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

Abstract

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.

Paternal genotype reconstruction reveals multiple paternity and sex ratios in a breeding population of leatherback turtles (Dermochelys coriacea)

“…This is the most comprehensive study on paternity in leatherbacks to date, and may be combined with information from other studies (e.g., Crim et al 2002) to evaluate within-species differences in reproductive strategies across the globe. For instance, the Crim et al (2002) study was conducted on a precipitously declining Pacific population (Spotila et al 2000;Spotila 2004), while our study focused on one of many rapidly increasing populations in the Atlantic (Turtle Expert Working Group 2007; Stewart et al 2010). From our examination of the clutches exhibiting multiple paternity (Table 5), it was clear that both the primary The year that each female was first observed and tagged is noted, as well as the number of nests assessed, hatchlings sampled per clutch (clutch size), total hatchlings assessed, and the number of alleles detected for each of seven polymorphic microsatellite loci.…”

Leatherback turtle conservation in the Caribbean UK overseas territories: Act local, think global?

“…Environmental factors have been proposed as important causal factors behind concurrent population recoveries at other West Atlantic nesting beaches [16,27]. However, within the NCNP, recorded population trends differ, with a decreasing trend in annual nesting activities at Culebra's protected and monitored beaches contrasting with the increasing trends recorded on mainland Puerto Rico [21].…”

“…The species is listed globally as 'critically endangered' by the International Union for the Conservation of Nature [13], and some authors have forecast imminent extinction for nesting populations in the Indo-Pacific [14]. In contrast, some leatherback nesting populations in the Atlantic basin appear to be increasing in size [15,16].…”

Going the extra mile: Ground-based monitoring of olive ridley turtles reveals Gabon hosts the largest rookery in the Atlantic

“…Stewart et al, 2011;Weber et al, 2014;Witherington et al, 2009), though aerial surveys are increasingly being employed to monitor sea turtle populations (e.g. McGowan et al, 2008;Troëng et al, 2004;Witt et al, 2009).…”