Evolution at its best
When the Galapagos volcanoes started to form the first Islands, some three to five million years ago, they were isolated from life, separated by about thousand kilometers from the mainland. Despite this, with the time a number of species have made the islands their new home, due to their capacity to disperse, whether actively or passively and their ability to establish themselves after arrival.
The Galapagos Islands have often been called a “laboratory of evolution” There are very few places in the world where it is possible to find such a variety of species, both plants and animals that show so many degrees of evolutionary changes in such a restricted area. Oceanic islands can have species that, though related to mainland forms, have evolved in ways that differ from their relatives because of their isolation in a new and different environment. This is the key factor in island evolution. It is not surprising that Charles Darwin was so struck by the life he found on these islands.
Darwin finches are a classic example of adaptive radiation in birds, which has served generations of evolutionary biologists. Thirteen species evolved within the Galapagos Archipelago from a common ancestor from the mainland.
The word endemic refers to organisms found nowhere else in the world because they evolved and remained isolated on a given area and developed unique characteristics. Today you will find several species that fall into this classification on the Islands, the endemic plants and animals of Galapagos. Please find below the descriptions of some of the endemic animals of the Galapagos Islands:
The Galapagos Land Iguana (Conolophus subcristatus) is a species of lizard in the Iguanidae family and one of three species of the genus Conolophus. It is endemic to the Galápagos Islands, primarily the islands of Fernandina, Isabela, Santa Cruz, North Seymour, Española and South Plaza.
The Galapagos Land Iguana varies in morphology and coloration among different island populations. There are two taxonomically distinct forms of Conolophus inhabiting the western part of the islands (C. rosada and C. pallidus) and one in the central part (C. subcristatus).
The Galapagos Land Iguana grows to a length of three to five feet (ca. 90cm – 120cm) with a body weight of up to twenty-five pounds (ca. 12 kilos), depending on which island they are from. Being cold-blooded, they absorb heat from the sun by basking on volcanic rock and at night sleep in burrows to conserve their body heat. These iguanas also enjoy a symbiotic relationship with birds; the birds remove parasites and ticks, providing relief to the iguanas and food for the birds. It is estimated that the Galapagos Land Iguana has a 50 to 60-year lifespan.
The Galápagos Fur Seal (Arctocephalus galapagoensis) breeds on the Galápagos Islands in the eastern Pacific, west of mainland Ecuador and is endemic to the islands. The seals live on the rocky shores of the islands which tend to be on the west side of the islands, leaving only to feed. These seals do not migrate and remain near the islands their entire lives, which averages at about 20 years. The Galápagos fur seal feeds primarily on fish and molluscs. They feed relatively close to shore and near the surface, but have been seen at depths of 169 meters. They primarily feed at night because their prey is much easier to catch then.
It seems the Galapagos fur seal is now no longer only found on the Galapagos Islands, as a colony has relocated to Northern Peru, according to Orca, Organisation for Research and Conservation of Aquatic Animals.
The Galápagos Green Turtle (Chelonia mydas agassisi) is a subspecies of the Green Turtle (Chelonia mydas). It is endemic to the tropical and subtropical waters of the Pacific Ocean. They are often categorized as one population of the east Pacific Green Turtle. This title is shared with the other Green Sea Turtle nesting populations inhabiting the Pacific Ocean.
The Galápagos Green Turtle is the only population of Green Sea Turtle to nest on the beaches of the Galápagos Islands. It has been difficult for researchers to obtain valid information on the lifestyles of the Galápagos Green Turtle due to their continuous migrations and submergence in the ocean; most information has been obtained through tagging experimentation. The Galápagos Green Turtle, along with all other population of Green Sea Turtle, is listed as endangered on the IUCN Red List of threatened species.
The Galápagos tortoise or Galápagos giant tortoise (Geochelone nigra) is the largest living tortoise, native to seven islands of the Galápagos archipelago. Fully grown adults can weigh over 300 kilograms (661 lb) and measure 1.2 meters (4 ft) long. They are long-lived, with a life expectancy in the wild estimated to be 100–150 years. Populations have fallen dramatically due to hunting and the introduction of predators and grazers by humans since the seventeenth century. Today only ten subspecies of the original twelve still exist in the wild. However, conservation efforts since the establishment of the Galápagos National Park and the Charles Darwin Foundation have met with success, and hundreds of captive-bred juveniles have been released back onto their home islands. They have become emblematic of the fauna of the Galápagos Islands.
