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Bighorn sheep were introduced to Tiburón Island in the Gulf of California in 1975, as a conservation measure to restock mainland sheep whose numbers were declining. Before that, bighorn sheep weren't thought to live on the island, but a new study in PLOS One indicates that they may have lived there before.

Researchers from the University of California, Riverside, analyzed mitochondrial DNA fragments obtained from fossilized dung, found in a remote cave, that resembled sheep droppings. By comparing the fossil dung shape and mtDNA to those from ox, deer, and others that live or may have lived in the area, the researchers determined that the samples came from bighorn sheep, though ones belonging to different haplotypes than are present on the mainland.

The researchers estimate that the original Tiburón Island bighorn sheep population went extinct in the past 1500 years or so, and note that the introduced population may be vulnerable to the same factors that lead to the demise of the original group.

"With extended biological baselines, such as the knowledge that the Tiburón bighorn sheep went extinct before, it is possible to refine conservation targets," Benjamin Wilder, a graduate student at Riverside, says in a statement. "Given the cultural and conservation significance of the Tiburón bighorn, actions can be taken to avoid their past fate."