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After Almost Going Extinct, Giant Tortoises Now Outnumber People in The Seychelles : ScienceAlert (opens in a new tab)

sciencealert.com · 2026-10-09

Short answerEvidenceSource

Short answer

Mostly not supported

Mostly not supported.

One claim goes further than the study. 3 other points were not covered by the paper.

  • 1 supported
  • 1 overstated
  • 3 not covered

Checked against the study summary. The full text wasn't available, so some details couldn't be settled either way.

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1
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NewsLink checks it

Mostly not supported

One claim overstates the study. One of five checks out. Three claims the study doesn't address.

  • 1 supported
  • 1 overstated
  • 3 not covered
Open claim evidence
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Evidence layer

Claim by claim

Each claim gets a verdict. Expand it to see the evidence directly below.

5 claims in this story

Showing all 5 claimsChoose a verdict to focus the list.

Claim 1 of 5OverstatedThe story frames the finding as evidence that long-term conservation can work and provide a benchmark for tracking future change.View evidenceHide evidence

Why this verdict

The paper profile supports that the authors interpret high/stable abundance as attributable to long-term conservation and recommend using the workflow for future monitoring. However, the story's quoted framing as 'proof' that long-term conservation works outruns the paper evidence: the attribution is interpretive and model-based, not a separate causal test of conservation actions. The benchmark/future-monitoring aspect is supported, but the causal-certainty framing is overstated.

1

Study evidence

Atoll-wide population estimated at approximately 180,000 Aldabra giant tortoises.≈180,000 individuals

“Between 2018 and 2021 the population was apparently relatively stable and numbered approximately 180,000 individuals”
2

Study evidence

Model-based inference indicated the Aldabra giant tortoise population was approximately 180,000 individuals and was relatively stable between 2018 and 2021.≈180,000 individuals

“We attribute this stability and high abundance to the extended history of conservation efforts on Aldabra”
Claim 2 of 5Not coveredThe article says there are more than 180,000 giant tortoises roaming freely on the atoll, and that this is the first time they have outnumbered Seychelles' human population in centuries.View evidenceHide evidence

As statedmore than 180,000

Why this verdict

The paper profile supports an approximate atoll-wide population estimate of about 180,000 Aldabra giant tortoises. However, the abstract-level evidence does not verify the stronger phrasing 'more than 180,000,' 'roaming freely,' or the comparison that tortoises outnumber Seychelles' human population for the first time in centuries. Those details may require full-text or external demographic evidence.

1

Study evidence

Atoll-wide population estimated at approximately 180,000 Aldabra giant tortoises.≈180,000 individuals

“Between 2018 and 2021 the population was apparently relatively stable and numbered approximately 180,000 individuals”
Claim 3 of 5Not coveredThe story says the numbers come from the first rigorous population survey since the 1990s and were modeled to produce the most reliable baseline yet for the species.View evidenceHide evidence

As statedfirst time ... rigorously surveyed since the 1990s

Why this verdict

The profile supports that the study used a Bayesian hierarchical distance-sampling model on 2018–2021 data and that no rigorous atoll-wide population estimate had previously been attempted. It also supports a reproducible workflow intended to improve abundance inference. But the abstract-level profile does not verify the specific 'since the 1990s' timing or the exact claim that this is the 'most reliable baseline yet.'

1

Study evidence

A Bayesian hierarchical distance-sampling (HDS) state-space model with data augmentation and habitat- and season-dependent detectability was developed to estimate abundance and detectability from irregular transect surveys.

“Here we develop a Bayesian Hierarchical Distance Sampling (HDS) model to infer habitat- and season-dependent detectability and abundance”
2

Study evidence

Atoll-wide population estimated at approximately 180,000 Aldabra giant tortoises.≈180,000 individuals

“Between 2018 and 2021 the population was apparently relatively stable and numbered approximately 180,000 individuals”
Claim 4 of 5Not coveredThe article says the tortoise recovery is not complete because sea level rise, drought, feral cats, and black rats still threaten eggs, hatchlings, and habitat.View evidenceHide evidence

Why this verdict

The profile supports a general management implication that invasive alien species eradication should be maintained and expanded. But the abstract-level evidence supplied does not mention sea-level rise, drought, feral cats, black rats, eggs, hatchlings, or habitat threats. The specific threat list is therefore not verifiable from the supplied abstract-depth paper profile.

