All of the fish in the acidic, black water of Brazil’s Rio Negro have super sharp teeth. Pieter deHart (Virginia Military Institute) is out to discover what organisms are at the base of the food web where everything seems to be a carnivore. Plus: Over the past 50 years, the Amazon rainforest has lost nearly 20% of its forest cover. Thomas Lovejoy (George Mason University) coined the term “biodiversity” in the 1970s, and has spent the last fifty years studying the effects of fragmentation on wildlife in the Amazon. And: Laura Mentore (University of Mary Washington) studies the Waiwai community in Guyana, and accidentally discovered the path of a special songbird from the rainforest to New York City.

Later in the show: For coastal cities around the world, surf tourism brings huge revenue, but it can also bring conflict. Lindsay Usher (Old Dominion University) studies the rough waves that are sometimes made between locals and surf tourists. And: It’s no surprise that dogs make friends at the dog park, but it turns out people do too. Ed Gomez (Old Dominion University) says that dog parks build community and cut back on crime. Plus: After starting an antique photo collection, Ann-Janine Morey (James Madison University) discovered that old photos of people with their pets can teach us a lot about class.