Once near extinction, these giant tortoises now outnumber people in the Seychelles, survey finds

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Giant tortoises once pushed to the brink of extinction now outnumber humans in their home of the Seychelles, according to a new survey on one of the African nation’s most remote islands.

The survey , led by the Seychelles Islands Foundation (SIF) and the University of Exeter in the UK, estimated that about 180,000 Aldabra giant tortoises live on Aldabra Atoll, an Indian Ocean island group off the east coast of mainland Africa.

It is the highest figure ever recorded for the species, and far exceeds the human population of around 122,000 living in the tiny archipelago nation.

Aldabra Atoll is one of only two places in the world where giant tortoises are found in the wild. A much smaller population lives on Ecuador’s Galápagos Islands.

One of the world’s most undisturbed island ecosystems, Aldabra Atoll is home to several unique species that thrive in the remote haven.

The species has rebounded from a dramatic decline. Heavy exploitation during the 19th century reduced its population on the island to fewer than 1,000, pushing the species to the brink of extinction.

A recovery program helped secure strict nature reserve status for the atoll in 1981. It became a UNESCO World Heritage site a year later, giving the population room to rebound.

“More than 180,000 giant tortoises roaming freely on our atoll is proof of what long-term commitment to conservation can achieve,” Frauke Fleischer-Dogley, CEO of SIF, said in a statement.

“This is wonderful news for Seychelles, for the world, and for everyone who has worked to protect Aldabra.”

Creating the new estimate required more than just a headcount. The figures are based on an analysis of five years of tortoise counts conducted between 2018 and 2022, and is the first update since a widely cited estimate of 100,000 tortoises in the late 1990s.

“Aldabra’s giant tortoise monitoring program is one of the longest running in the region, but the atoll’s dense vegetation makes counting tortoises genuinely difficult in places,” said Nancy Bunbury, one of the study’s co-authors.

Bunbury added the team of scientists on the study have produced the most reliable baseline for the species, which can be used as a benchmark to track its population for decades to come.

Despite the encouraging population estimate, the study’s authors said continued vigilance is crucial as the climate crisis brings longer and more frequent droughts that could reduce shade and food for the tortoises. Rising sea levels as the planet warms also threaten the atoll’s low-lying habitat.

The world’s oldest known tortoise, a 194-year-old called Jonathan , is likely to have come from the Aldabra Atoll or the Granitic Seychelles.

Guinness World Records lists Jonathan as the oldest living land animal and the oldest tortoise ever. He was believed to be about 50 years old when he was moved to the British Overseas Territory of St. Helena in 1882.

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根据一项在非洲国家塞舌尔最偏远岛屿之一进行的调查，曾经濒临灭绝的巨型陆龟现在在其栖息地塞舌尔的数量已经超过了人类。

这项由塞舌尔群岛基金会 (SIF) 和英国埃克塞特大学牵头的调查估计，约有 18 万只阿尔达布拉巨龟生活在阿尔达布拉环礁上，该环礁是位于非洲大陆东海岸附近的印度洋岛群。

这是该物种有记录以来的最高数字，远远超过了居住在这个小型群岛国家约 122,000 人的人口数量。

阿尔达布拉环礁是世界上仅有的两个野生巨龟栖息地之一。数量少得多的巨龟种群生活在厄瓜多尔的加拉帕戈斯群岛上。

阿尔达布拉环礁是世界上最未受破坏的岛屿生态系统之一，是多种独特物种的家园，它们在这个偏远的天堂里繁衍生息。

该物种已从急剧衰落中恢复过来。19世纪的过度捕捞导致岛上该物种数量锐减至不足1000只，濒临灭绝。

一项恢复计划帮助该环礁在 1981 年获得了严格的自然保护区地位。一年后，它成为联合国教科文组织世界遗产，这为当地人口的恢复提供了空间。

“超过 18 万只巨龟在我们的环礁上自由漫步，这​​证明了长期致力于保护工作能够取得怎样的成果，”SIF 首席执行官 Frauke Fleischer-Dogley 在一份声明中表示。

“这对塞舌尔、对全世界、对所有致力于保护阿尔达布拉的人来说都是个好消息。”

做出新的估算不仅仅需要统计数量。这些数据基于对2018年至2022年间五年陆龟数量统计的分析，也是自上世纪90年代末广为引用的10万只陆龟的估算以来的首次更新。

“阿尔达布拉环礁的巨龟监测项目是该地区持续时间最长的项目之一，但该环礁茂密的植被使得在某些地方统计巨龟数量变得非常困难，”该研究的合著者之一南希·邦伯里说。

邦伯里补充说，该研究的科学家团队已经建立了该物种最可靠的基线，可以作为未来几十年跟踪其种群数量的基准。

尽管种群数量估计令人鼓舞，但研究作者表示，持续的警惕至关重要，因为气候危机带来的干旱持续时间更长、频率更高，可能会减少陆龟的遮荫处和食物来源。随着全球变暖，海平面上升也威胁着环礁的低洼栖息地。

世界上已知最长寿的陆龟是一只名叫乔纳森的陆龟，它已经194岁了，很可能来自阿尔达布拉环礁或花岗岩塞舌尔群岛。

吉尼斯世界纪录将乔纳森列为现存最长寿的陆地动物和有史以来最长寿的陆龟。据信，1882年它被转移到英国海外领地圣赫勒拿岛时，大约50岁。