On escaping zoo tigers

I would like to weigh in with a few remarks about the recent tragedy at the San Francisco Zoo where on Christmas Eve a Siberian tiger escaped, killing a young man and wounding two others.

So far there are no witnesses to the escape, but Police Chief Heather Fong did not exclude the possibility of intentional or inadvertent human activities and called for a criminal investigation.

Such a notion is reinforced when a television zoo celebrity like Jack Hanna states that the tiger's leap from the moated enclosure would be "virtually impossible". Apparently he was under the impression that the moat was in compliance with AZA standards.

If working with wildlife teaches you anything, it teaches you not to underestimate the abilities of animals.

The depth of the tiger moat at the outer wall is now said to be 12.5 feet, which is less than 16 feet with a two-foot overhang -- the height recommended by the Association of Zoos and Aquariums (AZA). The width of the moat, as shown in a diagram in the SF Chronicle on Dec 27 -- is 15 to 25 feet, but SF Zoo Director Mollinedo reports that it is 33 ft.

This brings me to 2 observations which are common knowledge among zoo biologists.

First, the leaping or escape abilities of tigers or any other species obey the principle of the bell-shaped curve. A barrier may stop most animals--the ones with average abilities, but an exceptionally athletic or clever animal may be able to breach it.

Second, when an animal is strongly motivated to escape, it may perform feats perceived as "virtually impossible". Years or lifetimes may pass before rare circumstances compel a previously complacent animal to attempt escape. Designing an escape proof enclosure must take these realities into account.

Dave Rentz, a childhood habitue of the SF zoo recently posted a good example of the motivational factor at work. In 1959, Carey Baldwin, then the zoo's director tempted the resident tiger with a chunk of meat at the end of a pole. It motivated the cat to take the tremendous leap, which it accomplished on the first attempt. Fortunately, it ricocheted back into the enclosure. That was enough to decide the director to curtail the tiger's access to the outdoor enclosure.

That was nearly 50 years ago, and since then the zoo and the tiger exhibit have changed a lot.

It is possible that Tatiana simply decided to make her break at the time the three young men were outside the enclosure, and then the cat went into predation mode.

It is also possible that one or more of the young men crossed over the public guard rail and taunted the cat, thus giving it motive to breach the barrier and "pursue the prey". I have a feeling that the survivors of the attack may know some things that haven't yet come to light.

Zoo workers must protect the public from the animals and the animals from the public. In reality they are called upon to check the escape tendencies of their charges far less often than they are called to protect people from the consequences of their own ignorance or stupidity.

In any event, the zoo is ultimately held accountable when an animal escapes. More often than not, animal escape policies kick into practice and disaster if not embarrassment is averted. But now and then an animal escape takes a tragic turn, as did this one, and the zoo director's worse nightmare comes true. It remains to be seen whether the AZA accreditation team that routinely reviews the practices and conditions of member zoos, actually failed to note this deficiency and/or enforce its recommendation.

All of this reminds me of a similar tragedy that Dr Theodore Reed, former Director of the National Zoo in Washington DC related to me before his retirement. Nearly 50 years ago, a small child in the care of an inattentive grandparent squeezed through the public barrier and walked up to the lion cage. The cat reached through the bars and killed the child instantly. It took this tragedy for the US Congress to finally respond to the zoo's standing request to fund major renovation and safety upgrades.