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Kijyoka Beach is located in northwest Okinawa Island, Japan (26°42′32′′N, E128°08′40′′E; Fig. 1). It is a nesting site of loggerhead turtles (Caretta caretta), green turtles, and hawksbill turtles (Eretmochelys imbricata) (Kikukawa et al. 1999; Komesu et al. 2016). However, the environmental conditions for nesting and hatching of sea turtles on this beach are unsafe. Permanent vegetation grows wild in the hinterland of this beach (Figs. 2B and C), and the main road of Okinawa runs along the beach (Figs. 2A and C). In addition, the lighting along the main road illuminates this beach in the night, thereby inducing road kill of hatchlings (Komesu et al. 2016). Hatchlings are phototactic and thus attracted to light (Lohmann et al. 1997).

Figure 1. Figure 1. A map of Okinawa Island and Kijyoka Beach of Ogimi-son.

Figure 2. Photographs of the Kijyoka Beach where a female green turtle was killed in a traffic accident.

On the night of 16 August 2015, a female green turtle arrived for nesting on Kijyoka Beach and mistakenly entered the main road. Unfortunately, a car collided with the turtle. Although we went to the scene for her rescue, she was already dead by the time we arrived (Fig. 3A). Parts of the internal organs spilled out through its split carapace, which was a horrible sight (Fig. 3A). However, it seemed that the turtle was still alive just before our arrival. After inspecting her tracks on the beach, we concluded that she did not lay the eggs and that they were still in her oviducts. We proceeded immediately to examine her reproductive organs (Figs. 3B and C). We rescued 83 eggs from her oviducts in the early morning of 17 August (Fig. 3D). Simultaneously, the reproductive organs (left and right ovaries and the oviducts) without the eggs were also removed, fixed in Bouin’s solution, and stored in 70% alcohol and kept as an academic specimen at the Okinawa Churashima Research Center, Okinawa, Japan, for future analysis of oviduct structure.

Miller (1999) categorized oviposited eggs of sea turtles as: 1) normal eggs (of pliable shape, with albumen and yolk), 2) very small eggs (50% diameter of a normal egg, without yolk), and 3) odd-shaped eggs (unpliable shape, without yolk). Based on this categorization, the 83 rescued eggs were classified as: 49 normal, 1 very small, and 1 odd-shaped egg in the left oviduct and 31 normal and 1 odd-shaped egg in the right oviduct (clutch size: 80 normal, 1 very small, and 2 odd-shaped eggs in both oviducts). The diameter of the 80 normal eggs was 45.8 ± 0.8 mm (mean ± SD; range: 43.5 - 48.0 mm). Eighty normal eggs were incubated at a uniform air temperature of 29 °C and controlled humidity of more than 90%, maintained by fresh-water spray, in an incubator (Autoelex Co., Ltd., Gimhae, Korea; Fig. 3E).

Figure 3. Photographs of the female green turtle killed in a traffic accident (A and B), both oviducts (C), rescued eggs (D), the incubator used for hatching the eggs (E), and the hatchlings (F).

After 54 days of incubation (on 10 October 2015), a pip was confirmed, which continued until 14 October. After 58 days, 20 baby turtles hatched from the eggs (Fig. 3F; hatching success: 25%). Their straight carapace length was 47.8 ± 2.0 mm (range: 43.6 - 51.1 mm), and body mass was 26.0 ± 1.6 g (range: 23.3 - 28.5 g). After confirming that the baby turtles were in a frenzy (excitement phase), they were released at night on the Kijyoka shore where their mother had the accident. In other words, the baby turtles were released and journeyed into the ocean from the shore where they were meant to hatch.

To the best of our knowledge, this case is the first report of hatching success of eggs rescued from the female green turtle killed in a traffic accident. However, the rate of hatching success (25%) was lower than the rate of hatchling emergence observed in the wild, which usually exceeds 70% (Hirth 1980; Miller 1997). Miller (1999) categorized the different phases in embryo development and defined the egg content as follows: 1) undeveloped (unhatched eggs with no obvious embryo; 2) unhatched (unhatched eggs with obvious small embryo); and 3) unhatched term (unhatched, apparent full term embryo in intact egg shell or pipped, with a small amount of external yolk material). Based on this classification, there were 47 (58.8%) undeveloped eggs, 0 (0%) unhatched eggs, and 13 (16.2%) unhatched term eggs, out of the 80 rescued normal eggs. The number of undeveloped eggs (58.8%) was abnormally high, because the actual fertility of deposited eggs probably exceeded 95% (Miller 1997). We therefore believe that the shock from the car crash damaged to the eggs prior to embryogenesis, leading to the low hatching rate. Moreover, the eggs may have suffered other damage during egg removal (approximately 2 hours), although we gave scrupulous attention to manipulation of the eggs.

It is generally unusual to have succeeded in artificially hatching eggs that were removed from a turtle’s body and it was that much more gratifying to release the hatchlings. However, the most important action is the preservation of the shore environment so that sea turtles can safely lay their eggs. With lessons learned from this accident, we hope measures will be taken to prevent sea turtles from entering roads where there is heavy traffic alongside sea turtle nesting beaches.

Acknowledgments. We express our deep gratitude to the citizens of Kijyoka, Ogimi-son, Okinawa Prefecture, Japan, for providing us information about the traffic accident involving the green turtle. We also thank staff of the Okinawa Churashima Research Center for their help with the dissection of the green turtle and the artificial incubation of the rescued eggs.

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