Opportunism

Plants and animals which live in towns and cities often have to adapt to living in unusual habitats. Their interaction with other species (particularly humans) may also be different.

The urban niche

Within an ecosystem all living organisms occupy a niche. Their niche is the place where they live (their habitat) and how they interact with other species (their role in the ecosystem).

What is the niche of the common woodlouse (Oniscus asellus)?

The woodlouse's habitat is under logs and stones and, particularly at night when it's cool and damp, under leaf litter	The woodlouse's role in the ecosystem is (a) feeding on dead plant material, breaking it down into small pieces helping to speed up decomposition by fungi and bacteria and (b) providing a food source for a range of other species, e.g. toads, shrews, hedgehogs and other invertebrates

Here are some examples of how plants and animals have exploited the urban environment.

	The cowslip a meadow plant prefers neutral to alkaline soils. It is often found in churchyards where the soil is enriched with calcium from the weathering of limestone headstones and the decomposition of bones!
	Birds which naturally nest on cliffs or in trees like this kestrel, may make use of ledges on high rise buildings in urban areas
	These plants are growing happily on debris accumulating in the roadside gutter. In the drain ferns are taking advantage of higher moisture levels.
	Tons of decomposing household waste on rubbish tips form an open air restaurants for birds such as these herring gulls
	Over half a million mice are estimated to live in London 's underground system feeding on food and other rubbish discarded by travellers

Case study: the urban fox (Vulpes vulpes)

After World War One towns and cities began to rapidly expand into rural areas. The fox, a highly adaptable animal, was able to modify its way of life. It is now just as successful in urban environments as rural ones. The population of around 30,000 appears to be stable. So how has it adapted?

Places to live

The fox needs several holes or burrows to use as dens as well as day-time resting places. In the urban environment sites for dens are plentiful. Foxes use for example spaces under sheds or floor boards, basements and railway embankments, but daytime resting sites may be difficult to find and foxes therefore prefer the quieter suburbs away from too much human activity.

Food

Rural foxes feed on a wide range of foods including fruit, small mammals and birds, insects and other invertebrates particularly earthworms. In towns foxes supplement their diet from refuse discarded by humans. This site gives more information about foxes in London (Harris 1981). This will give gives you some idea of the wide range of things eaten by urban foxes. In fact they usually have a food surplus.

Territories

The plentiful supply of food means that urban foxes often live closer together than their rural relatives The territory of a rural fox for example is usually about 2-6 square kilometres whilst that of the urban fox may be less than 0.6 square kilometres. Living closer together has the disadvantage of making it easier for diseases like mange to spread more rapidly

Their role in the ecosystem

The urban fox has no natural predators although badgers occasionally take young cubs. It is usually the top carnivore in the ecosystem.

When eating fruit like blackberries they may help to disperse seeds in their faeces as well as dispersing seeds of other plants like the goose grass which cling to their fur.

In eating mice, rats and pigeons as well as competing with them for human leftovers they help to control vermin.

Their relationship with humans

Some people enjoy seeing foxes and even put food out to encourage them. Others dislike them as they scavenge around rubbish. They also see them as a threat to household pets even though foxes avoid cats and dogs and there are relatively few reports them eating pets such as guinea pigs or rabbits.

Human beings are the biggest cause of fox deaths. They may for example be deliberately killed, die of poisons that have accumulated in the food chain or be killed by motor vehicles. It is not surprising that foxes avoid humans as much as possible.