Recreational fishing is a pastime in which people have come to expect the fish they want in the places they happen to want them. That is, they want their fish stocked and ready to catch, even in places those fish never originally lived. This practice can seem harmless, or even beneficial. But the introduction of one “beneficial” species in Yellowstone National Park suggests how rejiggering the natural world for human convenience can cause ecological disaster for almost everything else.

The gray wolf population in Yellowstone National Park has dropped to about 80 wolves, officials say — less than half of the high population mark in the park. While Yellowstone leaders won’t have an accurate count until the fall after surviving pups are visible, the park’s top biologist doesn’t expect numbers to rise dramatically after litters are included in population estimates.

On the trail of a killer grizzly bear. By Jessica Grose