Stroll through the streets of Bangkok and you might fall in step with an elephant. Peer into a storm drain in Melbourne and you could find a metre-long eastern water dragon staring back. Scan the Chicago skyline and you may spot peregrine falcons perched atop church steeples.

Astonishing biodiversity can be found almost everywhere, even in the heart of densely populated cities. Mention urban wildlife and people generally think of mice, thrushes nesting in parks, cockroaches scuttling behind cabinets and pigeons on statues. Yet cities often contain greater biodiversity than the countryside around them.

Many species - as if to ignore zoning regulations - move from the countryside into town. As intensive agriculture and other developments shrink their natural habitats, resourceful animals seek shelter where they can. While at first glance modern cities with their crowds, congestion and concrete pavements might seem hostile places for animals to live, they are in fact peppered with little known wildlife havens - backyards, creeks, rivers, rooftop gardens and vacant lots - hosting miniature ecosystems, as well as officially designated parks, nature trails and lakes.

photo: Laurent Touzeau/Still Pictures

Just as with humans, there are some animals we like as neighbours, and others we wish would move away. Many city dwellers encourage wildlife to live alongside them by providing birdfeeders and brush piles. Others unwittingly invite unwanted guests by leaving out trash and pet food. Urban encounters with coyotes, panthers, mountain lions and other large carnivores are growing more common every year - but the biggest killers are deer, which cause vehicle collisions when they run into the streets.

Highly adaptable urban specialists, such as rats and squirrels, increase dramatically with abundant food and cover - often at the expense of less mobile, less amorous species like amphibians and reptiles. According to Stanford University biologist Stephen Palumbi, they 'travel around on our coat-tails' and as repeated success trains their behaviour, some come to depend so much on humans that they are no longer
truly wild