Kedzuf, Stephanie C.

The cues used by marine turtles to locate foraging areas in the open ocean are largely
unknown, though field observations suggest that some species [especially the green turtle
[Chelonia mydas], the loggerhead [Caretta caretta], and the leatherback [Dermochelys coriacea]]
somehow locate areas of high productivity. Do they do so by orienting toward chemical cues in
air, water, or both air and water? Previous studies have shown that loggerheads are capable of
detecting airborne odors from synthetic food [turtle pellets] as well as natural dimethyl sulfide
[DMS], which is found in productive oceanic areas. However, responses were brief, and a
capacity to orient was not investigated. We presented tethered loggerheads and leatherbacks to a
laminar airflow that contained DMS or natural food odors [squid, shrimp, sargassum, and moon
jellyfish]. We observed no tendency to orient upwind. Additional experiments examined if freeswimming
loggerhead and green turtles would respond to squid odor presented in air or water
with a visual stimulus [a small plastic ball suspended in the water present]. Both species showed
significant increases in biting behavior when exposed to squid odor in air or water. We conclude
that i. air currents carrying DMS or food do not induce turtles to orient upwind, ii. turtles can
detect and respond to food odors either in air or underwater, and iii. only odors from food
stimulate turtles to initiate feeding behavior. None of our results provide support for the
hypothesis that turtles can locate distant sources of food in the ocean using odor cues.

The cues used by marine turtles to locate foraging areas in the open ocean are largely
unknown though some species (especially the green turtle [Chelonia mydas], the
loggerhead [Caretta caretta], and the leatherback [Dermochelys coriacea]) somehow
locate areas of high productivity. Loggerheads can detect airborne odors, but a capacity
to orient has not yet been investigated. In this comparative study, tethered loggerheads
and leatherbacks were exposed to dimethyl sulfide (DMS) or food odors in a laminar
flow of air. Turtles did not orient into the air current. Free-swimming loggerheads and
green turtles were also exposed to air- or waterborne food (squid) odor plus a neutral
visual stimulus. Both species showed increases in swimming activity and biting behavior
to both stimuli. These results suggest that airborne odors are likely not used to locate
distant areas, but that they are used in localized food searching efforts.