The Galapagos Islands were officially discovered by Fray Tomas de Berlanga, the Bishop of Panama, in 1535. He was on a journey from Panama to what is now Peru. The Bishop and his crew were low on supplies when they came upon the island and had trouble finding food and water. He sent accounts of his discovery to Emperor Carlos V of Spain. These are the fist known accounts of the Galapagos Giant Tortoise and the incredible iguanas. He told Carlos V that the birds were so tame they didn't run from his men and many were actually caught by hand. He didn't even bother to give the islands a name. It wasn't until 1574 when the name "Islands of Galapagos" (Island of Tortoises) or "Encantadas" first appeared on a map and has remained ever since.
Most of the other, non-explorers, to visit Galapagos during this time were pirates and whalers. Pirates found Galapagos was a great place to base raids on Spanish colonies. They brought their raided goods back to the islands- perhaps there are still gold and silver caches to be discovered.
The Galapagos were officially annexed by Ecuador in February 12 1832 and were named "Archipelago del Ecuador." It is still today officially a province of Ecuador. Ecuador claimed the Galapagos Islands just three years before their most famous visitor, Charles Darwin, dropped anchor on the Beagle and stepped ashore and into history. His research on the islands eventually led to the formation of his theory of evolution of the species by natural selection.
The Voyage of the Beagle brought the survey ship HMS Beagle under captain Robert FitzRoy to the Galapagos on September 15, 1835 to survey approaches to harbours. The captain and others on board including his companion the young naturalist Charles Darwin made a scientific study of geology and biology on four of the thirteen islands before they left on October 20 to continue on their round-the-world expedition. The governor of the prison colony on Charles Island told Darwin that tortoises differed from island to island, and when specimens of birds were analysed on return to England it was found that many different kinds of birds were species of finches which were also unique to islands. These facts were crucial in Darwin's development of his evolution theory of The Origin of Species.
Jose Valdizan and Manuel Julian Cobos tried a new colonization, beginning the exploitation of a type of lichen found in the islands (Roccella portentosa) used as a coloring agent. After the assassination of Valdizan by some of his workers, Cobos brought from the continent a group of more than a hundred workers to San Cristobal Island and tried his luck at planting sugar cane. He ruled in his plantation with an iron hand which lead to his assassination in 1904. Since 1897 Antonio Gil began another plantations in Isabela island.
By far the most interesting settlers that arrived in the Galapagos were three groups of Germans who arrived in the 1930’s. The first group comprised of a baroness and her three lovers, the second, a couple from Cologne called the Wittmers, and the third, an eccentric, vegetarian Dr Friedich Ritter and his mistress.
In 1934, as more scientists became interested in the Galapagos’ unique environment, some islands were declared wildlife sanctuaries. However, the degradation of the islands wildlife still continued and in 1941 Waldo Schmidt of the Smithsonian Institute visited the island with the object of building a research station, to the great approval of President Roosevelt who had visited the islands himself in 1938. Unfortunately, Pearl Harbor intervened and instead of a research center, the United States used funds to build a US airbase.
Finally, in 1959, with funds raised from various scientists and the United Nations Educational, Scientific and Cultural Organizations (UNESCO) the Charles Darwin Research Center was established. That same year, Ecuador declared the Galapagos a national park and 95% of the archipelago was protected. Organized tourism began in the mid-60s with a little over 1,000 visitors a year, a number which has increased ten-fold over the decades with an estimated 60,000 tourists visiting the islands in 1991. UNESCO placed the Galapagos Islands on the World Heritage List in 1978.
The Galapagos Archipelago consist of thirteen large islands, (greater than 10 km2), six smaller islands and over forty islets that have official names. Many small rocks and islets remain unnamed. These islands are well isolated from other land masses and straddle the equator at the 90th meridian west. The nearestland, mainland Ecuador, is some 960 Km to the east. To the northeast lies Cocos Island (720 Km) and Costa Rica (1,100 Km). Sixteen hundred kilometers to the north is Guatemala, while to the south about 3,200km lie Easter and San Felix Islands.
The total land area of the islands is about 8,000 km2 spread over about 4,588 km2 and four other islands have an area greater than 500km2. The archipelago is 430 km long from Darwin Island, in the northwest, to Española Island in the southeast. From the Point San Cristobal at the southwest of the Isabela Island to Genovesa Island in the northeast is 220 Km.
