Global Impact: Animals Are Changing Their Sleep Cycles To Adamantly Avoid Us


Other mammals are absolutely terrified by us. Have you ever wondered why cute little chipmunks and rabbits run for their lives every time we come near? That’s because their parents and their parents’ parents have spread the knowledge from generation to generation that we as a species are bad news. We’re noisy and loud, we hunt them and build over their homes. They will do anything to get away from us, including switching their active hours from day to night when humans are least active.

A recent study done by Katelyn Gaynor and colleagues, published in Science magazine, showed that out of 62 species from six continents, all showed a strong shift in activity if these mammals resided in locations where many humans are present. The average nocturnality of these animals increased 1.36 percent in areas of high human disturbance, although much higher in certain species. Species such as the Red Brocket Deer were about 50 percent nocturnal in areas of low human disturbance and became 75 percent nocturnal when the danger of being hunted by humans was present. Sable Antelope went from 5 to almost 50 percent nocturnal due to a large degree of sport hunting.

Hunting isn’t the only reason these animals have switched their cycles. Because of urban development, the wild boar has changed its cycle from about 50 to almost 100 percent nocturnal. And if you thought we could only affect the prey animals, think again even apex carnivores are fearful of us. We have become this incredible apex ‘super predator’ by the massive degree of things we own. We have large destructive cars, guns, and other machines. Hiking and farming aren’t so harmless either. Well, Coyotes don’t find it harmless, they have switched from 50 to about 70 percent nocturnal to avoid hiking humans. Even Tigers in Nepal steer clear of farmers during the day, switching their cycles from 70 to about 80 percent nocturnal.  

Mammals haven’t had to retreat to the darkness since the age of dinosaurs when they first evolved. For the mammal’s first 100 million years on this planet, they used the night time to hide from their cold-blooded predators. Dinosaurs needed the warmth of the sun for their energy so since mammals are endothermic, producing their own heat, it really aided them in the night. Once the dinosaurs went extinct, the mammals were free to explore what mysteries the daytime brought, and they flourished, becoming larger and ruling the land.

Then came us to ruin their fun. We started to develop the land to suit our needs, destroying the mammals’ homes and hunted the native animals that got in the way. No wonder they’re deciding to retreat back into the darkness. Throughout the study, Gaynor discussed our role as the apex ‘super predator’ of which mammals have no refuge from. As our populations increase substantially every year, by two million people, there are fewer spaces for these animals to hide. Therefore, they have begun to hide temporally, through time.

This shows a great degree of behavioral plasticity within these animals, which is defined as changes in an animal’s behavior due to changing environmental conditions. This is how animals adapt or change quickly to become more fit for their environment. While some people may say this is fantastic, who wants to see coyotes and tigers during the day while they hike? We must also consider what this means for these animals. Animals such as the Sable Antelope, for example, have less access to water during the day and may become detrimentally dehydrated just because it doesn’t want to be hunted by humans.

There are a various cause and effect relationships happening in our ecosystem and these are called tropic cascades. An example of this would be the in the coyote. If the coyote, who naturally spends equal time out during the day and at night hunting becomes more nocturnal, it could affect how well it hunts its prey. If coyotes can’t hunt prey effectively, such as deer, then the deer may reproduce wildly and uncontrollably. A similar change happened in Yellowstone National Park when wolves were removed from the ecosystem. When the population of deer skyrockets, our foliage will be eaten until its bare and more tickborne diseases may spread to humans, as deer are an important hosts for ticks.

As that’s just a simple example of a tropic cascade, more intense interactions may result from similar shifts such as that one.  Animals may reshape their diets to acclimate to this new night shift eating schedule and ones that aren’t familiar with certain predators may have poor strategies to protect themselves against them. Poor social skills of non-nocturnal species may occur along with poor navigational strategies in those that aren’t used to the dark. There’s a whirlwind of effects that can occur and this is all new research, it opens up a new domain for conservation and awareness.

As this world becomes more and more crowded, mammals had no choice but to think of us as the new dinosaurs-like predator and switch up their strategies a bit in order to survive. Although, not all mammals are willing or able to do this just to avoid people because of many of those costs I mentioned earlier. Even the animals that are able to could be more vulnerable to the increasing footprint of humans as we expand further and further.

Even though other mammals are making it easier for us to not to notice them, they are still living along-side us and in areas of high human impact maybe managers should consider enacting policies that leave some daylight for the animals. They’ll never stop being fearful of us but maybe we can at least give them some space to eat dinner.