Lonesome George (Spanish: Solitario Jorge) is the last known individual of the Pinta Island Tortoise (Geochelone nigra abingdoni) which is one of the subspecies of Galápagos tortoises. He has been labeled the rarest creature in the world, and is a potent symbol for conservation efforts in the Galápagos and internationally.
George was first seen on the island of Pinta on the 1st of December 1971 by American biologist Joseph Vagvolgyi. The island’s vegetation had been decimated by introduced feral goats, and the indigenous tortoise population had been reduced to one single individual. Relocated for his safety to the Charles Darwin Research Station, George was penned with two females of a different subspecies, but although eggs have been produced, so far none have hatched. George is estimated to be 60–90 years of age, and is in good health.
The Marine Iguana (Amblyrhynchus cristatus) is an iguana found only on the Galápagos Islands that has the ability, unique among modern lizards, to live and forage in the sea. It has spread to all the islands in the archipelago, and is sometimes called the Galapagos Marine Iguana. It mainly lives on the rocky Galapagos shore, but can also be spotted in marshes and mangrove beaches.
The Marine Iguanas feed almost exclusively on marine algae, expelling the excess salt from nasal glands while basking in the sun, and the coating of salt can make their faces appear white. In adult males, coloration varies with the season. Breeding-season adult males on the southern islands are the most colorful and will acquire reddish and teal-green colors, while on Santa Cruz they are brick red and black, and on Fernandina they are brick red and dull greenish.
Another difference between the iguanas is size, which is different depending on the island the individual iguana inhabits. The iguanas living on the islands of Fernandina and Isabela are the largest found anywhere in the Galápagos. On the other end of the spectrum, the smallest iguanas are found on the island of Genovesa.
Adult males are up to 1.7 m long, females 0.6 – 1 m, males weigh up to 1.5 kg.
On land, the marine iguana is rather a clumsy animal, but in the water it is a graceful swimmer.
The reptile genus Tropidurus includes several species of ground lizard. It includes seven which are endemic to the Galapagos Islands, where collectively known as lava lizards. The distribution of these lizards and their variations in shape, color and behavior show the phenomenon of adaptive radiation so typical of the inhabitants of this archipelago. One species occurs on all the central and western islands, which were perhaps connected during periods of lower sea levels. On six other more peripheral islands one unique species occurs on each. All have most likely evolved from a single ancestral species.
Males and females of all Tropidurus species are marked differently. The male is usually much larger than the female, and its body is more brightly colored and distinctly patterned. The average size of lizards varies greatly from habitat to habitat as does the pattern of body markings, animals living mainly on dark lava are darker than ones which live in lighter, sandy environments. Markings vary considerably, even within an individual species and, like many lizards, they show changes of color with mood and temperature.
The Flightless Cormorant (Phalacrocorax harrisi), also known as the Galapagos Cormorant, is a cormorant endemic to the Galapagos Islands and a good example of the highly unusual fauna there. It is unique in that it is the only cormorant in the world that has lost the ability to fly. With only 1500 estimated individuals, it is one of the world’s rarest birds and is the subject of an active conservation program.
This unique cormorant is found on just two islands: Fernandina Island, where it is found mainly on the east coast, as well as on the northern and western coasts of Isabela Island. This species inhabits the rocky shores of the volcanic islands on which it occurs. It forages in shallow coastal waters, including bays and straits and rarely ventures further than one kilometer from the breeding areas.
The Galapagos cormorants evolved on an island habitat that was free of predators. Having no enemies, and taking its food primarily through diving along the food-rich shorelines, the bird eventually became flightless.
The Flightless Cormorant is the largest member of its family, 89–100 cm (35-40in) in length and weighing 2.5–5.0 kg (5.5-11 lbs), and its wings are about one-third the size that would be required for a bird of its proportions to fly. The keel on the breastbone, where birds attach the large muscles needed for flight, is also greatly reduced.
Darwin’s finches (also known as the Galápagos Finches or as Geospizinae) are a group of 14 species of Passerine birds (include one specie from Cocos Island), now sometimes placed in the tanager family rather than the true finch family. They were first collected by Charles Darwin on the Galápagos Islands during the second voyage of the Beagle. Charles Darwin studied and collected samples of the flora and fauna. His observations of the diversity of species on the islands, especially on mocking birds and finches, later became the basis for his elaboration of the “Theory of Evolution”. The Galapagos now became famous in the scientific world as a virtual laboratory of evolution.
Thirteen species of Darwin finches are found on the Galápagos Islands and one on Cocos Island. The term Darwin’s Finches was first applied by Percy Lowe in 1936, and popularized in 1947 by David Lack in his book Darwin’s Finches.
