A common anesthetic is being eyed by federal investigators as a potential cause of the dramatic slowdown in the country's last known wild jaguar that led to a decision to euthanize him.
Around the time of Macho B's death, state and federal officials also speculated in e-mails that the drug Telazol caused or could have caused his decline or exacerbated pre-existing health problems.
The jaguar was anesthetized with Telazol just after researchers found him in a snare trap on the morning of Feb. 18. He was released into the wild soon afterward. His activity slowed dramatically over the next week. He was later recaptured and euthanized on March 2.
Nationally and globally, Telazol is popular but controversial. The drug, in existence for about 25 years, has been widely used to tranquilize many wildlife varieties at many zoos and veterinary clinics. But zoos in Denver, Omaha, Neb., and Orange County, Calif., have stopped using it. There are few if any reports of it harming jaguars, but there have been several reports of it affecting tigers and lions, which are in the same family. Generally, Telazol's use is discouraged on older cats - Macho B was 15 or 16 - or on animals known to suffer from kidney disease- which Macho B may have had.
Still, "it's one of the most widely used drugs in the country. Tens of thousands of doses are given every day to kitties and dogs, and used in over 200 vertebrate species safely," said Terry Kreeger, a Wyoming state wildlife veterinarian and author of a widely used handbook on wildlife chemical immobilization.
But the veterinarian who tranquilized Macho B for his recapture, Ole Alcumbrac of Lakeside, said he avoids using Telazol on large cats because of concerns about its effects on tigers, African lions and other species dating back 20 years.
The U.S. Fish and Wildlife Service's law enforcement chief for the Southwest said the office is looking into the drug's effects on Macho B as part of its seven-month-old criminal investigation into the animal's capture and death, but provided few details.
Of Telazol, the service's Nicholas Chavez said: "We always have to look into what was used. It's just part of being thorough."
Shortly after Macho B's recapture at midday on March 2, an Arizona Game and Fish Department official wrote in an e-mail that "there has been a question raised as to whether the jaguar may be experiencing side effects from the slow metabolization of a component" of the drug. Metabolization refers to the body's physical and chemical processes that create and use energy and can refer to the breakdown of various components of a drug that has entered the body.
"Metabolization can be particularly slow in older animals and those with any renal problems," wrote the e-mail's author, Chantal O'Brien, Game and Fish's research branch chief. "Side effects include hallucinations and a dissociative state which could affect an animal's movements and should disappear as the animal finishes metabolizing the drug."
The next afternoon, Fish and Wildlife Service official Steve Spangle wrote in an e-mail that "it's likely that the sedative either exacerbated a pre-existing condition or was the sole cause of kidney failure."
Veterinarian Alcumbrac declined to say what anesthetic he used for the recapture, because Game and Fish didn't want him to speak on this matter due to the criminal investigation.
Past reports - none peer- reviewed - link Telazol to symptoms of central-nervous-system disease such as unsteadiness in the rear limbs, disorientation, hyperventilation, hyperactivity and muscle tremors in lions and tigers. Those reports are completely valid, Alcumbrac said. Telazol can also result in prolonged and/or stormy anesthetic recoveries in all species, he said.
These symptoms would get worse for 24 to 48 hours, then improve and disappear in three to 10 days on tigers, said a 1990 report for the American Association of Zoos, Parks and Aquariums.
The same warnings are in literature given to people heading for careers in animal control, zoological and veterinary medicine, research and conservation who take courses on wildlife- capture methods from the national Safe Capture International program, run out of Wisconsin.
Anecdotal reports also suggest these symptoms could occur in mountain lions, leopards, Geoffroy's cats (which live in southern South America) and servals (medium-sized, African wild cats), Safe Capture said.
However, those articles aren't scientific, and their warnings haven't held up in zoo or field use, said Kreeger, who co-authored a paper that has been submitted for publication in a peer-reviewed journal on the drug's effects on tigers. It concluded that tigers are no more likely to die after getting Telazol than any species has been shown to die after getting any drug.
"Yes, there have been and will continue to be some adverse reactions by all wild (cats) to this drug," Kreeger said. "But that doesn't necessarily mean that it shouldn't be used on tigers or jaguars under any circumstances."
Telazol has advantages, veterinarians said. The lengthy duration of its effects allows time to weigh, measure and take blood samples from a tranquilized animal, Kreeger said.
It is cheap and not highly controlled, has a long shelf life and works on a variety of species, said David Jessup, a California Fish and Game Department veterinarian.
But it is not advisable for use on animals with kidney problems because the drug is excreted through the kidneys, several manuals have said. It has a slow recovery period, and its effects aren't reversible.
"I have been anesthetizing wild cats for 30 years, and of all the different combinations of drugs I have used, this is the least desirable for use on cats. We don't use it anymore," said Joe Maynard, who runs the Feline Conservation Center, which breeds endangered cats and other rare animals in Southern California.
"The biggest problem with it is that you can knock a cat down, bring it back and think it is there, and five to 10 hours later the cat goes right back down and is sedated again. The recovery will be unpredictable."
Kreeger said he personally prefers another drug combining two anesthetics, ketamine and medetomidine, on large cats, because it wears off more quickly. But like Telazol, ketamine can damage an animal with kidney problems. Its effects also aren't reversible, although it can be combined with a reversible anesthetic, he said.