Being born is tough enough without having heavy sand piled on top of you and having to chip your way out of an egg, but this is the challenge faced by every hatchling turtle with its gaze firmly fixed on the wide blue yonder. Yet, each individual hatchling is not alone. Buried in clutches of up to 150 eggs, every youngster is accompanied by its siblings on its odyssey to the surface. Knowing that many creatures, such as fish and birds, move in unison to reduce energy consumption, Uzair Rusli and colleagues from The University of Queensland, Australia, and the Universiti Malaysia Terengganu, Malaysia, decided to measure the metabolic costs of burrowing to the surface for clutches of green turtle (Chelonia mydas) eggs ranging in size from 10 to 60 eggs.
However, Rusli and colleagues admit that designing the specially adapted respirometer required to measure the hatchlings’ oxygen consumption while they laboured was particularly challenging. After months of trial and error, the team eventually discovered that the youngsters could only burrow to the surface successfully if they provided air gaps around the eggs and the nest was shrouded in darkness in a peaceful laboratory setting.
Having cracked the logistical issues, the team recorded that it took the hatchlings between 3.7 and 7.8 days to reach the surface through a 40-cm-thick layer of sand, with individual hatchlings from the largest groups using approximately 4.4 kJ of energy (11% of their egg yolk), while the hatchlings from the smallest clutches consumed as much as 28.3 kJ (68% of the egg yolk). The team calculated the amount of energy left over for the hatchlings after they made it to the surface, and suspects that the youngsters from large clutches benefit more from the combined efforts of their siblings. This leaves them with additional reserves to fuel their dash across the beach and final swimming frenzy in a bid to make it to the ocean, where they can dine on something other than egg yolk at last.
