In the previous post, we talked about nesting behaviours of sea turtles? Well, what happens after that? Do the baby sea turtles face similar problems upon hatching?

The journal article that we will be looking at today examined green turtle (Chelonia mydas) hatchlings and their behaviour AFTER they have entered the sea from a beach at North West Cape. Of the 40 turtles monitored, half were exposed to artificial light while the rest were exposed to ambient lighting.

As expected, the study presented evidence that the hatchlings were strongly attracted to artificial light during the near shore zone (Thums et al., 2016). This meant that they linger more in this zone where there is a higher risk for predation and travel in the wrong directions due to artificial lighting. Furthermore, there did not find any correlation between speed of the hatchlings and artificial lighting, implying that artificial lighting mainly affects orientation of hatchlings (Thums et al., 2016). Apart from artficial lighting, other factors like direction, intensity and speed of wind and waves. also affects sea turtles. But these factors are likely to affect both the speed of the sea turtles as well as its direction of movement.

Tressnig et al. (2012) elaborates on how unfavourable conditions like debris on the beach like large pebbles or plastics, large size of sand grains and colder temperatures of the sand make it harder for hatchlings to transit to the ocean. I believe that debris would become more of an issue in today’s context where plastic pollution is more prevalent. Baby sea turtles are more likely to be caught in plastic cups, bags, nets and perhaps even masks due to COVID-19. With newly hatched sea turtles being so tiny and unable to do much yet, it is very difficult for them to overcome these obstacles on top of the difficulties in orientating themselves due to artificial lighting.

To add on, with hatchlings spending a longer duration of time on shore trying to navigate their way to the ocean, they are vulnerable to other health impacts as well. For instance, previous research state that they are at risk of thermal stress, dehydration, metabolic effects such as glucose reduction and lactate build-up which then could deteriorate crawling and swim performance due to muscle fatigue (Pankaew & Milton, 2018). This would then require them to rest which then prolongs their exposure to predators. However, in the actual experiment conducted Pankaew and Milton (2018) they were mostly unable to find evidence of such effects on crawl performances or swim performances where there we no significant differences in blood glucose levels or impact due to additional crawling distance. Perhaps, this could be due to the fact that they only took one blood sample per hatchling, where the results could have been unreliable or inaccurate. To get a better understanding on the health impacts of sea turtles, more research is definitely necessary.

All in all, it seems that these poor baby sea turtles go through so much just to reach the ocean… While artificial lighting seems to be the primary obstacle that disorientates them other factors equally affect their ability to reach the ocean safely. With so many obstacles, no wonder so many sea turtles do not reach the sea, and even get eaten by predators. 🙁

 

References

Pankaew, K. & Milton, S.L. (2018) The effects of extended crawling on the physiology and swim performance of loggerhead and green sea turtle hatchlings, Journal of experimental biology, vol. 221, no. 1, pp. jeb165225-jeb165225.

Thums, M., Whiting, S.D., Reisser, J., Pendoley, K.L., Pattiaratchi, C.B., Proietti, M., Hetzel, Y., Fisher, R. & Meekan, M.G. (2016) Artificial light on water attracts turtle hatchlings during their near shore transit, Royal Society open science, vol. 3, no. 5, pp. 160142-160142.