The National Geographic Islander sailed overnight around the eastern side of Santa Cruz to the small satellite island of South Plaza where we ventured after breakfast. Although small, South Plaza has a particularly high density of the Galápagos land iguana Conolophus subcristatus. The animals comprising this population are the smallest known in the species, and we saw many of them, basking in the morning sun to raise their body temperature above 30 degrees Celsius when they will begin foraging. We saw a few territorial battles between males, with the characteristic head-bobbing followed by one animal chasing the other at surprising speed. Fights between large and closely sized males may last over an hour and involve head-butting and biting; older males bear numerous neck scars as testament to their past travails.
The success of the restoration program of land iguanas in South Plaza has had an unforeseen consequence. Because of the eradication of Galápagos hawks from most parts of Santa Cruz, these predators are now scarce visitors to South Plaza and the iguanas consequently lack natural predators. Their dramatic population growth has now reached a point where it is preventing the establishment of new seedlings of the giant prickly pear cactus Opuntia echio, the iguana’s primary food plant. This illustrates the need for ongoing research and management efforts to understand and preserve the unique but fragile ecosystems of the Galápagos.
Following lunch, we moved south to Santa Fe Island for kayaking and snorkeling. The cliffs of this island are pristine with dramatic basalt strata and lava dykes adorned with the scattered vivid green foliage of Scalesia helleri, one of the many woody species of an endemic genus related to daisies and asters. Striated herons and yellow-crowned night herons patrolled the low rocks trying to snatch young Sally Lightfoot crabs, and the kayakers were able to view a low-perched Galápagos hawk at close range.
To round out the day, guests took Zodiacs into a shallow emerald-green bay, where they were treated to wonderful views of green sea turtles and a large shoal of spotted eagle rays, and then hiked a loop trail up the cliffs and into the interior of the island. Santa Fe is home to a second species of land iguana, Conolophus pallidus, found only on this island. In addition to observing this species, one group spotted a Galápagos snake, Alsophis dorsalis, one of three endemic snake species in the archipelago, and also witnessed the rather gruesome spectacle of a Galápagos mockingbird dispatching a large (about 15 cm) Galápagos centipede Scolopendra galapagoensis—yet one more endemic species to be found in this remarkable island archipelago.
