… American bullfrogs are not native to the Western US. Humans brought them to the region more than a century ago, largely as a food source. And in the years since, the frogs — which are forest green and the size of a small house cat — have multiplied dramatically. … They escaped from farms and, with other accidental and intentional introductions, proliferated until they were common in ponds, lakes, and other water bodies throughout much of the West, including Arizona, California, and the Pacific Northwest. … While western states have rivers and wetlands, permanent warm waterbodies weren’t common until the spread of agriculture and the need for irrigation. … Now ponds, reservoirs, and canals — which bullfrogs love — are everywhere.

Other invasive species news:

• Tahoe Daily Tribune (South Lake Tahoe, Calif.): Not your typical ad: Billboards donated to raise awareness of Tahoe’s latest threat​
• KREX (Grand Junction, Colo.): Zebra mussels update, treatment plan in Eagle County