ANTELOPE ISLAND — Hoping to counter the waning population of bighorn sheep in the western United States, researchers have been hard at work to determine what factors contribute to a successful and enduring re-introduction into the wild.
According to Defenders of Wildlife, a nonprofit organization aimed at protecting species and habitats, there were almost two million bighorn sheep in North America at the beginning of the 19th century. Today, there are fewer than 70,000.
In conjunction with the Utah State Parks and the Utah Division of Wildlife Resources, scholars and experts from Idaho State University and Brigham Young University teamed up to solve the problem.
In a study published this fall in the journal Animal Conservation, researchers found — amidst failing attempts to reintroduce the species — the importance of considering the quality of water sources available to bighorns as well as gender in a given habitat.
Along with the four other authors involved in the research, study co-author and former Idaho State University Ph.D. student Jericho Whiting discovered a separation of genders in bighorn sheep during the course of the year.
He said during the birthing period, males remain near the main water source while females retreat to rocky outcroppings away from the main water source.
Terry Bowyer, professor of biological sciences at ISU and co-author on the study, said this behavior occurs for two reasons.
First, during lactation and gestation, females alter their digestive system while males have little change and, as a result, can subsist on a much lower quality diet. Secondly, in an effort to protect their young and elude predators, females seclude themselves in rugged terrain — usually areas with poor water sources.
Bowyer said having habitats with available water sources is key in retaining bighorn populations — especially in shifting climates.
"The leading reason (for a decrease in bighorn population) is probably disease … and interactions with domestic sheep are often fatal," he said. "But if they had quality water sources during that period, they would probably have been able to resist. Water sources are critical in reintroducing."
Bowyer said the field work studying the bighorn sheep on Antelope Island was done by Whiting as part of his Ph.D. dissertation. The animals were transplanted to the location in 1997. In 2010, the population totaled about 80.
"Antelope Island is unique because of its accessibility," Bowyer said. "Several populations of sheep are close to one another and are readily observable to collect data."
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For more than a decade, research has been conducted on the enigma of the reintroduction and conservation of bighorn populations to better understand the cause of the species' population decline. Numerous studies have sought to track their survival in relation to recreational hunting, food loss from livestock grazing and disease from domestic sheep.
"Jericho (Whiting) has been pursuing those studies," he said. "(He has) worked on five different populations. He and some other researchers are now looking into the diseases aspect."
In addition to Bowyer and Whiting, John Kie and Vernon C. Bleich, — both from ISU — and BYU's J.T. Flinders also co-authored the study.