Squirrels  have been culled in Regent’s Park after scratching bark from trees

DISGUSTING air pollution is taking a heavy toll of grey squirrels according to new findings, which experts say come as a warning message from the animal kingdom about the climate catastrophe.

A research team boasting brains from the Royal Veterinary College and London Zoo has compared the lungs and throats of more than 100 of the city’s bushy-tailed tree-hoppers with those that had lived in picturesque countryside spots like Penrhyn Castle, Wales, or the Alice Holt forest of Surrey.

Both sets were checked for signs of lung disease.

Unsurprisingly they found that squirrels from Camden had “significantly higher” levels of the kind of sooty-like granules of black carbon often found in smokers’ lungs and prevalence of respiratory diseases.

The research paper, for the science periodical Environmental Pollution, raises questions about how common pets, like cats and dogs, might be affected by Camden’s bad air.

Dr Patricia Brekke, from the Zoological Society of London, told the New Journal: “Studying grey squirrels helps us to understand the impact that air pollution has on human and wildlife health.

“Squirrels live in both the highest polluted areas in central London and the least polluted rural areas of the country, allowing them to act as sentinel species for the exposure to the cocktail of pollutants in the air we breathe and provide us with vital information on how these pollutants affect our health and that of the other animals we share these urban spaces with.”

She said having healthier air for animals would lead to an all round “healthier and more biodiverse urban environment for us all”.

But the paper said that while much is known about how pollution causes havoc for human health, little in-depth research has been done on the impact of “traffic related air pollution” on mammals in inner city areas.

The testing was done on culled grey squirrels, which have been classified as pests. Ironically, the Camden squirrels used for the scientists’ study had been culled in parks where it has been feared they are killing the trees needed to combat air pollution.

The New Journal has reported on how dozens of squirrels have been killed in Primrose Hill and Regent’s Park in recent years to stop damage to “ornamental trees”, “horticultural displays” and “nesting birds”, according to the Royal Parks, which insists “no animal endures prolonged suffering” and the “most humane traps possible” are used.

Natalia Doran, founder of Urban Squirrels, said: “The fact that the animals in the study came from culls is very sad. Culling grey squirrels is self-evidently cruel and pointless, since the population re-establishes itself in a matter of weeks, not just by birth, but also by migration.

She added: “If the habitat can sustain a certain number of squirrels, the numbers would always return to that level, unless you are killing constantly.”

Eastern grey squirrels were introduced to this country in the late-1800s.