LLike other cold-blooded reptiles, large tortoises use the environment around them to control their body temperature. On Isabela Island—the largest in Ecuador’s Galápagos archipelago—Alcedo giant tortoises (Chelonoidis vandenburghi) dig basins to capture and store rainwater long after storms cease. Sitting in the wet pools moistens the tortoises’ skin and helps get rid of ticks. And because the mud retains heat from the day’s sunshine, it helps the tortoises stay warm when nights get chilly in the caldera of the Alcedo Volcano, which rises more than 3,000 feet above the tropical sea.
Creating communal baths isn’t the only way that large tortoises shape the ecosystems around them. Because of their size (males can grow to 500 pounds) and longevity (Galápagos tortoises commonly live more than 100 years), the creatures have a big impact on the islands where they are native. They make permanent paths and furrows with their travels, spread the seeds of flowering plants with their poop, and maintain open meadows like reptilian lawnmowers.
Everything on Alcedo seems to happen on tortoise time.
For many years, however, goats and donkeys introduced by whalers and other sailors made life difficult for Alcedo giant tortoises, as well as the other two tortoise species that live on Isabela Island. The non-native plant-eaters ate through forests of guayabillo trees, high-altitude tree ferns, and other vegetation. By the 1990s, over 100,000 goats and donkeys had stripped northern Isabela Island to a near-desert, leaving little food for slow-moving tortoises.
Additionally, tortoise populations were still recovering from another major setback. Sailors who passed through the Galápagos in the 18th and 19th centuries captured up to 200,000 live tortoises and packed them into their ships. Because the tortoises could survive months at sea without eating or drinking, sailors could kill one whenever they got hungry, ensuring a fresh supply of meat on long voyages. Two of the archipelago’s 12 tortoise species went extinct, and six more remain critically endangered.
In 1959, the Ecuadorian government established Galápagos National Park to help protect the remaining tortoises and other unique species, and in 2006, an ambitious program succeeded in eradicating goats and donkeys from northern Isabela Island. Today, although Alcedo giant tortoises are still listed as vulnerable by the International Union for Conservation of Nature, their population is growing. Scientists with the nonprofit Galápagos Conservancy recorded more than 15,000 Alcedo tortoises plodding, grazing, and wallowing on the volcano’s slopes, including a flush of juveniles in areas never before surveyed. The figure is a dramatic jump from the IUCN’s 2015 estimate of 6,320 mature individuals.
Two of the archipelago’s 12 tortoise species went extinct.
Photographer Tui De Roy has been fortunate enough to witness the tortoises’ comeback. In the five decades she’s spent photographing in the Galápagos, De Roy has hiked the Alcedo Volcano hundreds of times—in drought and deluge, on clear nights and foggy ones, at times when the air was filled with the grunts of mating tortoises and during dry spells when the animals were nearly dormant. “Everything on Alcedo seems to happen on tortoise time,” De Roy writes in her book A Lifetime in Galápagos. When she is there, she also moves more slowly, taking her time to capture the perfect photograph.
One year when the seasonal rains had stopped but the pools dug by tortoises still held water, De Roy was camping alone in the Alcedo caldera, her tent concealed behind bushes. As the sun went down beyond the volcano's edge, she took this picture of Alcedo tortoises gathering in the wet sunshine of a mud pool, as they have for many generations.
This story originally appeared in bioGraphic, an independent magazine about nature and regeneration powered by the California Academy of Sciences.
Tui De Roy is a well-known wildlife photographer, naturalist, writer, and conservationist. Originally from Europe, she was raised in the Galápagos Islands, where her innovative family settled over 60 years ago. De Roy travels the globe, documenting wildlife and wilderness in the most untouched, uninhabited areas of our planet, and has released numerous photo books, including Albatross: Their World, Their Ways, which encompasses all 22 albatross species.
