They don't like steep slopes, but they're capable of scrambling over rocky faces. Perhaps Tatiana got out that way, I thought, but I soon rejected the idea.
The aerials showed me the initial reports were inaccurate. There never was a wall and a moat. Tatiana's compound was nothing like Gretchen's. There was only a moat, and the so-called wall was simply the far bank. The moat isn't, in zoological terms, either a physical or a psychological fail-safe. It's simply a way of recessing a wall into the earth so it doesn't block human sight lines.
A dry moat can actually be worse than a wall because the far bank gives a tiger launching points. When the jump-off point is around the same elevation as the top of the far bank, as it is at the San Francisco Zoo, the moat's depth may not matter. The question becomes not how high the tiger can jump but how far it can leap. History and a close look at pictures of the grotto suggest that is exactly the question San Francisco and zoos everywhere should be asking.
One rule of thumb is that a moat needs to be four times the average body length of the species it is suppose to contain, which for an Amur is just an inch shy of six feet. That means a moat should be at least 24 feet across. I'm skeptical of this calculation. Mean body length for a mountain lion, for example, puts the recommended moat distance at just over 13 feet, yet there are credible reports of mountain lions leaping 35 feet.
An alternative is the cat's known leaping distance plus 20 percent. The oft-reported leaping distance is 20 feet, so the minimum width would again be 24 feet. There are accounts of tigers leaping 30 to 33 feet, but I have not been able to determine whether these were documented. In China, the Yangtze River runs through Leaping Tiger Gorge, so named because a tiger leaped the river to escape a hunter, according to local lore. The river at its narrowest is about 82 feet wide. The story is a fable, but it gives you a sense of the tiger's reputation as a prodigious leaper. Based on my years of observing tigers at play, 30 feet does not seem at all out of the question.
Such calculations likely contributed to the standards of two Association of Zoos and Aquarium committees. Both the AZA Felid Technical Advisory Group and the AZA Nutrition Advisory Group recommend a minimum width of 25 feet for a tiger moat.
So imagine my reaction when Zoo director Manuel Mollinedo stated his belief that the tiger could not have escaped from the moat, while also saying that according Zoo records, the moat was 20 feet across. I have never met Mollinedo, and he didn't return my calls, but in my opinion the man has no idea what he is talking about.
Then came reports that the moat is 33 feet across. Well ... sort of, maybe, kind of. It may be 33 feet from wall to wall, but the bank on the grotto side slopes to a flat floor 20 feet across. Some clever bloke decided to make the transition look more natural by placing fake boulders atop the slope. These project out into the moat and in some cases rise above the grotto floor. A tiger that launched from the lip of one of these would have to cross far less than 30 feet.
I asked the Zoo for the narrowest leap between the outside wall and these "rocks." Zoo officials didn't respond. So I went out there with my tape measure.
The tiger grotto is closed off, and Zoo officials also declined to answer my request for access to the area. But through a side window I was able to study a neighboring lion grotto with a similar design. A rock ledge stuck out into the moat more than seven feet, leaving a gap I measured along the outer wall at about 25 feet.