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Ethogram of Immature Green Turtles: Behavioral Strategies for Somatic Growth in Large Marine Herbivores.

Okuyama J, Nakajima K, Noda T, Kimura S, Kamihata H, Kobayashi M, Arai N, Kagawa S, Kawabata Y, Yamada H - PLoS ONE (2013)

Bottom Line: As large marine herbivores, immature green turtles do not need to allocate energy to reproduction but are at risk of shark predation, although it is a rare occurrence.Meanwhile, most of the remaining time was spent resting at locations close to feeding grounds, which allowed turtles to conserve energy spent travelling and reduced the duration of periods exposed to predation.These behavioral patterns and time allocations allow immature green turtles to effectively obtain/conserve energy for growth, thus maximising their fitness.

View Article: PubMed Central - PubMed

Affiliation: Graduate School of Informatics, Kyoto University, Sakyo, Kyoto, Japan ; Southwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, La Jolla, California, United States of America.

ABSTRACT
Animals are assumed to obtain/conserve energy effectively to maximise their fitness, which manifests itself in a variety of behavioral strategies. For marine animals, however, these behavioral strategies are generally unknown due to the lack of high-resolution monitoring techniques in marine habitats. As large marine herbivores, immature green turtles do not need to allocate energy to reproduction but are at risk of shark predation, although it is a rare occurrence. They are therefore assumed to select/use feeding and resting sites that maximise their fitness in terms of somatic growth, while avoiding predation. We investigated fine-scale behavioral patterns (feeding, resting and other behaviors), microhabitat use and time spent on each behavior for eight immature green turtles using data loggers including: depth, global positioning system, head acceleration, speed and video sensors. Immature green turtles at Iriomote Island, Japan, spent an average of 4.8 h feeding on seagrass each day, with two peaks, between 5∶00 and 9∶00, and between 17∶00 and 20∶00. This feeding pattern appeared to be restricted by gut capacity, and thus maximised energy acquisition. Meanwhile, most of the remaining time was spent resting at locations close to feeding grounds, which allowed turtles to conserve energy spent travelling and reduced the duration of periods exposed to predation. These behavioral patterns and time allocations allow immature green turtles to effectively obtain/conserve energy for growth, thus maximising their fitness.

No MeSH data available.


Video images of typical behaviour by the immature green turtles.(A) Feeding behaviour of CM8 on seagrass in shallow water and (B) resting behaviour of CM4 under the reef ledge. Video clips from which the images were taken are available in the Movie S1 and S2, which is available online.
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pone-0065783-g003: Video images of typical behaviour by the immature green turtles.(A) Feeding behaviour of CM8 on seagrass in shallow water and (B) resting behaviour of CM4 under the reef ledge. Video clips from which the images were taken are available in the Movie S1 and S2, which is available online.

Mentions: Out of 25.1 h of video data, CM8 migrated from the reef ledge to the seagrass meadow in shallow water, and then started feeding at 9∶07 (Figs. 3A and Movie S1). Feeding continued until at least 12∶01, but the termination time could not be confirmed because the video recording stopped due to low battery power. The food items could not be identified, but they likely included some species of seagrass and Halophila sp. (ovalis), based on their shapes. In the seagrass meadow, the turtle spent most of its time feeding in the seagrass, except when rising to the surface to breathe. During feeding, the turtle continuously moved its head to bite and then chew the food, which corresponded to the head movement pattern that was speculated from the acceleration data (Fig. 2) and feeding observation in the tank. Also, we observed three sporadic feeding events by CM3 on a jellyfish (Scyphozoa) at 8∶18–8∶22 during swimming at a depth of 5.5–7.5 m. Moreover, CM5 bit and then chewed something that was on a hard coral at 19∶17 while resting at a depth of 17.2 m; this food item could not be identified because it was outside the image frame. No feeding events were observed in the video data of the other turtles.


Ethogram of Immature Green Turtles: Behavioral Strategies for Somatic Growth in Large Marine Herbivores.

Okuyama J, Nakajima K, Noda T, Kimura S, Kamihata H, Kobayashi M, Arai N, Kagawa S, Kawabata Y, Yamada H - PLoS ONE (2013)

Video images of typical behaviour by the immature green turtles.(A) Feeding behaviour of CM8 on seagrass in shallow water and (B) resting behaviour of CM4 under the reef ledge. Video clips from which the images were taken are available in the Movie S1 and S2, which is available online.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3686772&req=5

pone-0065783-g003: Video images of typical behaviour by the immature green turtles.(A) Feeding behaviour of CM8 on seagrass in shallow water and (B) resting behaviour of CM4 under the reef ledge. Video clips from which the images were taken are available in the Movie S1 and S2, which is available online.
Mentions: Out of 25.1 h of video data, CM8 migrated from the reef ledge to the seagrass meadow in shallow water, and then started feeding at 9∶07 (Figs. 3A and Movie S1). Feeding continued until at least 12∶01, but the termination time could not be confirmed because the video recording stopped due to low battery power. The food items could not be identified, but they likely included some species of seagrass and Halophila sp. (ovalis), based on their shapes. In the seagrass meadow, the turtle spent most of its time feeding in the seagrass, except when rising to the surface to breathe. During feeding, the turtle continuously moved its head to bite and then chew the food, which corresponded to the head movement pattern that was speculated from the acceleration data (Fig. 2) and feeding observation in the tank. Also, we observed three sporadic feeding events by CM3 on a jellyfish (Scyphozoa) at 8∶18–8∶22 during swimming at a depth of 5.5–7.5 m. Moreover, CM5 bit and then chewed something that was on a hard coral at 19∶17 while resting at a depth of 17.2 m; this food item could not be identified because it was outside the image frame. No feeding events were observed in the video data of the other turtles.

Bottom Line: As large marine herbivores, immature green turtles do not need to allocate energy to reproduction but are at risk of shark predation, although it is a rare occurrence.Meanwhile, most of the remaining time was spent resting at locations close to feeding grounds, which allowed turtles to conserve energy spent travelling and reduced the duration of periods exposed to predation.These behavioral patterns and time allocations allow immature green turtles to effectively obtain/conserve energy for growth, thus maximising their fitness.

View Article: PubMed Central - PubMed

Affiliation: Graduate School of Informatics, Kyoto University, Sakyo, Kyoto, Japan ; Southwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, La Jolla, California, United States of America.

ABSTRACT
Animals are assumed to obtain/conserve energy effectively to maximise their fitness, which manifests itself in a variety of behavioral strategies. For marine animals, however, these behavioral strategies are generally unknown due to the lack of high-resolution monitoring techniques in marine habitats. As large marine herbivores, immature green turtles do not need to allocate energy to reproduction but are at risk of shark predation, although it is a rare occurrence. They are therefore assumed to select/use feeding and resting sites that maximise their fitness in terms of somatic growth, while avoiding predation. We investigated fine-scale behavioral patterns (feeding, resting and other behaviors), microhabitat use and time spent on each behavior for eight immature green turtles using data loggers including: depth, global positioning system, head acceleration, speed and video sensors. Immature green turtles at Iriomote Island, Japan, spent an average of 4.8 h feeding on seagrass each day, with two peaks, between 5∶00 and 9∶00, and between 17∶00 and 20∶00. This feeding pattern appeared to be restricted by gut capacity, and thus maximised energy acquisition. Meanwhile, most of the remaining time was spent resting at locations close to feeding grounds, which allowed turtles to conserve energy spent travelling and reduced the duration of periods exposed to predation. These behavioral patterns and time allocations allow immature green turtles to effectively obtain/conserve energy for growth, thus maximising their fitness.

No MeSH data available.