Thursday, April 14, 2022

Alcedo Volcano Giant Tortoise

The iconic animal of the Galapagos Islands is the giant tortoise. In fact the name of the islands comes from the Spanish word, galapago, which means tortoise. The Galapagos giant tortoise is the largest living species of tortoise. I remember seeing them at Hogle zoo in my youth and that impression has stayed with me. 
This is the first tortoise we saw on our walk. It was off to the left of the trail about 15 feet. 
There are 13 subspecies (2 more existed, but are now extinct) of Galapagos giant tortoise which vary by size and shape. In the humid highlands, the tortoises are larger, have domed shells and short necks. In the dry lowlands, they are smaller, have "saddleback" shells and longer necks. There were an estimated 250,000 of them in the 16th century. Their numbers plummeted to about 15,000 in the 1970s and have since climbed to an estimated 19,000 today. 
This is the second tortoise we encountered on our hike, walking straight down our trail. It hardly seemed bothered by us. 

Isabela Island, the largest island in the Galapagos, was established by six shield volcanoes with large summit calderas that merged together into one island. Five subspecies of the giant tortoise are on Isabela, and each is associated with a different volcano: (1) the Wolf Volcano tortoise is on the north end of Isabela on the northern and western slopes of the Wolf Volcano, the highest peak in the Galapagos at 5,600 feet, and there are currently about 1,139 of those tortoises; (2) the Sierra Negra giant tortoise is found near the center of the southern end of Isabela on the eastern, western and southwestern slopes of the Sierra Negra Volcano and there are currently about 694 of those tortoises; (3) the Alcedo Volcano tortoise is found on the caldera and southern slopes of the Alcedo Volcano in central Isabela, just south of the Darwin Volcano and there are currently about 6,320 of those tortoises, the most of any subspecies and about one-third of the entire giant tortoise population; (4) the Darwin Volcano tortoise is found on the southern and western slopes of the Darwin Volcano, which is south of the Wolf and north of the Alcedo Volcanoes and there are currently about 818 of those tortoises; and (5) the Iguana Cove tortoise is found on the slopes of the Cerro Azul Volcano, found at the southwest end of Isabela and there are currently about 2,574 of those tortoises. 
This tortoise was off to the edge of the grassy field with many tortoises. 
When we visited Urbino Bay on Isabela, we took a walk on the island and encountered quite a few of the Volcan Alcedo tortoises. It is very striking to be walking on a trail and encounter one of these huge behemoths walking down the center of the trail. We probably saw about five on the trail, or just off of it. Then there was a large area of tall grass where about eight tortoises were spread about munching on grass. 
This tortoise was hidden under a tree canopy about 15 feet off the trail. 
The Alcedo Volcano tortoise is sometimes considered a distinct species. It has a domed carapace and males and females reach about 51 inches (4  1/4 feet) and 36 inches (3 feet) in length respectively. During the dry season they are found on the rim of the volcano's caldera then descend to the lower slopes during the rainy season to graze on the new vegetation. It is mind boggling to think of these large animals plodding along to cover those distances. Its range is limited to 184 square miles. The population of this tortoise has declined 84% since 1840. 
This massive tortoise was rumbling down the trail in front of us. 

This was the last tortoise we saw, drinking from a small stream/puddle and fairly well hidden from the trail. 

1 comment:

  1. After having heard about them since my school days, it was a thrill to see these ponderous creatures. It was not something I ever imagined I would be able to do. I would love to be able to go back to Darwin's time and see them in all the splendor in undeveloped territory--no trails but their own.