Can leftovers from predators be reliably used to monitor marine turtle hatchling sex-ratios? The implications of prey selection by ghost crabs

Rebelo, Rui; Barbosa, Castro; Granadeiro, José Pedro; Indjai, Bucar; Novais, Bruno; Rosa, Gonçalo M.; Catry, Paulo

http://hdl.handle.net/10400.12/2376

Use this identifier to reference this record.

Name:	Description:	Size:	Format:
MB_159_613-620.pdf		328.35 KB	Adobe PDF	Download

Send Feedback

Authors

Rebelo, Rui

Barbosa, Castro

Granadeiro, José Pedro

Abstract(s)

In marine turtles, the sex of an individual is determined by temperatures experienced during embryonic development. Gonad histological observation is still the only reliable way to determine hatchling sex, hampering the study of reproduction and of the demographic consequences of context-dependent sex-ratios, a subject of interest in a warming planet. We investigated whether hatchling remains from predation by Ocypode cursor can be used to estimate sex-ratio trends in a green turtle rookery at Poila˜o, Guinea-Bissau (10 520N, 15 430W). Sex could be readily determined in 77 and 79% of the predated hatchlings in 2008 and 2009, respectively. By comparing hatchlings killed by crabs, hatchlings accidentally dying on the reefs, and live hatchlings, we show that ghost crabs select the smaller prey, but do not select according to hatchling sex, which is explained by the lack of hatchling size dimorphism in this population. The proportion of male hatchlings was 0.45 ± 0.06 and 0.15 ± 0.06 for early and late-season clutches, respectively, these differences most likely being explained by rainfall. Using leftovers from predation by crabs may be a good solution to non-invasively monitor broad trends in sex-ratios of sea turtles.