A seven-year record of fluctuating core body temperatures of nesting leatherback and hawksbill sea turtles

  1. Malcolm W. Kennedy

Reviewed by

Read the full article

Listed in

Log in to save this article

Abstract

Sea turtles experience changes in water temperatures during migrations and seasonal movements that will influence their body temperatures. Nothing is known of how sea turtles’ core body temperatures vary from season to season at nesting sites. Over seven consecutive seasons we measured the surface temperatures of freshly laid eggs as proxies of core temperatures of sea turtles using non-contact infrared thermometers. We measured egg temperatures of two species that have contrasting lifestyles - leatherbacks, the largest, which are adapted to migrate between tropical breeding sites to cold temperate waters, and the smaller hawksbills that are confined to the tropics and sub-tropics. We found considerable year-to-year variations in temperatures in both species (year means 30.4 °C to 31.5 °C in leatherbacks), hawksbills the more so (28.1 °C to 30.3 °C). These differences will likely be modified by both natural seasonal variations and anthropogenic changes in global ocean temperatures and resulting changes in currents and water temperatures local to nesting beaches. These previously unrecognised diversities in body temperatures of nesting turtles are pertinent to predicting environmental tolerances, reproductive success, and nest site selection by sea turtles, and could contribute to predicting which rookeries may remain viable or not during future ocean warming.

Article activity feed

  1. PREreview

    This Zenodo record is a permanently preserved version of a PREreview. You can view the complete PREreview at https://prereview.org/reviews/8279810.

    This review resulted from the graduate-level course "How to Read and Evaluate Scientific Papers and Preprints" from the University of São Paulo, which aimed to provide students with the opportunity to review scientific articles, develop critical and constructive discussions on the endless frontiers of knowledge, and understand the peer review process.

    The manuscript discusses changes in body temperatures of two distinct species of nesting sea turtles (Dermochelys coriacea and Eretmochelys imbricata) over a period of seven years. The experimental efforts proved to be sufficient to fulfill the research objective, with emphasis on the use of a non-invasive method, considering that these are threatened species. The manuscript is very well written with a cohesive introduction that offer adequate information allowing the reader to easily follow the discussion of the obtained results. However, two points could be better addressed: i. geographic contextualization could be described with more precision and details, and a map could be helpful for the reader; ii. a more complete discussion about the threat status of both species would be useful to contextualize the relevance of the work. Below are some comments.

    1. Keywords: Despite being a small detail, keywords contain terms already used in the title, which is not necessary. Thus, we suggest changing these keywords: leatherback turtle, hawksbill turtle, core body temperatures, nesting.

    2. Introduction: Addressed pertinent information that was little commented on in articles in the area about the physiology of the leatherback turtle species and its relationship with body temperature, for example, the ability of the species to maintain its body temperature above the average temperature of the ocean.

    3. Introduction: Despite mentioning the imminent risk of extinction of these species due to the increase in average global temperature, the risk of global and local extinction of both species was not mentioned. E. imbricata is known to be critically endangered and D. coriacea is classified as vulnerable worldwield, according to the IUCN.

    4. Study sites: As mentioned, the manuscript would benefit considerably of including a map, and mentioning the state and country of the nesting sites where the samplings took place. It could be also interesting to offer more information on the social context of the islands (e.g. are the islands protected areas? are there residents on the island?).

    5. Measurement of core body temperatures: it would be important to give more details on sampling efforts, for example: frequency and time of monitoring.

    6. Results: it would be interesting to add the variation in body temperature of each species of sea turtle in the result topic, as described in the article abstract, as it is an important information for the reader.

    7. Discussion: It would be interesting to mention other possible oceanographic and climatic influences, in addition to El Niño and La Niña, such as other sea surface temperature anomalies (e.g. Atlantic Dipole). For example: Kayano, M. & Capistrano, V. (2014). How the Atlantic Multidecadal Oscillation (AMO) modifies the ENSO influence on the South American rainfall. International Journal of Climatology. 34. 10.1002/joc.3674.

    8. Figures and tables:

      1. Table S1 mentioned in the body of the text has no title;

      2. S4 figure is not mentioned in the article?

      3. The caption of Figure 4 is confusing, did you mean the year 2013 or 1913?

      4. It is worth mentioning that the caption of Figure 2 has a succinct and didactic explanation, with visually interesting abbreviations of climate anomaly events inserted in the figure.

    Competing interests

    The author declares that they have no competing interests.

  2. Version published to 10.1101/2023.07.28.551020v1 on bioRxiv