The climate in the Galapagos Islands is equatorial, cooled by the Humboldt current. Generally speaking, the days are warm and the nights are cool. Humidity is low. The climate is very similar to that of California.
The Galapagos Islands see only two major seasons a year. The dry, or garua, season lasts from July to December. The hot, wet season occurs between January and June with March and April being the wettest months of the season. Around December, several changes occur in the atmospheric and oceanic currents. The trade winds slacken and the "International Convergence Zone" (the climatic equator located just north of the geographic equator) shifts southward toward the Galapagos. The slacking trade winds cause the Southern Equatorial Current, a westward current, to slow. This reduces upwelling, and warm water invades the islands. Ambient air, in turn, warms, and the inversion layer breaks down. Warm air then rises to the point where rain clouds form and daily afternoon showers occur. Even with this added precipitation, however, low elevations on the islands still receive only limited rain. Interestingly enough, the highland areas of the islands receive more moisture from the garua (the mist that develops at upper elevations) than from rain.
Charles Darwin was only twenty when he left England in 1831. Thirty years later he published his theory of evolution, unquestionable one of the most revolutionary ideas science has ever known. Because of Charles Darwin's "discovery" of these islands, much attention has been paid to them and many fascinating things have been discovered. One of the main questions was how so many different plants and animals arrived on the islands in the first place.
The periodically changing currents have allowed many different species to immigrate to the islands. Some, such as sea lions, fur seals, and penguins, could swim with the help of the currents and giant tortoises are known to float and could have been carried by the same currents. Also, during the rainy season, rafts of vegetation break off and float out to sea. Most of the reptiles, the only terrestrial mammals (the rice rats), and insects must have arrived by this route.
The light spores of many lower plants could have arrived in the islands by wind along with some vascular plants with lighter seeds. Spiders, small insects, and tiny land snails are frequently transported by wind as well. Land birds and bats, weak fliers, would have to have been blown to the islands, although the seabirds would easily have flown there.
The birds would often aid plants by ingesting seeds before takeoff and then expelling them at their destination. Other seeds, with tiny hooks, could have attached to feathers and feet and been given a free ride. Still other seeds, caked in mud and clinging to a bird's feet or feathers would have been transported there as well.
Darwin is generally credited with the theory of evolution by natural selection. Natural selection is that the strongest survive and propagate and therefore increase the strength of the species. Once on the islands, the various species established themselves and determined territories. Evolution then set in and many unique species, such as Darwin's finches, resulted.
These finches probably descended from one type of ancestor and then, due to isolation and through chance, different climates and natural forces such as food availability and type, they evolved into thirteen different types of finches.
The process of their evolution would probably have begun with immigrants from the mainland. As they dispersed to different islands, new populations would be formed. Every time these satellite populations dispersed, there would be greater difference between the individual species.
The Galapagos Islands are home to many endemic species, including the giant tortoise, marine iguana, blue- and red-footed boobies, Darwin's finches, and the only species of penguins residing in the Northern Hemisphere.
- Blue-footed booby
- Masked booby
- Red-footed booby
- Flightless Cormorant
- Waved Albatross
- Storm Petrel
- Galapagos penguin
The main way in which tortoises vary from island to island is in the shape of their carapaces. These range from the smaller "saddle-backed" types from Española and Pinta to the larger "dome-shaped" types from Santa Cruz and Alcedo Volcano, with many intermediates. The different carapace shapes and sizes are thought to have evolved, at least partly, as adaptations to the different environments of the various islands. The saddle-backed types with their long necks and limbs, and raised carapace-front, are found only on the lower drier islands, where the vegetation is not so dense and is more difficult to reach. On the higher, lusher, islands the dome-shaped types are found.