1

Study evidence

Model-based inference indicated the Aldabra giant tortoise population was approximately 180,000 individuals and was relatively stable between 2018 and 2021.≈180,000 individuals

“We attribute this stability and high abundance to the extended history of conservation efforts on Aldabra”
Claim 5 of 5SupportedRecent surveys of Aldabra Atoll found the Aldabra giant tortoise population has reached record-high numbers after decades of protection.View evidenceHide evidence

As statedrecord-high numbers

Why this verdict

The abstract-level profile supports an atoll-wide estimate of approximately 180,000 tortoises and describes this as the highest estimate so far for the population. It also reports that the authors attribute high abundance and apparent stability to an extended history of conservation efforts. The claim is acceptable as a headline-level shorthand if read as temporal/associational, not as independent causal proof.

1

Study evidence

Atoll-wide population estimated at approximately 180,000 Aldabra giant tortoises.≈180,000 individuals

“Between 2018 and 2021 the population was apparently relatively stable and numbered approximately 180,000 individuals”
2

Study evidence

Model-based inference indicated the Aldabra giant tortoise population was approximately 180,000 individuals and was relatively stable between 2018 and 2021.≈180,000 individuals

“We attribute this stability and high abundance to the extended history of conservation efforts on Aldabra”
Then look for missing context

Context layer

What the story left out

Important study details the story did not include.

  • The paper reports that the population was apparently relatively stable between 2018 and 2021.

    The story emphasizes recovery to record-high numbers after decades of protection, but it does not clearly convey the paper's narrower temporal finding of apparent stability during the 2018–2021 study window.

    From Bayesian Hierarchical Distance Sampling (HDS), state-space; interpretive synthesis

  • A material limitation is that the abundance and stability results depend on model assumptions about detectability, habitat/season effects, and handling of irregular survey data.

    The story notes that dense vegetation can make counting difficult, but it does not convey that the reported estimate is conditional on the model structure and detectability assumptions.

    From Bayesian hierarchical distance-sampling (HDS) state-space model with data augmentation; Bayesian Hierarchical Distance S

  • A material limitation is that the conservation attribution is interpretive rather than the result of a separate causal experiment isolating the effects of conservation actions.

    This caveat is not reflected in the story presentation. The story's 'proof of what long-term commitment to conservation can achieve' framing is stronger than the paper profile's interpretive attribution.

    From interpretive synthesis

6 things the story did carry across
  • The paper develops a Bayesian hierarchical distance-sampling state-space model with data augmentation and habitat-/season-dependent detectability for irregular or legacy transect data.
  • The paper applies the model to Aldabra Atoll survey data from 2018–2021 to estimate atoll-wide Aldabra giant tortoise abundance.
  • The paper estimates an atoll-wide population of approximately 180,000 Aldabra giant tortoises and describes this as the highest estimate so far for the population.
  • The paper states that no rigorous atoll-wide estimation of giant tortoise population size had previously been attempted.
  • The paper attributes high abundance and apparent stability to the extended history of conservation efforts on Aldabra, including invasive alien species eradication, and recommends maintaining and expanding those efforts.
  • The paper recommends using the Bayesian distance-sampling workflow on legacy datasets and future abundance surveys for similar species.
Then read the study layer

Study layer

Study at a glance

Scan the study first. Expand only the parts you want to inspect.

Pieces of work

3

Evidence read

study summary

Lead result

secondary data

1Lead resultsecondary dataApply the HDS model to Aldabra Atoll survey data (2018–2021) to estimate atoll-wide Aldabra giant tortoise abundance and assess apparent stability over time.Bayesian Hierarchical Distance Sampling (HDS), state-spaceExpand

In plain English

Applied a Bayesian Hierarchical Distance Sampling (HDS) model to irregular transect distance data collected across Aldabra Atoll (2018–2021) to infer habitat- and season-dependent detectability and estimate atoll-wide abundance; authors report an atoll-wide population of approximately 180,000 Aldabra giant tortoises and describe the population as apparently relatively stable over 2018–2021.

