# Modelling drift of cold-stunned Kemp's ridley turtles stranding on the Dutch coast

## TL;DR

This study models how cold-stunned Kemp's ridley turtles drift to the Dutch coast to improve their rehabilitation.

## Contribution

The study uses Lagrangian flow modeling to trace the drift and cold-stunning conditions of stranded Kemp's ridley turtles.

## Key findings

- Turtles likely drift to the Dutch coast via the English Channel.
- They experience temperatures below 10°C for up to three weeks before stranding.
- Cold-stunning occurs in the southern North Sea region.

## Abstract

Every few years juvenile Kemp’s ridley turtles (
Lepidochelys kempii) are found stranded on the Dutch coasts. The main population distribution of this critically endangered species primarily inhabits the Gulf of Mexico and east coast of the United States. This study focuses on five reports from the Netherlands over the past 15 years, where juvenile turtles were reported to strand alive during the winter, albeit in a hypothermic state. Between ambient ocean temperatures of 10°C and 13°C, Kemp’s ridley turtles are unable to actively swim and remain afloat on the ocean’s surface, a condition termed
‘cold stunning’. Understanding their transport in cold-stunned state can help improve the rehabilitation process of stranded turtles.

Cold-stunned turtles are back-tracked as passive, virtual particles from their stranding location using Lagrangian flow modelling. This study investigates when and where juveniles of the Kemp's ridley turtles cross the threshold temperatures between 10–14° C before stranding by tracking the temperature along the trajectories.

As expected, the simulations show transport of the turtles to the Dutch coast via the English Channel. More surprisingly, the analysis suggests that they likely experience cold-stunning in the southern North Sea region and encounter temperatures below 10°C for only a few days to up to three weeks, and below 12°C for up to a month before stranding.

Adherence to rehabilitation protocols for Kemp’s ridley and monitoring individuals post-release are recommended to improve their long-term survival.