Biodiversity
Plants
Many visitors to Galapagos are surprised to be greeted by desert-like vegetation—most are expecting a continuation of the lush greenery they witnessed on mainland Ecuador. In fact, the majority of the archipelago’s land area is covered by the brown and grey vegetation often found in deserts. The Galapagos Islands are situated in the Pacific Dry Belt, and in average years only the highest altitudes of the larger islands receive enough rainfall to support tropical plant life.
Geologically speaking, the islands are young, and much of the island’s plant life reflects this; many species seem to be in the midst of the evolutionary process, which makes classifying them a difficult task. To date, the Islands are believed to be home to more than 600 native species of vascular plants and approximately 825 introduced species, the majority introduced by humans. More than 100 of the introduced species have become established in the wild, with many of them extremely invasive and of major concern. Three introduced plant species have been eradicated.
Mainland Ecuador, on the other hand, has about 20,000 species. The discrepancy between species number on the Islands and the mainland highlights the fact that the Galapagos Islands are separated from the continent by a hostile saltwater barrier reducing the potential for arrival and, once a plant has arrived, establishment is difficult due to the harsh environment. It is worthy of note that more than 30% of native plant species found in Galapagos are endemic (not found anywhere else on earth).
The flora of Galapagos can be grouped into three major vegetation zones: the coastal zone, the arid zone, and the humid highlands.
- Coastal plants are found in the narrow zone near the shore and are distinctive because of their tolerance to salty conditions. Mangrove trees are one of the most common plants found in this zone, and they serve an important role as the breeding sites for many birds, such as pelicans and frigatebirds. They also provide much needed shade regions for iguanas and sea lions, as well as refuges for sea turtles.
- The dry area is the most extensive zone in Galapagos and is comprised of plant species that are highly adapted to drought-like conditions, such as succulent cacti and leafless shrubs that flower and grow leaves only in the brief rainy season.
- Located above the dry zones are the very lush and green, humid zones. In portions of this zone, Scalesia trees form a very dense forest in the humid zone, with their branches adorned with mosses, liverworts, and epiphytes — non-parasitic plants that use larger trees only for support. The humid zone is only found on the larger, higher islands. The majority of islands in the archipelago do not rise in elevation above the arid zone.
Giant Tortoises
The giant tortoises of Galapagos are among the most famous of the unique fauna of the Islands. While giant tortoises once thrived on most of the continents of the world, the Galapagos tortoises now represent one of the remaining two groups of giant tortoises in the entire world — the other group living on Aldabra Atoll in the Indian Ocean. The Galapagos Islands were named for their giant tortoises; the old Spanish word galapago meant saddle, a term early explorers used for the tortoises due to the shape of their shells.
The closest living relative of the Galapagos giant tortoise is the small Chaco tortoise from South America, although it is not a direct ancestor. Scientists believe the first tortoises arrived to Galapagos 2–3 million years ago by drifting 600 miles from the South American coast on vegetation rafts or on their own. They were already large animals before arriving in Galapagos. Colonizing the eastern-most islands of Española and San Cristóbal first, they then dispersed throughout the archipelago, eventually establishing at least 15 separate populations on ten of the largest Galapagos Islands.
Although there is a great amount of variation in size and shape among Galapagos tortoises, two main morphological forms exist — the domed carapace (similar to their ancestral form) and the saddle-backed carapace. Domed tortoises tend to be much larger in size and do not have the upward thrust to the front of their carapace; they live on the larger, higher islands with humid highlands where forage is generally abundant and easily available. Saddle-backed shells evolved on the arid islands in response to the lack of available food during drought. The front of the carapace angles upward, allowing the tortoise to extend its head higher to reach the higher vegetation, such as cactus pads.
Tortoise History in Galapagos
Of all of the native species of Galapagos, giant tortoises were the most devastated after the endemic rice rats, with the majority of rice rat species now extinct. One of the giant tortoise’s most amazing adaptations — its ability to survive without food or water for up to a year — was, unfortunately, the indirect cause of its demise. Once pirates, whalers and fur sealers discovered that they could have fresh meat for their long voyages by storing live giant tortoises in the holds of their ships, massive exploitation of the species began. Tortoises were also exploited for their oil, which was used to light the lamps of Quito. Two centuries of exploitation resulted in the loss of between 100,000 to 200,000 tortoises. Three species have been extinct for some time, and a fourth species lost its last member, Lonesome George, in June of 2012. It is estimated that 20,000–25,000 wild tortoises live on the islands today.