These races do not need to reach so high for their food and must be able to push their way through dense vegetation where a protected front end could be useful. Tortoises also vary noticeably in such features as skin colouration and scute striations. Recent genetic studies have shown that the races of giant tortoises have evolved from a common ancestor that probably first colonized San Cristobal Island. From this island, they succeeded in dispersing to other islands, where they diverged from their parent populations. It is also thought that the saddle-backed type carapace evolved independently several times as a reaction to dry environments. Tortoises are famed for their longevity but reliable records are scarce, as these animals may easily outlive a person. Many of the older Galapagos tortoises have extensive lichen and fungal growths on their carapaces, indicating their great age. The giant tortoises are vegetarian, eating a wide variety of plants. It takes one to three weeks for food to pass through the inefficient digestive system, and, even so, most ingested plant species are still easily identifiable in the large droppings. Galapagos giant tortoises are well known for their water storage abilities and drought resistance. Their ability to survive for long periods without water is in large part due to their ability to metabolise fat stored in their tissues which leads to water production. In whaling times, tortoises were popular as a source of fresh meat as they could remain alive on board ship for as much as a year without food or water.
Though capable of withstanding long periods of drought,
tortoises are fond of water and of wallowing in the mud of the moist highlands
of some islands. When the tortoise arrives at the spring, quite regardless of
any spectator, he buries his head in the water above his eyes, and greedily
swallows great mouthfuls, at the rate of about ten in a minute. In the moister
highland areas of Alcedo Volcano and Santa Cruz Island one often finds groups of
tortoises wallowing in rain-formed pools or even the dew ponds formed by garua-moisture
dripping off trees. These pools tend to be churned up into veritable mud baths.
The reasons for this behaviour are not clear but may relate to keeping cool,
reducing the number of ticks and mites, or avoiding mosquito bites. In spite of
their extensive body armour, their areas of exposed skin are vulnerable to
attacks by ecto-parasites. These can be a considerable nuisance to the tortoises
as the animals are not able themselves to remove such parasites. Fortunately,
tortoises and other large reptiles have developed mutually beneficial cleaning
relationships with mocking birds and
finches. When a tortoise wished to be
cleaned, after being approached by a finch or mockingbird, it stands up on all
fours and stretches its neck fully.
This exposes all its skin to the ministrations of these small birds which hop about looking for succulent morsels. Other birds, including hawks and flycatchers, often use tortoises as observation posts from which to sight their prey.
Tortoises, and other members of the turtle order, are unique amongst the vertebrates in having abony shell or carapace, which is an integral part of the skeleton. The bonyplates of the shell are fused with the ribs and other bones to form a rigid protective structure.
To compensate for this rigidity tortoises have long, flexible necks that can be withdrawn, together with the legs, until all are almost hidden by the carapace. The legs have hard scales that provide an effective armour when withdrawn. The scutes (or scales) of the carapace are not coincident with the underlying bony plates and grow at their outer edges. Tortoises thus keep their characteristic scute pattern throughout life. These do have annual growth bands but are not useful for aging as the outer layers are rubbed off in the normal wear and tear of living. Tortoises have no muscles to control the volume of their lungs. Breathing is controlled by the volume of the body cavity which can be altered by legand head movements. When startled, tortoises retract their head and limbs and this is always accompanied by a dramatic hiss of escaping air. Apart from the cow-like moans of the males during the mating season, this hiss is virtually the only sound they make.
Feeding giant tortoises move about slowly, taking a bite here and a bite there with no apparent direction; but if they have a purpose, such as moving to water or nesting grounds, they can move with surprising speed and determination: The tortoises, when purposely moving towards any point, travel by night and day, and arrive at their journey's end much sooner than would be expected. They are usually active from about 8 a.m. (two hours after dawn) until about 4 or 5 p.m., when they will find a place to sleep. Giant tortoises are mature at about 20 to 25 years of age, as the first animals reintroduced to Española have nested and produced young. In captivity, they can grow rapidly-a 13 kg tortoise taken from Isabela put on 175 kg in fifteen years! There are a few records of growth rates in the wild, but growth in the wild is likely to be much slower. For a month or so each year, usually towards the end of the warm season, the normally sedentary tortoises become occupied with the business of breeding. The males, which are much larger than the females, become aggressive and will chase and posture at each other. Posturing usually involves raising the head as high as possible, with the highest head indicating the dominant tortoise. The male's shell has a concave-shaped underpart (called a plastron) and a long tail.
