Aerial surveying of the world’s largest leatherback turtle rookery: A more effective methodology for large-scale monitoring

Witt, Matthew J.; Baert, Bruno; Broderick, Annette C.; Formia, Angela; Fretey, Jacques; Gibudi, Alain; Mounguengui, Gil Avery Mounguengui; Moussounda, Carine; Ngouessono, Solange; Parnell, Richard J.; Roumet, Dominique; Sounguet, Guy‐Philippe; Verhage, Bas; Zogo, Alex; Godley, Brendan J.

doi:10.1016/j.biocon.2009.03.009

Cited by 73 publications

(83 citation statements)

References 42 publications

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“…The major nesting grounds for this species remained undiscovered by scientists until the 1950s and many other rookeries were unknown until the 1960s and 1970s (Pritchard 1997). Significant populations of leatherbacks in the western Atlantic nest in French Guiana, Suriname, Guyana, and Trinidad (Pritchard and Trebbau 1984, Girondot and Fretey 1996, Hilterman and Goverse 2005, Eckert 2006, Ordoñez et al 2007, whereas the single largest colony worldwide is found in Gabon in the eastern Atlantic (Billes and Fretey 2004, Fretey et al 2007, Witt et al 2009). Nesting is currently widespread and is a regular seasonal occurrence throughout the Caribbean on many island and mainland beaches.…”

Section: Introductionmentioning

confidence: 99%

Leatherback nests increasing significantly in Florida, USA; trends assessed over 30 years using multilevel modeling

Stewart

Sims

Meylan

et al. 2011

Ecological Applications

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Abstract. Understanding population status for endangered species is critical to developing and evaluating recovery plans mandated by the Endangered Species Act. For sea turtles, changes in abundance are difficult to detect because most life stages occur in the water. Currently, nest counts are the most reliable way of assessing trends. We determined the rate of growth for leatherback turtle (Dermochelys coriacea) nest numbers in Florida (USA) using a multilevel Poisson regression. We modeled nest counts from 68 beaches over 30 years and, using beach-level covariates (including latitude), we allowed for partial pooling of information between neighboring beaches. This modeling approach is ideal for nest count data because it recognizes the hierarchical structure of the data while incorporating variables related to survey effort. Nesting has increased at all 68 beaches in Florida, with trends ranging from 3.1% to 16.3% per year. Overall, across the state, the number of nests has been increasing by 10.2% per year since 1979. Despite being a small population (probably ,1000 individuals), this nesting population may help achieve objectives in the federal recovery plan. This exponential growth rate mirrors trends observed for other Atlantic populations and may be driven partially by improved protection of nesting beaches. However, nesting is increasing even where beach protection has not been enhanced. Climate variability and associated marine food web dynamics, which could enhance productivity and reduce predators, may be driving this trend.

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Section: Introductionmentioning

confidence: 99%

Leatherback nests increasing significantly in Florida, USA; trends assessed over 30 years using multilevel modeling

Stewart

Sims

Meylan

et al. 2011

Ecological Applications

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“…Indeed, the duration of each time series affects the precision of the estimated trend and so surveys have to be prolonged to get most accurate and reliable assessments. Although it is possible to derive total seasonal nesting effort from parsimonious counts at ground monitoring locations [26,27,36] or even from aerial survey [41], it is important to recall that field patrols by local teams are also a way to finance local communities. Using few aerial surveys during a nesting season and mathematical modeling, it is possible to get a precise estimate of the nesting activity.…”

Section: Discussionmentioning

confidence: 99%

“…Furthermore, the power to detect change in seasonality is low when less than 10 aerial surveys are done per year as proposed by Witt at al. (2009) [41]. It will leave us without a thorough knowledge of the inter-annual change in spatial distribution of nesting and its temporal variability.…”

Section: Discussionmentioning

confidence: 99%

Marine Turtles Nesting Activity Assessment and Trend along the Central African Atlantic Coast for the Period of 1999-2008

Girondot¹,

MC²

2016

IJMO

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“…L: maximum likelihood; AIC: Akaike's information criterion; w i : Akaike weight tion abundances and trends. For example, it has been shown that data could be obtained simply by a few aerial surveys during the nesting season (Witt et al 2009). Such data could be analyzed with the methodology described here to estimate total nesting and its standard error.…”

Section: Discussionmentioning

confidence: 99%

“…It seems that the same methodology was used to estimate missing counts for leatherbacks in Gabon; however, the exact methodology used is not explained beyond: '…we used a cubic spline approach.' (Witt et al 2009). However, in this last case, only 12 or 13 counts were missing, which would not strongly affect the final result.…”

Section: Generalized Additive Modelmentioning

confidence: 99%

Estimating density of animals during migratory waves: a new model applied to marine turtles at nesting sites

Girondot¹

2010

Endang. Species. Res.

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Migratory species are sensitive to population declines because they require good habitat across their broad geographic distributions. For this reason, populations of migratory species require careful monitoring to permit detection of any change in their conservation status. An easily implemented technique is a census of individuals at a particular location along the migratory route, which can be used as an index of population status. However, in most situations, censuses are only performed during a portion of a particular season, especially when the presence of the species spans several months at a remote place. To be able to make comparisons among years, it is, thus, important to correct for partial counts. Several such procedures have been developed recently for marine turtles at nesting sites, birds during migration and the phenology of flowering in plants. In the current paper, I review different existing approaches, and then present a new statistical framework improving on those previously used. The method was tested with various time-series of marine turtle nest counts during the nesting season. Results demonstrate that the method is very efficient, and has the additional advantage of being easy to use by a wide variety of researchers.

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Aerial surveying of the world’s largest leatherback turtle rookery: A more effective methodology for large-scale monitoring

Cited by 73 publications

References 42 publications

Leatherback nests increasing significantly in Florida, USA; trends assessed over 30 years using multilevel modeling

Leatherback nests increasing significantly in Florida, USA; trends assessed over 30 years using multilevel modeling

Marine Turtles Nesting Activity Assessment and Trend along the Central African Atlantic Coast for the Period of 1999-2008

Estimating density of animals during migratory waves: a new model applied to marine turtles at nesting sites

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