Galapagos Geology
It is generally accepted that the Galapagos islands are made of primarily mantle plume, like many other oceanic islands. Mantle plumes are much hotter than surrounding rock, and therefore, less dense. This causes them to rise, slowly but surely. Melting close to the surface, mantle plumes become magma chambers that create a platform a few meters below the Earth’s surface. The Galapagos islands sit on top of this platform. Sometimes, when the lithosphere moves over top of a mantle plume, it creates volcanoes. The hot rock explodes toward the surface. Since the lithosphere is constantly moving, it will eventually move the volcano away from the mantle plume (its source), and then the volcano will no longer be active.
Galapagos Biodiversity
Plants- The flora of the Galapagos islands is similar to that which would be found in the desert. Since the islands are geologically young, plants are still evolving as the islands change. We classify the flora into three groups. The first are coastal plants. They have adapted to high salinity levels. Arguably, the most important in this group are the mangroves, which provide habitats for birds, fish, turtles, and more.
Giant Tortoises- Tortoises arrived on the Galapagos islands 2-3 million years ago. How they arrived, exactly, is unclear, but more than likely their ancestors floated from the mainland and ended up on the islands. There are populations of tortoises across all the islands, adapting to the environment in which they are located. They males can make grunting sounds in order to communicate, but they mostly use body language to show dominance and such things. In the past, the tortoises were used as food for sailors, since they can survive for up to a year without food. Their oil was used to light lanterns. Because humans exploited the tortoises, several species went extinct. There are an estimated 25,000 tortoises still living in the Galapagos today.
Iguanas & Lizards- Iguanas and lizards arrived to the Galapagos in the same way tortoises did, probably on vegetation floats from the mainland or by floating from the mainland. The iguanas soon split into two groups: land iguanas and marine iguanas. From that divergence came several subspecies in each group.
Land iguanas live in the drier parts of the islands, eating low-lying plants and shrubs. This is how they get the necessary water and nutrients needed for survival. In 1975, much of their population was lost due to feral dogs eating the iguanas. To save them, some of the iguanas had to be removed from the island and then reintroduced after the dogs were eliminated. Today, their populations are once again stable.
Marine iguanas live on the rocky shorelines of the islands. They get their food by diving into the sea, eating seaweed and algae. Adults are threatened by very few predators, but the young are easy targets for larger birds, like hawks or herons. They’ve actually adapted to absorb some of their bone if there isn’t food present in order to survive. Adults can grow and shrink depending on the current environment.
Mammals- The Galapagos islands are home to several mammals as well. Some live on the islands all the time, while others are just visitors. These species include sea lions, seals, four types of rice rats, two types of bats, dolphins, and whales. Sea lions are the largest animals on the Galapagos. They hunt for fish and hang out in large groups called harems. The fur seals present on the islands are actually a type of sea lion. Fur seals are much smaller and "furrier" than the large sea lions we talked about before. Fur seals hunt at night, eating fish and squid. Their coats keep them insulated in cold waters.
Rice rats live on three of the Galapagos islands that are uninhabited by humans. Only four of the original seven endemic species are alive today. Some were eliminated by disease and competition brought by the invasive black rats.
There are two species of bats living on the Galapagos today. Unfortunately, we don't know very much about them. They eat insects and live in mangroves or shrubs during the day.
Dolphins and whales that live in the Galapagos have a layer of blubber, instead of fur, to keep them warm. Since whaling was widely acceptable in the 19th century, many whales were murdered and used for oil. Bottle-Nosed Dolphins and Common White-Bellied Dolphins can travel in schools of over 100 individuals in the Galapagos.
Land Birds- Twenty-two species of land birds on the Galapagos islands are endemic species. Over half of those endemic species are Darwin's finches; the rest include mockingbirds, hawks, flycatchers, doves, and even owls. Eight of those species are on a watch list- in danger of becoming extinct if conservationists can't work to protect their homes.
Giant Tortoises- Tortoises arrived on the Galapagos islands 2-3 million years ago. How they arrived, exactly, is unclear, but more than likely their ancestors floated from the mainland and ended up on the islands. There are populations of tortoises across all the islands, adapting to the environment in which they are located. They males can make grunting sounds in order to communicate, but they mostly use body language to show dominance and such things. In the past, the tortoises were used as food for sailors, since they can survive for up to a year without food. Their oil was used to light lanterns. Because humans exploited the tortoises, several species went extinct. There are an estimated 25,000 tortoises still living in the Galapagos today.
Iguanas & Lizards- Iguanas and lizards arrived to the Galapagos in the same way tortoises did, probably on vegetation floats from the mainland or by floating from the mainland. The iguanas soon split into two groups: land iguanas and marine iguanas. From that divergence came several subspecies in each group.
