Global decline in the size of sea turtles

Changes in mean adult body size may be a universal response to global warming and sometimes lead to conservation concerns. We show that size reductions in sea turtles are now the norm and have another explanation. From 18,707 measurements of nester size (curve carapace length) spanning 30 years from Redang Island (Malaysia), where nearly all nesting individuals have been tagged, we show that the mean size was initially fairly stable and then decreased by 4.0 cm from 100.8 cm in 2005 to 96.8 cm in 2022, which likely translates to a change in mean mass from 120 kg to 105 kg. At the same time, nesting increased from around 300 to 2,000 nests per year. Consistent with this finding of a size reduction in an expanding population, at 27 of 31 sites across the globe where changes in the mean size of nesting sea turtles have been assessed, mean size is decreasing, and the most marked decreases are at sites where population size is increasing most dramatically. Taken together, these focal and glo..., , # Global decline in the size of sea turtles

Dataset DOI: [10.5061/dryad.fqz612k41](10.5061/dryad.fqz612k41)

## Description of the data and file structure

Throughout 1993–2022, the body size of nesting green turtles (*Chelonia mydas*) was assessed at the Chagar Hutang Turtle Sanctuary on Redang Island, Malaysia. Every time a turtle was encountered nesting, the curved carapace length (CCL) was measured and included in the database.

### Files and variables

#### File: Hays\_Table\_S2.xlsx

**Description:** The studies assembled from the literature that included information on changes in mean size and abundance. Species are the green sea turtle *Chelonia mydas* (Cm), hawksbill *Eretmochelys imbricata* (Ei), leatherback *Dermochelys coriacea* (Dc), loggerhead *Caretta caretta* (Cc), and olive ridley *Lepidochelys olivacea* (Lo). NA means that the parameter was not available for that study site and the study doesn't pose any risks to these species.

#### File: Hays\_etal\_Table\_S1.xlsx

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