Migration corridors depend on maintaining both habitat connectivity and animals' knowledge of the landscape, demonstrated by these migrating bighorn sheep in Park County, Wyo. Travis Zaffarano Trailcam, Wyoming Migration Initiative/University of Wyoming hide caption

Former President Barack Obama at a gathering during the North American Climate Summit last year in Chicago. Since he left the White House, Obama has stayed quiet, declining to directly challenge his successor. Scott Olson/Getty Images hide caption

At Florida's Tampa Stadium in 1991, Whitney Houston delivered an iconic performance of "The Star-Spangled Banner" to kick off Super Bowl XXV. George Rose/Getty Images hide caption

The Justice Department has charged a North Korean cyber-operative with attacks and mayhem that prosecutors say was carried out under orders from Kim Jong Un. Terence Tan /Singapore Ministry of Communications and Information via Getty Images hide caption

Juan Valiente Velazquez's phone shows a picture of his son, Derickson, who remains in a youth shelter in New York. They were separated by the Border Patrol in Texas in May. Velazquez was deported to Guatemala. Derickson calls his parents three times each week. John Burnett/NPR hide caption

Justin Link leaves court in chains after a plea hearing in Deschutes County Circuit Court in Bend, Ore., Monday, June 11, 2001. Link, along with four other teenagers charged in connection with the murder of Barbara Thomas. He is appealing his sentence in the case. DON RYAN/Associated Press hide caption