Not only do cold-blooded reptiles and birds inhabit the Galapagos Islands. Mammals – from mice to men, from sea lions to whales – also live on these isles.
Sixty species of mammals have been recorded in the Galapagos Islands. Of these, 16 are endemic or native, three are native and 13 are migratory. Introduced species number 16. Eight endemic species are extinct; five disappeared from the Galapagos landscape before the arrival of humans, and are known only by their fossils. As with reptiles and birds, mammals may be found at sea and on land.
More details about each of these mammals may be found in Galapagos natural history guides.
Galapagos Sea Mammals
Most Galapagos mammals are found in the waters surrounding the islands, migrants who seasonally swim through, leaping near the bow of your cruise ship. These include several types of whales and dolphins. Others, like sea lions, are found on land and at sea. You may find yourself swimming with a playful pup!
Whales are Cetaceans. They differ from land mammals in that they do not have fur or hair. Instead, to protect them from frigid ocean temperatures, they have a thick layer of blubber. This feature made them important in 19th century industry. During that era, hundreds of whaling ships plied the Galapagos seas in search of these valuable marine mammals.
Your first sign of a whale may be their blow, when they send a stream of water into the air. They usually swim in small groups of two to ten. These marine mammals fall into two groups: baleen whales, which have a fringed bone to filter foods like plankton, and toothed whales.
As far as is known, whales are strictly migrants in the Galapagos Islands. None are known to breed or give birth in the marine reserve.
The most prevalent whales in the Galapagos are the baleen. Frequently seen inshore and offshore are Bryde’s whale (Balaenoptera edeni) and the humpback whale (Megaptera novaeangliae). Less often spotted are fin whale (Balaenoptera physalus), Sei whale (Balaenoptera borealis), blue whale (Balaenoptera musculus) and minke (Balaenoptera acutorostrata).
Two species of sperm whales, another type of baleen whale, are found in the Galapagos archipelago. The more common one is the dwarf sperm whale (pygmy sperm whale, Kogia simus). The sperm whale (Balaenoptera borealis) is rarer.
Toothed whales that migrate through the Galapagos Islands are Blainville’s beaked whale (Mesoplodon densirostris) and Cuvier’s beaked whale (Ziphius cavirostris), both occasionally seen in the marine reserve.
- Spanish name – ballena
- Best islands to see them – throughout the archipelago, best especially in the west
- Best time of year to see them – June-November
Dolphins also are cetaceans, but are smaller and sleeker. You’ll see them leaping alongside your ship during your Galapagos cruise. They are fast and acrobatic swimmers. As far as is known, no dolphin species breeds in the Galapagos.
Common dolphin (Delphinus delphis) is grey above and light grey to white along its underside. The dorsal fin is black. Adults are 1.7-2.4 meters (5.5-7.8 feet) in length. They may be seen singly, or in groups of up to 2,000 individuals. These are the most commonly seen dolphin in the Galapagos Islands.
Bottlenose dolphin (Tursiops truncates) is nearly twice the size of the common dolphin (1.9-3.9 meters / 6.2-13 feet). It is a uniform great, sometimes a little lighter on the underside. Its forehead bulges. These may be seen in groups of up to 25 dolphins.
Although also called killer whale, the orca (Orcinus orca) is the largest member of the dolphin family, reaching 5-9 meters (16-30 feet) in length. It is black with distinctive white marks on the belly, and a tall dorsal fin. It swims in groups of two to thirty. In the Galapagos, they hunt other sea mammals, like the sea lions, sperm whales and Bryde’s whales.
Other members of the dolphin family that may be seen in the Galapagos Marine Reserve are short-finned pilot whales (Globicephala macrorhyncus), false killer whale (Pseudorca crassidens) and the melon-headed dolphin (melon-headed whale, Peponocephala electra).
- Spanish name – delfín
- Best islands to see them – throughout the archipelago, but especially in the Bolívar Channel between Fernandina and Isabela, and along the west coast of Isabela Island
- Best time of year to see them – June-November
Galapagos Sea Lion
With a population of about 50,000, the Galapagos Sea Lion is one of the most common mammals in the archipelago. They are the largest Galapagos animal, with males weighing up to 250 kilograms (550 pounds). These are an endemic subspecies of the California sea lion.
Male sea lions (bulls) are distinguished by their bulging forehead. During the mating season, adult bulls may be seen fighting for control of large harems. At this time, males may be quite aggressive, so be sure to keep your distance. Bachelor pups are quite playful and frequently join human swimmers and surfers. Sea lions prefer sunny beaches and shallow water.
- Scientific name – Zalophus californianus wollebacki
- Spanish name – lobo marino
- Best islands to see them – common throughout the archipelago; especially large colonies on San Cristobal
- Breeding / birthing season – July-November
Galapagos Fur Seal
Galapagos fur seals are not true fur seals, but rather a furry cousin to the sea lion. They are easy to confuse. These fur seals, though, are smaller than sea lions, and they have a broader and shorter head with protruding eyes and ears, and longer front flippers. Because of their fur, they were hunted almost to extinction in the 19th century. Their population has recovered quite well.