The birds are all about the same size (10–20 cm). The most important differences between species are in the size and shape of their beaks as the beaks are highly adapted to different food sources.
Darwin Finch Species:
- Large Cactus-finch, Geospiza conirostris
- Sharp-beaked Ground-finch, Geospiza difficilis (Vampire Finch)
- Medium Ground-finch, Geospiza fortis
- Small Ground-finch, Geospiza fuliginosa
- Large Ground-finch, Geospiza magnirostris
- Common Cactus-finch, Geospiza scandens
- Large Tree-finch, Camarhynchus psittacula
- Medium Tree-finch, Camarhynchus pauper
- Small Tree-finch, Camarhynchus parvulus
- Warbler Finch, Certhidea olivacea
- Vegetarian Finch, Camarhynchus crassirostris
- Woodpecker Finch, Camarhynchus pallidus
- Mangrove Finch, Camarhynchus heliobates
- Cocos Island Finch, Pinaroloxias inornata
The Galapagos Penguin (Spheniscus mendiculus) is a penguin endemic to the Galápagos Islands. It is the only penguin to live on the equator and can survive due to the cool temperatures resulting from the Humboldt Current and cool waters from great depths brought up by the Cromwell Current. The Galápagos Penguin occurs primarily on Fernandina Island and the west coast of Isabela Island, but small populations are scattered on other islands in the Galápagos archipelago.
The Galapagos Penguin is one of the smallest penguins and it is the only penguin to cross the Northern Hemisphere which means they live farther north than any other penguin.
The penguins stay in the archipelago. They usually stay in the waters of the Cromwell Current during the day since it is cooler and return to the land at night. The average size for the penguins is 48-50 cm (19-20 in) and 2.5 kg (5.5 lbs). The female penguins are smaller than the males, but they are still a lot alike. They eat small schooling fish, mainly mullet, sardines, and sometimes crustaceans. They only go searching for food during the day and normally within a few kilometers of their breeding site.
The Galapagos Rail Laterallus spilonotus, is a small rail endemic to the Galapagos Islands. The Galapagos Rail is a small (15 cm) nearly flightless ground living bird. It has dark plumage, black overall with a greyer head and breast, and white spots on the back. It has a scarlet eye, a black bill, and short, nearly useless wings. They are very vocal with a wide range of calls.
The Galapagos Rail lives in moist grasslands and forest, skulking in deep cover. In the Galapagos these habitats are generally found on islands with higher elevations particularly on the islands of Santiago, Santa Cruz and Sierra Negra, and the rails are commonest higher up. They feed on invertebrates, mostly snails, dragonflies, bugs, ants, also taking berries and some seeds. They feed during the day, moving along the ground tossing leaves and investigating the leaf litter.
The Galápagos Dove (Zenaida galapagoensis) is a species of bird in the Columbidae family. It is endemic to the Galápagos Islands. Its natural habitats are subtropical or tropical dry forests and subtropical or tropical dry scrubland. A small (20cm) rather dumpy pigeon it has chestnut back and head and reddish-brown breast and underparts.Wing coverts are black with white egdes. A pale patch, bordered by black is just behind the eye which has a conspicuous china blue ring around it.The bill is dark and downcurved, the legs are bright red.
The Galapagos dove is a reluctant flyer. It nests all year round though mainly in rainy season from February to June when food is most abundant. This brid can best be viewed in the drier parts of all main islands.
The Galápagos Hawk (Buteo galapagoensis) is a large hawk endemic to the Galápagos Islands. Known for its fearlessness towards humans and authority over the islands as the only original predator, this raptor has inhabited the Galápagos archipelago for over 300,000 years.
The Galápagos Hawk is about 55 cm from beak to tail with a wingspan of 120 cm. Females are noticeably larger than males as in many species of birds of prey. Other than the difference in size, the male and female look quite similar.
This hawk lives mainly on insects as well as small lava lizards, snakes and rodents. It is not uncommon for it to take young marine and land iguanas, and sea turtle and tortoise hatchlings. This predator has also been spotted near nesting areas of Fork-tailed Gulls, where it steals eggs as well as young.
Other birds of the island fear it. Although it is not able to catch healthy adults, it has been known to pick off weak or sick adults and young. It is the only predator on the entire chain of islands. Fearless of man, the young especially being quite curious, they often wander around human camps and scavenge for scraps of food.
Because the seasons of the island are unchanging due to the close proximity of the equator, there is no regular mating season. While males tend to be monogamous, the females will mate with up to seven different males during mating season. Throughout the entire nesting period, the female and her males take turns protecting the nest and incubating the eggs, even participating in the feeding.
