Giant tortoises reintroduced to a Galapagos island by Spanish scientists have started a cactus boom thanks to their seed-spreading faeces, a new study has revealed.
The 742 Hood Island giant tortoises were moved to Santa Fe island over a six-year period, says the ecological study.
Now – after a week-long study of the impact they have had on the local wildlife – experts have revealed that plant life is thriving because of their potent poo.
Prickly pear and other cacti are booming, says the study, with more juvenile plants growing than ever before,
The Ecuadorian Ministry of Environment, Water and Ecological Transition said in a statement on 12th July: “For seven days, a team of 12 people including a Spanish team with park rangers from the Galapagos National Park Directorate and technical and scientific staff from the Galapagos Conservancy carried out annual monitoring on Santa Fe Island, with the aim of verifying the status of the tortoises Chelonoidis hoodensis that were introduced from 2015 to 2021 to fulfil the role of main herbivore and modellers of the ecosystem…
“The team was divided into four working groups to fulfil different activities.
“In order to assess the status of the 742 introduced tortoises on the island and document how they have dispersed, three groups conducted a census of the giant tortoise population using the mark-recapture method.
“The main finding was to show that most of the tortoises move around an area of 5.5 square kilometres of the island and that gradually they move on to new places in Santa Fe.
“Another group monitored the status of the prickly pear population on the island and analysed interactions with giant tortoises and land iguanas.”
Galapagos National Park director Danny Rueda said: “The return of the tortoises has been favourable for the growth of opuntias, which is why a greater number of juvenile cacti were found during the monitoring in Santa Fe.”
The team collected information from 20 vegetation plots that were established in 2014; half with fencing to isolate tortoises and iguanas and the other half without it.
Jorge Carrion, conservation director of Galapagos Conservancy, said: “The goal is to identify in the long term, how turtles and land iguanas influence the dynamics of plant communities on the island.”
The statement continued: “Finally, a smaller team took high-resolution panoramic photographs to make future comparisons and record changes in the island’s ecosystems. The staff that worked on this activity underwent training to be able to replicate this methodology in other Galapagos areas.
“All the information collected is being processed by the technical and scientific team that participated in the expedition in order to adequately document the changes that have occurred on the island.”
Several studies including work by James P. Gibbs from the State University of New York College of Environmental Science and Forestry have found that the likes of Galapagos giant tortoises and land iguanas that depend on opuntia cacti as a food source also contribute to opuntia regeneration through seed dispersal.
The original species of giant tortoise from Santa Fe became extinct more than 150 years ago.
The new species are said to be a close genetic match to the originals.