A new scientific study reveals that ancient foxes were gorging on remains discarded by humans 42,000 years ago, just as they do today.
The sight of urban foxes rummaging through our garbage bags and serving themselves for our food scraps is common in Britain’s towns and cities today.
But these scavengers have been stuck in our fleshy leftovers since the Upper Paleolithic period.
Researchers in Germany studied fox remains found at various archaeological sites across the country for carbon and nitrogen isotopes, which indicate the diet.
They found that when Neandethales occupied the areas more than 42,000 years ago, foxes fed primarily on small mammals that they could catch.
However, when humans appeared during the Upper Paelolithic period, their diet suddenly changed to include more reindeer, an animal that was hunted by humans and that foxes were unable to catch and kill on their own.
The researchers claim that because the diets of ancient foxes were influenced by humans, these tiny carnivores could be tracers of human activity over time.
In the wild, foxes regularly feed on the debris left by larger predators such as bears and wolves, but the closer foxes live to human civilization, the more of their diet is made up of food that humans leave behind. .
“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 Tübingen University in Germany.
“The more humans populated a particular region, the more foxes adapted to them.”
In the wild, foxes regularly feed on debris left by larger predators such as bears and wolves.
But the closer foxes live to human civilization, 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 an estimate by the Department for Environment, Food and Rural Affairs, one fox for every 150 people.
Foxes exist in what is known as a commensal relationship with humans, which means they obtain food and other benefits from humans without harming or helping us.
Dietary sources of the foxes as indicated by the nitrogen isotope (y-axis) and the carbon isotope (x-axis). For example, low levels of nitrogen isotope indicate low traces of reindeer intake, while high carbon isotope indicates intake of mammoth.
In this study, Baumann and colleagues hypothesized that if this commensal relationship dates back to ancient times, foxes could be useful indicators of human impact in the past.
The authors compared the proportions of carbon and nitrogen isotopes between the remains of various herbivores, large carnivores, and red and arctic foxes from archaeological sites in Germany dating from the Middle and Upper Palaeolithic periods.
In total, the animal remains samples represented a minimum of 62 individual carnivore specimens.
The researchers used stable isotope analyzes of bone collagen extracted from animal remains from various archaeological sites in the Swabian Alb, in southwestern Germany.
The samples covered a time range during three major cultural periods: the Middle Paleolithic (older than 42,000 years ago) during which Neanderthals existed, and the early Upper Paleolithic period, 42,000 to 30,000 years ago, attributed to modern humans.
The researchers say that at sites more than 42,000 years old, when Neanderthals scarcely occupied the region, the diets of foxes were similar to those of their large local carnivores.
But at younger sites, as human activity became common in the area, foxes developed a more unique diet that consisted primarily of reindeer.
Reindeer are too big to hunt foxes, but they are known to have been an important game for the ancient humans of the time.
Chronology of fox diets. The blue area marks the impact of humans on dietary resources. For low delta-N-15 foxes (those with low levels of the nitrogen isotope) humans had no influence on their diet, while for intermediate delta-N-15 foxes, human foxes had a very strong influence. High delta-N-15 foxes may be influenced by human activity (eg, killing at killing sites) or may be of natural origin (eg, killing from naturally dead megafauna)
Stable isotope analyzes of elements such as carbon and nitrogen are used to track nutrient flow 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 samples with low traces of delta-N-15 showed that humans had no influence on their diet.
Meanwhile, foxes high in delta-N-15 may be influenced by human activity (such as harvesting at sites where humans killed animals for food) or may be of natural origin (such as gathering naturally-occurring megafauna) .
The study suggests that foxes waited for homo sapiens to finish eating before devouring their remains while humans occupied sites and developed settlements during the Upper Paleolithic period.
During this time, about 42,000 years ago, foxes went from feeding on the debris left by large local predators to eating food left by humans, showing early dependence on us as a way to get a good diet.
Foxes’ eating habits evolved from hunting small, manageable mammals to fully searching for human food debris.
The authors propose that, with more studies investigating this fox-human relationship, the diets of ancient foxes may be useful indicators of human impact on ecosystems over time.
The findings have been published in the journal PLOS One.
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