Although Brookfield Zoo officials said the injuries of a 4-month-old tiger cub that lost its right foreleg and part of its tail were not life-threatening, the male Amur tiger died Sunday.
The cub died while coming out of anesthesia for ongoing treatment after his father bit off the cub's foreleg Sept. 27, a news release from the Chicago Zoological Society stated. The preliminary examination did not determine why the cub died, but the zoo says it plans to conduct more pathology tests in a week.
Though no one witnessed the attack, zoo officials said the cub's father apparently bit off the leg when the cub extended his right front paw between the bars of a gate separating the two.
The cubs' frantic mother then chomped on the tails of the male cub and his twin sister to try to drag them out of reach.
In an assessment completed Friday, the Chicago Zoological Society determined it is responsible for the attack, and significant changes are being made to the housing policies for young carnivores, as well as training and staffing, the zoo's statement said.
The assessment, which included staff interviews, an evaluation of the holding pens, internal policy reviews and a report by a U.S. Department of Agriculture investigator, concluded "a questionable staff evaluation had been made of the cubs' ability to interact with the adult male."
Zoo authorities overlooked a "very small gap" in the door placed between the cages of the adult and the cubs, the news release stated.
The USDA inspection cited the zoo for inadequately separating the tigers, and the society's investigation agreed the zoo should not have used a barred gate between the cages, the release states. In response, adjustments have been made to staffing and housing policies, and off-site training for some keeper staff is scheduled.
The female cub continued to recuperate at the animal hospital Sunday.
The cubs' maiming occurred about 8:15 a.m. in an indoor holding pen behind the public tiger exhibit, said Kim Smith, Brookfield's vice president for animal care.
After hearing a commotion from the animals, keepers ran to the tigers' pen. By the time they arrived, the mother had pulled the cubs out of reach of the father.
The 13-year-old male, Robeki (pronounced ROE-kee), fathered the cubs with his mate, 12-year-old Tiara, but they are a tiger family in name only. In the wild, Amur tigers live solitary lives, getting together only to mate. Males don't participate in rearing and protecting their young, which are cared for in isolation by the mothers.
Last year, in March, a Mexican gray wolf in a back holding area also lost a leg in mysterious circumstances. Keepers found the wolf hobbling on three legs one morning but could not find the severed portion.
Both the zoo and the USDA launched investigations, surmising that the wolf may have gotten its leg caught in a fence, breaking it so severely that the wolf or another animal chewed it off. The wolf recovered and is now living in a wildlife rehabilitation center in Arizona.
The zoo subsequently redesigned its wolf exhibit fencing. Jessica Milteer, a USDA spokeswoman, said her agency found no "indication that anything happened at the zoo that was in violation of animal welfare regulations," and no enforcement action was taken.
Smith said experts who run captive breeding programs for Amurs said the female cub's shortened tail should not affect her.
There are 438 Amur tigers living in North American and European zoos, so many that zoos limit their breeding, but in the wild they are extremely endangered, with perhaps only 500 living in far eastern Russian provinces and a few scattered in China and North Korea. Once called Siberian tigers, they no longer exist in Siberia.
The tigers grow larger than any other cat species: 800 pounds at full maturity for males and 500 pounds for females. They are fierce, muscular hunters that live in rugged mountain forests.
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