Frogs are not mammals, therefore, no nipples. However frogs are vanishing all over the world, and they are in the middle of the food chain. So, ecologically, their mysterious vanishment threatens the entire world.
Here is an interesting ecological note: Mao Tse Tung said that sparrows stole grain from The People. Chinese killed sparoows in the billions. As a result, the insect population spiked so, the Chinese used so much chemicals to destroy them, they destroyed their bees. Now, humans have to pollinate fruit trees in China. It's pathetic. And they do not do it as well as bees.
Sparrows are omnivorous, they may eat a rice grain or two, but they love a caterpillar.