In addition to their direct exploitation by humans for both food and oil, giant tortoises faced other challenges due to the introduction of exotic species by human visitors. They suffered — and continue to suffer on some islands — predation on tortoise eggs and hatchlings by rats, pigs, and voracious ants, and competition for food and habitat with goats and other large mammals.
With the establishment of the Galapagos National Park and the Charles Darwin Foundation in 1959, a systematic review of the status of the tortoise populations began. Only 11 of the 14 originally named populations remained and most of these were endangered if not already on the brink of extinction. The only thing saving several of the populations was the longevity of tortoises, keeping some old adults alive until conservation efforts could save their species.
Tortoise Taxonomy
The taxonomy of giant tortoises has changed over the decades since they were first named. Today the different populations are considered separate species of the genus Chelonoidis. There are currently 15 species. Giant tortoises were native to each of the big islands (Española, Fernandina, Floreana, Pinta, Pinzón, San Cristóbal, Santa Cruz, Santa Fe and Santiago) as well as the five major volcanoes on Isabela Island (Wolf, Darwin, Alcedo, Sierra Negra and Cerro Azul). Two species have been identified from Santa Cruz. Tortoises are now extinct on Fernandina (due to volcanism), Floreana, Santa Fe and Pinta (due to exploitation). Pinta Island had a single known tortoise, Lonesome George, who lived until June of 2012 at the Tortoise Center on Santa Cruz where he spent the final 40 years of his life. A taxidermy specimen of Lonesome George is now on display at the Tortoise Center.
The Life of a Tortoise
Compared to humans, giant tortoises might deserve to be called “lazy,” spending an average of 16 hours a day resting. Their activity level is driven by ambient temperature and food availability. In the cool season, they are active at midday, sleeping in in the morning and hitting the sack early in the afternoon. In the hot season, their active period is early morning and late afternoon, while midday finds them resting and trying to keep cool under the shade of a bush or half-submerged in muddy wallows. During periods of drought, they can be found resting/sleeping for weeks at a time.
Galapagos tortoises are herbivorous, feeding primarily on cactus pads, grasses, and native fruit. They drink large quantities of water when available, which they can store in their bladders for long periods of time.
Tortoises breed primarily during the hot season (January to May), though tortoises can be seen mating any month of the year. During the cool season (June to November), female tortoises migrate to nesting zones (generally in more arid areas) to lay their eggs. A female can lay from 1-4 nests over a nesting season (June to December). She digs the hole with her hind feet, then lets the eggs drop down into the nest, and finally covers it again with her hind feet. She never sees what she is doing. The number of eggs ranges from 2-7 for saddle-backed tortoises to sometimes more than 20-25 eggs for domed tortoises. The eggs incubate from 110 to 175 days (incubation periods depend on the month the nest was laid, with eggs laid early in the cool season requiring longer incubation periods than eggs laid at the end of the cool season when the majority of their incubation will occur at the start of the hot season). After hatching, the young hatchlings remain in the nest for a few weeks before emerging out a small hole adjacent to the nest cap. The sex of a tortoise is determined by the temperature of incubation, with females developing at slightly hotter temperatures.
Tortoise Speak
Tortoises have several ways of communicating with each other. The only known vocalization in Galapagos tortoises is the sound that males make when mating — a bellowing, periodic “groan” that sounds similar to a loudly mooing cow. Female tortoises make no vocalizations at all. The main method of tortoise communication is behavioral. Like many other species, they have ways of conveying dominance and defending themselves. Competing tortoises will stand tall, face each other with mouths agape, and stretch their necks up as high as possible. The highest head nearly always “wins,” while the loser retreats submissively into the brush.
Fine Feathered Friends
It is quite common to see the tiny birds of Galapagos, such as Darwin’s finches and Vermilion flycatchers, perched on top of the shells of their oversized giant tortoise companions. Some finch species have developed a mutualistic relationship with giant tortoises, feeding on the ticks that hide in the folds of the tortoise’s reptilian skin or on their shell. In fact, these birds will dance around in front of the tortoise to indicate that they are ready to eat, and the tortoise then responds by standing tall and stretching out its neck to “expose the buffet.”
Iguanas and Lizards
There are seven different species of lava lizards in Galapagos, and they all likely evolved from a single species. They are able to change color when threatened in order to camouflage themselves, and if their tail is grabbed by a predator they have the handy ability “drop” it — a new tail will eventually grow back in its place. As a result of this defense mechanism, lava lizards can live up to 10 years.
