Crested Porcupine, Hystrix cristata (1596–1610) by Anselmus Boëtius de Boodt. Original from the Rijksmuseum.… Free Image from public domain license 
Cpl. Rory Hamill, a combat-wounded Marine, takes his and his girlfriend's dog Tank for an early morning walk in Lakehurst… Free Image from public domain license 
Dalmatian sitting in red car. Original public domain image from Flickr Free Image from public domain license 
Blue Whale painting. Original public domain image from Wikimedia Commons Free Image from public domain license 
Polar bear at the Arctic. Original from NASA. Digitally enhanced by rawpixel. Free Image from public domain license 
Gigantic Whale: The Greenland Whale (or Baloena Musculus), Blue Whale, Balaenoptera musculus (Linnaeus,1758) (1832) by George… Free Image from public domain license 
A red fox prowls for voles, hidden beneath the snow, in Yellowstone National Park in the western U.S. state of Wyoming.… Free Image from public domain license 
Elephant by the waterfall. Original public domain image from Wikimedia Commons Free Image from public domain license 
A mixed herd of wild and domesticated horses frolics on the Ladder Livestock ranch, at the Wyoming-Colorado border. Original… Free Image from public domain license 
Architecture of two persons turning their backs to one another at Burning Man. Original public domain image from Wikimedia… Free Image from public domain license 
A red fox prowls for voles, hidden beneath the snow, in Yellowstone National Park in the western U.S. state of Wyoming.… Free Image from public domain license 
Lions in the grass at the Wild Animal Sanctuary near Keenesburg, Colorado. Original image from Carol M. Highsmith’s… Free Image from public domain license 
Fox lying on snow. Original public domain image from Wikimedia Commons Free Image from public domain license 
Wild red fox watches prey in the winter. Original public domain image from Wikimedia Commons Free Image from public domain license 
Horses head for the corral in the daily roundup of horses, Riverside, Wyoming. Original image from Carol M. Highsmith’s… Free Image from public domain license 
Darkened image of dolphin. Original public domain image from Wikimedia Commons Free Image from public domain license 
Sharks underwater. Original public domain image from Wikimedia Commons Free Image from public domain license 
Jellyfish. Original public domain image from Wikimedia Commons Free Image from public domain license 
Leopard perched in a tree stalks its prey from above in Masai Mara Game Reserve. Original public domain image from Wikimedia… Free Image from public domain license 
Cat looking up from the kitchen floor. Original public domain image from Flickr Free Image from public domain license 
A thoughtful black-and-white photo of a giraffe's head. Original public domain image from Wikimedia Commons Free Image from public domain license 
Squirrel jumps upon a tree. Original public domain image from Flickr Free Image from public domain license 
Gray and white tabby cat. Original public domain image from Wikimedia Commons Free Image from public domain license 
A herd of grey and white horses on a green pasture in Wales. Original public domain image from Wikimedia Commons Free Image from public domain license 
Sioux Falls, United States. Original public domain image from Wikimedia Commons Free Image from public domain license 
Brown monkey. Original public domain image from Wikimedia Commons Free Image from public domain license 
White sheep. Original public domain image from Wikimedia Commons Free Image from public domain license 
Georgia Aquarium, Atlanta, United States. Original public domain image from Wikimedia Commons Free Image from public domain license 
A wild fox sitting in a field of dry grass. Original public domain image from Wikimedia Commons Free Image from public domain license 
Brown fox sitting on grass field. Original public domain image from Wikimedia Commons Free Image from public domain license 
Close-up of a blue-eyed cat looking up. Original public domain image from Wikimedia Commons Free Image from public domain license 
Fox beside a field in Silverthorne, United States. Original public domain image from Wikimedia Commons Free Image from public domain license 
Herd of dairy cattle. Original public domain image from Wikimedia Commons Free Image from public domain license 
An elephant with ivory tusks walking next to a baby elephant in the wild. Original public domain image from Wikimedia Commons Free Image from public domain license 
Face to face with a highland cow in Elgol, United Kingdom. Original public domain image from Wikimedia Commons Free Image from public domain license 
Close-up of a black Persian cat. Original public domain image from Wikimedia Commons Free Image from public domain license 
Livestock at Doug Jernigan Farms, a three-generation family farm and employer who, a few months earlier, refinanced a first… Free Image from public domain license 
Horses head for the corral in the daily roundup of horses, Riverside, Wyoming. Original image from Carol M. Highsmith’s… Free Image from public domain license 
Family of zebra stand in a grassy savanna. Original public domain image from Wikimedia Commons Free Image from public domain license 
Person holding flag with explore word. Original public domain image from Wikimedia Commons Free Image from public domain license 
Black and white shot of shark swimming underwater with bubbles. Original public domain image from Wikimedia Commons Free Image from public domain license 
Joe Purcell, owner of the Purcell Ranch near Lolo, Mont., raises hogs and uses the manure byproduct to augment his soil where… Free Image from public domain license 
Fawn pug lying on the floor. Original public domain image from Wikimedia Commons Free Image from public domain license 
Close-up of a tabby cat looking up with wide eyes. Original public domain image from Wikimedia Commons Free Image from public domain license 
Bunny in a field. Original public domain image from Wikimedia Commons Free Image from public domain license