Online News Editor David Grimm joins host Sarah Crespi to discuss a controversial new paper that estimates how many rodents are used in research in the United States each year.

Though there is no official number, the paper suggests there might be more than 100 million rats and mice housed in research facilities in the country—doubling or even tripling some earlier estimates. 

Next, Staff Writer Jennifer Couzin-Frankel talks with Sarah about a new theory behind the cause of irritable bowel syndrome—that it might be a localized allergic reaction in the gut. Sarah also chats with Taline Kazandjian, a postdoctoral research associate at the Centre for Snakebite Research & Interventions in Liverpool, U.K., about how the venom from spitting cobras has evolved to cause maximum pain and why these snakes might have developed the same defense mechanism three different times.