A retrospective analysis of sea turtle nest depredation patterns

Abstract

Nest predation can significantly reduce hatchling recruitment in sea turtle populations. We examined 20 yr of data from Canaveral National Seashore, Florida, which has pristine and altered beaches. We used chi-squared test to determine if secondary predation events were related to the nests' primary predation events, and proportional hazard regression analysis to determine the relative risk of individual nest predation. To determine if human beach use and nest predation risk were spatially or temporally linked, we ranked human beach use and examined predation frequency across all screened and marked nests. We found that once a nest has experienced predation it has an increased likelihood of experiencing a subsequent predation event when compared to other nests on the beach. Primary and multiple predation events occurred with greater frequency in limited beach use areas and with lowest frequency in moderate use areas. Predation risk decreased by an average of 29.5% from 2000 to 2008, relative to the initial year of study. Nests deposited mid-season were 9.8% more likely to be predated than early or late season nests. We conclude that where anti-nest predator management efforts are required but restricted (e.g., by funds, available personnel, or multiple management goals) resources should be concentrated to protect mid-season nests and those in limited access areas, if enhancing hatchling numbers is a management goal. ß 2011 The Wildlife Society.

Buried treasure—marine turtles do not ‘disguise’ or ‘camouflage’ their nests but avoid them and create a decoy trail

“…Nest site selection and the excavation, and refilling of the egg chamber, are probably crucial to the reproductive success of sea turtles given the vagaries of weather and wave action [4], the need for suitable egg incubation conditions [5][6][7] and the escape of hatchlings to the surface [8]. Buried sea turtle egg clutches are also vulnerable to a range of predators [9,10] and dipteran parasite attack [11][12][13], with nest predation rates of more than 50% occurring on some beaches [14][15][16]. The mitigation of these risks is the most commonly presumed reason for the prolonged sand-scattering phase of nesting that follows completion of egg chamber refilling [3,17,18].…”

Protecting nests of the Critically Endangered South Pacific loggerhead turtleCaretta carettafrom goannaVaranusspp. predation

“…Because the species is not categorized as threatened on the IUCN Red List, Lei & Booth (2017b; Lei et al, 2017) suggest the temporary removal of male yellow spotted monitors (the primary predators of turtle eggs) during the turtle nesting season. However, given the monitor's ecological role as a mesopredator, resource managers must first understand the local predator–prey interactions and the ecosystem-level effects of any predator control method selected (Prugh et al, 2009; Welicky et al, 2012). Studies on the raccoon Procyon lotor , another mesopredator that targets marine turtle clutches, showed its removal had no effect on mainland clutch depredation (Ratnaswamy et al, 1997; Barton & Roth, 2007).…”

“…Goanna predation and nest selectivity is probably driven by olfactory and visual cues and influenced by spatial and temporal nest deposition (Blamires & Guinea, 2003; Blamires, 2004; Welicky et al, 2012), proximity to urbanized areas (Smith & Engeman, 2002; Blamires & Guinea, 2003; Prange et al, 2004) and human and goanna conspecific activity (Ferreira, 2012). In contrast to Welicky et al (2012), predation risk in this study was more probable on the north beach in areas heavily utilized by humans, with campsites and food waste. This raises the question of why goannas have become more abundant at Wreck Rock beach (they were considered uncommon in the 1970s; C. Limpus, 2017, pers.…”

“…Such studies should include research into the biology and behaviour of goannas, examination of long-term predation effects and human impacts on predator behaviour. An examination of clutch predation could uncover vital information regarding the timing of predation (Ferreira, 2012; Welicky et al, 2012), repeated visitation by predators, and complete (Limpus, 1971) vs partial clutch loss (Chatto & Baker, 2008). For example, further research could provide insights into why control clutches were predated less than anticipated, and why nests not included in this study but directly adjacent to control plots were also predated (as per the simulation in Blamires & Guinea, 2003).…”

Large-scale investment in the excavation and “camouflaging” phases by nesting Leatherback Turtles (Dermochelys coriacea)

“…Sea turtle eggs are unattended after laying and are susceptible to threats that include flooding by the incoming tide, rising water table, exposure by sand erosion, and predation (Welicky et al 2012). …”