Master of Science
Frank V. Paladino
Date of Award
Many animals vocalize to communicate. While this vocal communication has been studied extensively in mammals and birds, far less attention has been paid to reptile vocalizations. Sea turtles vocalize in the nest, but the purpose of these vocalizations is unknown. I aimed to characterize the vocalizations of the olive ridley turtles (Lepidochelys olivacea) in the nest during incubation, hatching, and emerging. I also aimed to characterize and compare the vocalizations of olive ridley, leatherback (Dermochelys coriacea), and East Pacific green (Chelonia mydas agassizii) turtle hatchlings. I relocated three olive ridley nests at Parque Nacional Marino Las Baulas, Costa Rica, and buried them next to a plexiglass window, which was used to obtain video recordings using a Canon digital camera. A hollow tube leading from above the eggs to the sand’s surface was used to insert an Earthworks M30 microphone that was attached to a Marantz PMD61 MKII recorder to record audio. Each recording was categorized as incubation, hatching, or emerging. 60 minutes of each stage was analyzed using Raven Pro sound analysis software. The type (harmonic, non-harmonic, pulse) and characteristics (highest frequency, dominant frequency, lowest frequency, duration, and frequency range) were documented. In addition, I recorded olive ridley, leatherback, and East Pacific green hatchlings in buckets. The same characteristics of vocalizations were documented from the bucket recordings as the nest recordings. For statistical purposes, the Chi-Squared Test, Friedman Test, and Kruskal-Wallis tests were used. I recorded a total of 157 vocalizations from the nests. The frequency of the vocalizations ranged from 0.05 - 11.4 kilohertz and the duration ranged from 0.01 - 0.54 seconds. I found significantly more vocalizations in the incubation stage than the other two stages (p < 0.05). The pulse vocalizations were only found in the incubation stage. Also, there was no significant difference seen in types or characteristics of vocalizations among the stages (p > 0.05, all cases). The bucket recordings revealed that the frequencies were not significantly different, but the duration of the leatherback hatchling vocalizations were significantly longer than the other two species (p < 0.05). The other characteristics of the vocalizations between species were not different. The olive ridleys hatchlings in the bucket vocalized more often than the hatchlings in the nest (p < 0.05). The frequencies in the bucket were within the same range as the frequencies in the nest, which was also seen when comparing the leatherbacks in the bucket to Ferrara et al. (2014). The results suggest that the number of vocalizations or the pulse vocalizations could possibly be used in synchronizing hatching. The significance of the frequencies of the vocalizations in the nest is unable to be determined from this study. The similar frequencies of vocalizations among the three species suggest that all sea turtle species vocalize within the same frequency range both in the nest and in other situations such as a bucket. Elucidating the importance of vocalizations in hatchlings can help develop more conservation plans to make sure development and other noise pollution isn’t interfering with any vocal communication.
Lindsay N. McKenna (2016).
Vocalizations of Sea Turtle Hatchlings and Embryos.