Day 5: Marine iguanas of Tintoreras
Today, our species of interest was the marine iguana, Amblyrhnchus cristatis.
This large lizard is black like the lava rocks where it sunbathes, and has long digits and claws to allow it to cling to rocks while munching on algae. We were particularly interested in the age class and spatial distribution of the iguana, which we studied on the island of Tintoreras.
In the morning, we met at IOI at a leisurely 9 am, while church bells tolled throughout Puerto Villamil, calling everyone to morning Mass. First we had a short lecture on the biology and life history of marine iguanas. Then we discussed our sampling method and practiced estimating the size class — juveniles, females or males — by looking at iguanas through clear plastic grid, which we “calibrated” by estimating the size of known objects in the front yard of IOI. Larissa, our resident photographer, found this quite a spectacle.
With our sampling techniques solidly under our belts, we took a late morning siesta in the hammocks before heading to lunch at the only two restaurants in town open on Sundays.
After lunch, we reconvened at IOI and headed down to the town docks to catch our boats out to the island of Tintoreras. The island is about 5 minutes south of Isabela by water taxi, small open boats usually painted bright teal and powered by outboard motors. Instead of going directly to the docking site on the island, our captains took us on a little tour around Tintoreras, where we saw Galapagos penguins (one of the smallest species of penguins in the world!), a sting ray, as well as pelicans and a Galapagos shark feeding on scraps tossed out by fishermen, and of course, more frigate birds.
Once on Tintoreras, we got started with our sampling; we were hot and the promise of a swim powered us through the mid-day heat. Using the trail that runs around the perimeter of the island as our transect, we sampled plots 20 meters in diameter along that transect.
It was a life-sized game of Where’s Waldo: the iguanas camouflage well with their lava rock habitat and we had to spot them without leaving the path. Working in pairs, we assigned iguanas to size classes according to the techniques we’d practiced in the morning. In some plots there were many iguanas, all basking in the sun together, while there were none in other plots.
My partner and I had an anticlimactic day of sampling, finding only one iguana over all the plots we sampled, however we did see two lava lizards fighting, which was just as exciting in real life as in the National Geographic documentary. Our wildlife sighting continued, as on the boat back to Isabela, we saw a sea turtle!
Then we took our much-anticipated swim from the beach near the dock, before returning to IOI to discuss our data and methods of analysis. Over the next few days we will continue to analyze this data, as we hope to find trends in the spatial distribution of iguanas and the abiotic habitats of the island. We’ll let you know what we find!