All together now! Hatching synchrony in freshwater turtles

• Published in: Behavioral ecology and sociobiology 2020-05, Vol.74 (5), p.1-15, Article 58
• Main Authors: Riley, Julia L., Hudson, Sean, Frenette-Ling, Coral, Davy, Christina M.
• Format: Article
• Language: English
• Subjects: Adaptiveness; Animal Ecology; Apalone spinifera; Behavioral Sciences; Biomedical and Life Sciences; Chemical stimuli; Chemoreception; Eggs; Fresh water; Graptemys geographica; Hatching; Incubation; Life history; Life Sciences; ORIGINAL ARTICLE; Overwintering; Overwintering behavior; Reptiles & amphibians; Species; Synchronism; Turtles; Variance; Yolk; Yolk sac; Zoology
• ISSN: 0340-5443; 1432-0762
• DOI: 10.1007/s00265-020-2800-y

Synchronous hatching is widespread among oviparous taxa. However, the adaptive significance of this phenomenon is unclear, as are the cues mediating hatching synchrony. We took a comparative approach and experimentally tested for synchronous hatching in two freshwater turtles with different life histories (Apalone spinifera and Graptemys geographica). We also aimed to disentangle the cues and mechanisms facilitating any synchronisation and explored its potential costs. For each species, we incubated eggs of different ages and from different mothers in two conditions—in direct contact with other eggs, or physically isolated but able to receive acoustic or chemical cues. We found evidence of hatching synchrony in A. spinifera, but not in G. geographica. Apalone spinifera eggs of different ages that developed in-contact hatched together, implicating mechanical cues. Younger eggs that were incubated in isolation also synchronised with in-contact eggs, which also implicates acoustic or chemosensory cues. Hatchling yolk sac size and mass were similar among treatments. Overall, A. spinifera exhibits hatching synchrony and there was no evidence of developmental costs. The lack of hatching synchrony in G. geographica may reflect their different life-history strategy, as this species can overwinter in the nest after hatching. Clutch effects explained a large and significant proportion of variance in both hatching date and incubation duration in both turtle species. Future research on hatching synchrony should control for these potentially confounding clutch effects. Variation in hatching or emergence synchrony among freshwater turtles raises questions about the selective forces that favour evolution of this behaviour.