Like sea lions, males keep a harem of numerous females. They prefer cool, shady rocky shores and deep waters. They hunt at night, and are preyed on by sharks and orcas.
- Scientific name – Arctocephalus galapagoensis
- Spanish name – lobo de dos pelos de Galápagos
- Best islands to see them – Santiago (James Bay), Genovesa (Darwin Bay)
- Breeding / nesting season – August-December
Galapagos Land Mammals
Only a few species of land mammals are endemic to the Galapagos. Because most Galapagos ancestors arrived on floating rafts of vegetation, the survival rate of mammals was slim and only the smallest, mice and bats, lived to establish roots in the islands. All of the larger land mammals, such as goats, arrived courtesy of one other mammal: Homo sapiens. These introduced mammals have caused immense damage to the Galapagos Islands’ fragile ecosystem and its endemic fauna.
Galapagos Rice Rats
Originally, seven species of rice rats inhabited the Galapagos. The surviving four species are found on islands with no human population. These small rodents are island-specific. Each species is found on particular islands: the petite Santa Fe rice rat (Oryzomys bauri) and small Fernandina rice rat (Nesoryzomys fernandinae), both approximately 20 centimeters (8 inches), and the Santiago rice rat (Nesoryzomys swarthi) and large Fernandina rice rat (Nesoryzomys narboroughii), both measuring in at 35 centimeters (14 inches). All species are light to dark greyish-brown.
Because they are active at night, you probably won’t see the endemic rice rats during your Galapagos vacation. Not much is known about the breeding habits of these rats, though it appears it occurs during the warm, wet the season (December-May). The Santiago rice rat is the only endemic species that is known to be able to compete with the introduced black rat (Rattus rattus).
Two species of endemic bats wing across the night skies of the Galapagos Islands. The Galapagos red bat (Lasiurus borealis) is found in both the lowlands and the highlands of San Cristobal and Santa Cruz. It is bright burnt orange, with yellow forequarters and underside. It forages near the ground.
The Galapagos hoary bat (Lasiurus cinereus) is larger and light-brown colored. It has a blunt head with no nose. Its preferred habitat is mangrove forests on San Cristobal, Santa Cruz, Floreana, Santiago and Isabela islands. This bat is a higher flyer, foraging in trees and the air.
Like other bats, Galapagos bats are active at night. You may see them fluttering around street lights, or roosting in lava tunnels during the day. Nothing is known about their breeding habits.
Mammals Introduced to the Galapagos Islands
Over the centuries, several very destructive mammals have been introduced into the Galapagos Islands – and all at the hands of another mammal, Homo sapiens (humans). The worst of these is perhaps the black rat (Rattus rattus) which undoubtedly arrived with the first pirate ships to sail into the Galapagos archipelago. The black rat not only competes with endemic rice rats for food, but they also destroy giant tortoise and bird nests, and eat the eggs. On Santiago, Pinzon and several other islands, the black rat has been successfully eliminated.
Whalers brought a whole menagerie of mammals to the Galapagos Islands. They left a few animals of each species on islands, to guarantee a steady supply of meat for passing ships. One of the most important of these was the goat (Capra hircus). This mammal has caused great havoc in the Galapagos. They not only compete with the endemic animals for food, but also indelibly alter the terrain of the islands. In a project scientists worldwide never thought would be possible, Isabela Island was completely erased of this species in a ten-year project. Other smaller islands have also seen successful eradication of goats.
Other livestock introduced into the islands by whalers were pig, cattle, horse and donkey. Wild populations of these animals have been eradicated from Santiago and several other smaller islands, allowing the ecosystems to recover. Once this mission has been accomplished, the islands have seen endemic fauna and flora rebound. On Pinzon and other isles, giant tortoises have been successfully reintroduced.
In modern-day Galapagos, several of these mammal species are kept as livestock, restricted to the agricultural zones of the four human-inhabited islands.
The most important of the introduced mammal species is the human being (Homo sapiens). Besides the sea lion, this is the most easily encountered mammal in the Galapagos. The first long-term human settlement in the Galapagos occurred on Floreana Island. Over the centuries, humans have lived primarily on San Cristobal, Santa Cruz, Baltra, Floreana and Isabela, where they are permitted to live under national park regulations; Santiago also was once populated. Three percent of Galapagos National Park is reserved for Homo sapiens’ urban and agricultural needs.
The Galapagos has a permanent human population of approximately 25,000 (2010 census). As well, almost 225,000 tourists arrive each year, mostly from December to January, and June to August. Galapagos natives have adapted their lives and culture to the natural limitations of the islands. As the islands cannot produce enough food for the human population, much must be shipped in from continental Ecuador. Galapagos residents celebrate a number of holidays, both Ecuadorian and religious, like Day of the Dead and Christmas, as well as village patron saint holidays. They also have annual sporting marathons on each of the major islands.
Photo credit: Amos Wright