See 8 animal species that came back from the dead

Pictured are two golden pheasants (Chrysolophus pictus), a species native to mountainous forests of western China. The birds were photographed by Joel Sartore, a National Geographic fellow and frequent contributor to the magazine. Sartore recently produced the book RARE: Portraits of America’s Endangered Species. He also founded the Photo Ark, an online archive of pictures of threatened species (from which this gallery was sourced).

Not all threatened species are beautifully plumed birds or other charismatic megafauna. Some of the most endangered species include freshwater mussels, like the Cumberlandian combshell (Epioblasma brevidens) pictured from the Photo Ark. The species makes its home in rivers in North America, but it is listed as critically endangered by the International Union for Conservation of Nature (IUCN), largely thanks to habitat loss and pollution. href="http://newswatch.nationalgeographic.com/2012/05/18/delaware-river-basin-mussels-freshwater-species-of-the-week/">Freshwater mussels tend to be highly sensitive to subtle changes in water clarity, as well as presence of toxins. Yet they serve valuable ecosystem services by filtering water and providing food for a host of wildlife. Sartore added, "Each loss of a species is tragic, epic, and absolutely an unacceptable outrage. All can be used to elevate the level of attention needed to save those species that remain. Public awareness, funding, and action are all needed to move the ball forward when it comes to saving species."

The nene or Hawaiian goose (Branta sandvicensis) is officially listed as “vulnerable” by the IUCN. The goose is native to the islands of Maui, Kauaʻi, and Hawaii, and it is the state’s official bird. Like many species of birds on Hawaii, as well as many other islands, the nene declined precipitously after human colonization of its habitat. Hunting and predation by introduced species—including mongoose, dogs, and pigs—drove the population down from an estimated 25,000 when James Cook arrived in 1778 to a mere 30 birds by 1952.

The nene responded well to captive breeding, and birds were released in the 2000s. The nene is gradually growing in number, although scientists worry about genetic diversity.

Sartore said, “When we save other species, we're actually saving ourselves. We must have healthy, functioning ecosystems to provide us with clean air, clean water, a moderate climate, food, you name it. It is folly to think that we can doom so many other species to extinction and not have it come back to bite us ... hard.”

Pictured is a Chinese cave gecko (Goniurosaurus luii) from the Photo Ark. Little is known about the ecology of these reptiles, although they are thought to inhabit rocky forested and scrubland areas. In recent years, they have gained popularity in the pet trade, in part due to their attractive coloration. Sartore said, "Each species is unique, and so we try to give each the special care and attention to detail that it deserves. Each is a work of art in a very real sense, the result of thousands upon thousands of years of evolution. Each has a story to tell. My job is to tell that story so well that others will care about it enough to stop and learn about it."

The American magpie or black-billed magpie (Pica hudsonia) inhabits a swath of the western United States. It is one of only four North American songbirds whose tail makes up more than half of its total body length. The magpies were long persecuted by people, who considered them rivals to game birds and pests. Several states had bounties on them. As a result, their numbers declined, although they are not currently listed as endangered. Sartore added, "Many times, it only takes one person to make a real difference and save a species. Because so many of the animals I photograph have never been given any attention in the mainstream media, there are a multitude of ways that these species can be helped. To put it another way, many species are doomed by a lack of attention."

The dyeing poison frog (Dendrobates tinctorius) is one of the largest species of poison dart frog, reaching a length of two inches (50 millimeters). The amphibian makes its home in Brazil, Guyana, Suriname, and French Guiana. The frog contains a relatively mild toxin that can cause pain and cramping if handled. It got its name from the fact that local indigenous people have long used it to dye feathers for ceremonial purposes. They would pluck the feathers from a parrot, and then rub the frog on the exposed skin. The feathers would then grow back yellow or red, instead of green. Of the Photo Ark, Sartore added, "It seeks to educate, inform, and most of all, stop the extinction cycle that so many of Earth's creatures find themselves in. We won't save them all, but we will save some. That's what keeps me going."

The Mexican gray wolf (Canis lupus baileyi) is the most rare subspecies of gray wolf in North America. It is listed as critically endangered by the IUCN. The Mexican gray wolf formerly ranged in the Sonoran and Chihuahuan Deserts, from central Mexico into Texas, New Mexico, and Arizona. After its natural prey began to decline as human settlement encroached on its habitat, the wolf began taking livestock. Ranchers responded with eradication programs, and the wolf was extirpated from the wild by the 1950s. But several captive breeding programs also began in the U.S. and Mexico, and several hundred of the animals now live on behind bars. Beginning in the 1990s, wildlife managers also began reintroducing Mexican gray wolves to the Blue Range in Arizona.

The striking panther chameleon (Furcifer pardalis) is native to tropical forests of Madagascar. The reptile is highly prized by collectors for its bold colours and relatively large body size (up to 9 inches or 23 centimetres long).

Local groups of the panther chameleon often display their own colour ranges, with the changes affected by temperature, light, and the animal’s mood. For a few years, the panther chameleon was heavily exported for the pet trade, but after the species was listed on Appendix II by CITES that was curtailed. Still, the colourful chameleon faces threats from loss of habitat, since Madagascar has an ongoing deforestation process.

The springhaas (Pedetes capensis) is a rodent native to southern and eastern Africa. The nocturnal animals had experienced decline in recent decades thanks to habitat loss, although its numbers have stabilised, according to the IUCN.

The attractive Brazilian rainbow boa (Epicrates cenchria cenchria) is a subspecies of the rainbow boa, a reptile found in Central and South America. The animal is named for its iridescent sheen, which is caused by structural colouration (cells that have microscopic surfaces that refract light). During the 1980s and 1990s, large numbers of Brazilian rainbow boas were exported for the pet trade, but that has slowed greatly, and most kept examples originate from captive breeding. The reptile is not currently listed with a special status. See more photos from the Photo Ark.