Grey squirrel

The grey squirrel, introduced to Britain from North America during Queen Victoria’s reign, is one of our most successful and notorious non-native species. It also presents us with a problem: it can be the death knell for our native red squirrels due to its role as a carrier of disease. But it is also one of the few mammals city dwellers are likely to see, often entertaining us with its acrobatic antics and helping to introduce urban children to the natural world. Grey squirrels are found throughout much of the UK in towns and cities as far north as Dundee, the border country between the reds and the greys.Illustration: Alan Baker

Fox

Of all our native mammals, surely none has adapted so well to city life as the fox. From London to Glasgow, and in towns and cities all over Britain, foxes have moved into leafy suburban neighbourhoods. They survive by scavenging and killing small mammals and birds; and breed in well-hidden dens known as “earths”, often underneath a garden shed or in a railway cutting. Males keep us awake in early winter, baying as they pursue females to mate; the cubs are born in spring and emerge in April or May. Despite much media coverage, fox attacks on humans are virtually unknown.Illustration: Alan Baker

Otter

Once driven to the brink of extinction in England through a combination of persecution and pollution, otters have made a remarkable comeback. They can now be found throughout the UK, using river corridors such as the Tyne, Tees and Thames – as well as many smaller rivers and streams – to enter urban areas. They are mainly nocturnal, so your best chance of catching sight of one is at dawn or at dusk. Otters are large (as long as a medium-sized dog) and chocolate brown in colour. Beware confusion with the smaller and darker American mink, an unwelcome alien invader to Britain’s waterways.Illustration: Alan Baker

Pipistrelle bat

With our smallest bat, you get two species for the price of one. To hunt, bats use “echolocation”, making a series of clicks which bounce back and tell them where their prey is. Just over a decade ago, scientists realised that different groups of pipistrelles “echolocated” at different frequencies. Closer investigation revealed, to the scientists’ amazement, that these were two completely separate species – the common and the soprano. Both species can be seen during the spring and summer in most British towns and cities, usually soon after dusk, but occasionally during daylight hours as well. Like all bats, they feed on flying insects and hibernate in winter.Illustration: Alan Baker

Hedgehog

One of our most familiar and best-loved mammals, the hedgehog is also becoming one of our most endangered. A combination of poisoning by slug pellets and other garden chemicals, being run over by motor vehicles and, in some areas, being eaten by badgers has driven Britain’s hedgehog population to dangerous lows. The good news is that these creatures often find refuge in urban parks and gardens, where they can roam along wildlife corridors without danger from traffic. If you want to feed them, avoid bread and milk as it gives them indigestion – dog or cat food is far preferable.Illustration: Alan Baker