Galapagos Iguanas
Galapagos iguanas are thought to have had a common ancestor that floated out to the islands from the South American continent on rafts of vegetation. The divergence between land and marine iguanas has been estimated at 10.5 million years ago. Geneticists estimate that the pink iguana diverged from the other land iguanas approximately 5.7 million years ago — before most if not all of the current islands existed, while the divergence between the two yellowish iguanas is fairly recent.
There are three species of land iguana found in the Galapagos Islands. The well-known yellowish land iguanas include Conolophus subcristatus, native to six islands, and Conolophus pallidus, found only on the island of Santa Fe. A third species of land iguana (Conolophus marthae), the pink or rosada iguana, was first seen in 1986 and remained unstudied until the 2000s. It is found only on Wolf Volcano at the northern end of Isabela Island. It has a pinkish head, and pinkish and black body and legs, often with black stripes. The new species is morphologically, behaviorally, and genetically distinguished from the other two.
Land iguanas are large — more than 3 feet long — with males weighing up to 30 pounds. They live in the drier areas of the Islands, and in the mornings can be found sprawled beneath the hot equatorial sun. To escape the heat of the midday sun, they seek the shade of cacti, rocks, trees or other vegetation. At night they sleep in burrows dug in the ground, to conserve their body heat. They feed mainly on low-growing plants and shrubs, as well as fallen fruits and cactus pads. These succulent plants provide them with the moisture they require during long, dry periods. Land iguanas show a fascinating symbiotic interaction with Darwin’s finches, as do giant tortoises, raising themselves off the ground and allowing the little birds to remove ticks.
Land iguanas reach maturity between 8 and 15 years of age. Males are territorial and will aggressively defend specific areas that typically include more than one female. Following the mating period, female iguanas find suitable nesting sites, dig their nesting burrow, and lay between 2 and 20 eggs. The female defends the burrow for a short time, to prevent other females from nesting in the same place. The young iguanas hatch 3-4 months later, and take about a week to dig their way out of the nest. If they survive the first difficult years of life, when food is often scarce and predators are a danger, land iguanas can live for more than 50 years.
In 1959, the status of the extant populations of land iguanas was considered good. Then in 1975, two populations on different islands (Cerro Cartago on Isabela and Conway Bay on Santa Cruz) were decimated in less than six months by feral dog packs. Unlike tortoises, adult iguanas are not predator-proof. Saving them meant removing them from their natural habitat until dogs were eliminated.
A breeding and rearing center was quickly established, but it was not large enough for all of the adults. A management technique used only once before in Galapagos, in the 1930s, was implemented. Thirty-eight Santa Cruz iguanas, about half of the original group brought to the center, were released on the small islets of Venecia off the northwest coast of Santa Cruz. This semi-captive population lived under natural conditions, but the islets had no large areas suitable for nesting. Approximately 100 m3 of soil was moved to Venecia from Santa Cruz and an artificial nesting area was built. The population thrived. The iguanas on Venecia continue to breed today and many of the resulting juveniles are repatriated to Santa Cruz, approximately every three years.
Unlike tortoises, the young land iguanas could not be repatriated to their original habitat unless the introduced predator problem was solved. Dogs eat adults as well as young iguanas, while cats eat only young animals. Once feral dogs had been eliminated on both southern Isabela and northwestern Santa Cruz, iguana repatriations were generally successful.
The land iguanas of Baltra have a very different history. Historically, the Baltra iguanas were the largest in the archipelago. However, when the Hancock Expedition visited the island in 1932 and 1933, the iguanas appeared malnourished. Introduced goats had devastated the vegetation. In an attempt to help the iguanas, members of the expedition transferred 70 iguanas to North Seymour, the island to the north of Baltra where there were no land iguanas and no goats. Within 20 years, the iguanas on Baltra disappeared due to a combination of habitat destruction resulting from the construction of the U.S. air base in World War II, predation by dogs and cats, and competition by feral goats. The informal experiment of the Hancock Expedition had saved the Baltra land iguana from extinction.
In the 1980s, iguanas from North Seymour (where the population seemed to be in decline) were brought to the breeding and rearing center, with the idea of eventually repatriating the young to Baltra. Given that Baltra has two military bases, air force and navy, iguana repatriations required the collaboration not only of the CDF and GNPS, but also the Ecuadorian Armed Forces. The first 35 young iguanas were released in June 1991. A total of 420 iguanas have been repatriated to Baltra and their survival rate appears high. Recent surveys have shown that both populations, Baltra and North Seymour, are healthy and increasing.