Hawks are probably the only native predator of the tortoise hatchlings. Tortoises are much less abundant than they used to be, numbering only some 15,000 compared to an estimated 250,000 original population (MacFarland et al. 1974a,b), but they can still be seen by visitors in captivity and the wild. Several are kept at the Research Station in pens for captive-breeding purposes and for viewing and include representatives from many islands. To see tortoises in the wild one must either hike into the tortoise reserve on Santa Cruz or make an expedition to the rim of Alcedo Volcano, where tortoises are still abundant.
The Galapagos penguin (Spheniscus mendiculus) is the bird
that seems most out of place in the equatorial Galapagos Islands. Standing only
35 cm tall, it is the third smallest of the eighteen species in the penguin
family and the only species to occur north of the Ecuador and nest entirely
within the tropics. Penguins are a group of flightless seabirds characteristic
of the Antarctic oceans and islands. It comes as a surprise to find a little
penguin swimming amongst the stilt roots of tropical red mangroves. The closest
relatives of the Galapagos penguin are the Humboldt and Magellan penguins of
southern South America. The Humboldt penguin occurs primarily in the cold waters
of the Humboldt or Peru currents and is only rarely seen off the coast of
The Galapagos penguin is most likely descended from stray individuals of this species that managed to find the cool upwellings of the western islands. It breeds only on the west coast of Isabela and on most of Fernandina's coasts. Some are seen in other parts of the archipelago and may breed in sites such as by Pinnacle Rock on Bartolome Island.
Recent estimates put the population of these birds at between two and five thousand individuals and they are common within their breeding range. They are frequently seen sunning or resting on rocks, especially in the early morning and late afternoon, but most often are found swimming, singly or in groups of up to fifty or more, along the shoreline.
The adults are black above and white on the underparts, with a stripe around the breast and on the face. The juveniles are greyer, without the white lines, and have a pale patch on the side of the head and chin. They rise before dawn and spend the day swimming, with a few breaks on land. In the mid-afternoon, they start returning to their colonies. On the surface, penguins swim slowly, half submerged, but underwater, they fly through the water using their wings for propulsion and their feet as rudders. They can travel quickly through the water (as much as 40 km/h), especially when they "porpoise" on the surface. They usually do so when pursuing a school of fish. The kinds of fish taken are small, ranging from 10 to 150 mm; some crustaceans are taken as well.
The penguin has different feeding strategies dependent on the water temperature. If the water is below about 23°C, they feed in large groups of twenty or more, as fish are abundant when the water is cool and rich. When the water is warmer they tend to feed in smaller groups or singly, as fish are less abundant. This indicates that group fishing is more efficient when fish are abundant.
Galapagos penguins must adapt to two environments, hot land and cool water, while their more southerly relatives need only adapt to cold. In the water, the temperature may range from a cool 16°C to a warm 28°C, while on penguin, has observed a case of a bird watching over its nest in the open sun, becoming overheated to the point where it had to either cool itself or die. It left the nest and took to the water-unfortunately, when it returned to the nest the eggs had heated and died. The penguin spends much time preening, as its feathers and down have extremely important insulating properties. The value of the insulation is demonstrated by Dr. Boersma's observations of moulting birds. During the moulting period, they fast and do not enter the water at all. After a few days, the feathers all stand on end and the birds have a great aversion to entering the water.
One bird that entered the water lost 6°C body temperature in thirty seconds before it managed to scramble out. During the first few days of moulting, birds often stand out in the open, but once the old feathers start to drop out and expose the new plumage, they seek cover. Heat stress would be highest at this stage because the new plumage is dark and much of the insulating fat stores have been used up. After ten to fifteen days of fasting and staying out of the water, the penguin resumes its normal life. Often they will start to breed after moulting. The Galapagos penguin chooses a mate for life, barring accidents. It lays its one or two eggs in holes, caves, or crevices to keep them out of the sun. One parent will always stay with the eggs or young while the other will be gone for several days to feed. The parents will take turns at this for a full five weeks, after which the fluffy brown down-covered chicks appear. If there is not enough food available, the nest may be abandoned. However, if conditions are good, a pair may lay as frequently as three times in fifteen months. Starvation is thought to be a major cause of death for these penguins; predation seems to be insignificant though at sea, sharks, fur seals, and sea lions are potential threats. On Isabela, the introduced cats, dogs, and rats are predators but their effect on the population is not known. Sometimes when the penguins feel threatened, they will turn their backs toward the perceived source of danger and thus camouflage themselves against the black lava rocks.
