In fact otters are merely the latest in a long line of rural immigrants. Most notable is the urban fox, which began to crop up in numbers during the Sixties, prompting a hysterical reaction from some who predicted that children would be attacked and rabies would run rampant. This was unduly pessimistic, of course, but in other respects the foxes certainly seem to have set a trend, which mirrors mankind's own migration from town to country.
Badgers were the next to attract attention (although most of them were old residents whose presence had previously gone largely unremarked) and since then the list has grown every year. Along with otters, peregrines are the latest high-profile entrants. Thirty years ago the British population of these birds was reeling from the effects of DDT and they were on the verge of dying out. Today there are around 1,200 pairs, each in search of a suitable cliff on which to nest. Indeed, now almost every natural site is occupied and the population pressure is so great that some are turning to man-made alternatives. One pair has already bred on Swansea Post Office Tower, another on a Derbyshire power station, while a third is currently nesting on a block of flats in Brighton.
There seems every likelihood that these are just the vanguard. Urban peregrines are well established in America (albeit from introduced, captive- bred stock) where they thrive on the seemingly limitless supplies of feral pigeons. There is no shortage of these in our own cities, along with thousands of potential nest ledges. And, after all, the peregrine's smaller cousin, the kestrel, has not only thrived on motorway verges, but has become a familiar sight in most big towns, while the elusive sparrowhawk is far more common in suburbia than many human inhabitants may realise.
Similarly, until recently the bird guides proclaimed that tawny owls were exclusively woodland dwellers, but now their characteristic "too- wit-too-woo" can be heard ringing out across Highbury Fields in the heart of Islington, one of London's most built-up boroughs. Greater spotted woodpeckers and woodpigeons have also made the transition from trees to concrete, not to mention the ubiquitous bluetit which has long since swapped its diet of oak canopy caterpillars for doorstep milk bottles. Cormorants have also chosen to move in from the coast, and now their characteristic, long-necked silhouettes are a common sight around inland lakes, gravel pits and rivers - much to the chagrin of anglers and fish farmers.
It is, of course, relatively easy for birds to wing their way into town, but you might have thought that Tarmac, walls and traffic would deter mammals. Far from it; there are plenty of green corridors into the hearts of even our largest cities: along railway lines, canals, even sewers.
The water vole is one that has made it. Although it has recently disappeared from two-thirds of its former geographical range, some of its healthiest strongholds are within built-up areas. There are thriving populations in central Sheffield and Twickenham's Crane Park, for example, while a study in Avonmouth revealed increasing numbers.
The voracious American mink, which is the main cause of the vole's general decline, shuns human disturbance, particularly when this comes from people exercising dogs. In addition, it prefers richer habitat than the generally degraded urban areas and so steers clear of cities. In contrast the voles are relatively at ease in the presence of man, knowing that the safety of their burrows is only a few feet away, and they can eke out a living from even the meagre pickings of a canal bank. As a result, voles living along tow paths and in popular parks have suffered less than most.
The trend is not confined to small mammals, however, with creatures as large as deer being spotted in cities for the first time. Most reports, of course, are from leafier suburbs and concern the dog-sized muntjac and roe, but occasionally much larger examples crop up, such as the sika (a red deer lookalike) spotted bounding through central Leeds.
So what makes normally shy creatures suddenly swap the peace and quiet of the countryside for our built-up areas? In the case of the otter and the water vole, improved water quality is a partial answer, while population pressure and habitat shortage accounts for the inflow of peregrines and owls. And what of the future? Which of today's unfamiliar creatures will be living alongside our children during the new millennium? Red kites are front-runners. Currently listed as one of our rarest birds, they are likely to be commonplace tomorrow. This large fork-tailed raptor was confined to mid-Wales at the beginning of the century, but numbers have slowly mushroomed, helped by successful introductions to the Chilterns, Northamptonshire and southern Scotland. And the prospect of urban kites now seems a very real possibility. After all, they were once sufficiently common for Shakespeare to warn housewives to guard their washing lest kites steal it for nesting material. Indeed, they are a familiar sight over many Continental cities. Anyone still raising an eyebrow should note that one was seen circling over Reading last week.
Despite this bright backdrop, Isobel Bretherton of the Wildlife Trusts cautions against complacency.
"Although the urban picture is generally encouraging, there's a lot more we could do," she says. "Local authorities ought to be working more closely with wildlife trusts to improve parks as natural habitats, and there's a long way to go before we reverse the insensitive developments of the past."Reuse content