Geographically closed, yet so different: Contrasting long-term trends at two adjacent sea turtle nesting populations in Taiwan due to different anthropogenic effects

Authored by I-Jiunn Cheng, Wan-hwa Cheng, Y-T Chan

Date Published: 2018

DOI: 10.1371/journal.pone.0200063

Sponsors: Ministry of Science and Technology of Taiwan

Platforms: No platforms listed

Model Documentation: Other Narrative

Model Code URLs: Model code not found

Abstract

Marine turtles are endangered megafauna that face both natural disturbances and anthropogenic threats. The islands of Wan-an and Lanyu support two important green turtle nesting populations in Taiwan and are separated by 250 km. Nesting activity was first documented on Wan-an Island in 1992, with 8 nesting females being documented. A further 11 nesting females were first documented on Lanyu Island in 1997. However, by 2015, the Wan-an Island population declined to only 2 nesting females, whereas the Lanyu Island population showed peaks in abundance (up to 24 nesters) every 3-5 years with no long-term decline. Additionally, the recruitment of new nesters to the Wan-an Island population decreased to 15\%, whereas recruitment into the Lanyu Island population remained high (66\%). The decrease of the nesting population on Wan-an Island might be due to illegal poaching on the high seas along the migratory corridor of the turtles, whereas the stable nesting population on Lanyu Island showed no evidence of such a threat. The two nesting populations use different migratory corridors to their foraging grounds, resulting in different fates of development in population trend.

Tags

Individual-based model Chelonia-mydas Northern australia Lepidochelys-olivacea Wan-an island Green turtle Remigration intervals Conservation efforts Encouraging outlook Penghu archipelago