Once upon a time, there were tens of millions of bison on the North American continent. Today, there are somewhere between 400,000 and 500,000. Most are in commercial herds, with a relative few in private herds and on public lands.

Should there be more bison on the continent? There potentially is space for them on places like the 550,000-acre Thunder Basin National Grassland in Wyoming, the nearly 600,000-acre Buffalo Gap National Grassland in South Dakota, and the roughly 440,000-acre Comanche National Grassland in Colorado, just to name three locations.

And a new study out this past week explains why bison are more beneficial for grasslands than traditional livestock, and the benefits increase as herd size does. To understand what’s going on, we’re joined today by Professor William Hamilton from Washington and Lee University in Virginia, one of the study's co-authors.

It’s been said that the night skies are the other half of the National Park System. And it only makes sense, for when you’re in a park and the sun goes down you tend to look into the night sky to spot constellations or, if you’re lucky enough and in the right place, a comet overhead.

Keeping that other half of the park system in mind, today’s podcast will be a somewhat dark one. Our guest is Jeff Pfaller, a fine arts photographer who spent five years capturing night skies over national parks and other public lands.

A book coming out in October by Pfaller showcases synchronous fireflies at Great Smoky Mountains National Park, the famous illumination that makes Horsetail Fall in Yosemite National Park look like a cascading stream of lava, a shot of the whirling Milky Way against a colorful stump of petrified wood at Petrified Forest National Park, and many other nighttime images that remind us of that other half of the park system is overhead.

National Parks Traveler readers can obtain a $15 discount on the book's purchase price by using this link to order it.

Vessel-whale collisions are a significant concern in Glacier Bay National Park and Preserve, where nutrient-rich waters support a seasonal influx of humpback whales and other marine mammals. As one of the most visited marine parks in Alaska, Glacier Bay sees a high volume of vessel traffic, including cruise ships, tour boats, and private craft.

This summer an adult humpback whale was seen with a fresh, one-foot gash behind its dorsal fin which appeared to be from contact with a boat propeller. This week the Traveler’s Lynn Riddick reaches out to biologist Chris Gabriele to discuss this incident and the park’s strategies to reduce whale collisions, including monitoring whale activity, warning systems, and public education.