The Animal Rescue League offered this demonstration last year in Boston, with a stuffed dog, on how hot the inside of a car can get. Boston Globe via Getty Images hide caption
Humane Society of the United States
Wayne Pacelle, former CEO of the Humane Society of the United States, at a 2015 news conference. Pacelle resigned Friday. Jonathan Bachman/AP Images for The Humane Society of the United States hide caption
Humane Society CEO Wayne Pacelle speaks on the importance of farm animal protection in 2015. Jeff Lewis/The Humane Society of the United States hide caption
Macaques are social animals, whether in a group enclosure like this one at the Gelsenkircen zoo in western Germany, or in the wild. But many research monkeys are still housed in separate cages. Patrik Stollarz/AFP/Getty Images hide caption
Trainers (from left) Joe Sanchez, Brian Faulkner and Kelly Aldrich work with orcas Trua (front to back) Kayla and Nalani during the "Believe" show in Shamu Stadium at the Aquatica by SeaWorld theme park in Orlando, Fla., in 2011. Phelan M. Ebenhack/AP hide caption
A screen grab from an undercover video released by the Humane Society of the U.S. shows a pig in a gestation crate at Iron Maiden Farms in Owensboro, Ky. Courtesy of The Humane Society of The United States hide caption