There is evidence that suggests that most animals rely to some extent on odor detection for finding food, selecting homes and/or egg laying sites, avoiding predators, and selecting mates. A noninvasive way to estimate particular species' utilization of their olfactory receptor system is to sequence olfactory receptor genes and estimate the percentage of these genes that are functional. This method was used to estimate the degree of the olfactory receptor system use in 7 turtle species (Dermochelys coriacea, Caretta caretta, Chelonia mydas, Chrysemys picta bellii, Sternotherus odoratus, Terrapene Carolina, and Gopherus polyphemus), the results of which show a trend toward a reduction in the number of odorants that they can perceive as their association with water increases.