An apex predator is a killer. Usually large and terrifying, they enjoy the privilege of life at the top of a food chain. Nothing will eat them, leaving them free to wreak carnage on more vulnerable creatures. In biology, it’s a term normally reserved for animals like polar bears, tigers and wolves. But CrowdScience listener Eoin wonders whether there’s a non-animal candidate for apex predator: the car. After all, worldwide, more than 1.5 million humans die on the roads each year, while pollution from traffic kills millions more. And that’s just the impact on us. What are cars doing to all the other species on this planet? Host Anand Jagatia hits the road to investigate. En route, we’ll be picking up some scientists to help answer the question. It turns out to be so much more than a question of roadkill: cars, and the infrastructure built to support them, are destroying animals in ways science is only now revealing. How did the wildlife cross the road? We go verge-side to test four different approaches. And we hear how cars manage to kill, not just on the roadside, but, in the case of some salmon species, from many miles away. Gathering as much evidence as possible, we pass judgement on whether the car truly is an apex predator. Contributors: Samantha Helle - Conservation Biologist and PhD student, University of Wisconsin–Madison Paul Donald – Senior Scientist, BirdLife International and Honorary Research Fellow, University of Cambridge Zhenyu Tian – Environmental Chemist and Assistant Professor, Northeastern University Presenter: Anand Jagatia Producer: Marnie Chesterton Reporter: Camilla Mota Editor: Cathy Edwards Studio manager: Donald MacDonald and Giles Aspen Production co-ordinator: Ishmael Soriano (Image: Illustration of a deer in front of a car - stock illustration Credit: JSCIEPRO/SCIENCE PHOTO LIBRARY via Getty Images)
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So a neutron star is kind of.
About the size of Chicago.
Unexpected elements from the BBC World Service.
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I was out with two tiger trackers from Nepal, Tiger Trust, and we had found a set of tiger pug marks.
That's what they're called.
It's a special word for tiger tracks.
And we start hearing a barking deer and they make a very distinct alarm call and the birds just start to settle a little bit, and we all kind of look up and we go, oh, there's a tiger around.
The.
The air just seems to kind of stand still for a moment, especially after barking deer are really the first alarm calls for when there's a predator in the area and that there's danger.
And so all the other animals kind of follow suit and then everything starts to pick up again.
So we go back down the same pathway we came, and we see another set of tracks going in the opposite direction.
These were not there before.
And this tiger had gotten within probably 50, 60 yards of us and completely avoided us and gone in the opposite direction within a matter of five or ten minutes that we were measuring these tracks.
Very Sneaky.
Welcome to CrowdScience from the BBC World Service.
That thrilling account of an encounter with a big cat comes from zoologist Sam Heller, who's been studying them in Nepal for decades.
I'm Anand Jagatiya, and this is the show that answers your science questions.
The reason why we're talking to Sam about big predators like tigers is because that is sort of what this week's question is all about.