Lions, leopards and tigers —all apex predators — have evolved to dominate their respective environments. Over millions of years, they have sharpened their hunting abilities to the point where they have no predators. What a lion wants, it kills. But now, with the dominance of humans, these predators are being forced to change and hide from what is now the apex predator.
The long-term effect of humans on animals is increasingly well documented. The United Nations warned earlier this year that a million species face extinction this century.
We are living through the sixth mass extinction of life on Earth. The fifth mass extinction came with the end of the dominance of dinosaurs. Now, as a result of the expansion of human civilisation, plants and animals have fewer resources and less space in which to survive.
With this cataclysm occupying the time of scientists, less attention given to the day-to-day effect of humans on how life exists around us. This has been the focus of a team from the University of California-Berkeley, in the United States.
Publishing in the journal Science earlier this month, they concluded that humans are driving animals to spend more of their waking lives at night, to avoid us. The research — The Influence of Human Disturbance on Wildlife Nocturnality — looked at 62 mammal species on six continents.
It found that 83% of the animals had started doing more at night — “separating themselves in time rather than in space”. Where an animal might normally split its hunting, eating and mating evenly between night and day, it would now spend 68% of its time doing these things at night.
Animals are doing this because of humans, according to the researchers. “We assert that fear of humans is the primary mechanism driving the increase in wildlife nocturnality.”
Humans are noisy, they cut down forests, destroy other habitats and chase away — or kill — insects that buzz around their homes or animals that threaten their livestock and pet animals. As humans sprawl across more parts of the world, so the space to get away from humans decreases.
The bigger the animal, the greater the negative effect of human activity. The researchers say this is “perhaps because they are more likely to be hunted or harassed”. Also, because an elephant or a tiger need more space to eat and thrive, they are more likely to come into spaces occupied by humans.
But the researchers say that humans don’t even have to hunt or harass animals for them to adapt to live at night. “Animals perceive and respond to humans as threats even when they pose no direct risk.”
This has all sorts of short-term effects. For example, predators aren’t able to hunt as well, which takes away their role as natural population controls for other animals lower down in the food chain. That prey is also adapting to live in areas where there are humans, albeit doing much of their living at night, so they can escape wary predators.
These changes being exacerbated by the changing climate, as droughts, wildfires and floods dramatically alter the conditions that animals have evolved to thrive in.