Positive signs for bighorns: breeding and lamb survival

Another positive development: There is, so far, a 100 percent survival rate among bighorn lambs observed recently in the Catalinas north of Tucson.

“It’s been great news, and we haven’t had a bighorn mortality in the Catalinas for a while” — since last December, said Raul Vega, regional supervisor for the Arizona Game and Fish Department.

Bighorn sheep from healthy herds elsewhere in Arizona were released in the Catalinas in November 2013 and November 2014. Some animals have fallen prey to mountain lions, but 40 sheep are known to be alive now based on data from GPS collars on the animals.

Lambs previously have been born from ewes that were pregnant at the time they were brought to the Catalinas — but recent observations indicate breeding has taken place in the range.

“An observation of ewes from the 2013 translocation, with lambs this year, is evidence of a ram from the same translocation breeding last year,” says a report this week from the Game and Fish Department. “This marks the first breeding in the Catalina Mountains among individuals of this reintroduction effort.”

The report notes that ewes brought to the range in the November releases were already pregnant at the time they were captured from source populations, so their lambs weren’t the result of breeding in the Catalinas. But births this year from ewes released in 2013 are evidence of breeding last year in the range.

Concerning lamb survival, the report said, “Also of note was a group of 6 ewes and 6 lambs observed last week, representing 100 percent survival of lambs in this particular group thus far. Continued survival is good news at this juncture. The statewide survival rate of lambs within their first year is approximately 25 percent. Time will tell how many of these lambs will persist.”

Vega said the bighorns appear to have settled in habitat conducive to their survival.

“They are grouped together and have found the best location, with good escape routes from predators,” he said.