We’ll have a look at some of the island's animal species and consider the factors that may be driving evolutionary adaptations today.
Charles Darwin Research Station (Puerto Ayora)
In 1831, the British ship HMS Beagle set out on a trip around the globe, sailing around the tip of South America and eventually up to a little-explored cluster of islands called the Galápagos.
LIFE Photo Collection
Aboard the ship was a young geologist and naturalist (an amateur scientist interested in all aspects of the natural world) named Charles Darwin. Darwin’s discoveries on the Galapagos led to a revolution in biology, and his ideas continue to influence scientific study on the Galapagos today.
Charles Darwin Research Station
The Galápagos Islands in Ecuador are a volcanic group of islands about 1,000 kilometers off South America’s Pacific coast. The Charles Darwin Research Station in Puerto Ayora town is the main scientific facility and laboratory on the islands.
The Beagle voyage was intended to last 2 years but stretched to 5 years. From Tierra del Fuego to Tahiti, Darwin wrote vivid observations about the rocks, plants, animals, and people he saw and collected important fossils and specimens.
Darwin’s scientific passion led to his being introduced to Robert FitzRoy, another scientific hobbyist and commander of an upcoming expedition to explore the world’s tropics. That expedition, the HMS Beagle, would eventually make Darwin, and his theory of evolution, famous.
Charles Darwin Research Station vertebrate collection
In 1859, Darwin put forward a revolutionary idea in his book On the Origin of Species: the many different species of finches he observed on the Galápagos Islands had once been a single species that arrived on the archipelago and gradually began to split into different species as each population adapted to the particular conditions on its island over time.
On the Origin of Species was the first comprehensive description of what we know as the theory of evolution.
Is each of the Galápagos Islands’ tortoises a separate species, variations of a single species, or something in between? As scientists have analyzed tortoises’ DNA, they’ve come to realize groups of organisms are constantly changing in response to their environment.
The different Galápagos species are examples of dispersal, in which one original population spreads out across many locations and adapts to different environments. Over time, the shapes of finches’ beaks, their nesting times, and their need for water have changed.
The Galápagos Islands are relatively young. The islands’ animals are still quite similar to each other. They’re at the beginning of the evolution process, giving scientists a snapshot in time of how populations spread out, diversify, and eventually evolve.
Charles Darwin Research Station herbarium
Galápagos plants rarely get as much attention as animals, but they’re critically important to the island ecosystem. They’re also particularly vulnerable to destruction by invasive species. The Darwin Research Station studies the plants of the Galápagos and attempts to preserve or restore the native ecosystem.
The Galápagos lie in the Pacific Dry Belt, an area associated with dry weather and desert plants like cacti. Many visitors are surprised to find the islands covered in dry grasses and cacti. At the same time, the cold Humboldt Current of the Pacific Ocean keeps the island unusually cool and foggy. Some trees capture moisture from passing fog, creating lush “fog forests” on parts of the islands.
One way of cataloging plants is by their pollen—tiny grains that carry the plants’ sperm cells. The pollen’s outer coating is often ornamented with extremely complex patterns. Each pollen grain is unique to the plant species, like a human fingerprint.
Scientist and workstation
Research Center scientists and volunteers try to restore areas on the islands where vegetation has been damaged by agriculture, development, or invasive species. The Herbarium also researches sustainable farming techniques that could be used on the Galápagos.
Plants arrived on the Galápagos much the way that animals did—mostly by accident, probably blown there by storms. Some plants, however, are adapted specifically to colonize remote islands. Coconuts are large, light seeds designed to germinate when they reach land.
Like many isolated islands, the Galápagos are a breeding colony for sea birds. The blue-footed booby is one of the most famous Galápagos residents. About half of the world’s blue-footed boobies breed on the Galápagos.
They get their unusual name because of their obvious blue feet and their clumsiness and lack of fear when on land. At sea, however, the blue-footed booby sails effortlessly on a wide wingspan and makes plunging dives into the sea for their favorite food, sardines.
Blue-footed Booby (2014-08/2015-12) by Jane Kim, Ink Dwell StudioCornell Lab of Ornithology
Blue-footed boobies pair for life, and both parents help raise chicks. Their blue feet serve not only to attract mates, but also to strengthen the bond between pairs. Males perform a comical, foot-flapping dance in order to attract females.
The blue-footed booby lays between 1 and 3 eggs and incubates the eggs so that they hatch at different times. Scientists have found that this spaced-out hatching leads to more or less surviving offspring depending on the food supply.
Magnificent Frigatebird (2014-08/2015-12) by Jane Kim, Ink Dwell StudioCornell Lab of Ornithology
Frigatebirds are one of many seabirds that use the predator-free Galápagos Islands as a breeding ground. Before the arrival of humans, the islands had almost no predators that fed on birds, eggs, or nestlings—the exception being other birds. Frigatebirds are known for their habit of raiding the nests of other seabirds. But they also take advantage of the isolated safety of the Galápagos to raise their own families.
The frigatebird’s bright throat pouch is a mating display. Males inflate their bright-red sack of skin and aim it skyward to attract females cruising overhead. Males also use the large skin sac to produce a bellowing call.
