British deer could face the same fate as the red squirrel, experts have warned – as a study reveals they are being outcompeted by a hardier, more aggressive species.
Researchers have discovered that invasive sika deer are experiencing a population boom while our native red deer struggles to maintain numbers.
The sika, which were introduced to Britain in the 19th century from east Asia, are smarter and more fertile than their British counterparts.
They can also tolerate poorer habitats and weather, maintain better overall condition on the same feed and are harder to hunt.
This species is recognisable by their small head and pointy antlers and have a grey winter coat which turns brown with white spots during the summer months.
Now, experts are warning that the UK needs to focus culls on the invasive species to secure the future of our majestic native deer.
If efforts are unsuccessful, the red deer could face the same fate as red squirrels, whose numbers have been decimated as a result of the introduction of the grey squirrel from North America, experts say.
A study, published in the journal Ecological Solutions and Evidence, looked at deer populations on estates in Scotland.
A herd of red deer stag are pictured in the bracken in Richmond Park, south west London early in the morning of January 3
The sika are recognisable by their small head and pointy antlers and have a grey winter coatwhich turns brown with white spots during the summer months
Analysis showed that despite increased culling, sika populations grew by 10 per cent in 2024–25 while the red deer population declined by 22 per cent.
Scientists have now warned that the sika’s advantages could see the red deer struggle to survive, as current culling approaches do not discern between species.
Calum Brown, lead author of the study from the Karlsruhe Institute of Technology and co–chief scientist at Highlands Rewilding, said land managers were ‘finding equivalents’ in deer populations with what happened to red squirrels.
‘It is often mostly sika and there are very few native deer around, and that might be something that happens more and more,’ he told the Sunday Telegraph.
‘We could actually move in the wrong direction if sika gets a toehold across larger areas.’
It is possible the situation in Scotland is being replicated across the country, he said, adding that a national and local strategy needs to be introduced to better control deer populations.
‘Sika do better in poor weather and with poor resources,’ he added.
‘They do better on limited food, they can survive without problems at high densities that would cause issues for other species, they breed more, and when you combine that with their tolerance for poor conditions it means the populations are growing faster than native species.
The natural advantages that sika have in each stage of their life cycle, which make them more likely to outcompete native red deer in the same area,
Analysis showed that despite increased culling, sika populations grew by 10 per cent in 2024–25 while the red deer population declined by 22 per cent. Pictured: Red deer at Raby Castle
‘They’re then really hard to cull too and they are a very clever species. They learn and adapt very quickly. They seem more tolerant of parasites and pathogens and they eat a wider range of things.’
Experts also warned that sika and red deer can mate – and that the hybrid young may also have competitive advantages that make it even harder for native deer to thrive.
‘Our article highlights the risk that, by managing all deer in the same way, we could inadvertently favour Sika deer over native species,’ Highlands Rewilding said.
‘Without strategic action, Scotland could find itself with a landscape increasingly dominated by a species that is more invasive, more prolific and harder to manage than its native cousins.’
