Desert bighorn sheep at Grand Canyon National Park are testing positive for the pathogens that cause pneumonia, a disease that has reduced bighorn herd sizes across the Southwest.

The Grand Canyon Association, the park's official nonprofit partner, said in a news release that about 75 percent of Grand Canyon bighorns tested so far are positive for the disease pathogens. Pneumonia has been confirmed in at least three of them, the GCA said.

Grand Canyon wildlife biologist Brandon Holton says monitoring the Canyon's bighorn herd is essential to learn how the disease spreads and how it affects the animals. To that end, the GCA is hoping to raise $134,000 to fund a two-year research program that includes collars for GPS monitoring and an overall assessment of the bighorns' health.

To contribute to the program, visit www.grandcanyon.org.

Photo: A desert bighorn sheep at the Grand Canyon. | Patricia Watkins