foxes might be useful indicators of human impact in the past.
The authors compared ratios of carbon and nitrogen isotopes between the remains of various herbivores, large carnivores and red and Arctic foxes from archaeological sites in Germany dating to the Middle and Upper Palaeolithic periods.
In total, the samples of animal remains represented a minimum of 62 single carnivore specimens.
Researchers used stable isotope analysis of bone collagen extracted from animal remains from several archaeological sites in the Swabian Jura, southwest Germany.
The samples covered a time range over three important cultural periods – the Middle Palaeolithic (older than 42,000 years ago) during which Neanderthals existed, and the early Upper Palaeolithic period, 42,000 to 30,000 years ago, attributed to modern humans.
At sites older than 42,000 years, when Neanderthals sparsely occupied the region, fox diets were similar to their local large carnivores, researchers claim.
But in the younger sites, as human activity became common in the area, foxes developed a more unique diet consisting largely of reindeer.
Reindeer are too big for foxes to hunt but which are known to have been important game for ancient humans of the time.
Stable isotope analysis of elements such as carbon and nitrogen are used to trace the flow of nutrients through food webs.
Specifically, they recorded delta-N-15, a measure of the ratio of the two stable isotopes of nitrogen, and delta C-13, a measure of the ratio of stable carbon isotopes.
Fox specimens with low traces of delta-N-15 showed humans had no influence on their diet.
Meanwhile, high delta-N-15 foxes may be influenced by either human activity (such as scavenging at the sites that humans killed animals to eat) or may be of natural origin (such as scavenging from megafauna that died naturally).
The study suggests that foxes waited for homo sapiens to finish eating their meal before devouring their scraps as humans occupied sites and developed settlements during the Upper Palaeolithic period.
During this time, around 42,000 years ago, foxes made a shift from feeding on scraps left by local large predators to eating food left behind by humans, showing an early reliance on us as a way to get a good feed.
Foxes’ eating habits evolved from hunting small, manageable mammals to outright scavenging on human food remains.
The authors propose that, with further studies investigating this fox-human relationship, ancient fox diets may be useful indicators of human impact on ecosystems over time.
The findings have been published in the journal PLOS One.