Foxes wandering the streets of London, monkeys hanging out in front of food vendors and coyotes raising families in parking lots – cities are not only human spaces, but they have become dwelling areas for a lot of animals, too. Whilst some have learnt to adapt to their new surroundings, others are actively coming into urban areas in order to reap the benefits of city life.
Animals adapting to change
In the past decades, researchers have been observing some remarkable adaptability amongst animals living in an urban environment. Some have even evolved to feed off industrial leftovers. For instance, a particular group of earthworms (dubbed “superworms”) found in parts of Northern England and Wales feed off heavy metals such as copper, iron and zinc that can be found around mining areas. These animals have changed so much through adaptation that they are considered an entirely new species – in contrast to these superworms, regular earthworms are unable to survive in such areas. Similarly, researchers have observed that some urban-dwelling birds sing at a higher pitch than their rural counterparts, most likely in order to be heard amongst the drone of traffic. It has also been observed that reservoir-dwelling fish have gone through quite dramatic changes since moving away from moving waters. Blacktail shiners, for instance, have become almost unrecognisable from their counterparts, with smaller heads, shorter dorsal fins and wider bodies. Most probably, this is in response to decreased water flow in their environment, which has affected their manoeuvrability.
Animals moving into urban spaces
A further phenomenon has seen animals moving into the cities and making the urban arena their new home. Many have adapted to the new selection pressures of the environment, which often offers easier food accessibility and relative safety, given that they learn the way of the streets. Some have become nocturnal, for instance, taking advantage of lesser people and traffic. For those of us in the UK, the animal that probably first comes to mind is the red fox, whose number of urban colonisers has roughly quadrupled in the last 20 years – about one fox for every 300 urban residents. The reason why creatures like foxes and badgers are seemingly doing so well in cities is that they are generalists – meaning that they don’t really rely on a particular diet or habitat in order to survive; they have simply adjusted their foraging strategies to a more anthropogenic diet. A similar case follows for other parts of the world. In America, for instance, the coyote has spread into almost every corner of the US in the last few decades, and they have shown remarkable adaptability, observing traffic patterns and finding hiding places – in downtown Chicago, one coyote pair raised a litter of pups in the parking lot of the Soldier Field Stadium, home of the Chicago Bears.
Photo Credit: CCO Public Domain | Fox In The Street
Whilst earthworms and birds generally go unnoticed by the majority of the population, huge numbers of animals moving into cities has sometimes resulted in large-scale complications. For forest-dwelling monkeys, their dwindling natural habitat means that they have had to wander into cities in search of resources, living mostly on urban detritus or snacks they snatch from unassuming tourists. In countries like India, this has developed into quite a problem. And we’re not talking about a few loitered bins – in 2007 the Deputy Mayor of New Delhi fell to his death after he was attacked by a group of rhesus monkey on a balcony. Last year, confidential military documents were stolen from a camp in Malaysia. The perpetrators? A group of (unusually politically-driven) monkeys. As extreme as such situations may be, the fact of the matter is that these animals are adapting to a changing environment caused by human interference. Adaptation is not just a fun quirk. Ultimately, humans have created a habitat in which we, as selective agents, have the power to eliminate or accommodate those species that hope to co-habit our urban environment. Thanks to food availability and relative shelter from predators, we have created spaces which will undoubtedly attract animals. Even by curating our natural surroundings, we inadvertently attract parts of a foreign ecosystem – for instance, gardens that house numbers of non-native plants such as lavender and rosemary will attract animals that feed on them.
Photo Credit: Wikimedia Commons | Bijaya2043 | Own Work
What does this mean in the long term?
Looking to the future, the interesting question arises of how urban life will steer the evolutionary path of these animals. Some research has shown a fluctuation in brain size for city-dwelling animals, most likely a response to a change of cognitive demands, such as threats, food sources and shelter. The unpredictability of city life means that many have adapted their physiological responses to cope with constant bedlam – for instance, a mouse in an underground station has muted its stress responses in order to cope with the noise of passing trains. So far, there has been little certainty on the hereditary nature of such traits. A lot of the time, the process is learnt, with animals going through a sort of cultural evolution by copying the behaviour of others. There’s not a single formula that can be applied to advantageous behavioural traits, either. A shy bird may do better than a forceful raccoon, depending on its immediate environment and survival skills.
Cities have become evolutionary hotspots, creating an encapsulated environment within which animals seek adaptation. By adapting our urban spaces, we can strive to accommodate our new neighbours – but it is just as important for us to leave the remaining natural spaces alone to guarantee their continued survival.