Today, all of the populations appear to be healthy, although the National Park must continue to do periodic cat control in critical land iguana habitat at Cerro Cartago and Cerro Dragón. The last repatriations were made to Cerro Dragón in 1991 (except for transfers from Venecia), Cerro Cartago in 1993, and Baltra in 2008. The land iguana breeding and rearing program was considered a complete success and ended in 2008.
Marine Iguanas
Just about every rocky shoreline in the Galapagos Islands is home to the marine iguana (Amblyrhynchus cristatus), the only sea-going lizard in the world. The marine iguana is an extraordinary animal that lives on land but feeds in the sea, grazing on a variety of seaweed – on exposed rocks, in subtidal areas, or by diving deeper into the cold seawater. This habit, totally unique in iguanas and in fact all lizard species of the world, provides them with an abundant food source. However, they cannot withstand the cold temperatures of the sea for too long and must pull out on land to warm up.
Marine iguanas also mate and nest on land. While they have few predators in the sea, on land, young iguanas fall prey to hawks, herons, and other birds. Predation by introduced cats has had a major impact on many populations. Found throughout the islands, concentrations of up to 4,500 individuals per mile are not uncommon in some areas. The total population has been estimated at between 200,000 and 300,000.
The short, blunt nose is well-adapted to feeding on algae growing on rocks. The flattened tail is perfect for swimming, propelling the iguana through the water while its legs hang useless at its sides. Iguanas rid themselves of excess salt, consumed along with the algae, by a special gland connected to their nostrils. Marine iguanas are an excellent example of a species well-adapted and continuing to adapt to their environment. While marine iguanas feed mainly on algae, they have also been known to consume crustaceans and grasshoppers. On one or two islands, a small percentage of marine iguanas have been observed feeding on terrestrial vegetation, perhaps an adaptation to the near complete absence of nutritional sea algae during strong El Niño events.
When marine iguanas go hungry, they don’t just become thinner, they get shorter too. A scientist recently found that in times of El Niño-induced famine, the marine iguanas will shrink in length and then regrow as food becomes plentiful again. This finding, reported in the scientific journal Nature, is the first of a shrinking adult vertebrate. The adult iguanas can switch between growth and shrinkage repeatedly throughout their lifetime – a perfect adaptation to the boom and bust cycles in Galapagos associated with El Niño. The researchers postulate that bone absorption accounts for much of the reduction, with iguanas literally digesting part of their bones to survive.
Marine iguanas show their color as they mature – the young are black, while adults range from red and black, to black, green, red and grey, depending on the island, with Española marine iguanas being the most colorful of all, and earning them the nickname “Christmas Iguanas.” Marine iguanas become more colorful in the breeding season, at which time males defend territories on land where they mate with the females, who then lay their eggs in burrows. Marine iguanas lay 2 to 3 large eggs, which hatch between 2 ½ and 4 months later. Marine iguanas are known to live up to 60 years.
El Niño events cause the greatest mortality in marine iguanas, with up to 70% dying in some populations in the great 1982-83 El Niño. Recent research has also found high mortality of Galapagos marine iguanas on Isla Santa Fe resulting from the subtle long-term effects of the 2001 oil spill from the grounded tanker Jessica.
Mammals
The variety of mammal species in the Galapagos Islands is rather limited, as is typical for most islands located far from mainland continents. In fact, there are only 6 mammal species (that can be found on land) that are considered native to the islands, plus a number of aquatic mammals that swim in and out of the Galapagos Marine Reserve.
Sea Lions
With a population size of about 50,000, the Galapagos Sea Lion (Zalophus californianus, subspecies: wollebacki) is one of the first animals that visitors to the Galapagos Islands encounter. They can often be found sprawled on the docks or benches where tourists board their cruise boats, and are found lounging on beaches or low rocky shorelines throughout the islands. Their playful and inquisitive behavior makes them a tourist favorite, and lucky divers or snorkelers may be treated to underwater gymnastic displays from these graceful creatures. Despite their curiosity, sea lions are wild animals and can be unpredictable in their behavior – especially the males – and people will occasionally be bitten for not respecting their space and privacy.
Sea Lions are the largest animals found in Galapagos – full-grown males (bulls) can weigh up to 550 pounds. Besides their larger size, males differ from females in that they have a large “bump” on their foreheads and have extremely thick necks that provide protection.
