At one time, the Mexican gray wolf roamed the mountainous regions of western Texas, Arizona and New Mexico in the thousands.

By 1998 — for reasons that still remain a bit of a mystery to researchers — none remained in the wild.

So on Monday, two of Brookfield Zoo’s own specimens endured a little indignity for the greater good. A researcher with the St. Louis Zoo, home to the gray wolf survival-plan program, extracted sperm samples using a special type of electrode.

“It causes sperm to be expelled,” explained the researcher, Cheryl Asa, of her work.

The sperm samples — which Asa described as “high quality” — will be stored in canisters of liquid nitrogen before being returned to St. Louis.

Asa, who has been involved with the gray wolf program since 1990, estimates she’s repeated Monday’s procedure hundreds of times through the years. The wolves are anesthetized during the procedure, she said.

The idea is to ensure genetic diversity, in case the male in question is unable to reproduce during its lifetime.

The numbers are tiny, but the Mexican gray wolf is now making a comeback in the wild — having been reintroduced in parts of New Mexico, Arizona and across the border into Mexico. Last month, researchers released data showing 83 wolves in the wild. For years since their reintroduction in 1998, the numbers ran in 40s and 50s, Asa said. The wolves typically hunt elk and deer.

“The challenges we face are really in the areas where they are being re-introduced and how well they are being accepted by the people who live there,” Asa said. “In Arizona and New Mexico, some people really like the idea of wolves being there. … Some ranchers see them as a threat and don’t want them there.”

Email: sesposito@suntimes.com

Twitter: @slesposito