London: Urban animals are widely regarded as the dregs of the natural world. But according to biologist Simon Watt, cities represent some of the world’s hotspots for evolution and behavioural adaptation.
Speaking at the Cheltenham science festival, Watt, who is founder of the Ugly Animal Preservation Society, said that the ice caps are melting, the rainforest is shrinking, the one environment that is growing is cities. “If we’re going to look for evolutionary shifts right now in our world, the place to look is citiesm,” he was quoted as saying by the Guardian.
Watt cited a host of examples of how the urban environment is prompting new genetic shifts and unexpected behaviours. A proportion of black cap warblers, which used to migrate to Morocco or southern Spain, have shifted their route to Britain where urban heat islands and garden bird feeders allow them to survive at more northerly latitudes than was previously possible.
In Australia, the mating croak of the male pobblebonk frog has been steadily rising in pitch, an adaptation that means it can still attract females in the presence of the background rumble of motorway traffic.
He said pobblebonks never hear their parents, so it’s an evolutionary shift. Watt noted that outside the urban setting the frogs with the deepest croak tend to be most attractive to females. He said they still would be the most attractive males if they could be heard, but it’s become an advantage to have a falsetto.
Birds have also changed their vocalisations, although this appears to be acclimatisation rather than evolution. According to him, in general, we can say that birds in cities have a couple of things in common. They tend to sing at a higher pitch, they tend to use fewer notes and they tend to sing faster.
He said they have their own urban music. Watt explained that it happens across all the species, they sing at different times – at night because they’ve got street lights. He added that they are not quite sure when it’s bedtime, and it does mean that some of these birds are stressed out.
A weed, called Crepis sancta – which looks like a delicate version of the dandelion, is evolving to release higher numbers of heavy seeds and fewer light floaty ones (the plants produce a mixture) because of its concrete-bound existence.
There is even a species, sometimes known as the London Underground mosquito, which has adapted from a southern mosquito variety to survive in the warm underground spaces of northern cities.
Watt said the types of species that are able to thrive in urban environments tend to be adaptable omnivores, relatively intelligent and scavengers by nature.