This month one of my papers was published in Behavioural Ecology and Sociobiology about hatching synchrony in two Ontario freshwater turtles. This was a collaboration with Dr. Christina Davy, Sean Hudson, and Coral Frenette-Ling, who conceived and collected the data for this study as part of the Wetlands and Reptile Project.
We tested for hatching synchrony in Map Turtles (Graptemys geographica) and Spiny Softshells (Apalone spinifera). Many turtles coordinate hatching and emergence from their nests. Hatching synchrony may make digging out of the nest easier, and/or reduce predation risk across individuals. The trade-offs of this behaviour are not exactly clear, nor how widespread it is.
We found that Spiny Softshell hatchlings synchronised their hatching, potentially using multiple cues. Eggs that were in contact with one another hatched at similar times, along with eggs that had access to auditory and chemosensory cues! But, Map Turtles did not hatch at the same time. This might be because of a key life-history strategy of these turtles - they can overwinter in the nest. So, there might not be any rush to get out of their eggs all together!
Our experimental design allowed us to also examine the role parental/clutch effects may play in hatching synchrony. Research studying hatching synchrony often incubates less and more advanced siblings together. But, we found that clutch/parental effects strongly influenced both hatching date and incubation duration. So it is very important to consider and control for these effects moving forward!
This figure shows that clutch/parental effects explained a large and significant proportion of variance in both hatching date and incubation duration. It will be important to control for these effects moving forward in this field.
Check out our study here! And please cite it as:
Riley JL, Hudson S, Frenette-Ling C, and Davy CM. (2020) All together now! Disentangling the mechanisms of hatchling synchrony in freshwater turtles. Behavioral Ecology and Sociobiology, 74: 58. https://doi.org/10.1007/s00265-020-2800-y