Updated: Jun 18, 2022
By Jamie Li
March 30, 2022
UPDATED 12:00 PM EST
[Photo Credit: Robert Rich]
An essential component of Charles Darwin’s theory of evolution is that the struggle for existence only allows those with favourable traits to survive. Cities are demonstrating Darwin’s evolution theory in unexpected ways. Urban blackbirds, underground mosquitos and cleverer crows are changing significantly from their rural counterparts. Learn about how these species adapt and what that means for future animals.
An example of the adaptation for species within cities is urban blackbirds. Most adaptations are small changes, such as behavioural or physical transformations. However, the urban blackbirds have evolved where a new species appears to emerge. City blackbirds stop migrating, respond to stress differently, have shorter beaks and sing in a different pitch. Compared to the shy forest blackbirds, the city blackbirds have adapted to an ecological niche and have changed drastically. The city blackbirds' changes prevent them from crossbreeding with the forest blackbirds. Similar to Darwin’s finches on Galapagos Island, the urban blackbirds demonstrate evolution in cities.
Furthermore, an insect that displays the adaptations species have in cities is the London Underground mosquito. Although it has a specific location in its name, the London Underground mosquito is found in basements and cellars across the world. The London Underground mosquito separated from the wild mosquitoes after moving underground. The above-ground mosquitoes only feed on birds and form mating swarms. The London Underground mosquito is significantly different as it feeds on mammal blood, mates one on one, and the female does not require a blood meal before it lays eggs. The adaptation has some worrying consequences, as some wild mosquitoes carry the West Nile virus. The London Underground mosquito also transports the virus and feeds on mammals. London Underground mosquitoes could transmit the virus to humans, which is a health risk.
Finally, crows in Sendai, Japan have developed a personality gene after living in cities. Originally, crows would crack open walnuts by dropping them from high up to eat the nut within the hard shell. During the 1980s, the crows found it was easier to crack open the walnuts by putting them in front of the wheel of a slow-moving vehicle. Crows would move walnuts in front of driving school cars and allow the wheels to crack open the walnut for them. This behaviour broadened to crows in other cities as well. Rather than physical changes, this adaptation demonstrates the personality traits tailored for animals within cities.
What do these changes mean for animals and ecosystems of the future? On one hand, it is fascinating that animals are changing dramatically to adapt to cities. However, certain sensitive species are dying off because of human intervention. Cities have changed the natural landscape drastically, uprooting hundreds if not thousands of species. Although observing species' changes in cities are beneficial to understanding their adaptations, we need to remember that this change is not entirely positive. Instead of forcing species to adapt to our cities, humanity should make space for species to exist.
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