On land, Galapagos penguins have three methods of transportation: walking, which they do with more grace than most penguins, perhaps because of their smaller size; scrambling after a fashion over rough terrain, using both flippers and feet; and hopping or jumping which is used to get on top of a rock or places they cannot otherwise reach. To avoid missing, the penguin seems to measure the distance by putting its beak on the spot it is attempting to jump to before doing so. When entering the water it usually hops or flops in feet first. Penguins are social birds that maintain a personal territory within the group. They have both a defended area around the nest and also an invisible curtain around themselves which must not be invaded.
iguanas have the same features as other diving animals: when they dive, their
blood moves away from the surface to save body heat, and their heart beat slows
down drastically. Only the largest males dive because larger animals lose less
Marine Iguanas live in large colonies for most of the year. In the breeding season, usually December and January, they become territorial. Males establish and maintain territories in the dry places above the water line, and near the nesting groungs. Males fighting begins with a head bobbing display, with their mouths wide open.
After a while the males charge each other, locking heads using the triangular crests on the top of their heads, and then pshing and shoving. The fights can last for up to 5 hours. Once he has won his territory, a male waits to attract a female to his territory, and then mating takes place. The females then leave, and about 5 weeks later they lay their eggs in a soft, sandy spot. They dig the nest by pushing the dirt back with their front legs, then out with their hind legs. During nesting, the females are aggressive towards each another, and will guard their nests for some time after laying.
The marine iguana feeds almost entirely on algae (seaweed) that it finds between the tide-lines or below the sea's surface. Whether above or below the sea, the food consists of small red or green algae. It does not seem to be very choosy as to which species of algae it eats, except that itavoids the large brown seaweed Blossevillea. This is an indigestible species for the marine iguana. If you take a close look at the intertidal rocks, you will find abundant small clumps of dark red-brown or green algae, mostly less than 1 cm tall. It is these insignificant-looking species that form the bulk of the marine iguana's diet (as well as that of many crabs). One may ask how so many iguanas and crabs can be feeding off such small amounts of algae; the answer lies in the fact that the algae are very fast-growing. These plants cover a large proportion of the lower intertidal zone and are known to double their length and increase their weight by up to six times, in two weeks. The barren-looking rocks are very productive, but the turnover is fast. This is why the animals appear to be more abundant than the plants. In most ecosystems, the plants usually outweigh the animals by orders of magnitude, but for the Galapagos inter-tidal zone this is not the case.
As well as feeding on seaweed, these iguanas occasionally feed on the faeces of their own species and those of sea lions and red crabs. To cope with the high salt intake in its diet, the marine iguana must excrete salt. It has the most effective salt glands of any reptile. These are located above the eye and are connected via a duct to the nostrils. The salt is then forcibly expelled by frequent sneezing. This looks like spitting and results in the iguanas frequently having salt encrusted heads. Most marine iguanas feed once a day, but some of the larger ones will feed only every second or third day. The pattern of daily activity is largely determined by the temperature and the state of the tide. The larger males will usually wait until the middle of the day when the sun is at its hottest and they have had time to warm up before they will swim offshore and start diving to feed. The rest of the population leave the colonies a little before the tide has reached its lowest ebb and feed on the shoreline. 1 heyeat until the tide again starts to wash over them. It is remarkable that two parts of the same population have such different activity cycles. This may well be a result of the difficulties of offshore feeding for smaller individuals which cannot store much heat or swim well. They thus cannot make use of the more abundant offshore food resource. These activity patterns were elucidated from a population on Santa Cruz Islands and may not be typical of all other parts of the archipelago.
The Galapagos sea lion (Zalophus californianus wollebacki) is found in the Galapagos Archipelago where it is one of the most conspicuous and numerous marine mammals. Well adapted to its semi-aquatic lifestyle, it has a streamlined body and powerful fins, and as a member of the eared seals (Otariidae family), which includes fur seals and sea lions, this aquatic mammal is able to control its hind flippers independently.
This adaptation allows it more agility on land than seals, which cannot move their hind limbs independently. Furthermore, unlike the true seals (family Phocidae), Z. c. wollebaeki swims using its strong and well developed fore flippers. Adult males are much larger than females and are brown in colour while females are a lighter tan. Adult males are also distinguished by their raised foreheads, and the hair on the crest may be a lighter colour.
