Month: January 2021

Longevity records in sea turtles

Description

This is a project that has been on mind for quite a while and it is time to get it started. The purpose of this post is to gather in one place all the longevity records regarding sea turtles worldwide. By longevity records here I mean long time spans for which people have information for specific individuals. This can be for instance:

  • Reproductive longevity: maximum (conservative estimate of the) number of years that a specific sea turtle has been known to reproduce. Typically this concerns female sea turtles.
  • Longevity regarding presence in foraging grounds: this will typically be a result of capture-mark-recapture projects.
  • Absolute longevity: Actual age of an individual sea turtle (or an estimate of this).

This will be a dynamic post, that is, it will be continuously updated as new information or new records come to my attention. After all, as time goes by, it is expected that researchers and conservationists will record larger and larger time spans for different sea turtle life stages.

THE LATEST UPDATE IS : 24 January 2021

Disclaimer: This is not a scientific publication. Even though I try to provide as many sources as possible eventually the article will be as reliable as its sources. It is also important to stress that I will gather here every publicly available information that I find. Even though emphasis will be given to scientific publications sometimes information can also be found in other online articles as well as social media posts. I aim to have at least a link to a source per case and permission will be asked to reproduce any information for which I cannot find a link to an online resource.

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Big Bertha: An northwest Atlantic female loggerhead estimated to be at least 71-85 years old and have at least 48-62 years of reproductive longevity

“Big Bertha” is a female loggerhead who has been nesting in the state of Georgia in the southeast United States. She first came to my attention by a series of Facebook posts. At the moment, it looks like that Big Bertha holds the worldwide record for both estimated minimum absolute longevity (71-85 years) and reproductive longevity (48-62 years). In summary her story is as follows:

  • She was first tagged (with traditional flipper tags) in 1980 on Cumberland island, Georgia. Source: These two Facebook posts by the Georgia Sea Turtle Center, one from 2013, and one from 2016.
  • She also nested in 2016 on Cumberland island with previous visits also to the nearby Jekyll island. That was also according to the Georgia Sea Turtle Center in this Facebook post. This means that as far as traditional tagging techniques are concerned Big Bertha has been nesting for at least 36 years. But now it’s the cool part!
  • The Northern Recovery Unit Loggerhead DNA project led by Brian Shamblin has been aiming to collect genetic data from sea turtle nests in the southeast USA, in order to genetically tag the nesting females there. One egg from every single nest is removed and the genetic signature of the mother loggerhead is identified, providing new insights in nesting site selection and mean clutch frequency that were difficult to obtain through traditional flipper tagging techniques. Through this project it was discovered that Big Bertha has a daughter who was first observed nesting in Georgia in 1991! See for instance this Facebook post by Georgia Sea Turtle Center where they also inform us that Bertha has a curved carapace length (CCL) of 113 cm (in 2011). Given our knowledge on reproductive biology of that loggerhead population it is not possible that this daughter was born in 1980 when Bertha was observed nesting for the first time or later on, that is to lay eggs in less than 11 years of age. She would have been too young to nest. This means that Bertha must have been nesting even before 1980. But how much before? At least how old must that daughter have been in 1991? This depends on the minimum age of sexual maturation for this particular population. This number is continuously being updated as research techniques become more elaborate. It looks that the most recent estimate can be found in the paper of Larisa Avens et al., calculated at 22.5 years (we will henceforth use 23 years for the sake of rounded calculations). This means that Big Bertha must have been nesting at least since 1968 (23 years before 1991) thus having at least 48 years of reproductive longevity. With the same argument, Bertha must have been born at least 23 years before that year that is in 1945. We conclude that the last time she was seen, in 2016, she must have been at least 71 years old. However if instead of the minimum we take the average age of sexual maturation calculated in Avens et al. (37 years), we can conclude that it is likely that Bertha has been nesting at least since 1954, i.e. at least 62 years of reproductive longevity. That would make her birth year to be no later than 1931 and would rise her minimum age at 2016 at 85 years old. Important to note that in the same paper by Avens et al., the authors estimate that female loggerheads in that population can reach a reproductive stage (more precisely post-maturation stage) of 46 years. Big Bertha seems to beat that!

Interestingly, in this 2013 note in the Marine Turtle Newsletter about the ”History of sea turtle Tagging and Monitoring on Jekyll Island”, the authors mention the case of “a nesting female who was tagged as far back as 31 years ago“. It seems that they refer to Bertha but I could not be sure.

Let’s hope that we will hear more from Big Bertha in the future!

