By Elizabeth Hunter, PhD candidate at the University of Georgia.
Almost all of my experience in the Galapagos has been on Pinta Island, where I spent a total of four and a half months studying the group of 39 sterilized hybrid tortoises released there in 2010. Pinta Island is very special to me, so I was delighted when the Galapagos Conservancy invited me to participate in this unprecedented expedition to Wolf Volcano to recover the Pinta tortoise species and continue the restoration of the island.
Upon arriving on Wolf, my initial perception was that it was similar to Pinta. We landed on a small beach surrounded by a thicket of mangroves, and then walked across a lava field and through spiny shrubs and palo santo trees to get to our campsite nearly a mile from the coast. All of these features were reminiscent of Pinta: the aromatic scent of palo santo in the air, the crunch of lava underfoot, the sounds of Darwin’s finches and mockingbirds. As we began to search for tortoises the next day, however, it became apparent that something was missing: the giant arboreal Opuntia cactus.
This cactus is numerous on Pinta and drives much of the behavior of saddleback tortoises. On arid islands, the cactus is often the only reliable source of water for tortoises and other animals during periods of drought. In the low arid zone of Wolf, however, I found very few cacti, with only a few small individuals scattered around a landscape of densely packed shrubs. I felt the absence of the cactus keenly as we covered new ground each day, and I was constantly struck with the idea that the saddleback tortoises that we found do not belong in this cactus-less landscape.
I was lucky, though, to be assigned to a search zone encompassing a feature that does play a substantial role in the behavior of the giant tortoises on Wolf Volcano. A small canyon, perhaps 30-50 feet deep at parts, cut through the center of our search zone, running more than a half a mile down slope. Here the lava rock is transformed from jagged heaps to a consolidated, smooth flow. We stumbled upon the canyon at the end of our first day of searching and found several tortoises there, all sitting motionless under deep shade, seemingly waiting for something.
The true importance of the canyon did not reveal itself to us until the third day. It rained heavily through the second night and continued into the following day. Pools of water collected in small crevices and bowls in the lava, and as we approached the canyon we were struck with the sight of dozens of tortoises congregating there. They jostled for position at the small, muddy pools where they thrust their faces into the water and drank deeply until the pools ran dry. It was an incredible sight to behold and somewhat overwhelming, as we rushed to measure, mark, and collect blood from as many tortoises as we could before they had drunk their fill and returned to the brush outside the canyon.
It was a long day in the rain, and as we walked back down the canyon to camp, we encountered another saddleback tortoise new to the scene. I scanned the tortoise’s leg for a PIT tag (microchip), and a number popped up on the screen. My heart was racing as we searched the list for a match, and there it was: a Pinta tortoise! (That is, one of the 17 known hybrids with Pinta genes.) There were high-fives all around, and I felt an unimaginable thrill at seeing this descendant of wild Pinta tortoises — a once-in-a-lifetime feeling.
I was struck with gratitude for all of the time, effort, and resources from the Galapagos Conservancy and the Galapagos National Park Directorate that it took to arrive at such a triumphant moment. I am also grateful for all the hard work of my excellent teammates: park rangers Milton Calva and Alexis Tualombo, and evolutionary biologist Nikos Poulakakis. I have no doubt that without the tireless tortoise-tracking skills of Milton, our group leader, we would not have brought back as many tortoises to the Santa Cruz Tortoise Center as we did.
There was only one other confirmed tortoise with Pinta ancestry found during the trip; luckily it was a male, and ours a female. So we now have the foundation for a species reconstruction program. Hopefully, some of the other saddleback tortoises collected during the Wolf Expedition will also have Pinta genotypes, and a robust population with genetic variability can be created for release on Pinta Island.
In our small canyon, we found some of the highest densities of saddleback tortoises on the volcano. I couldn’t help wondering what Pinta would be like with so many tortoises roaming its slopes. Though it has no similar canyon where water collects, drawing hundreds of tortoises after a rain, I could imagine an extensive network of tortoise trails through the woody shrubs connecting the water-giving Opuntia cacti. I look forward to the day when the descendants of these now captive saddleback tortoises will return to their home island — Pinta — and restore their ancient connections with the ecosystem.
Elizabeth Hunter is a PhD candidate at the University of Georgia, and has contributed to tortoise research and ecosystem restoration on Pinta and Española Islands. She completed her MSc on the 2010 tortoise release on Pinta at SUNY with Dr. James Gibbs.
All photos © Elizabeth Hunter unless otherwise credited.
This is Part 3 of a six-part blog series from various participants of the expedition documenting the events of the 2015 expedition to Wolf Volcano. Read Part 1: Overview by Wacho Tapia or Part 4: Return to Galapagos by Milton Yacelga.