Do Local Environmental Factors and Lunar Cycle Influence Timing and Synchrony of Oviposition of a Turtle with Strict Nocturnal Nesting?

Abstract

Timing of nesting affects fitness of oviparous animals living in seasonal environments, and females may cue on environmental factors for their nesting behavior, but these relationships are understudied in tropical turtles. Here, the timing and synchrony of egg-laying relative to environmental factors were examined in the South American freshwater turtle Podocnemis unifilis on 11 nesting beaches during three nesting seasons. Daily measurements included number of nests laid, rainfall, river level, air temperature, and the phase of the lunar cycle (full moon, last quarter, new moon and first quarter). Results confirmed that P. unifilis nested at night and revealed that females in our population nest in groups from 2 to 17 females at a time. Nesting was not correlated with rainfall, but a significant relationship was found with river level, such that nesting started at the onset of the dry season when river levels dropped and nesting grounds emerged. Importantly, we found that (1) nesting events concentrated on days with intermediate daily maximum air temperature (although maxima changed annually), and that (2) larger groups of females nested around full moon, suggesting the reliance on visual cues to initiate nesting activities (consistent with social facilitation behavior). Altogether, the timing of nesting in P. unifilis may be shaped by a combination of environmental factors, moon phase and social facilitation, where visual cues play an important role.

Charapa Turtles (Podocnemis unifilis), an Opportunity to Improve Community Tourism and Contribute to Their Conservation in Yasuní National Park, Ecuador

“…Scopus and Web of Sciece 17 [23,24,35,[38][39][40][41][42][43][44][45][46][47][48][49][50][51] "Turismo", "Conservación", "Charapa" y "Ecuador" Redalyc and Scielo 2 [52,53] With respect to the second objective and to learn about perceptions, field visits were made to the Río Indillama community, where a meeting was held with the community president and the rest of the inhabitants. During the visits to the study area (Figure 2b), semistructured interviews (Table 2) were conducted, that is, open-ended questions directed to focal groups in the community (Figure 2a).…”

Turtle Nest-Site Choice, Anthropogenic Challenges, and Evolutionary Potential for Adaptation

“…For instance, social facilitation is an important component in some species, such as the yellow-spotted Amazon river turtle (Podocnemis unifilis). Some females nest in large groups, following other females (perhaps more experienced nesters), particularly during full moon (Escalona et al, 2019), and laying their eggs at nearby sites (Escalona et al, 2009). Social facilitation is adaptive in this species because eggs of females that nest in larger groups suffer lower predation (Escalona et al, 2009).…”

“…Some females nest in large groups, following other females (perhaps more experienced nesters), particularly during full moon (Escalona et al, 2019), and laying their eggs at nearby sites (Escalona et al, 2009). Social facilitation is adaptive in this species because eggs of females that nest in larger groups suffer lower predation (Escalona et al, 2009). A consequence of this behavior is that clutches may experience comparable environmental conditions resulting in more similar sex ratios than otherwise.…”

Influence of Moon Luminosity, Seasonality, Sex and Weather Conditions on the Activity Levels of the Nocturnal Javan Slow Loris

“…Examples of masking factors are nocturnal luminosity (that is influenced not only by moon phases but also by weather conditions), predation risk, anthropogenic disturbance (including noise and light pollution), and food availability [8][9][10][11][12]. Masking factors can also have a direct inhibitory or excitatory effect on several physiological and behavioral variables [3,13,14].…”