State wildlife officials say the deaths of more than a dozen bighorn sheep relocated to the Catalina Mountains north of Tucson does not mean the project is a failure.
Some animal welfare advocates are divided over the transplanting last November of 31 bighorns from the Yuma area to the Catalinas.
Some are calling for an end to the project.
But the Center of Biological Diversity, a Tucson-based nonprofit focused on conservation, says the effort will benefit bighorn populations.
Arizona Game and Fish officials say 15 sheep have died, most from encounters with mountain lions.
They recently killed a third mountain lion after it preyed on at least one sheep.
The agency says it is premature to gauge the project's success and the mortality rate doesn't account for recent lamb births.
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