A new study conducted by the University of Exeter and the Seychelles Islands Foundation (SIF) has found roughly 180,000 giant tortoises tucked away on the green shores of Aldabra, a remote coral atoll in the Seychelles.
The population is one of just two in the entire world, with the other being on the Galapagos Islands. This recent figure is the highest ever recorded — a far cry from the mere 1,000 which were found in the 19th century. The Aldabra population has been exploited in the past but has since then been conserved by scientists, allowing the population to grow. Support for this process arose after it became a nature reserve in 1981 and a UNESCO World Heritage Site (WHS) in 1982.
In the late 1990s, a figure of just 100,000 was recorded. However, Dr Nancy Bunbury, one of the study’s co-authors said that “The atoll’s dense vegetation makes counting tortoises genuinely difficult in places.” This means the population has definitely risen, but not necessarily by 80,000 tortoises, since the earlier figure may have been hindered by the difficulty of observing these gentle giants.
The atoll is one of Seychelles’ most distant islands. The scarcity of fresh water, dense shrubland and geographical isolation has made it unappealing for civilization and so it has never been properly inhabited. Due to this, the biodiversity of the atoll has been outstandingly preserved, contributing partly to its status as a UNESCO WHS, and providing the perfect environment for tortoises.
An integral part of the SIF’s research is how closely intertwined the tortoises are with their environment. Aldabra is the only place on the planet where giant herbivorous reptiles are the most dominant animal. Remarkably, many of Aldabra’s ecosystems have actually been created, structured and maintained by the tortoises’ presence. An example is the habitat ‘tortoise turf,’ which is formed of open grassland and mixed scrub. In the recent survey, scientists found the highest density of tortoises existed in this environment.
Despite the survey’s success, Dr Dave Hudson, a research associate at the University of Exeter, reminds us that “it’s important to remember that the numbers provide a baseline – not an endpoint,” and that the tortoise population is still at risk. Many of these risks include harmful invasive species and climate-related pressures. Although the population is currently thriving, the survey authors warn that vigilance is essential in order to maintain these magnificent creatures.
Photo by Dan Maisey on Unsplash
