A six-year project to reintroduce giant tortoises into the wild in Madagascar could repopulate the island with thousands of giant 350kg herbivores for the first time in 600 years.
The first group of Aldabra giant tortoises (Aldabrachelys gigantea) were introduced from the Seychelles in 2018 and have been breeding on their own ever since. Ecologist Grant Joseph explains how reintroducing the turtle to areas degraded by cattle grazing could help restore the island's former forests, grassy forests and shrublands. To do. It could also help prevent future catastrophic forest fires.
What is the Aldabra giant tortoise and why is it important?
The Aldabra giant tortoise is the second largest land tortoise species in the world after the Galapagos tortoise.black serrations). They can live for over 100 years and have an interesting history.
This turtle evolved from an ancestor of. Aldabrachelis ablupta, one of two giant turtles that lived in Madagascar for 15 million years. 4 million years ago Aldabrachelis ablupta This lineage migrated to the Seychelles, probably through combination with floating plants and aided by natural buoyancy and excellent swimming ability.
From there it migrated to Aldabra (an island 1,000 km southwest of the Seychelles) where it evolved into a third species, today's Aldabra giant. (Aldabrachelys gigantea). 600 years ago, all giant tortoises in Madagascar were wiped out by hunters. The reintroduction of the Aldabra giant tortoise marks the first time giant tortoises have been released in Madagascar since the 1500s.
Aldabra giants are particularly sociable, gathering in large groups to forage and sleep together. Madagascar is thought to have historically been home to hundreds of thousands of giant tortoises.
They played an important role in maintaining ecological balance in the now-lost mosaic of habitats (where different habitats exist next to each other). They ate the fruits of various trees and dispersed their seeds in their dung. This process is known as megafauna-dependent germination. This helped promote the growth of forests, woodlands, shrublands, and patchy grasslands. Today, most of these habitats have been burned down by humans, and the areas where giant tortoises once lived are now mostly treeless grasslands.
How difficult was it to reintroduce this turtle to Madagascar?
In 2018, Miguel Pedrono, a Madagascar-based tortoise expert and conservation biologist, was part of a group working with the Malagasy government to reintroduce Aldabra giant tortoises to the Anjajabi Reserve in northwestern Madagascar. I'm an ecologist and conservation biologist working in Madagascar, and I've modeled the effects of turtles on vegetation.
The first group of 12 giant tortoises, five males and seven females, arrived and were fitted with transponders before being released. Reintroducing the turtles was much less difficult than expected. Two babies were born the year after the turtles were resettled in Madagascar, and 152 more turtles have hatched in the five years since.
All baby turtles (newly hatched) are taken to the Anjajavi tortoise farm as soon as they are born and released back into the wild once their carapaces (the convex part of the shell made up of the turtle's ribs) have fused. It's a schedule. bones) are large enough to protect themselves from predators. Because hatchlings are so small, potential predators include feral cats, dogs, and mice, as well as birds of prey (raptors) and the fossa, Madagascar's largest endemic carnivore.
Young turtles, on the other hand, are raised in environments similar to those into which they are released, in order to develop the foraging skills they need to survive in the wild. The project aims to increase the number of wild tortoises in the Anjajabi Reserve by 500 by 2030 and approximately 2,000 by 2040 through natural breeding.
Why is it important to bring back turtles?
My recent research shows that large parts of Madagascar are burned down by people every year to create pasture for cattle. In other areas, forests and woodlands have been cleared and the ground burned for agricultural land. Our research predicts that reintroducing Aldabra tortoises will limit such fires in the future. Turtles suppress fires by eating grass and dead leaves on the forest floor, leaving less dry fuel available for ignition within the forest.
Madagascar's original shady forests and woodlands also limited the fire's ability to spread. For the past 600 years, native trees would not have been able to reproduce as quickly as they did without the help of turtles to germinate their seeds. We believe that reintroducing turtles will significantly accelerate forest and woodland growth. On the islands of Rodrigues and Ile-aux-Aigrette in Mauritius, research shows that ebony forests have returned after reintroducing giant tortoises.
Our dream is to expand the Aldabra Giant's habitat beyond the Anjajabi Reserve, allowing this turtle to contribute to as many forests and forest regenerations as possible across Madagascar. Aldabra Island in the Seychelles (155 square kilometers) is home to 100,000 Aldabra giant tortoises. The Mascarene Islands (Mauritius, Rodrigues, and Réunion) once had a population of several hundred thousand giant tortoises. However, between 1700 and 1840, all species of mascarene tortoises were driven to extinction by humans. Through this project, we hope to reintroduce similar numbers to Madagascar.
If reintroductions continue to be successful, we are optimistic that these turtles could one day be returned to their native rangelands, benefiting biodiversity and tourism. This will also increase animal biodiversity. A mosaic of wooded habitat will return, providing habitat for animals such as lemurs, native birds and chameleons.
Madagascar has recently experienced famine, and people also stand to benefit, as climate change may have exacerbated famine in some areas. Large-scale reintroductions are likely to increase tree cover, which will help reduce the effects of climate change.
Grant Joseph is a research fellow at the Fitzpatrick Institute of African Ornithology, Faculty of Biological Sciences, University of Cape Town.
This article first appeared on The Conversation.