Staff Writer Kelly Servick joins host Sarah Crespi to talk about the ins and outs of coronavirus contact tracing apps—what they do, how they work, and how to calculate whether they are crushing the curve. Read all our coronavirus coverage. Edward Gregr, a postdoctoral fellow at the Institute for Resources, Environment, and Sustainability at the University of British Columbia, Vancouver, talks with Sarah about the controversial reintroduction of sea otters to the Northern Pacific Ocean—their home for centuries, before the fur trade nearly wiped out the apex predator in the late 1800s. Gregr brings a unique cost-benefit perspective to his analysis, and finds many trade-offs with economic implications for fisheries For example, sea otters eat shellfish like urchins and crabs, depressing the shellfishing industry; but their diet encourages the growth of kelp forests, which in turn provide a habitat for economically important finfish, like salmon and rockfish. Read a related commentary article. This week’s episode was produced with help from Podigy. Listen to previous podcasts. About the Science Podcast Download a transcript (PDF). [Image: Oregon State University/Flickr; Music: Jeffrey Cook]