Experimental Analysis of an Early Life-History Stage: Water Loss and Migrating Hatchling Turtles

The effect of water dynamics is well known for some aspects of turtle biology, particularly for egg incubation. The role water plays during migration from the nest to the aquatic environment, however, is not well understood. To evaluate water loss and movement patterns of hatchling turtles during migration, we conducted an experimental release of 463 hatchling snapping turtles, Chelydra serpentina, under ecologically relevant field conditions. We recaptured 62.9% of hatchlings released, and 90% of these were caught during the first four days following release. Hatchlings migrating for less time lost more water than those migrating for a longer time; changes in water content ranged from +1.2% to −4.7%. Mean air temperature during the recapture interval was positively correlated with water loss. Furthermore, hatchlings lost significantly more water when recaptured during periods with no rainfall compared to intervals with rainfall (14.5% and 8.3% water loss, respectively). Additionally, more hatchlings were recaptured during precipitation events and intervals with intermediate mean air temperatures. Alternative strategies for migration may exist such that some hatchlings move quickly to the water, minimizing exposure to predators, but increasing water loss and risk of desiccation. Other hatchlings may wait for optimal weather conditions (i.e., moderate air temperatures and precipitation), increasing exposure to predators, but limiting water loss. Further studies are needed to elucidate the relative risks and benefits associated with each strategy.

Fig. 1.

Number of hatchlings recaptured during each of the 35 recapture intervals. Interval 1 was the 1300 h check on 11 August 1998, interval 2 was the 1900 h check on 11 August 1998, interval 3 was the 0700 h check on 12 August 1998, and so on. This pattern was continued for all 35 intervals. Note that every 0700 h check was a 12-h interval, whereas 1300 and 1900 h checks were 6-h intervals. Hatched bars indicate intervals when precipitation events occurred and solid bars indicate no precipitation. Precipitation amounts for the intervals when it rained are as follows: Interval 7 = 5 mm, Interval 12 = 10 mm, Interval 13 = 2 mm, Interval 19 = 12 mm, Interval 31 = 9 mm, and Interval 33 = 8.5 mm. The dashed line indicates the mean air temperature for each recapture interval and the solid line indicates the mean percent water loss for hatchlings recaptured in each recapture interval