Do sea turtles communicate among themselves?

Verbal communication is less evident among sea turtles compared to freshwater turtles and tortoises. Although sea turtles have existed since 120 million years ago, it was only in the year 1999 that humans have finally recorded sounds from sea turtles. But why did researchers take so long before knowing this aspect of the sea turtle’s behaviour? It was because of the literature published back in the 1950s that claimed that sea turtles did not vocalise and were “deaf as a stump.” Because of this belief, not many scientists bothered to research any further.

Sea turtles start making their first sound before they hatch. The sounds can be described as chirps, click, meow, cluck, grunts and “complex hybrid tones.” Scientists assumed that the sounds that they made while they were still in their shell triggered the others in the group to hatch all at once. It synchronises the time for them to crawl out and leave their nest. This explains why there are so many premature hatchlings found at the bottom of a nest. They may have heard their siblings’ call and emerge from their shells even before they are fully ready. On a positive note, these sounds are crucial for their survival as large numbers of sea turtles emerging at once will increase their chances of survival. The first few minutes after they hatch is very important as they have not picked up any defence mechanism yet. By leaving their nest all at once, it will reduce the risk of being predated upon.

Although the hatchlings’ communication is somewhat well-documented by now, documentation on communication amongst adult sea turtles is scarce. Nevertheless, vocalisations of female sea turtles during nesting have been reported. In one study to investigate the sounds produced by nesting leatherback turtles throughout the stages of nesting from laying the eggs to camouflaging their nests, the authors found that there are three different types of sounds produced by female leatherback turtles.

The sounds came from breathing (inhale/exhale), gular grunts and also pumps. Breathing is the longest sound that they made with an average of 800 ms followed by grunts at 400 ms and pumps at 200 ms. The breathing and pump rates increased from laying eggs to covering their eggs and then camouflaging their nests whereas grunts were only let out during camouflaging. All of these sounds are low in frequency and special devices were needed to detect them. However, these sounds are produced as a result of the exhausting nesting activity by the female sea turtles and not considered as a form of communication between each other.

Sea turtles are solitary animals and because of this, they rarely communicate. The only time that there is a need to communicate is during their mating period. This type of communication is known as nonverbal communication. As part of the mating behaviour, a male sea turtle will approach and bite a female’s neck and flippers gently. If the female does not pull away, this is a sign for the male sea turtle to climb onto her shell and grasp hold of the female’s back with its sharp, long claws. Even during mating, other males can compete with the male by biting his tail and flippers so that he lets go of the female.

Sea turtles also communicate when they are aggressive or provoked. For example, the green turtle has been recorded to produce pulsed sounds when divers come near them and quite a number of reports have disclosed audible growls from sea turtles especially the leatherback sea turtle.

In conclusion, sea turtles do communicate but their communication is scarce as there is a lesser need to communicate between each other because most of them are solitary. Perhaps their communication is considered as adequate as they have survived millions of years until today.

References:

1. No longer ‘deaf as a stump’: Researchers find turtles chirp, click, meow, cluck. (2014). Retrieved March 7, 2021. Link.
2. Bittel, J. (2017). Female turtles “talk” to their hatchlings, scientists discover. Retrieved February 28, 2021. Link.
3. Sea turtles are silent … until there is something important to communicate: First sound recording of a sea turtle (2019). Retrieved February 28, 2021. Link.
4. How do sea turtles hear? (2020, January 07). Retrieved February 28, 2021. Link.
5. Cook, S. L. (2005). Sounds Produced by Nesting Leatherback Sea Turtles (Dermochelys coriacea). 36(4), 387–390.
6. Rothe, N. (2021). How do turtles do it? Retrieved March 7, 2021. Link..
7. Yates, A. (2020). How do turtles communicate? (hint: Verbally & nonverbally). Retrieved March 9, 2021. Link.
8. Nuwer, R. (2014). Baby turtles coordinate hatching by talking to one another through their egg shells. Retrieved March 10, 2021. Link.