The Galápagos Mockingbird (Nesomimus parvulus) is a species of bird in the Mimidae family. It is endemic to the Galápagos Islands.
The Galapagos Mockingbird is easily spotted on the Galápagos Islands due to its feathers which are streaked brown and gray, long tail, and smaller size, and black, angled beak. The bird has a darker color than the other mockingbirds on the islands causing it to blend in with the coral sand of the islands that it mainly inhabits. Its natural habitats are subtropical or tropical dry forests and subtropical or tropical dry scrubland. It preys on small lava lizards, insects, centipedes, carrion, seabird eggs, and young finches. It has a very clear call that sometimes varies, but unlike other mockingbirds, Galápagos mockingbirds are not mimics. Although they can fly, they are known to be seen running around more than flying which has let to comparisons to road-runners. The birds build their nests in trees and cacti. There are three other species of mockingbirds found on the Galapagos Islands (see below), but the Galapagos Mockingbird is the first one that was found in Darwin’s trip to the islands in 1835. They had a greater influence than any other animal on Darwin’s theory of evolution when he arrived there because it was the first species that Darwin noticed distinct differences among when he looked from island to island. The Galapagos Mockingbird is seen on the islands of Santa Cruz, Santiago, Isabela, Fernandina, Santa Fe and Genovesa, but is thought to have originated in San Cristobal. Although they seemed alike on both the islands of San Cristobal and Isabela, they seemed different on Floreana and Santiago.
Mimus is a bird genus in the family Mimidae. It contains the typical mockingbirds. The Nesomimus group is endemic to the Galápagos Islands. In 2007, the genus Nesomimus was merged into Mimus by the American Ornithologists’ Union.
The Nesomimus group includes the following species:
- Hood Mockingbird, Mimus macdonaldi
- Galápagos Mockingbird, Mimus parvulus
- Española Mockingbird or Charles Mockingbird, Mimus trifasciatus
- San Cristóbal Mockingbird, Mimus melanotis
The Galápagos Petrel (Pterodroma phaeopygia) is a large, long-winged gadfly petrel. The species was once known as the Dark-rumped Petrel, although recent taxonomic changes have eliminated that name from current use. The local people in the Galápagos Islands often call this species the “patapegada.”
The Galapagos Petrel is an endemic marine bird that nests in areas of high humidity in the highlands (generally above 200 m elevation) of five islands of the Galapagos Archipelago (islands San Cristóbal, Santa Cruz, Santiago, Floreana, and Isabela). Recently the petrel has been placed in the category of Critically Endangered species listed in the Red Book of Threatened Birds. The reproductive period of the petrels covers about eight months of the year. A study carried out in 2002 showed an egg-laying period between March to the end of October, with a peak occurring during the first two weeks of August.
The Lava Gull (Leucophaeus fuliginosus) is a large gull. One of the rarest gulls in the world, the entire population lives on the Galapagos Islands and is estimated at 400 pairs.
The adult plumage, acquired in the third year of life, consists of a black head, black wings, and with a dark gray body and a paler gray belly. The bill and legs are black, and the inside of the mouth is scarlet. They have white upper and lower eyebrows, with red lids. Immature gulls are generally dark brown.
Lava Gulls are solitary nesters, laying two olive-colored and well-camouflaged eggs that take 30 days to incubate. Young birds fledge at 60 days and are cared for by adults for a short period.
They are omnivores like most gulls, generally scavenging or stealing from nests, but will also catch fish, small crustaceans, and newly-hatched lizards.
The Lava Gull is categorized as “vulnerable” by the IUCN Red List because it exists in small numbers and though the population is stable, it faces numerous threats.
The Lava Heron (Butorides sundevalli) also known as the Galapagos Heron, is a species of heron endemic to the Galapagos Islands. The adult is slate-grey, which helps it blend in with the hardened lava. The back feathers typically have a silvery sheen and it has a short crest on its head. When breeding, the heron has a black beak and bright orange legs, but they fade to grey after the breeding season. Lava Herons are typically seen hunched over and they have a sharp alarm call. These highly territorial birds are found in intertidal zones and mangrove groves on all of the Galapagos islands.
The Lava Heron stalks small crabs and fish slowly before quickly spearing and eating them. They have also been known to eat the flies that gather near cacti. Unlike most herons, these birds nest in solitary pairs in either the lower branches of mangrove trees or under lava rocks. They can breed year-round, though typically from September to March, and can mate up to three times a year. These birds have no fear of humans.