Juvenile Galapagos sea lions are chestnut brown in colour and measure around 75 cm at birth. Sea lions show an extreme degree of sexual dimorphism, with males much larger than females. A male sea lion may measure up to 2.4 meters (8 feet) and weigh 270 kg (600 lbs); a female may measure up to 1.8 meters (6 feet) and weigh 90 kg (200 lbs.)
Galapagos sea lions do not migrate, remaining around the islands all year and feeding at shallow depths, mainly for sardines. On land this sea lion prefers sandy or rocky flat beaches where there is vegetation for shade, tide pools to keep cool and good access to calm waters. It also spends much of its time in the cool, fish-rich waters that surround the Galapagos Islands
Galapagos Sea Lions are especially vulnerable to human activity. Their inquisitive and social nature makes them more likely to approach areas inhabited by humans, to come in contact with human waste and with fishing nets and hooks. Sea Lions can be seen all over the islands. Snorkeling and kayaking with the playful pups is often the highlight of a visit to the Galapagos.
In Galapagos finch language, the result is 13 different species in Galapagos, plus an extra one in Coco Island (400 miles north of Galapagos).
- Small Ground Finch
- Medium Ground Finch
- Large Ground Finch
- Sharp-beaked ground Finch
- Cactus Ground Finch
- Large Cactus Ground Finch
- Small Tree Finch
- Medium Tree Finch
- Large Tree Finch
- Woodpecker Finch
- Mangrove Finch
- Vegetarian Finch
- Warbler Finch
- Cocos Island Finch
Charles Darwin discovered on the Galapagos Islands. Darwin's voyage on HMS Beagle, and the finches in particular, are known to have influenced his thinking so that he would later produce a basic theory of evolution by natural selection.
Darwin reasoned that there had to be a common ancestor. Later, much work was done by Peter and Rosemary Grant. The birds are all about the same size (10–20 cm). They mainly differ in the form of the bill. The bill is adapted to the food they eat. The birds are all brownish or black. They have short rounded wings and a rounded tail that often appears cocked to one side. Most male finch mature to a solid black color, while the females mature to a drab grayish color.
Exceptions are made for the Vegetarian and Tree Finches the males never become completely black rather they have a black head, neck and upper breast. Warbler, Woodpecker and Mangrove Finches have more of an olive color.
The Galapagos hawk (Buteo galapagoensis) is the only diurnal raptor with established populations in the Galapagos, where they inhabit nine islands. Their mating system varies between islands, from standard pairs on some to polyandrous groups comprising single females with multiple males on others. Because populations exhibiting polyandry are almost exclusively polyandrous, this species represents the most extreme example of this unusual mating system in birds.
The adult Galapagos Hawk is generally a sooty brownish black colour; the crown being slightly blacker than the back. The feathers of the mantle are partially edged with paler brown, grey, or buff, with their white bases showing to some extent. The tail coverts are also barred with white. The tail itself is silvery grey above, with about ten narrow black bars; below it is quite pale. The wing feathers are paler on inner webs, barred with white. Below it has indistinct rufous edges to the feathers of the flanks and lower abdomen. The under-tail coverts are barred with white. Under-wing coverts are black, contrasting with the pale bases of the wing quills. The eyes are brown, the bill greyish black, paler at its base; the cere, legs and feet are yellow. The male is a good bit smaller than the female.
This bird subsists almost entirely on giant centipedes,
locusts, small lava lizards, snakes and rodents. It takes young marine iguanas
rather commonly. It also catches young land iguanas, hatchling tortoises and
probably also hatchling sea turtles. It has been seen to remain near nesting
Fork-tailed Gulls and probably takes young and perhaps eggs of these and other
birds, as well as poultry. Carrion is taken even when very putrid, except seals.
It has also been seen to pick bits of flesh and fat from staked out hides.
During the breeding season, this is a very noisy species. The usual call is a series of short screams, varying from bird to bird, and from situation to situation.
As the only hawk in the Galapagos Islands, identification is not generally a problem. When soaring at a great height, it might be mistaken for a Frigate Bird - the only other island species likely to be seen soaring.