Key findings

  • Atoll-wide population estimated at approximately 180,000 Aldabra giant tortoises.≈180,000 individuals
  • The Aldabra giant tortoise population was apparently relatively stable between 2018 and 2021.relatively stable (2018–2021)
“Between 2018 and 2021 the population was apparently relatively stable and numbered approximately 180,000 individuals”
What this piece can’t prove
  • Results are conditional on model assumptions about detectability, habitat/season effects, and the data-augmentation approach used to handle irregular survey data.

2 further details could not be confirmed from the summary.

2in silicoDevelop a Bayesian hierarchical distance-sampling (HDS) state-space model and reproducible workflow to estimate habitat- and season-dependent detectability and abundance from irregular/legacy transect data.Bayesian hierarchical distance-sampling (HDS) state-space model with data augmentationExpand

In plain English

The paper develops a Bayesian hierarchical distance-sampling (HDS) state-space model and accompanying reproducible workflow that uses data augmentation and explicit habitat- and season-dependent detectability to infer abundance and detectability from irregular or legacy transect surveys. The workflow is presented as suitable for integrating irregular, inconsistently collected data and for application to conservation monitoring.

Key findings

  • A Bayesian hierarchical distance-sampling (HDS) state-space model with data augmentation and habitat- and season-dependent detectability was developed to estimate abundance and detectability from irregular transect surveys.
  • The authors provide a reproducible workflow for Bayesian distance-sampling methods designed to integrate legacy and irregular datasets and to enable robust inference of abundance and detectability under inconsistent survey designs.
“Here we develop a Bayesian Hierarchical Distance Sampling (HDS) model to infer habitat- and season-dependent detectability and abundance”
What this piece can’t prove
  • Abstract does not report posterior uncertainty summaries, model validation, or diagnostics to assess fit and robustness.

2 further details could not be confirmed from the summary.

3otherDerive conservation-relevant interpretation (e.g., high/stable abundance attributed to conservation actions) and recommend applying the workflow to future/legacy monitoring for similar species.interpretive synthesisExpand

In plain English

Interpretive conservation conclusions and management recommendations based on the paper's Bayesian hierarchical distance-sampling results: the Aldabra giant tortoise population was estimated as relatively stable during 2018–2021 at roughly 180,000 individuals; the authors attribute this stability and high abundance to ongoing conservation actions (explicitly including invasive alien species eradication) and advise maintaining and expanding such eradication efforts; they also recommend applying the presented Bayesian distance-sampling workflow (data augmentation, habitat-dependent detectability) to legacy datasets and future surveys for similar species to obtain robust abundance and detectability inference from irregular monitoring data.

Key findings

  • Model-based inference indicated the Aldabra giant tortoise population was approximately 180,000 individuals and was relatively stable between 2018 and 2021.≈180,000 individuals
  • The authors attribute the observed stability and high abundance to the extended history of conservation efforts on Aldabra, explicitly citing invasive alien species eradication.
“We attribute this stability and high abundance to the extended history of conservation efforts on Aldabra”
What this piece can’t prove
  • The statements summarized are interpretive recommendations derived from the modelling results rather than findings from a separate experimental evaluation of conservation actions.
  • Applicability of the recommended workflow to other species or datasets may be limited by differences in detectability processes, survey designs, and available covariates.

1 further detail could not be confirmed from the summary.

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Papers considered

The selected paper, plus nearby candidates.

PubMed, Europe PMC, Crossref · 15 candidate papers

Candidate

Changes in plasma oestradiol, testosterone an progesterone concentrations during an annual reproductive cycle in wild Aldabra giant tortoises (Aldabrachelys gigantea)

Herpetological Journal · 2020 · Crossref

Source (opens in a new tab)

And 9 more candidates considered.