Cities are home to millions of people, but also to thousands of animals. Some animals have adapted to live in urban environments, while others have been displaced or excluded by human activities.
Urban animals face many challenges, such as finding food, avoiding predators, and dealing with pollution.
But one of the most pressing threats they face is heat. Cities are often hotter than their surrounding areas due to the urban heat island effect, which is caused by the absorption and emission of heat by buildings, roads, and other artificial structures.
Climate change is expected to worsen this effect and increase the frequency and intensity of heat waves in urban areas.
How do urban animals cope with high temperatures? How does heat affect their behavior, physiology, and survival?
A new study has tried to answer these questions by comparing the thermal tolerance and activity patterns of urban and rural mammals across North America.
How urbanization affects wildlife
Urbanization is the process of transforming natural habitats into human-dominated landscapes, such as cities, suburbs, and industrial areas.
It can have various impacts on wildlife, such as habitat loss, fragmentation, pollution, noise, light, and heat.
Some animals can adapt to urban environments and exploit the resources and opportunities they offer, such as food, shelter, and reduced predation.
These animals are called urban exploiters, and they include species like raccoons, pigeons, rats, squirrels, and crows.
Other animals are more sensitive to urbanization and avoid or decline in urban areas. These animals are called urban avoiders, and they include species such as bears, wolves, deer, and songbirds.
How climate change exacerbates the urban heat island effect
Climate change is the long-term alteration of the Earth's climate system due to human activities that emit greenhouse gases into the atmosphere.
Climate change can cause global warming, which is the increase in the average temperature of the Earth's surface.
Global warming can have various consequences for wildlife, such as shifting ranges, altering phenology, reducing biodiversity, and increasing extinction risk.
One of the effects of global warming that is particularly relevant for urban animals is the urban heat island effect.
The urban heat island effect is the phenomenon that urban areas are warmer than their surrounding rural areas due to the absorption and emission of heat by buildings, roads, and other artificial structures.
It can create a thermal mismatch between urban exploiters and their natural habitats, making them more vulnerable to heat stress and dehydration.
Also Read: Interactions With Nature Are Declining as a Result of Urbanization
How a new study reveals the thermal tolerance of urban mammals
A new study published in the journal Global Change Biology by researchers from North Carolina State University and other institutions has investigated how urban mammals cope with high temperatures in different cities across North America.
The study used camera traps to monitor the activity patterns of 24 mammal species in 29 cities from Vancouver to Miami.
The researchers also measured the air temperature and humidity at each camera trap location.
The study found that most urban mammals have a lower critical thermal maximum (CTmax), which is the highest temperature at which they can maintain normal body functions, than their rural counterparts.
This means that urban mammals are less tolerant of heat than rural mammals.
The study also found that urban mammals tend to reduce their activity during hot days and shift their activity to cooler times of the day or night, concluding that urban mammals are not well adapted to cope with high temperatures and may face increased mortality and reduced reproduction in the future as climate change intensifies the urban heat island effect.
Urban animals are not immune to the effects of climate change. They face a double challenge of coping with both urbanization and global warming.
Experts have suggested that urban planners and wildlife managers should consider the thermal needs of urban animals and provide them with adequate shade, water, and vegetation to mitigate the impacts of the urban heat island effect.
Related article: How Urbanization Affects the Biodiversity and Ecosystem to Bees, According To Study