Land iguanas live in the drier parts of the islands, eating low-lying plants and shrubs. This is how they get the necessary water and nutrients needed for survival. In 1975, much of their population was lost due to feral dogs eating the iguanas. To save them, some of the iguanas had to be removed from the island and then reintroduced after the dogs were eliminated. Today, their populations are once again stable.
Marine iguanas live on the rocky shorelines of the islands. They get their food by diving into the sea, eating seaweed and algae. Adults are threatened by very few predators, but the young are easy targets for larger birds, like hawks or herons. They’ve actually adapted to absorb some of their bone if there isn’t food present in order to survive. Adults can grow and shrink depending on the current environment.
Mammals- The Galapagos islands are home to several mammals as well. Some live on the islands all the time, while others are just visitors. These species include sea lions, seals, four types of rice rats, two types of bats, dolphins, and whales. Sea lions are the largest animals on the Galapagos. They hunt for fish and hang out in large groups called harems. The fur seals present on the islands are actually a type of sea lion. Fur seals are much smaller and "furrier" than the large sea lions we talked about before. Fur seals hunt at night, eating fish and squid. Their coats keep them insulated in cold waters.
Rice rats live on three of the Galapagos islands that are uninhabited by humans. Only four of the original seven endemic species are alive today. Some were eliminated by disease and competition brought by the invasive black rats.
There are two species of bats living on the Galapagos today. Unfortunately, we don't know very much about them. They eat insects and live in mangroves or shrubs during the day.
Dolphins and whales that live in the Galapagos have a layer of blubber, instead of fur, to keep them warm. Since whaling was widely acceptable in the 19th century, many whales were murdered and used for oil. Bottle-Nosed Dolphins and Common White-Bellied Dolphins can travel in schools of over 100 individuals in the Galapagos.
Land Birds- Twenty-two species of land birds on the Galapagos islands are endemic species. Over half of those endemic species are Darwin's finches; the rest include mockingbirds, hawks, flycatchers, doves, and even owls. Eight of those species are on a watch list- in danger of becoming extinct if conservationists can't work to protect their homes.
Species Arrival to the Galapagos
Millions of years ago, when the Galapagos islands first appeared above the ocean, they were empty of all life. The creatures we talked about above had to arrive in one way or another. As it turns out, many of their ancestors were very good swimmers, and with the help of the ocean currents, those species were able to inhabit the Galapagos. Even the plants that currently live there were likely brought by the ocean as seeds. Other seeds were carried by the wind, landing on the islands by chance. Only very hardy plants were able to survive since the early conditions there were so harsh. Sea birds that are capable of flying longer distances found their way to the island, bringing other seeds stuck to their feathers. Smaller birds and insects couldn't make that journey themselves, so they were also likely carried there by the wind. Today, humans are responsible for bringing many invasive species to the Galapagos. Unfortunately, these species are usually harmful to the endemic species who are very well-adapted to their specific environments.
Eradicating Feral Pigs, Donkeys, and Rats from the Galapagos (NPR Radio)
Hundreds of years ago, the Galapagos Islands were a popular port used by pirates and sailors. When they stopped there, they would pick up tortoises to store in the ship for meat later on. To make room for the tortoises, they would drop off their goats on the islands where they would grow in population. The goats were destroying all of the tortoise habitat, so in the 90's, locals and environmentalists decided they needed to eliminate the goats to save the threatened tortoises and their homes. So it was decided that helicopters would track down the herds of goats and shoot them, until all of the herds were eliminated. But some of the goats became smart, recognizing the sound of the helicopters as dangerous. They would hide under trees or stand very still until the hunters passed by. So to get even the sneakiest goats, one goat would be captured, sterilized, and given a tracking device. These "Judas goats" would travel from family group to family group, each time leading the hunters to a new group to eliminate. Today, the Judas goats still remain on the island to live out their lives peacefully until their services are needed again.
Mangrove Forests
Mangrove forests protect the intertidal areas of tropical coastline. They are the equivalent of wetlands in a temperate climate. Mangrove forests are very biodiverse, and they provide plenty of resources for humans as well. They act as a natural barrier to the mainland from storms and battering waves. The trees have special adaptations that allow them to tolerate extreme fluctuations in water level and salinity. Even the leaves are designed to turn away from the sun in the hottest times of the day to prevent water loss. Mangroves are an important ecosystem, providing nurseries and shelter for many species of fish, along with plentiful food, like detritus. In recent years, mangrove forests have been exploited and are at risk of complete destruction if we don't work to save this important habitat.