What are the “lost years”?
The so called “lost years” are not exclusive to Galapagos giant tortoises, but in fact apply to all chelonids (the group name for tortoises, turtles and terrapins).
The “lost years” begin at hatching. Infant turtles and tortoises are often too small to be tracked effectively, particularly as hatchling mortality is often very high and huge numbers of hatchlings need to be tracked in order to recover viable data. In the case of sea turtles, hatchlings also move over vast distances in the ocean so radio-transmitters frequently go out of range. Until the advent of tiny satellite transmitters, baby turtles and tortoises were simply lost, remaining unknown and unstudied until they grew. As a result, almost nothing is known about the lives of infant turtles and tortoises, and a fundamental part of their life history has not been documented.
Why are the “lost years” important?
Unlike sea turtles, Galapagos giant tortoises do not move over vast distances, but they do remain almost completely concealed for several years within the cracks and caverns of old lava flows and thus evade effective research on their behaviour, movement ecology and survival. Mortality rates during the first years of life have important repercussions on future population dynamics, and what happens in the “lost years” may hold the key to understanding future trajectories of populations. This information is almost completely absent for wild Galapagos giant tortoises and these first critical years remain “lost”.
In some locations, invasive species, particularly feral pigs ant fire ants, can have significant impacts on giant tortoise nests and hatchlings. With potentially high mortality rates being caused by introduced species in recent decades, monitoring nest sites and researching hatchling movement and natural mortality rates is essential to designing and implementing a rigorous conservation management strategy.