The value of long-term, community-based monitoring of marine turtle nesting: a study in the Lamu archipelago, Kenya M IKE I. O LENDO ,G LADYS M. O KEMWA ,C OSMAS N. M UNGA ,L ILIAN K. M ULUPI L ILY D. M WASI ,H ASSAN B. M OHAMED M XOLISI S IBANDA and H ARRISON O. O NG ’ ANDA Abstract Monitoring of nesting beaches is often the only feasible and low-cost approach for assessing sea turtle popu- lations. We investigated spatio-temporal patterns of sea tur- tle nesting activity monitored over  successive years in the Lamu archipelago, Kenya. Community-based patrols were conducted on  stretches of beach clustered in five major locations. A total of , nests were recorded: , (.%) green turtle Chelonia mydas nests,  (.%) hawks- bill Eretmochelys imbricata nests,  (.%) olive ridley Lepidochelys olivacea nests and  (.%) unidentified nests. Nesting occurred year-round, increasing during March–July, when % of nests were recorded. A stable trend in mean annual nesting densities was observed in all locations. Mean clutch sizes were . ± SE  eggs (range –) for green turtles,  ± SE  eggs (range –) for hawksbill turtles, and  ± SE  eggs (range –) for olive ridley turtles. Curved carapace length for green tur- tles was – cm, and mean annual incubation duration was . ± SE . days. The mean incubation duration for green turtle nests differed significantly between months and seasons but not locations. The hatching success (pooled data) was .% (n = ,) and was higher for in situ nests (. ± SE .%) compared to relocated nests (. ± SE .%). The results highlight the important contribution of community-based monitoring in Kenya to sustaining the sea turtle populations of the Western Indian Ocean region. Keywords Clutch size, community-based monitoring, green turtle, hatching success, hawksbill turtle, incubation duration, sea turtles, Western Indian Ocean Supplementary material for this article is available at https:// doi.org/./S Introduction S urveys of nesting beaches are often the only feasible and low-cost approach for assessing and monitoring sea tur- tle populations over long time frames (Schroeder & Murphy, ). Four species of sea turtles are known to nest within the Western Indian Ocean region: the green tur- tle Chelonia mydas, the hawksbill turtle Eretmochelys imbri- cata, the olive ridley turtle Lepidochelys olivacea and the loggerhead turtle Caretta caretta (Frazier, ; Bourjea et al., ). All are on the IUCN Red list (IUCN, ): the hawksbill is categorized as Critically Endangered, the green turtle as Endangered, and the loggerhead and olive ridley turtles as Vulnerable. Sea turtle populations in Kenya are generally perceived to be declining (Wamukota & Okemwa, ) because of poaching, loss of nesting habitats, and bycatch in fishing gears (Frazier, ; Okemwa et al., ; Wamukota & Okemwa, ). Other factors include pollution from marine debris, preda- tion, and disease (Frazier, ; Wamukoya et al., ; Church & Palin, ). The Lamu archipelago provides the most significant nesting beaches for sea turtles along the Kenyan coast (Frazier, ; Wamukoya et al., ; Church & Palin, ), and is estimated to support . % of reported nests (Okemwa et al., ). In  WWF initiated a community-based sea turtle monitoring and conservation programme in the Lamu archipelago in partnership with the Kenya Wildlife Service and local communities. Conservation strategies implemented include monitoring of nesting activity and strandings on index beaches, nest re- location, and flipper tagging, which was introduced in . Long-term monitoring is crucial to provide insights into sea turtle population dynamics and to evaluate the effective- ness of conservation activities (Wallace et al., ). The use of volunteers in monitoring is an essential aspect of community-based sea turtle conservation (Frazier, ), and has been successfully adapted in the Western Indian Ocean region (Garnier et al., ; Humber et al., ). There are a number of published studies describing long- term trends in sea turtle nesting within the region (e.g. Bourjea et al., , ; Lauret-Stepler et al., ; Allen et al., ; Mortimer et al., ; Garnier et al., ; Nel et al., ; Derville et al., ) but to our knowledge this MIKE I. OLENDO,LILIAN K. MULUPI,LILY D. MWASI and HASSAN B. MOHAMED WWF Coastal Kenya Programme, Lamu, Kenya GLADYS M. OKEMWA (Corresponding author) and HARRISON O. ONG’ANDA Kenya Marine and Fisheries Research Institute, Mombasa, Kenya Email gokemwa@kmfri.co.ke COSMAS N. MUNGA Department of Environment and Health Sciences, Marine and Fisheries Programme, Technical University of Mombasa, Kenya MXOLISI SIBANDA International Programmes Support, WWF-UK, Woking, UK Received  November . Revision requested  January . Accepted  May . First published online  August . Oryx, 2019, 53(1), 71–80 © 2017 Fauna & Flora International doi:10.1017/S0030605317000771 https://www.cambridge.org/core/terms. https://doi.org/10.1017/S0030605317000771 Downloaded from https://www.cambridge.org/core. IP address: 54.82.56.168, on 07 Oct 2021 at 13:55:03, subject to the Cambridge Core terms of use, available at