A Mexican gray wolf at Cleveland Metroparks Zoo in February 2022.

David Petkiewicz | cleveland.com (TNS)

CLEVELAND, Ohio – When it comes to keeping its animal residents separated from its human visitors, Cleveland Metroparks Zoo turns to the Association of Zoos and Aquariums for standards and guidance.

But that wasn’t enough to prevent a Mexican gray wolf from escaping an off-exhibit holding area at the zoo Labor Day morning and briefly roaming a public walkway used by zoo visitiors.

The 4-year-old female named Sarra apparently climbed a nylon-coated, chain link mesh fence and chewed its way through a connection between the fencing and the mesh lid that tops the holding area, Chris Kuhar, the zoo’s executive director, said.

Kuhar said the zoo was in compliance with AZA standards and that the holding area was properly maintained, but that the wolf acted in a way that wasn’t expected.

“She seemed to have other ideas,” he said.

Cleveland Metroparks Zoo is required to file an incident report with the Association of Zoos and Aquariums that details how the wolf breach occurred and what the zoo is doing to prevent it from happening again.

The incident is likely to provide a learning opportunity for the zoo and the Maryand-based AZA that has 238 members, mostly in the United States, and offers dozens of manuals on the care and housing of animals, everything from wolves, big cats and bears to indigo snakes, red pandas and Japanese spider crabs.

The association is the gold standard for private zoo accreditation and is far more detailed in its guidelines than the U.S. Department of Agriculture, which is responsible for licensing animal exhibitors, said David Favre, a law professor at Michigan State University who specializes in animal law.

“It’s the book that most zoos would look at when making plans for their exhibits,” Favre said.

The AZA provides not only general standards that must be met, stating for example, “All animal exhibits and holding areas must be secured to prevent unintentional animal egress,” but also recommends best practices for doing so.

The manual on lions, for example, states how their jumping ability “should not be underestimated” and provides dimensions for enclosures without tops.

“Current practice for new exhibits in AZA institutions has been a minimum 4.5 m (15 ft) height with a turnback/overhang. However, the type of barrier must be considered when determining necessary height. Themed rock walls may be easier for animals to climb if not designed with sufficient negative relief, and chain link fences may be easily climbed by agile animals.”

And when housing chimpanzees, the AZA states, “An outdoor exhibit barrier height of 5.2 m (17 ft) has proven adequate to contain chimpanzees in most cases. However, exhibits should be designed to limit the ability to use trees, structures, or sloping hills to extend jumping heights.”

The AZA manual for large canids, which includes gray wolves, strongly recommends frequent inspection of fences.

“All mesh fencing should be checked for gaps or stretching at bar attachment and extra precautions should be taken where there is any compromised fencing that would allow a canid to get its carnassial teeth close enough to the mesh to bite it,” the manual states.

It also states that “canids are skillful climbers and good jumpers” and recommends “the vertical height of a mesh wall be at least 2.5 m (8.2 ft)” with an overhang extending inward at an upward angle of 35-45 degrees. The wall height can be slighly lower for maned wolves.

The guidelines in the manuals are further augmented by an evolving body of knowledge that AZA members share among its members, said Dan Ashe, president and CEO of the association and a former director of the U.S. Fish and Wildlife Service during the Obama administration.

Ashe said if there was a design flaw in the holding area at Cleveland Metroparks Zoo that information will be shared among the zoo community so they can update their facilities accordingly. No facility is perfect, he said, adding that while the wolf escape was a failure, the quick and safe containment of the animal by the trained zoo staff was a success.

The holding area is connected by a hallway to the Wolf Wilderness exhibit area viewable to the public from Wolf Lodge and has been used many times over the years without incident, according to the zoo. Kuhar said Sarra made her escape probably within an hour of being taken to the holding area along with the zoo’s four other Mexican gray wolves.

The enclosure is checked daily as required by the AZA and no issues with the holding area were documented, he said.

Kuhar said the zoo has re-laced and reinforced the chain link mesh that was chewed apart and also installed an electrified wire for further protection. The extra measures are being taken wherever the fencing meets the lid.

The Wolf Wilderness exhibit area is constructed differently. The mesh fencing is more than 8 feet high and turns back on itself, he said, “and we don’t appear to have any issues there.”

It’s rare that animals escape their zoo enclosures, but it does happen.

One notable incident occurred in 2013 when a relatively harmless red panda named Rusty was discovered missing from the Smithsonian National Zoological Park in Washington, D.C. Hours later he was safely nudged from a tree in the nearby neighborhood of Adams Morgan. It was later determined that Rusty escaped by climbing across vegetation weighed down by heavy rain.

According to the AZA’s red panda manual, they “are adept climbers and swimmers, so enclosure barriers should be constructed with this in mind. Barriers should be at least 1.2 m (4 ft) in height, and the surface should be very smooth or they should be topped with a smooth overhang. Water moats should only be used in combination with other barriers. It has not been determined if hotwire is an effective barrier. Hotwire is used in some cases to keep wildlife from entering the exhibit.”

Sarra and the rest of her pack are now back in the main Wolf Wildnerness exhibit and showing their normal group dynamics, said Jacqueline Gerling, director of communications for Cleveland Metroparks.

Favre said it doesn’t seem like the Cleveland Metroparks Zoo could have reasonably anticipated the wolf escape and that the incident could encourage other zoos to examine their enclosures, especially those that contain four legged animals that can climb.

“I’m not too worried about penguins,” he said.