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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.


The extraction results of feeding behaviour from head acceleration data.(A) Depth distribution of feeding events by immature green turtles calculated from head acceleration data. (B) Distribution of the total time period of feeding events at each depth. (C) Depth distribution of feeding dives (dives with feeding events). (D) Distribution of the duration of consecutive feeding dives occurring in shallow water than 3 m.
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pone-0065783-g001: The extraction results of feeding behaviour from head acceleration data.(A) Depth distribution of feeding events by immature green turtles calculated from head acceleration data. (B) Distribution of the total time period of feeding events at each depth. (C) Depth distribution of feeding dives (dives with feeding events). (D) Distribution of the duration of consecutive feeding dives occurring in shallow water than 3 m.

Mentions: If head acceleration data was not recoreded at the same time as depth data, it was still possible to identify feeding behaviors solely from depth data. Initially, we had acceleration data and depth data, we defined ‘feeding dives’, which were dives that contained ‘feeding events’ determined from head acceleration data. Secondly, when we had both sets of data, using the analysis of the characteristics of a ‘feeding dive’ from the head acceleration data (see Results, and Fig. 1), a ‘feeding bout’ in a dive depth profile was extracted as follows: (1) a feeding bout consisted of a series of U-shaped dives with a fluctuation of depth profile in the flat bottom phase (Type 1b in the definition of dive types by Houghton et al. [38]), (2) the depth was less <3 m during >80% of the dive duration, and (3) the consecutive dives continued for more than 30 min. This ‘feeding bout’ was defined as feeding behavior extracted from depth data. For accuracy evaluation of a feeding bout, see Results and Fig. 1. Therefore, we were able to apply this same extraction criteria for dive depth data when we did not have head acceleration data.


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)

The extraction results of feeding behaviour from head acceleration data.(A) Depth distribution of feeding events by immature green turtles calculated from head acceleration data. (B) Distribution of the total time period of feeding events at each depth. (C) Depth distribution of feeding dives (dives with feeding events). (D) Distribution of the duration of consecutive feeding dives occurring in shallow water than 3 m.
© Copyright Policy
Related In: Results  -  Collection

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

pone-0065783-g001: The extraction results of feeding behaviour from head acceleration data.(A) Depth distribution of feeding events by immature green turtles calculated from head acceleration data. (B) Distribution of the total time period of feeding events at each depth. (C) Depth distribution of feeding dives (dives with feeding events). (D) Distribution of the duration of consecutive feeding dives occurring in shallow water than 3 m.
Mentions: If head acceleration data was not recoreded at the same time as depth data, it was still possible to identify feeding behaviors solely from depth data. Initially, we had acceleration data and depth data, we defined ‘feeding dives’, which were dives that contained ‘feeding events’ determined from head acceleration data. Secondly, when we had both sets of data, using the analysis of the characteristics of a ‘feeding dive’ from the head acceleration data (see Results, and Fig. 1), a ‘feeding bout’ in a dive depth profile was extracted as follows: (1) a feeding bout consisted of a series of U-shaped dives with a fluctuation of depth profile in the flat bottom phase (Type 1b in the definition of dive types by Houghton et al. [38]), (2) the depth was less <3 m during >80% of the dive duration, and (3) the consecutive dives continued for more than 30 min. This ‘feeding bout’ was defined as feeding behavior extracted from depth data. For accuracy evaluation of a feeding bout, see Results and Fig. 1. Therefore, we were able to apply this same extraction criteria for dive depth data when we did not have head acceleration data.

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.