They leap out of planes: A U.S. Army soldier with the 10th Special Forces Group and his military working dog jump out of a helicopter during water training over the Gulf of Mexico. | (REUTERS/Manuel J. Martinez/U.S. Air Force/Handout)

They join the circus: Hans Klose, left, and his wife Maria Klose hold a rope for their dog to balance on as they train for the Ringling Bros. and Barnum & Bailey Circus in Mexico City. | (AP Photo/Eduardo Verdugo)

They put in 40-hour weeks: Hazel, a pediatric therapy dog, rests her head on the lap of patient Myleen Lesenana, 13, at Sutter Memorial Hospital's Children Center in Sacramento, Calif. Hazel retired in 2011 after nine years on the job. | (AP Photo/Rich Pedroncelli)

They face the ring of fire: A Belarussian military instructor trains her dog near the town of Smorgon, Belarus. | (REUTERS/Vasily Fedosenko)

They earn frequent flyer miles: Dan McManus and his service dog Shadow hang glide together outside Salt Lake City. McManus suffers from anxiety and Shadow's presence and companionship help him manage the symptoms. The two have been flying together for about nine years with a specially made harness for Shadow. | (REUTERS/Jim Urquhart)

They work search-and-rescue: An emergency responder and a dog look for victims in the debris of the damaged dam of Sayano-Shushenskaya hydroelectric power station near the Siberian village of Cheryomushki, Russia, in 2009. | (REUTERS/Ilya Naymushin)

They brave the elements: A mountain rescuer and his dog take part in a drill on Vitosha mountain, in Bulgaria. | (REUTERS/Stoyan Nenov)

They put up with primping: Sophie, a Standard Poodle, is groomed before her showing at the 2012 Westminster Kennel Club dog show, in New York. | (AP Photo/Craig Ruttle)

They show their respect: Dogs from the Hope Animal Assisted Crisis Response stand at attention during the memorial service for the five firefighters who died fighting the Esperanza Fire, in Glen Helen, Calif., in 2006. | (REUTERS/Mario Anzuoni)