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Marine Turtle Newsletter 68:2-4, © 1995

Long-Term Breeding Histories of Male Green Turtles and Fidelity to a Breeding Ground

Nancy N. Fitzsimmons¹, Anton D. Tucker¹ and Colin J. Limpus^2
1Zoology Department, University of Queensland, Brisbane, QLD 4072, Australia
²Queensland Department of Environment and Heritage, P. O. Box 155, N. Quay, QLD 4002, Australia

Many nesting studies for sea turtles now span 20-30 years. These studies not only provide extended female reproductive histories, but also document strong, long-term site fidelity. In contrast, little information has accumulated concerning reproductive longevity or site fidelity for male sea turtles because of the difficulties in studying pelagic migratory animals. Herein we report evidence to indicate that both considerable reproductive longevity and site fidelity exist among male green turtles (Chelonia mydas).

Since 1974, extensive data have been collected on female green turtles nesting on Heron Island in the southern Great Barrier Reef, Australia (Limpus et al. 1984). Numerous female reproductive histories at this site are now documented to extend for at least 12-14 years (Queensland Turtle Research Project, unpubl. data). As the use of titanium tags (a tag which shows excellent retention) is continued, it is expected that many turtles will be followed for even longer periods. Mating and feeding ground studies conducted from 1974-1992 in the adjacent courtship areas of Heron and Wistari lagoons have provided complementary data on the reproductive status of breeding males and females captured by the "turtle rodeo method" (see Limpus and Reed 1985). Reproductive status of these individuals has been quantified using laparoscopy (Limpus and Reed 1985).

We resumed mating ground studies on 24-29 October 1993 by capturing courting turtles at Heron Reef as part of an ongoing study of male green turtles. We preferentially sampled courting males, resulting in captures of 48 adult males, of which 27 were classified as breeders and 21 as non-breeders. A male was considered to be of breeding status only if

1. he was observed mounted or courting a female turtle,
2. he was an attendant male to a mounted pair, or
3. he had recent courtship damage on his rear flippers and/or tail inflicted by competing males (Limpus 1993).

In this recent sample of adult males, 37.0% of breeding males were recaptures and 47.6% of non-breeding adults were recaptures. Five recaptured males had been recorded as breeding males in previous years, and four of these were recorded as breeding in 1994 as shown in Table 1.

Table 1. Long-term breeding records of recaptured male green turtles from Heron Lagoon, southern Great Barrier Reef, Queensland.

Site fidelity to the Heron Lagoon courtship area was exhibited by two males (X38260 and T36016) which were observed either in courtship, or with fresh courtship damage both in 1994 and in previous years. The recaptures of these two males after 12 and 5 years, respectively, is consistent with the theory that breeding males exhibit long-term fidelity to traditional courtship areas (Limpus 1993). Because the courtship damage recorded in previous years was not recent for the males X2608 and T15700, the previous breeding location for those males is unknown. It is likely that the remaining recaptured male (X22050) did not breed during the 1994 season because he is a resident at the site and the sampling period occurred well into the breeding season.

These breeding data extend the known reproductive lifespan of male green turtles to at least 18 years. This documents male reproductive histories of similar duration as recorded to date for female green turtles both at Heron Island (present maximum = approx. 22 years, originally tagged by R. Bustard; Queensland Turtle Research Project, unpubl. data) and at Tortuguero, Costa Rica (20 year history; Carr et al. 1978). The lack of larger samples of turtles followed over decades of reproductive life is largely the result of high tag loss with the monel flipper tags originally used in these studies (Limpus 1992).

Carr, A., M. Carr, and A. Meylan. 1978. The ecology and migration of sea turtles, 7: The west Caribbean green turtle colony. Bull. Amer. Mus. Nat. Hist. 162:1-46.

Limpus, C. J. 1992. Estimation of tag loss in marine turtle research. Wildl. Res. 19:457 -469.

Limpus, C. J. 1993. The green turtle, Chelonia mydas, in Queensland: breeding males in the Southern Great Barrier Reef. Wildl. Res. 20:513-523.

Limpus, C. J., A. Fleay, and M. Guinea. 1984. Sea turtles of the Capricornia Section, Great Barrier Reef, p.61-78. In: The Capricornia Section of the Great Barrier Reef: Past, Present and Future (W. T. Ward and P. Saenger, Editors), Royal Society of Queensland and Australian Coral Reef Society.

Limpus, C. J. and P. C. Reed. 1985. The green turtle, Chelonia mydas, in Queensland: a preliminary description of the population structure in a coral reef feeding ground, p.47-52. In: Biology of Australasian Frogs and Reptiles (G. Grigg, R. Shine and H. Ehmann, Editors), Surrey Beatty and Sons, Sydney.