You Washingtonians may have heard the news about the deer that jumped into the cheetah den at the National Zoo last week. The cheetahs did pounce the deer, but animal keepers were able to distract the cats while the deer escaped with just a tail wound.

Some people wondered, however, how could deer escape from the yard so easily while cheetahs could not? Amy was wondering the same thing, and emailed the Zoo to ask about it. Here’s the wonderfully detailed reply she got from zoologist and African Savanna animal keeper Craig Saffoe, who’s allowing me to reprint it here:

First you should know that the Post didn’t get the story 100% accurate. True – a deer did manage to get into one of the cheetah enclosures, however he did not get out on his own.

It is not difficult (especially for an animal with the athleticism of a white tail deer – they can clear 10 foot fences easily) to get into the cheetah enclosures from the public side. It’s just a matter of jumping the 4 foot guardrail and clearing a moat that is only about 3 feet wide. As long as the jumper can clear the hotwires the only thing left to do is make the 13 foot drop to the ground without hurting itself. Again no problem for a deer. Getting out is another story. The animal would have to make a 15 foot leap up (without getting tangled in the 10,000 volts of hotwire) and clear the 3 foot moat in the same leap. Quite difficult even for a white tail. In fact it appears that this guy tried to do just that in an effort to escape the cats, but got tangled in the wires (probably didn’t feel very good) and couldn’t get out of the yard. The deer did manage to get into a pond in the cheetah yard and was smart enough to realize the the cats wouldn’t go into the pond after him (cheetahs are hydrophobic). When we (keepers) arrived, we shifted the cats out of the yard and escorted the deer out of the yard through a series of open gates that lead to the main road of the zoo and out into the Rock Creek area. This is not the first deer to get into the cheetah yards (there have been 3 others in the past 10 years) – but he was the first one to survive.

Why can’t the cheetahs just jump out? Very good question but you needn’t worry. Short story – cheetahs can move far on a cursorial path, but can’t jump very high at all. Long story – Cheetahs are incredible runners, but they are not good jumpers. Almost all of the cheetahs speed is generated from it’s back. These animals have about 60% of their entire muscle mass packed onto their spine which allows them incredible flexion and extension of their backbones at an almost unfathomable rate. With that much muscle allocated to the back, there is surprising little muscle mass on their hind legs (where jumping power comes from). Next time you get a chance compare a picture of a cheetah with a real jumping cat like a cougar or a jag and you’ll see the differences. A good cheetah jump is about 6 or 7 feet up. Like I said earlier, the fences in our enclosures are 13 – 15 feet high and are laced with hotwires (in case we get the ultra motivated cheetah). A cougar, leopard or jaguar would be out of these enclosures in a heartbeat, but cheetahs just can’t do it.

There you have it. The deer only got out with some zoo help, cheetahs can’t jump as high, and my favorite part: this isn’t the first time a deer has gotten in there, but it’s the first time one has survived. Happy cheetahs!

Here’s more on Craig Saffoe, who works in that most enviable of jobs: head cheetah keeper at the National Zoo.