Urban Wildlife
The constant thrum of life in the city is harming many urbanized species, including humans
The constant thrum of life in the city is harming many urbanized species, including humans
Cities are noisy. At its worst, the street-level experience can be literally deafening, with wailing sirens, pounding jackhammers, and inconsiderate car and motorcycle owners showing off their barely legal exhaust systems. Some cities, like my hometown, even have advertising trucks driving around with rotating billboards and blaring sounds — gratuitous air, light and noise pollution on wheels.
Even cities at their most quiet — on an early summer Sunday morning, or a cold midwinter Tuesday night — emit a constant buzzy hum. Like a city’s other forms of pollution, noise degrades urban environments and negatively affects our lives. Consistently, studies confirm what most of us already know intuitively: that being exposed to persistent, loud, unwanted noise causes elevated blood pressure, loss of sleep, increased heart rate and other cardiovascular effects, and changes in brain chemistry. There is a cost to these effects. According to the World Health Organization, these health effects lead to “social handicap, reduced productivity, decreased performance in learning, absenteeism in the workplace and school, increased drug use, and accidents.”
Of course, nature can be noisy too. And that’s why most species have adapted and evolved to be aware of, responsive to and even interactive with the sonic landscape in the wild. Animals process sounds in ways that sometime surprise humans: frogs’ low rumbles communicate location, affinity and allure to friends and foes alike; squirrels listen in on the communication calls of opportunistic blue jays, assessing any risk of invasion to their cache while they are out and about. Such behaviours are what keep them alive, whether they are prey in the instance, or predator.
For urban wildlife too, sonic overload has terrible health effects. After all, persistent noise will interfere with an animal’s capacity not just to communicate, but to protect itself, to procreate and raise its young, even to navigate. A recent study identified permanent damage to mice DNA resulting from acoustic overload, as well as elevated mortality rates among everything from rats to seahorses.
While the effects may be subtle, they can be lasting and profound. For fish in busy urban harbours, prolonged exposure to noise will eventually damage their swim bladders, which serve as their “ears”; bladders also control buoyancy, so effects can be devastating. Duck, chicken and quail embryos, among others, facilitate “hatching synchrony” with other eggs in a nest through a kind of vibration-detection/hearing response. It is a useful trait that eases the burden on the adults caring for them, improving the odds of survival for all involved. But with too much anthropogenic ambient noise, the messages are unheard, leading to fledglings with nutritional deficits and developmental problems incapable of competing and surviving. The flock suffers.
Food gathering is also affected. Many species’ capacity to identify their next meal relies on their highly evolved auditory acuity, which is rendered useless by the urban acoustic overlay. Owls and bats are two city-dwelling animals, both highly effective nocturnal hunters, that rely on low-frequency sound localization to identify, locate and capture their prey. The particular wave frequency of road traffic sounds interferes with their foraging efficiency by masking prey movement sound. As a result, populations dwindle, and the effects reverberate through the local biosphere as it is thrown out of balance. Some but not all species of bat can switch to sonar-based echolocation and somewhat less effectively home in on their prey that way.
When it comes to communications in the wild, there are two types: the deliberate and the inadvertent. In the former, where the animal is attempting to communicate, many species are adapting to city soundscapes by modifying their calls’ timing, increasing repetition, altering tone and raising volume to overcome the buzz’s masking effect. You can hear the changes in bird chicks’ begging, in squirrels’ alarm signals, in the echolocation cries of bats and in the mating communication signals in birds. What’s not heard are the inadvertent signals: the beetle’s rustle on a leaf, the splash of a leaping fish or greedy blue jays chirping as they circle an unattended cache. Without these sonic cues, the precise physical and behavioural adaptations of virtually every species that are so central to staying alive are rendered useless. Survival becomes that much harder.
For many Canadian urbanites, the noise of the city is a constant, to the point that it is a comfort even as it makes us sick. For urban wildlife too, the urban soundscape presents life-threatening challenges. For those that can adapt, the rewards are considerable. But for those whose essential daily functions are impeded or even nullified by the urban cacophony, life in the city is hard and getting harder.