Biologists and veterinarians expect to learn more about the medical conditions that led to the demise of a collared jaguar that was euthanized this week due to kidney failure.
Veterinarians from the Phoenix Zoo conducted a necropsy immediately following the death of the cat on Monday, but did not find anything unexpected for an older jaguar. Veterinarians Dr. Dean Rice and Dr. Julie Swenson from the zoo performed the necropsy.
Multiple tissue and organ samples, including from the kidneys, liver, adrenal glands and heart, were submitted for histopathology study to an outside laboratory. Histopathology is the study of microscopic anatomical changes in diseased tissue.
“During the necropsy, we didn’t find anything out of the ordinary for a cat of Macho B’s advanced age,” said Dr. Rice, a veterinarian and executive vice president at the Phoenix Zoo. “But, given the extremely small size of his bladder despite aggressive intravenous fluid therapy, it was apparent that his kidneys were shutting down. I expect the histopathology reports to show that this animal had been experiencing kidney failure for awhile. Kidney failure is more a matter of weeks or months, not days.”
The histopathology report may also reveal if the jaguar had any other medical conditions that were not evident during the physical necropsy. Results are expected in several weeks.
Veterinarians indicated that Macho B showed no physical signs of illness that could have been detected by the biologists that originally collared him after he was unintentionally captured during a mountain lion and bear study. Diagnosis of kidney failure depends on running blood tests to analyze the blood urea nitrogen (BUN) and creatinine levels, which are the two most important indicators of kidney function.
Blood tests run Monday upon arrival at the zoo showed Macho B’s BUN was greater than 180, but an exact level could not be determined because the maximum reading on the diagnostic equipment was 180. The upper limit of a normal BUN level is 30. The cat’s creatinine level was 15.2 with the normal range being .3 to 2.1.
Kidney failure is a common ailment in older cats.
Arizona Game and Fish Department biologists had hoped to learn more from blood samples taken at the original capture, but the samples were deemed to be inadequate for testing. The blood samples were collected for use in DNA analysis in accordance with the capture protocol developed by leading jaguar experts. They were not intended to determine the health or condition of the animal at the time of the collaring, which would have required a different blood handling process.
The decision to euthanize the jaguar was made based on the results of the zoo's blood work. The decision was made jointly between Game and Fish, the U.S. Fish and Wildlife Service and the Phoenix Zoo.
The jaguar was recaptured on Monday after data monitoring revealed a decreased level of activity over the weekend. The cat was brought immediately to the Phoenix Zoo for further medical assessment.
Macho B was believed to be the oldest known jaguar in the wild at 15-16 years old, but biologists hope to better determine the animal’s age from studying one of his teeth using cementum annuli tooth aging, a common technique used to assess an animal’s age.
The jaguar’s initial capture was guided by protocols developed in case a jaguar was inadvertently captured in the course of other wildlife management activities. The plan, which was created in consultation with leading jaguar experts, includes a protocol for capture, sedation and handling.