Superb Sea Birds
Frigatebirds have the largest wingspan in relation to their body weight of any bird. They also have incredibly light bones. These adaptations make them superb gliders, with the ability to fly continuously for more than a week at a time.
A Long Childhood
Frigatebird chicks have one of the longest childhoods of any bird, spending over a year dependent on their parents for food. Both parents help feed chicks for roughly the first 3 months, but females assume the remaining months of work.
Galápagos Giant Tortoise Breeding Center
Galápagos tortoises are tourist favorites due to their slow, tame nature and stunning size. They have also become a symbol of the Galápagos. They first achieved fame when Darwin described the variation among subspecies in On the Origin of Species.
More recently, Lonesome George (who was the last surviving Pinta Island tortoise until 2012) and other tortoises have come to symbolize the need for conservation on the islands and around the world.
Islands have a specific effect on the species that colonize them. Smaller animals tend to grow larger than their mainland relatives, and large animals tend to get smaller. The giant tortoises of Galápagos are much larger than their closest relatives.
Galapagos Giant Tortoise by Stuart HumphreysAustralian Museum
A Long, Healthy Life
Galápagos tortoises regulate their body temperature by exposing themselves to heat and cold in the environment. They spend most of their days warming themselves in the sun, napping, and eating. Their slow lifestyle results in an incredibly long lifespan.
Large, but Vulnerable
Galápagos tortoises can survive up to a year without food. This led to sailors collecting island tortoises to kill, cook, and eat after months at sea. Sailors also collected and ate turtle eggs. Today, the tortoises are strictly protected.
The Tortoise Breeding Center
One of the Charles Darwin Foundation’s major missions is to preserve the Galápagos Islands’ most famous residents, the giant tortoises. When humans began settling the island, invasive rats began preying on the eggs and young, and feral pigs and goats destroyed the cloud forests that provided them with shade, shelter, moisture, and vegetation for food.
Nineteenth-century sailors hunted several subspecies of Galápagos tortoises to extinction. Island tameness and human greed also caused the extinction of dodo birds on the islands.
Rats, which aren’t native to the islands, prey on tortoise eggs and small young. However, adult tortoises have a much better chance of survival. By breeding tortoises in captivity, the Foundation ensures eggs and young turtles are safer from rats.
Small, isolated islands are often free from predators. This results in a phenomenon known as island tameness. Since island species are unusually calm and unafraid of other animals, this can be devastating to animals that encounter predators or human hunters.
The Last of Their Kind
Today, 11 of the original 15 tortoise subspecies survive. One victim of extinction is the Pinta Island tortoise. The last survivor of this species, Lonesome George, died of old age in 2012.
Bahia Cartago - Invasive Species
An invasive species is a plant or animal that’s been introduced into a new environment, where its population explodes. Invasive species have been incredibly destructive on the Galápagos, in part because they prey on native animals that have no defenses against them. Some were brought to the islands accidentally—think of rats brought in as stowaways on ships.
Others, like goats, were brought in as domesticated agricultural animals, some of which escaped and survived in a feral state in the wild. Feral goats are possibly the most destructive species on the Galápagos. Goats eat nearly every kind of vegetation and can destroy entire forests. Without trees and the shade they cast, parts of the Galápagos dried out and turned to semi-desert.
Invasive plants like blackberry engulf enormous areas of land, crowding out native plants and blocking animal habitats. Invasive plants are often more difficult to control than invasive animals. A tiny seed carried off by a visitor can start an invasion.
Project Isabella, a campaign to remove feral goats from the islands, began in 1997. Hunters systematically shot thousands of goats, effectively eradicating them from the islands by 2006. This was considered necessary to save the forests and their native species.
By William VandivertLIFE Photo Collection
Scientists once used “Judas goats” while eradicating the islands’ goats. They captured a goat alive, fitted it with a tracking collar, and released it. Since goats are social, the Judas goat would soon lead human hunters to the herd.
During the voyage of the Beagle, Darwin’s interest in geology made him excited to visit the Galápagos, an archipelago still being formed by active volcanoes. Galápagos volcanoes remain active, and erupted as recently as 2015.
This lava tube provides evidence of the geologic activity on the island. A lava tube is basically a volcanic cave, formed when the tops and sides of a lava stream are exposed to the cool air, quickly hardening into solid rock.
Many lava tubes have one end in the ocean, making them inaccessible, or turning them into sea caves. The thin crust of some lava caves crumbles, providing an opening. Inside, the cave is very long, shallow, straight, and jet-black.
Galápagos volcanoes, like Hawaiian volcanoes, produce extremely thin, runny lava that flows easily. The lava on Galápagos flows quietly and relatively slowly, like honey, rarely threatening people or animals. However, especially large lava flows can damage plants and habitat.
Islands still forming
Lava from the Galápagos’s active volcanoes often flows into the sea, where it quickly solidifies and forms brand-new land. This occurs especially on Fernandina, an island which is still under formation and geologists believe is the youngest of the islands.
The thin, runny lava from this volcano is called Pahoehoe (pa-HOH-ay-HOH-ay). Pahoehoe forms distinctive ropey, dark lava fields that can resemble asphalt or even gooey brownies. If Pahoehoe cools quickly enough, it can even form obsidian, a black volcanic glass.