March 3, 2009—The first wild jaguar to be caught in the U.S. was recaptured just a few weeks later on Monday and put to sleep the same day, wildlife officials said.

The jaguar, named Macho B, was caught accidentally on February 18 during a research study on black bears and cougars.

Biologists fitted the cat with a satellite-tracking collar (above, Macho B recovers from anesthesia in February) and released him in the same area, southwest of Tucson, Arizona.

Arizona Game and Fish Department biologists following the cat's movements noticed that Macho B had become lethargic in recent days.

The scientists recaptured the predator Monday and ran tests at the Phoenix Zoo that revealed "severe and unrecoverable" kidney failure—a common ailment in older cats.

Macho B was probably the oldest jaguar known in the wild. He had been photographed around the Arizona-Mexico border since 1996 and was estimated to be 14 to 16 years old.

(See a picture of the first jaguar seen in central Mexico since 1900.)

A necropsy will tell biologists how long the cat had been sick, and those results will be compared to blood work done during his capture.

Comparing the results may show whether Macho B's capture hastened his death—a valid possibility, said Bill Van Pelt, a program manager for Arizona Game and Fish.

Alan Rabinowitz, head of the wild cat conservation group Panthera, said that when older animals of any kind are captured and anesthetized, it can cause sometimes fatal stress.

Jaguars, once common throughout the southern United States, were mostly killed off by the early 1900s.

Observations of a few animals around the Arizona border resulted in the species being placed under the protection of the U.S. Endangered Species Act in 1997.

But the U.S. won't likely be seeing more jaguars anytime soon, Rabinowitz said: Macho B was an anomaly, and there's no evidence of a resident jaguar population in the country.

—Christine Dell'Amore