Georgia Sea Turtle Center Facebook post from 2013
Georgia Sea Turtle Center Facebook post from May 2016 giving more info about Big Bertha
Georgia Sea Turtle Center Facebook post from November 2016 mentioning that Big Bertha nested in
2016
At least 41 years of reproductive activity for an Australian flatback sea turtle

Many online articles in 2015 (for instance here) reported a flatback sea turtle that had been nesting in Mon Repos, Australia for 39 years (seemingly firstly encountered in 1976 even though it is not mentioned explicitly). As Colin Limpus, who has been working with sea turtles in the area for more than 50 years, explained, that year that turtle returned for her 13th nesting season, having been seen overall 65 times in 39 years. Furthermore in this 2017 article about his 50 years celebration it was mentioned that this turtle (tag X23103) also nested that year. This means that she has been nesting for at least 41 years. According to his sayings in the first article, flatbacks reach sexual maturity at about 20 years old [reference needed] something that would make this female at least 61 years old.

We will be really looking forward to the exciting facts that the 50+ year old dataset of Col Limpus and coworkers will bring into the surface in the future!

At least 38 years of reproductive activity for a Hawaiian green sea turtle

In this report, by Irene Nurzia Humburg and George H. Balazs, 40 years of research on the green turtles 0f Hawaii were summarised. On the page 8, they mention the case of a turtle originally tagged in 1973 and still nesting in 2011, which implies at least 38 years of reproductive longevity. They also mention that she had been encountered 62 times while nesting at East Island or basking at Trig Island. Furthermore, that paper, by Van Houtan, Hargrove and Balazs reports that age at sexual maturity for that population is 23 years (95% interval: 16.8–28.1). That would make that female to be at around 61 years old (at least 55 years old) by 2011.

A Hawaiian green sea turtle basking on a beach, on Maui island
At least 33 years of reproductive longevity for two female loggerheads nesting on Zakynthos island, Greece

ARCHELON the Sea Turtle Protection Society of Greece has been tagging nesting females in Zakynthos island and Kyparissia Bay since 1982, the oldest sea turtle tagging program in the Mediterranean. Recently in this paper, its scientific team reported some reproductive longevity records for both sites. For Zakynthos two female loggerheads have been nesting for at least 33 years , (1984-2017 and 1986-2019) and in Kyparissia Bay one female have been found to be nesting for at least 29 years (1986-2015). According to a paper by Casale at al. the minimum sexual maturation age for the Mediterranean loggerheads is 14.9 years (we round this to 15 years for the sake of presentation). That means that these Zakynthos loggerheads must be at least 48 years old.

We also expect these records to increase in the future – after all, some of these loggerheads are still nesting!

An old female loggerhead from Zakynthos island, Greece
At least 25 and 24 years of reproductive longevity for Cyprus female loggerheads and greens respectively

Staying in Mediterranean, this paper by Omeyer et al. reported one loggerhead turtle that has been nesting in Alagadi beach for at least 25 years and one green that has been nesting on the same beach for at least 24 years. Sea turtle tagging has been carried out since 1992 at that beach by Marine Turtle Research Group there and SPOT- North Cyprus Society for the Protection of Turtles. [References needed for age at sexual maturity for these populations]

At least 32 years of reproductive longevity for a female loggerhead nesting in Brazil

Likewise, project TAMAR in Brazil has been tagging female loggerheads since 1982. In this paper, they report the case of a loggerhead with at least 32 years of reproductive longevity (1982-2014). Remarkably this loggerhead has grown approximately only 2 cm in 32 years (Curved Carapace length 101 -> 103 cm). Regarding ages at sexual maturity for the loggerheads in Brazil, this paper by Petitet et al. reports an average value of 32 years, and a lower bound for a 95% confidence interval of 26 years (rounded up values). This would make this female loggerhead to be at least 58 years old, possibly at least around 64 years old.

A captive green turtle with an estimated age of at least 70 years

In this paper, the authors mention a personal communication with Kara Dodd and Charles Innes about “a captive green turtle (Chelonia mydas) that has been housed at a New England (USA) Aquarium since the 1960s, and that is still alive (2017)”. They estimate this individual to be at least 70 years old.

More than 27 years of residency in foraging grounds for Australian turtles

As we have already mentioned, the long-term database of Colin Limpus provides some amazing facts. In this supplementary material associated to this paper by Shimada et al., one can find some capture-mark-recapture
(CMR) data that span more than two decades for certain individuals. For example, for a male loggerhead, a minimum of 27.5 years of residency in a foraging site was found. A female loggerhead was found to have at least 27.9 years of residency in a foraging site (from 1/9/1990 to 15/7/2018) in the southwest pacific. A female green sea turtle had at least 27.7 years of residency in a foraging site at the south great barrier reef (10/11/1990 to 1/7/2018). More cases of 20+ years can be found in the references above.

A capture-mark-recapture period of 31 years for a loggerhead in southeast United states

The Inwater Research Group recently reported in the following Facebook post a male loggerhead in southeast United States that has a capture-mark-recapture period of 31 years (1989-2020) and it has been encountered for 49 times!