Sea Lions mainly eat fish that they catch out in ocean on extended foraging trips. When on land, they congregate in harems (a group of females with one dominant male bull) or in bachelor colonies (males without harems to defend). However, females are free to move from harem to harem, as it is the territory where the females lie that a dominant bull defends, more so than the actual females in the territory. A dominant bull will spend the majority of his day patrolling the shallow coastal waters along his territory, ensuring that other bulls do not come near. It is exhausting to defend a harem, and for this reason, defense of a harem generally only lasts for a few days up to three months for a single bull. Fights between bulls for territories are quite common, with pushing, neck-biting, and dramatic water chase scenes ensuing. Harems are usually found in the most desirable beach locations, and the bachelor colonies are located in less desirable places, sometimes high atop rocky cliffs or farther inland near lagoons.
Once a year, females give birth to single pups, which they rear for one to three years. For this reason, it is common to see one mother with two suckling pups of different ages. Mothers will stay with their newborn pups for about 5 days, as they get to know each other’s sounds and smells, and then she will venture out to fish and replenish her energy. Baby sea lions will gather in shallow water nurseries that are watched over by one female, while the other mothers go out fishing. Bulls will even join in defending the nurseries from sharks, who may come looking for a defenseless pup meal. At about five months old, young sea lions will begin to learn to fish on their own.
Females are sexually mature at around 5 years old, and can live to be about 20 years old – males mature a bit more quickly, but will not guard a harem until they are older, and they do not live as long as females.
Fur Seals
Many people think Galapagos Fur Seals (Arctocephalus galapagoensis) are much less abundant in Galapagos than Sea Lions, but their population numbers are similar. Fur Seals typically prefer more rugged, rockier, and shadier shores than sea lions in areas that less likely to be frequented by people. Fur seals are less tolerant of heat than sea lions, which is why they prefer cooler water and shaded areas. And despite their “seal” name, they are actually a type of sea lion.
Galapagos Fur Seals and Sea Lions are morphologically similar, but there are some key physical differences that can help people tell them apart. Fur seals are generally smaller with broader and shorter heads. Fur Seals have bulging eyes and ears that protrude more than sea lions’, and larger front flippers that aid in climbing rockier coasts. The biggest difference is probably in their fur coat, which is much thicker and appears “furrier” on fur seals than on sea lions.
Because of their remarkably insulating coats, fur seals were hunted by the tens of thousands in the 1800s, nearly to extinction. They have made an amazing comeback in their population numbers, and can be seen most easily by Galapagos tourists at James Bay on Santiago Island and in Darwin Bay on Genovesa Island.
Fur seals eat fish and squid, and they are nocturnal hunters. Scientists have found that they tend to hunt less when the moon is full, probably because they become more visible to shark predators and their prey tends to move into deeper waters.
Fur seals’ social and breeding behaviors are quite similar to that of sea lions (see above), with a few differences. With regards to bulls defending territories, a fur seal bull will defend his harem from land, rather than from the water. Pups begin to hunt at about a year old, but will suckle from their mothers for two to three years. Though females can give birth every year, they will, at most, successfully raise one pup every two years. Should a second pup be born while a yearling is still suckling, the new pup has little chance of survival, despite being defended by its mother.
Rice Rats
Unfortunately, only four of the original seven endemic Rice Rat species still exist in Galapagos; not surprisingly, these four species live on three islands that are not inhabited by humans – Santa Fé, Santiago, and Fernandina. The other three species of rice rats became extinct since humans colonized the islands and brought black rats with them. Competition with and/or a virus carried by the black rats is likely what brought about the demise of these three species.
The ancestors of the native rats of Galapagos originally arrived to the Islands via rafts of vegetation that floated from the South American mainland out to Galapagos – these rats actually hold the world record for terrestrial mammal ocean crossings.
Bats
There are two bat species present in Galapagos, but little is actually known about them.
Lasiurus cinereus, the Hoary Bat from North America, is light brown with white fur tips, eats insects, and tends to prefer roosting in Mangrove trees or scrub bushes during the day. It is quite widespread and is found on Santa Cruz, San Cristóbal, Isabela, Santiago, and Floreana Islands.
Lasiurus brachyotis is found on Santa Cruz and San Cristóbal in the highlands and coastal zones, and it is believe to migrate seasonally between the two zones. This bat forages near the ground while the Hoary Bat forages higher in the trees and air, which explains why they can coexist. L. brachyotis is believed to be closely related to the Red Bat of South America.
