Biophysical factors influencing the choice of nesting sites by the green turtle (Chelonia mydas) on the Kenyan coast

Fridah D Obare,Dorcus Sigana,Andrew Wamukota,Robert Chira

doi:10.4314/wiojms.v18i2.5

Fridah D Obare, Dorcus Sigana + Show 2 more

Open Access

https://doi.org/10.4314/wiojms.v18i2.5

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Abstract

The green turtle (Chelonia mydas) is the most common sea turtle nesting along Kenya’s coastline. Varying biophysical factors influence choice of nesting sites where eggs are laid. This study was conducted between February and November 2016 and was designed to establish the relationship between numbers of C. mydas nests on the beach and biophysical variables such as vegetation cover, organic matter content (OMC), beach width, and beach slope. Multiple regression analysis was employed to assess the factors that contribute to the number of C. mydas nests on a beach. This analysis did not allow prediction of the number of nests in a statistically significant way (F (4, 26) = 0.094, p > 0.05, R = 0.120). However, there was a decrease in the number of nests with increased vegetation cover (b = - 0.013), OMC (b = - 8.114), beach width (b = - 0.089) and slope of the beach (b = - 0.352). Approximately 70% of nests occurred on beaches with medium and fine sand. Beaches with intense human activities were associated with high OMC which significantly affected the number of nests on the beach. It is therefore recommended that existing laws should be enforced to control beach development and human activities along the Kenyan coast to protect nest sites. Additionally, long term monitoring should be put in place to evaluate the impact of human disturbance on the favourable biophysical factors influencing the number of nests on a beach, as a management tool in the conservation of C. mydas.

Highlights

Green turtles (C. mydas) tend to prefer to nest in areas that possess specific beach qualities such as gentle slope, moderate vegetation cover, absence of barriers and pollution, medium sized sand particle, darkness and minimum human disturbance (Mortimer, 1990)
This data was obtained from various institutions and organisations engaged in turtle conservation such as Kenya Wildlife Service (KWS) for the Malindi and Watamu area, World Wide Fund for Nature (WWF) for the Lamu area, Baobab Trust (Kilifi and Mombasa areas), and BMUs (Kwale area)
Coordinates collected by GPS showed the distribution of C. mydas nest sites along the Kenyan coast

Summary

Introduction

Green turtles (C. mydas) tend to prefer to nest in areas that possess specific beach qualities such as gentle slope, moderate vegetation cover, absence of barriers and pollution, medium sized sand particle, darkness and minimum human disturbance (Mortimer, 1990). Kenyan beaches have been adversely affected by anthropogenic activities that have the potential to impact negatively on this critical habitat in life cycle of C. mydas. There is inadequate information on nest site ecology on the Kenyan coast, leaving institutions mandated to manage the species without a proper baseline for making decisions to conserve and protect them. There is, inadequate information on C. mydas nesting on the coast of Kenya (Okemwa and Wamukota, 2006). The information on factors affecting turtle nesting is either inadequate or not harmonised, hampering conservation and management efforts (IUCN SSC, 1996).

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