Deer in the headlights and what it means for our kids
Why do so many deer get hit by cars? Cars are big, they are loud, and they are predictable. They are basically predators with zero stealth.
As Mary Roach explains in Fuzz: When Nature Breaks the Law (Amazon), it comes down to speed.
Let’s start at the beginning. Running from a predator is a lot of work and animals don’t do it just for fun (except for humans, because we are weird) so if an animal doesn’t have to run, they will typically stay put.
A deer may freeze when she spots a predator because chances are it has not seen her or is not interested. A bird may take one last bite of tasty roadkill before he flees from a car. As long as the prey maintains a spatial margin of safety, there’s no point in running… yet.
When a predator is spotted, the prey animal will mentally calculate how close it can let the predator get and still have a good chance of escape. This is called the Flight Initiation Distance. and until the predator comes within that distance, the prey might as well keep its position.
The Flight Initiation Distance depends on the predator’s speed which the prey judges by how quickly the predator “looms,” or changes in size as it approaches. Looming perception tells the animal “how long will it take that predator to get from A to Me?”. Or put simply, “Do I have the time/space to escape?”
This system works pretty well, unless that predator approaches extra fast. How fast is that? It appears that prey accurately judge looming at speeds up to their natural predator’s speed. The fastest land predators in America can run at around 45 mph so it’s probably somewhere in that range for deer.
What happens if the predator has an engine and exceeds that 45 mph speed cap? The studies suggest that anything over that speed cap is perceived as that speed cap. Put simply, if a car barrels down the road at 85 mph, the deer’s brain will think it is only going 45 mph and greatly overestimate the amount of time it has to get away.
This is the “deer in headlights” phenomenon as the poor deer’s brain struggles to gauge looming and decide to run. It has no reason to believe that this hunk of metal and aluminum is barreling towards him at a speed greater than his brain can process. Not to mention that looming is probably harder to perceive when it’s two lights rather than an actual animal body.
But what about people? Adults seem to accurately judge looming fairly well and we have the benefits of experience, but in kids, this skill is not fully developed. For children, 20mph may be the max speed at which they can perceive looming and accurately judge how much time they have to get out of the way. Anything above 20 mph may look like 20 mph to them.
“It’s not that kids aren’t looking when they cross; they’re also not seeing”
This means that even if your kids look both ways, they can’t accurately judge a car’s speed. They might think they have time to cross when in fact they do not, being caught like a deer in the headlights. Short answer: Keep your kids away from the street and obey neighborhood speed limits!
For more on animals jaywalking and breaking other laws, check out Fuzz: When Nature Breaks the Law (Amazon).
For ways to help keep yourself and your kids safe when crossing the street at night, check out our blog post where we discuss a strategic way to use a flashlight when crossing the street: Illuminate Your Path: Using a Flashlight for Safe Street Crossing at Night