The Galapagos Hawk often comes to carrion such as dead goats and stranded fish, and catches locusts and centipedes by walking about on the ground. It is, however, an active, aggressive and versatile predator. The feet and talons are strong like the closely related Red-backed Buzzard (Buteo polyosoma) and White-tailed Hawk (Buteo albicaudatus). It is, however, usually compared to the smaller and weaker Swainson's Hawk (Buteo swainsoni), though it less closely allied to that species. It is seen in pairs, singly, or in trios, a pair and an immature, presumably of the previous year's nesting. It favours a commanding perch on a lava outcrop or a high dead limb, but also spends some time on the ground. Where it is present in large numbers, or when numbers are attracted to carrion, several may be together, but it is generally not social in numbers above a small family group. Sometimes heard screaming in the dusk of evening, it frequently flies to roost when it is too dark to be seen, except silhouetted against the sky. A pair, or an individual, often rise to great heights, and, after soaring for some time and perhaps engaging in courtship passes, they may then descend in long criss-crossing slants.
Dark gray above, light below, fins plain or with slightly dusky tips. Maximum length 3.7 m; maximum weight: 86 kg.
World Range & Habitat
A common but habitat-limited tropical shark found close inshore as well as offshore near or on insular or continental shelves. Prefers clear water with coral and rocky bottoms. Although a coastal pelagic species, it is capable of crossing considerable distances of open ocean between islands (at least 50 km). Juveniles restricted to shallower water, in 25 m or less. Found in superficial aggregations.
Circumtropical with a preference for waters around oceanic islands. Eastern Atlantic: including St. Paul's Rocks. Western Indian Ocean: including Walter's Shoal, south of Madagascar. Western Pacific: including Middleton and Elizabeth Reefs. Tropical; 39°N-33°S Benthopelagic; marine; depth range 0-180 m.
Tends to feed near the bottom but may take bait from the surface. Feeds mainly on bottom fishes, also squid and octopi. In the Galapagos Islands it preys on sea lions and Marine iguanas as well.
Viviparous, with a yolk sac placenta. 6-16 young born at 60-80 cm. Distinct pairing with embrace.
The desert vegetation of Baltra Island comes as a shock to most visitors arriving at the archipelago's major airstrip. After the lush greens of mainland Ecuador, the browns, greys, and only occasional greens of this island seem inappropriate as an introduction to one of the world's most famous wildlife paradises. Baltra is one of the driest islands, but, even so, most of the archipelago's land area is covered by semi desert or desert vegetation. The islands lie in the Pacific Dry Belt and only the higher parts of the larger islands receive enough rain to be considered tropically lush.
The plants of the Galapagos Islands had a great influence on Charles Darwin's work. His interest in plant geography and dispersal mechanisms was closely tied to the results of his collections on the islands. Field work in the Galapagos is not easy. Lack of water and tough terrain make it difficult for botanists to undertake extensive collecting trips. The flora is still not as well known as we would like, especially that of the uninhabited islands. The number of plant species known from any island was recently shown to be strongly related to the number of collecting trips made to that island, rather than to any ecological factors. Recent collecting trips have continued to discover numerous new species and records.
By virtue of their isolation for thousands to millions of years, many Galapagos plants differ from mainland relatives and frequently from those of neigh boring islands. The islands are young geologically and many plants seem to be in the process of evolving into new species and forms. Under these circumstances, it is often difficult for botanists to decide whether a plant is a new species, subspecies, or variety. Consequently, there is often confusion about the status of Galapagos plant populations. This in itself indicates the interesting evolutionary status of the Galapagos & than of botanical inadequacies.
There are roughly 600 native taxa (species, subspecies, and varieties) of vascular plants and some 190 species introduced by humans margin of error reflects the questionable distinctness of some species the fact that some species have only been collected once. By most standards, this is a species-poor flora. By comparison, mainland Ecuador about 20,000 species. This fact highlights the problems of colonisation establishment in the islands, as well as the severity of the environment the flora is so species-poor makes it easier to identify most plants also makes it easier to understand ecological and evolutionary r ships.
Duncan Porter has calculated that less than 400 original colonists account for the 550 or so indigenous species. (The 250 or so endemics thought to have arisen from about 110 arrivals.) To botanists it is n number of species that is most important in the Galapagos but their nature. Leaving aside the plants introduced by humans, 34 per cent of the vascular plant species are endemic, while varieties and subspecies are considered, 42 per cent of the taxa are endemic.