Dolphins and Whales
The aquatic mammals (cetaceans – whales, dolphins) form the last group of mammals found in the Galapagos Islands. Unlike most land mammals that are generally covered in hair or fur, these aquatic mammals have little, if any, hair. Instead, they have a fat layer of blubber which helps to maintain their body heat and to provide a reserve of energy when needed during long migrations or strenuous activity.
The blubber of whales can be used to make oil, and this is what made them so valuable to humans in the 19th century when the Galapagos Islands were central to Pacific whaling activities. Fortunately today, whaling does not take place anymore in the Islands. Whales are occasionally seen passing through Galapagos, and dolphins are likely to be seen all around the islands.
The Cetaceans fall into two major groups – those with teeth, and those with baleen (fringed whalebone that enables filter-feeding of plankton and small marine animals). Both groups of cetaceans, and several species from each group, can be found in the Galapagos Islands. Humpback whales are one of the easier baleen whales to identify because of their angled back, as well as their tendency to breach and splash dramatically back into the sea.
Many species of toothed whales show up in the Galapagos Marine Reserve, including the Sperm Whale, Killer Whale, False Killer Whales, the Pilot Whale, as well as several species of dolphins. There are two dolphin species that are quite abundant and easy to spot– the Bottle-nosed Dolphin and the Common White-bellied Dolphin. The Bottle-nosed Dolphins are often found racing alongside boats, and sometimes they get close enough that people on board can hear their delightful squealing. Common Dolphins are more likely to be found in large schools of 100 or more individuals.
Landbirds
Sea and Shorebirds
Of the 56 native bird species of Galapagos, 45 (80%) are endemic (only found in Galapagos) and 11 are indigenous (native to Galapagos but also found elsewhere). In addition to the native birds, there are 29 migrant species (migratory and native) and 64 species that have been observed once or twice. Galapagos birds can be separated into sea birds, shore and water birds, and land birds.
Island birds are one of the groups most subject to extinction worldwide following the arrival of humans. The loss of birdlife in the tropical Pacific may exceed 2000 species (a majority of which were species of flightless rails). Galapagos is the exception, primarily because humans arrived so much later than on other islands. While there are extinct bird populations on certain islands, Galapagos still retains all of its native bird species.
There are also six introduced bird species in Galapagos that have become naturalized in the wild, five of which were accidentally introduced and one was introduced for agricultural or other use. These include Smooth-billed Anis, Cattle Egrets, Quails, Guinea Fowl, Peacocks, and the Guayaquil Red-masked parakeet. One introduced bird species has been eradicated – the Rock Dove.
Seabirds
The Galapagos Islands are a mecca for tropical seabirds, including Blue-footed, Red-footed, and Nazca Boobies, Flightless Cormorants, Great and Magnificent Frigatebirds, Red-billed Tropicbirds, Waved Albatross, Swallow-tailed Gulls, Lava Gulls, Galapagos Penguins, and many more. Seabirds provide some of the greatest opportunities to observe wildlife in the islands – especially in the large breeding colonies.
While a large majority of the land birds are endemic, there are only six endemic species among the seabirds: the Galapagos Penguin, Flightless Cormorant, Waved Albatross, Galapagos Petrel, Lava Gull and Swallow-tailed Gull. While the two gull species are found on many islands, the others have more restricted ranges. Each species has evolved its own behavior patterns related to feeding and breeding, and in any month you will find some seabirds displaying, incubating eggs, or feeding their young.
Galapagos Penguins, one of the smaller penguins of the world, are the only penguins that live at or just above the equator. The penguin population of about 2000 individuals is concentrated in the colder, nutrient-rich waters in the western islands – Fernandina and Isabela (about 95% of the population). However, small isolated populations are found at some small satellite islands off the coast of Santiago and along small sections of the northern coast of Floreana.
Galapagos penguins breed throughout the year and nest at sea level in caves. They forage relatively close to shore and at relatively shallow depths. Long-term monitoring has shown that this species undergoes severe fluctuations, primarily related to El Niño events and their effects on the availability of fish. The extreme El Niños of 1982-83 (77% reduction in the population) and 1997-98 (66% reduction) caused a long-term reduction in the population over the last 30 years. Although the current population is relatively stable, the species is listed as Endangered by the IUCN due to small population size, restricted range, and its vulnerability to El Niños. Climate change may lead to an increase in the frequency and intensity of El Niño events further endangering this population.
