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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.


Typical profiles of vertical (depth) and horizontal (north-south and east-west distance) movements by an immature green turtle (CM5).Horizontal bars at the bottom indicate the period of feeding resting and other phases, respectively.
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pone-0065783-g006: Typical profiles of vertical (depth) and horizontal (north-south and east-west distance) movements by an immature green turtle (CM5).Horizontal bars at the bottom indicate the period of feeding resting and other phases, respectively.

Mentions: In total, 41 feeding bouts that took 84.4 h were extracted from depth data in six turtles (CM2–7). In individual turtles, feeding bouts occupied 19.1±10.1% of their time. The duration of a feeding bout was 2.1±1.5 h. The occurrence pattern of feeding bouts showed two peaks within a day, with concentrations between 5∶00 and 9∶00 and between 17∶00 and 20∶00; individuals mostly rested between bouts (Figs. 4 and 5, Table S2). Only one feeding bout occurred at night under moonlight, by CM4 (Fig. 4). GPS data showed that the turtles started to move into shallower areas at the beginning of each feeding bout, and that they generally stayed in intertidal areas during these events (Figs. 6 and 7). The area of activity for all of the feeding bouts largely overlapped in each turtle, but during each bout, the turtles used slightly different locations (Fig. 8B and Table 2). The total area used during feeding bouts by an individual turtle was 141.7±121.3 ha and 59.1±50.5 ha for the 95% and 50% FK isopleths, respectively (Table 2). The result of GLM analysis showed that the occurrence of feedinng behavior was significantly affected by time especially 5–9 h and 17–20 h of a day, and not by tidal level and tidal movement (Table S2). Also, there was no significant relationship between the duration of feeding and tidal level (ANOVA, N = 41, F1,40 = 1.00, P = 0.32). Moreover, mean duration of feeding in individual turtles was not significantly related with the body condition index (ANOVA, N = 6, F1,5 = 0.23, P = 0.66).


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)

Typical profiles of vertical (depth) and horizontal (north-south and east-west distance) movements by an immature green turtle (CM5).Horizontal bars at the bottom indicate the period of feeding resting and other phases, respectively.
© Copyright Policy
Related In: Results  -  Collection

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

pone-0065783-g006: Typical profiles of vertical (depth) and horizontal (north-south and east-west distance) movements by an immature green turtle (CM5).Horizontal bars at the bottom indicate the period of feeding resting and other phases, respectively.
Mentions: In total, 41 feeding bouts that took 84.4 h were extracted from depth data in six turtles (CM2–7). In individual turtles, feeding bouts occupied 19.1±10.1% of their time. The duration of a feeding bout was 2.1±1.5 h. The occurrence pattern of feeding bouts showed two peaks within a day, with concentrations between 5∶00 and 9∶00 and between 17∶00 and 20∶00; individuals mostly rested between bouts (Figs. 4 and 5, Table S2). Only one feeding bout occurred at night under moonlight, by CM4 (Fig. 4). GPS data showed that the turtles started to move into shallower areas at the beginning of each feeding bout, and that they generally stayed in intertidal areas during these events (Figs. 6 and 7). The area of activity for all of the feeding bouts largely overlapped in each turtle, but during each bout, the turtles used slightly different locations (Fig. 8B and Table 2). The total area used during feeding bouts by an individual turtle was 141.7±121.3 ha and 59.1±50.5 ha for the 95% and 50% FK isopleths, respectively (Table 2). The result of GLM analysis showed that the occurrence of feedinng behavior was significantly affected by time especially 5–9 h and 17–20 h of a day, and not by tidal level and tidal movement (Table S2). Also, there was no significant relationship between the duration of feeding and tidal level (ANOVA, N = 41, F1,40 = 1.00, P = 0.32). Moreover, mean duration of feeding in individual turtles was not significantly related with the body condition index (ANOVA, N = 6, F1,5 = 0.23, P = 0.66).

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.