Compared to the flora of the other well-known Pacific archipelago, the Hawaiian Islands, with 95 per cent of their flowering species endemic, this is not a high rate of endemism. This is because Galapagos are much younger, much closer to the mainland, and much d than the Hawaiian Islands. Considering these factors, the amount of endemism is strikingly high. Thus, a most notable characteristic of the Galapagos flora is what is not there rather than what is. This disharmony, or unbalanced taxonomic composition, is shown clearly by the animals as well as the plants.
One feature of the flora that most surprised Darwin was how close the relationships between species are with those found on the American main-land, even though many of the island species are unique. This shows that a high proportion of the plants, 87 per cent of the endemics and 97 per cent of the non-endemic indigenous species, are descendants of either widespread tropical species or are otherwise restricted to the South American mainland nearest the islands. The plants of lowland Galapagos are closely related to those of the semi-desert area bordering the Gulf of Guayaquil in southern Ecuador and northern Peru. These areas all have similar climates, largely as a result of the cool Peruvian coastal currents.
It was mentioned earlier that some 40 per cent of the native Galapagos plants are endemic to the archipelago. The five to ten million years that the islands have existed have provided plenty of time for evolutionary change to occur. The mechanisms of evolution on oceanic islands are essentially the same as on continents, but are often more rapid and clear cut. Not only are there two hundred or so endemic species but, also, seven genera from three families are endemic (Porter 1979). These are: Darwiniothamnus (four taxa), Lecocarpus (three taxa), Macraea (one taxon), and Scalesia (twenty taxa) from the Compositae (Asteraceae or dandelion family); Brachycereus (one taxon) and Jasminocereus (three taxa) from the Cactaceae (cactus family); Sicyocaulis (one taxon) from the Curcurbitaceae (cucumber family). That these species have become sufficiently different from mainland relatives to be distinguished at the genus level indicates the great amount of evolutionary change that has occurred in these islands.
Less well known than Darwin's finches, which have undergone
the evolution of several divergent forms from a single ancestral form, are the
nineteen genera of Galapagos vascular plants that have undergone adaptive
radiations. In addition to these nineteen genera, ten others have evolved two
indigenous taxa. The genera Alternanthera, Scalesia Opuntia, Chamaesyce, and
Mollugo are notable in having developed eight a more taxa in the archipelago.
The most common difference leading to the speciation within these groups is that
each species is on a different island. Ecological separation on a single island,
however, has played an important role in the development of some species of
Scalesia and Darwiniothamnux The genus Scalesia shows the greatest evolutionary
changes of any Galapagos plant group and can be compared with
and the giant tortoises as excellent examples of how ecological and geographic
isolation have led to the development of new species.
Though most of the islands have broadly similar environments, the species composition of plant communities are often different. These differences are often a reflection of isolation and the lack of inter-island colonisation. Some species have a broad distribution over much of the archipelago but are not present in certain parts. For example, Jasminocereus thouarsii has three subspecies which occur in almost all the central and western islands but not in the northern islands; Lecocarpus pinnatifidus is found only on Floreana, while L. lecocarpoides is found on Espanola and San Family Cristobal the genus is notfound elsewhere in the archipelago; Alternanthera galapagensis is found on the satellite islets of Floreana but not on Floreana itself; the non-endemic Palo Santo, Bursera graveolens, is a widespread and common plant in the islands and occurs in the Arid and Transition zones. Surprisingly though, on Seymour, Baltra, and Daphne islands it is replaced by B. malacophylla (which is endemic), and neither is found on Pinzon (one tree has recently been reported there!).
Plants are the foundation of most biological communities. The Galapagos are no exception. Tortoises and land iguanas depend to a great extent on the juicy pads of the Opuntia, or prickly pear cactus. Darwin's ground finches are adapted to feed on the variety of seeds produced by Galapagos plants while other finches feed largely on the insects that live off the plants. Plants are often disregarded in favour of animals with their interesting behavior patterns, but the world of plants has a special interest. The minuscule beauty and many hidden relationships are all the more satisfying once discovered by amateur and professional alike.