Identification of adults
Identification of adult sea turtles from external characteristics is based upon the carapace length, number of prefrontal scales and the number and arrangement of costal scutes. As there are only five species in Indian waters, identification is fairly straightforward when the turtle or carapace can be examined.
Identification of tracks and nests
The features used to differentiate species based on their tracks include track width, body pit depth and track pattern (symmetrical or asymmetrical). Even though sea turtles can be identified by their tracks, this can be difficult even for experts, particularly with loggerheads, hawksbills and ridleys. Tracks can vary between populations and even between individual animals, and hence it is essential for field personnel to observe nesting turtles and note the characteristics of their tracks. Track identification should be confirmed by checking for remains of hatchlings, egg shell sizes, and other, more concrete evidence.
Body pit types: While loggerheads, hawksbills and ridleys make shallow body pits, green turtles and leatherbacks make large deep body pits.
Track types: A symmetrical track is formed when the front flippers of the turtle move synchronously to pull the turtle forward, while an asymmetrical track is formed when the front flippers move alternately. Sometimes other animals (crocodiles, monitor lizards) leave tracks on the beach as well, but these can be easily distinguished by the pattern and size of the tracks
Identification of hatchlings
Hatchlings can be identified using the same characteristics as adults (number of costal scutes, etc) but one needs to be careful since coloration can vary considerably. If the hatching season has started, one must also be alert for hatchling tracks, which are, of course, small, but usually numerous as the hatchlings would have emerged and crawled to the sea simultaneously. One can follow hatchling tracks to a nest, which can be uncovered to examine nest contents and estimate hatching success.
Adapted from http://www.seaturtle.org/documents/ID_sheet.pdf. Illustrations from: Pritchard, P.C.H. & J.A. Mortimer. 1999. Taxonomy, external morphology, and species identification. Pp. 21–38. In: Eckert et al. 2009 (see bibliography).
Shanker, K. (2003) (Series Editor) Manuals on sea turtle conservation. A GOI UNDP Sea Turtle Project. Centre for Herpetology/Madras Crocodile Bank Trust, Tamil Nadu, India.