Squirrels closely mimic bird warning calls and help spread the alarm through the forest that hawks, owls or other predators are nearby. iStockphoto hide caption

itoggle caption iStockphoto

Male treehoppers make their abdomens thrum like tuning forks to transmit very particular vibrating signals that travel down their legs and along leaf stems to other bugs — male and female. Courtesy of Robert Oelman hide caption

itoggle caption Courtesy of Robert Oelman

African forest elephants stampede in the Central African Republic jungle. Courtesy of Cornell Lab or Ornithology hide caption

itoggle caption Courtesy of Cornell Lab or Ornithology

Humpback whales and tanker in Stellwagen Bank National Marine Sanctuary in Massachusetts Bay. Green Fire Productions/Flickr hide caption

itoggle caption Green Fire Productions/Flickr

Humpback whale and calf, off the Revillagigedo Islands, Mexico. Reinhard Dirscherl/Look-foto/Corbis hide caption

itoggle caption Reinhard Dirscherl/Look-foto/Corbis
Hanna Barczyk for NPR

3-D renderings of four skeletons found buried near the altar of an early church in the Jamestown settlement in Virginia. Smithsonian X 3D hide caption

itoggle caption Smithsonian X 3D

The area around the confluence of the Silverthrone and Klinaklini glaciers in southwestern British Columbia provides a glimpse into how the terrain traveled by Native Americans in Pleistocene times may have appeared. David J. Meltzer/Science hide caption

itoggle caption David J. Meltzer/Science

Floodwaters from rising sea levels have submerged and killed trees in Bedono village in Demak, Central Java, Indonesia. As oceans warm, they expand and erode the shore. Residents of Java's coastal villages have been hit hard by rising sea levels in recent years. Ulet Ifansasti/Getty Images hide caption

itoggle caption Ulet Ifansasti/Getty Images

A plume of steam billows from the coal-fired Merrimack Station in Bow, N.H. in January 2015. Jim Cole/AP hide caption

itoggle caption Jim Cole/AP

A Maasai boy and his dog, near the skeleton of an elephant killed by poachers outside of Arusha, Tanzania, in 2013. Jason Straziuso/AP hide caption

itoggle caption Jason Straziuso/AP

This clay facial reconstruction of Kennewick Man, who died about 8,500 years ago in what's now southeast Washington, was based on forensic scientists' study of the morphological features of his skull. Brittney Tatchell/Smithsonian Institution hide caption

itoggle caption Brittney Tatchell/Smithsonian Institution

Chris Tremblay, a member of the Passive Acoustics group at NOAA's Northeast Fisheries Science Center, deploys an underwater recording device along the Eastern Seaboard to listen for the mating sounds of Atlantic cod. Courtesy of Chris Tremblay hide caption

itoggle caption Courtesy of Chris Tremblay

Plankton collected in the Pacific Ocean with a 0.1mm mesh net. Seen here is a mix of multicellular organisms — small zooplanktonic animals, larvae and single protists (diatoms, dinoflagellates, radiolarians) — the nearly invisible universe at the bottom of the marine food chain. Christian Sardet/CNRS/Tara Expeditions hide caption

itoggle caption Christian Sardet/CNRS/Tara Expeditions