Flightless Cormorants, with a population of approximately 1600 adults, are endemic to Fernandina and Isabela Islands. They live around most of the coast of Fernandina but only on the north and west coasts of Isabela. Their range is very similar to that of the Galapagos Penguin, centering on the cold, nutrient-rich waters of the western archipelago. Unlike other cormorants around the world, the Galapagos Cormorant has lost its ability to fly. With no predators, swimming ability was more valuable and after centuries of evolution, Galapagos Cormorants have only vestigial wings but very strong legs. Its food includes eels, octopuses, and fish. It usually nests in sheltered areas, mostly within 100 m of the shore, and in small groups, mainly during the cool season (July-October) when marine productivity is highest and the risk of heat stress to chicks and incubating adults is reduced.
As is true for the Galapagos Penguin, Flightless Cormorants are also negatively affected by El Niño events. However, after the 1997-98 El Niño, the population has grown more rapidly than ever during the years of censuses (1977 on). The population appears to be stabilizing and the IUCN has downlisted the Flightless Cormorant to Vulnerable.
Waved Albatross breed only on Española Island in the Galapagos, and perhaps on Isla de la Plata off Manabí province, Ecuador. On Española, the overall breeding population was considered to have been stable until recently. The Española population was estimated at approximately 12,000 pairs in 1970-1971, 15,600-18,200 pairs in 1994, and at least 34,694 adults in 2001. On Isla de la Plata, there are probably fewer than 10-20 pairs. Analysis of birds caught as intentional and incidental take in inshore fisheries has revealed that a disproportionate number of males are taken, which will result in further decreases to the effective population size given that this species has obligate bi-parental care.
Waved Albatross breed annually, arriving at colonies in late March and laying eggs from mid-April to late June. Pairs mate for life and, each year, perform an elaborate mating dance to ensure they have the right partner. Chicks fledge between late December and early January. Breeding adults travel to the Peruvian upwelling region to feed, and, in the non-breeding season, the albatross abandon Española and move mainly east and south-east into the waters of the Ecuadorian and Peruvian continental shelf. Waved Albatross feed on squid, fish, and crustaceans. This species is classified as Critically Endangered because it has an extremely small breeding range, is essentially confined to one island, and evidence suggests that it has experienced a substantial recent population decline related primarily to fisheries, especially long-lining.
Galapagos Petrels are the only seabird in the islands that breed in the humid highlands of the larger islands – Santa Cruz, Floreana, Santiago, San Cristóbal, and Isabela. The petrels nest in burrows or natural cavities usually on sloped hillsides. This nesting behavior makes them extremely vulnerable to introduced predators, including cats, rats, and pigs. By the 1980s all of the populations had plummeted. Conservation efforts, aimed at controlling the introduced predators at the nesting grounds, have resulted in the recovery of the petrel numbers. The global population estimate is now 10,000-20,000 individuals.
However, the IUCN continues to list them as Critically Endangered due to the continued presence of both rats and cats in the majority of their nesting areas, potential of nest destruction by goats, donkeys, cattle and horses, and impacts from agriculture and invasive plants on their habitat. Increased construction in the highlands and long-line fishing are also impacting these birds. In addition, El Niño events seem to have a detrimental impact on both nesting and productivity. Galapagos petrels feed mostly on squid, fish, and crustaceans.
Swallow-tailed Gulls breed mainly on the Galapagos Islands but also on Malpelo Island, Colombia. The population is estimated at 10,000–15,000 pairs and appears to be stable. When not breeding, these gulls can be found along the Pacific coast of South America from Ecuador to northern Chile. Swallow-tailed gulls, unlike all other gulls in the world, forage mostly at night, feeding on squid and some fish. They appear to suffer from periodic food shortages and are often observed feeding 500 km from the nearest land.
Swallow-tailed Gulls breed throughout the year and asynchronously across the Galapagos, with individual sub-colonies being synchronized by social interactions. They nest on steep slopes or broken cliffs, on ledges, and also just above the wave line on gravelly beaches and under vegetation. Adults leave the colony after breeding and become highly pelagic, returning in 4-5 months often to their previous nest site. Their range is very large and does not approach the threshold for the Vulnerable category – and thus Swallow-tailed Gulls are listed as Least Concern.
Lava Gulls are one of the least known of the seabirds. Although widespread throughout the archipelago, Lava Gulls do not form large breeding colonies and are usually observed in single pairs. The population is estimated at 900-1200 individuals. The reason for the tiny population and the solitary nesting behavior is not fully understood but is thought to be related to its feeding behavior. Lava Gulls nest solitarily in scrapes on sandy beaches or low outcrops close to water. The female lays two eggs. A gull’s territory is large and adults are extremely wary when nesting. They are scavengers but will also take seabird eggs, juvenile marine iguanas, small fish, and crustaceans. This poorly known species is considered Vulnerable because of its small population size. Although its numbers appear stable, there are numerous potential threats.
