Humans take up a lot of real estate—around 50-70% of Earth’s land surface. And our increasing footprint affects how mammals of all sizes, all over the planet, move.
A recent study found that, on average, mammals living in human-modified habitats move two to three times less far than their counterparts in areas untouched by humans. And we can see this pattern globally, from African forest elephants to white-tailed antelope squirrels in North America. The study is the first of its kind to log movement behaviors for such a wide range of mammals across the globe. More than 100 researchers contributed information on 803 individual mammals representing 57 species in total.
Curator of Mammals Bruce Patterson tracked three lions in a pristine wilderness area in Tsavo, Kenya (near where our Tsavo lion specimens lived 120 years ago). Using high-tech collars that continually tracked the lions’ movements through GPS, Patterson monitored these three individuals from 2002 to 2009. One lion—in its natural habitat—patrolled an area twice the size of Chicago to find food, attract mates, and repel intruders.
“All organisms need space,” says Patterson. “They need space to gather their resources, find mates, and perform their ecological services.” For instance, bats need room to find and consume insects and pollinate plants (which amount to $3.5 to 50 billion worth of agricultural labor annually in the US alone). Apex predators need room to hunt and control other species’ populations.
But habitat loss, like clearing rainforests, and fragmentation—constructing a road through the savannah—disrupt these critical animal behaviors. When habitat spaces become too small or too isolated, animals can no longer afford to visit them, changing their space use.
Across the wide array of species examined, the study points to a clear conclusion. For mammal species, the effects of habitat loss and habitat fragmentation don’t discriminate by geographic location, body size, or where that species sits on the food chain—the human footprint threatens most other mammals.