eli5, why do deer run at the slightest sound or movement, but just stand there and stare when a car is coming towards them at full speed?
In: 10337
Grad student here!
Deer protect themselves from predators by waiting until they’re a certain distance away, then bolting. This makes them very difficult to catch and lets them avoid exhausting themselves every time a potential predator is in the area.
This flight distance is not significantly affected by the speed of approach. In other words: the deer *absolutely* see that car approaching, but it’s often traveling faster than any natural threat. When that car is three seconds from impact, it may still be too far away to be inside that flight distance. Therefore, they wait another second or two before bolting–and get run over instead.
Also, deer have an unfortunate tendency to keep moving in whatever direction they were facing to begin with. If a deer is on the roadside and you cross into its flight distance, it might bolt straight forward–in other words, right in front of you.
Edit: Since there seems to be some confusion, I’ve given multiple presentations on whitetail deer behavior and how environmental factors affect risk. I also worked with a deer ranch prior to grad school, which is how I got interested in the first place.
[This paper](https://www.sciencedirect.com/science/article/abs/pii/S1361920919315330) and [this one](https://www.sciencedirect.com/science/article/abs/pii/S0001457519302052) both have some good background info.
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