Three Species of Boobies
The three booby populations are the most common and most frequently seen of the seabirds. Similar in appearance to gannets, they are large birds (70-90 cm in length) with long narrow wings. Their long pointed beaks gave rise to their Spanish name piquero. Boobies have a strong direct flight movements, with several powerful rapid wing beats followed by a glide. All of the booby species feed by spectacular plunge diving into the sea and then catching fish on their way back to the water surface. All three species tend to live in groups, but in the Galapagos Islands, they range from widely distributed small colonies of Blue-footed Boobies to the larger, less frequent colonies of the Nazca Boobies, to the few huge colonies of Red-footed Boobies.
The number of eggs laid by each species is related to where they feed, with Blue-footed Boobies feeding near shore, the Nazca Boobies feeding further offshore, and the Red-foots feeding out in the open ocean. The farther they must go to their feeding grounds the fewer eggs they lay. Blue-footed Boobies lay 1-3 eggs. When times are good, they may successfully fledge all three chicks. Nazca Boobies lay two eggs with only a single chick surviving. The death of the second chick is usually due to siblicide (death caused by a sibling or close relative) by the older chick (born a few days earlier). Siblicide is apparently obligatory in the Nazca Booby species.
Although the smallest and least often seen by humans in Galapagos, Red-footed Boobies are the most abundant of the three species. However, since they feed far out to sea, they nest in the outermost islands with access to open ocean and lay a single egg. While the Blue-footed and Nazca Boobies nest on the ground, Red-foots nest in trees and shrubs. The Red-foots also have two color phases, the large majority (95%) with a brown body and the rest with a white-and-black body.
Frigatebirds
Two of the world’s five species of frigatebirds are found in Galapagos – the Magnificent Frigatebird and the Great Frigatebird. The frigatebirds or “man of war” birds got their name from their pirate-like habits. Large black birds with long wings, long hooked beaks and deeply forked tails, they are often seen soaring overhead. They are superlative flyers, and feed by snatching up flying and other fish, squid, and scraps from the surface of the ocean – and, most notably, by stealing from other seabirds in flight. When feeding off the surface of the sea, only their beak will touch the water as frigatebird feathers are not oiled and waterproofed like most seabirds. If their plumage gets too wet, a frigatebird can become waterlogged and drown.
Frigatebirds are occasionally seen “bathing” in the freshwater ponds in the highlands of some of the larger islands. While Waved Albatross and Blue-footed Boobies have a more elaborate courtship ritual, watching the courtship of Frigatebirds is spell-binding. The male frigatebird has a bright red gular pouch that usually sits tight to the bird but can be inflated when breeding to attract the female. The males sit together or singly in trees where they nest, waiting for females to fly overhead. On sighting a female, the males turn their head and wings upward, shake them vigorously, display their bright red pouches, and call loudly. If a female is attracted, she will descend to the nest and courtship continues. Females lay a single egg and both parents share incubation duties.
Shorebirds
The most commonly seen shore and water birds include the Galapagos flamingo, the many heron species including Great Blue Herons, Yellow-crowned Night Herons, Lava Herons, Black-crowned Herons and Striated Herons, Oystercatchers, White-cheeked pintails, Gallinules, and Common Egrets.
The Galapagos Flamingo population is approximately 320-350 individuals. The small population size has resulted in changes in breeding behavior compared to other flamingo populations worldwide, which all need very large groups of birds for breeding to occur. Galapagos Flamingos can breed with just a few pairs present. They live in the saltwater lagoons close to the sea and filter feed primarily on brine shrimp. Young flamingos hatch with grey plumage. The pink color of the adults is due to aqueous bacteria and beta carotene obtained from their food supply. The population appears stable but they are threatened by introduced animals such as rats, cats, and pigs. Intense El Niños can affect their food supply and severely impact their habitat making nesting impossible.
The largest of the herons, the Great Blue, eats much larger prey than the other heron species. The Lava Heron catches fish by stealth, watching from a rock just out of the water until a fish passes and then grabbing it. The Lava Heron also eats small crabs, but the Yellow-crowned Night Heron, which hunts at night, could be considered the crab-eating specialist.
