With a treasure trove of endemic species, the Galapagos Islands are renowned for natural wonders and unique wildlife. Darwin's studies of the plants and animals there played a pivotal role in the development of his theory of natural selection. Check out some of the unique animals that reside in this Pacific Ocean archipelago.

1 of 14 Galapagos Tortoises Ian Kennedy / Shutterstock These giant tortoises are so iconic that the islands received their name after descriptions of the animals reached the Spanish court of King Charles V ("galapago" means "tortoise" in Spanish). They are the largest living species of tortoise and are among the longest-living vertebrates, with potential lifespans over 170 years. In the absence of any significant predators, adult tortoises evolved a docile demeanor, which unfortunately made them easy to exploit by early human settlers. An estimated population above 250,000 once existed on the islands as recently as 200 years ago, but there are about 20,000-25,000 alive today. The good news is that intense conservation efforts have been successful for most of the subspecies, and the islands' tortoise populations are, for the most part, on the rebound.

2 of 14 Marine Iguana Vince Smith / Flickr / CC BY 2.0 This incredibly unusual species of iguana found on all Galapagos islands is the only extant (or still existing) marine lizard on Earth. The coloration, shape, and size of marine iguanas vary significantly between islands. The ones found on Espanola are the most colorful and are nicknamed "Christmas Iguanas" because of their red and green coloration. These iguanas likely evolved an aquatic lifestyle because of the sparsity of nutritious vegetation on land, opting instead for seaweed. To get rid of the excess salt that it consumes, this iguana has specialized nasal glands that filter the salt and expel it from the nostrils. When there is scarce food, the iguanas don't just get thinner; they become shorter. These lizards are listed as vulnerable and undergoing population decreases by the IUCN Red List. Factors that may lead to eventual extinction include marine plastics and climate change, the latter which decreases the available seaweed stocks on which they rely.

3 of 14 Flightless Cormorant robert cicchetti / Shutterstock A candidate for the most unusual endemic species on the Galapagos, the flightless cormorant is the only cormorant in the world that has lost the ability to fly. As a result, it has grown to become the heaviest cormorant species in the world. Because this species does not fly, it is susceptible to predation from introduced predators such as dogs, cats, rats, and pigs. Today, only around 2,080 of these unique birds exist.

4 of 14 Galapagos Finches Paul Krawczuk / Flickr / CC BY 2.0 Since they played such an important role in the development of Darwin's theory of natural selection, the remarkable finches of the Galapagos are among the most famous animals on the islands. There are 13 species of Darwin's Finch alive today in the Galapagos Islands, and they all evolved from a single ancestral species. Each species is most easily distinguished by differences in beak size and shape. The evolution of the finches of the Galapagos illustrates an ideal example of adaptive radiation, in which organisms rapidly diversify.

5 of 14 Galapagos Penguin Alfie Photography / Shutterstock One of the smallest penguins in the world, the Galapagos penguin is also the only penguin with a range over the equator. That makes it the most northerly breeding penguin. Like many species of penguin, these creatures form monogamous pair bonds and typically mate for life. These penguins are listed as endangered by the IUCN. Major threats are oil spills and climate change, as the latter creates more severe La Nina and El Nino weather patterns.

6 of 14 Galapagos Fur Seal guenterguni / Getty Images There are few endemic species of mammal in the Galapagos, but the Galapagos fur seal is one exception. It is the smallest seal in the world. These creatures are also one of the most land-loving seals, spending around 70 percent of their time out of the water. Their raucous, charismatic barks are a familiar sound to anyone who has ever visited the islands.

7 of 14 Blue-Footed Boobies BlueOrage Studio / Shutterstock Blue-footed boobies are not found exclusively on the Galapagos Islands, but about half of the world's population breeds there. The funny name almost matches these Galapagos creatures' funny looks. Blue-footed boobies are most easily recognized by their signature feet. The birds' mating ritual is also an entertaining affair, as males lift their feet up and down in a strutting display for the females. The color of their feet is an indicator of their health, as the blue hue is caused by pigments obtained from a diet of fresh fish.

8 of 14 Galapagos Hawk A.Davey / Flickr / CC BY 2.0 As the only diurnal raptor to inhabit the islands, the Galapagos hawk is hard to miss. Though it mostly preys on small animals such as locusts, centipedes, and lizards, this raptor is a top predator known to swoop down on iguanas and giant tortoise hatchlings. Despite being a top predator, the hawks' population is not exceptionally high, with an estimated 270-330 mature hawks in existence. Human retaliation because of hawk predatory behavior toward farm animals and pets and competition for prey from invasive species has limited the population.

9 of 14 Lava Lizards Stacy Funderburke / Shutterstock One of the most common animals found on the Galapagos Islands are small lizards, often affectionately referred to as "lava lizards." There are at least seven recognized species, each with unique traits. Like with the Galapagos' finches, the variety of species of lava lizards represents a remarkable example of adaptive radiation.

10 of 14 Magnificent Frigatebird Brian Gratwicke / Flickr / CC BY 2.0 There are few birds easier to recognize than the male magnificent frigatebirds of the Galapagos Islands. They have a big red throat pouch, making for a bright, stunning display when it's fully inflated. It's almost comical to see them puff up. Of course, the brighter the pouch, the more attractive they appear to females. Though magnificent frigatebirds are migratory birds found across the Atlantic Ocean and Central and South America, the colonies that inhabit the Galapagos Islands are genetically distinct, not having bred with mainland counterparts for more than half a million years.

11 of 14 Large Painted Locusts NH53 / Flickr / CC By 2.0 The beautiful large painted locusts, endemic to the Galapagos Islands, typically grow to just over 3 inches. The large painted locusts are an essential part of the food chain on the islands, serving as principal prey for lava lizards and the Galapagos hawk. The locusts don't make it easy for those who want to prey upon it, however; they can leap almost 10 feet and are strong flyers as well.

12 of 14 Waved Albatross Clara / Shutterstock The largest bird found on the Galapagos Islands is the waved albatross. It's also the only species of albatross found entirely in the tropics. Though this species does glide over long distances, it breeds exclusively on the Galapagos Islands. These beautiful birds mate for life and have one of nature's more charming mating rituals. They clack their beaks together in rapid circles, almost like a clumsy form of kissing. Between "kisses," they raise their bills skyward and let out a "whooo-ooo" call. This species is critically endangered and has a decreasing population. Major threats are climate change, plastic pollution, fishery bycatch, and avian illnesses.

13 of 14 Galapagos Mockingbird Henry Lien / Shutterstock The Galapagos mockingbird may have been the first example of adaptive radiation that Darwin encountered on the islands even though the finches got the fame. This common bird was the first one Darwin found that showed distinct adaptive differences from island to island. Though they can fly, Galapagos mockingbirds are also known to hunt by running after prey, which occasionally draws comparisons to roadrunners.