For Immediate Release, October 29, 2007
Contact: Michael Robinson, (575) 534-0360
Government to Capture Endangered Mexican Gray Wolves:
Could Reduce Wild Wolf Population’s Genetic Viability
SILVER CITY, N.M. — Today the U.S. Fish and Wildlife Service authorized the trapping of two genetically vital endangered Mexican gray wolves from the wild in the Gila National Forest of New Mexico.
The wolves are the alpha male of the Aspen Pack and his yearling daughter, whose removal may exacerbate the genetic problem known as “inbreeding depression” that has recently been documented among Mexican gray wolves — just the latest blow in an ongoing battle against this beleaguered animal.
“The Aspen Pack may hold the golden genes to enable the Mexican gray wolf to survive in the face of long odds,” said Michael Robinson of the Center for Biological Diversity. “Trapping these animals will worsen inbreeding depression and may push birth rates downward in a population that is already under siege from government shooting and trapping.”
“The Mexican wolf population just can’t afford the loss of these particular two wolves,” he added.
Inbreeding depression is in part caused by the fact that all the Mexican wolves in the wild trace their ancestry back to just seven animals captured in Mexico — the only known survivors of a previous Fish and Wildlife Service poisoning and trapping program aimed at exterminating the species in both the United States and Mexico. The last wild wolf was caught in 1980, and none have been confirmed in the wild since then.
But not all Mexican wolves are created equal. The seven founding animals came from three founding populations (or lineages) that were bred in captivity separately at first and later combined. All the wolves in the wild contain DNA from one of those lineages, “McBride” (for the name of the government trapper who caught them). But the other two lineages are much rarer.
According to a July 2007 peer-reviewed study by four scientists including two at Arizona State University, Philip W. Hedrick and Richard J. Fredrickson, and Mexican Wolf Recovery Team leader Peter Siminski, McBride-only-lineage wolves have lower birth rates and may include infertile males. In contrast, bi-lineage and especially tri-lineage wolves display enhanced fitness.
The alpha male of the Aspen Pack stems from two of the three lineages of Mexican wolves: McBride and Ghost Ranch (named for the former roadside zoo in New Mexico where they were held). In addition, his yearling daughter, who will be trapped from the wild along with him, is one of only seven mature wolves in the wild known to have genes from all three lineages, including the rarest, Aragon (named for Aragon Zoo in Mexico City).
The Aspen Pack has four young pups, the most among any pack documented this year and likely a reflection of their greater genetic diversity; they are tri-lineage also. Those pups and their mother will lose crucial members of their family, which may hurt their chances for survival.
The Aspen Pack have killed cattle in an area near the Beaverhead Ranger Station, where wolf pack after wolf pack have met their demise as a result of scavenging on dead livestock they did not kill, then beginning to prey on cattle. It is not known whether the wolves whose trapping was just authorized followed the same pattern.