Body Mass and the Energy Budget of Gravid Hawksbill Turtles (Eretmochelys imbricata) during the Nesting Season

Abstract

Female Hawksbill Turtles (Eretmochelys imbricata) nesting along the southeast coastline of the state of Rio Grande do Norte Brazil (6u139400S, 35u039050W) were captured and weighed during the 2006–07 and 2007–08 nesting seasons. The mean value for the first postoviposition mass was 79.6 kg. Individuals that were subsequently recaptured showed a mean mass change of 1.6 kg in the interval between two consecutive postovipositions (i.e., after one internidal interval). We plotted the mass of the individuals against the curvilinear carapace length. An analysis of residual mass above average body condition reveals that females with good body condition start nesting at the beginning of the season. Preoviposition mass was measured when the female aborted the nesting process. Gross mass change was 5.46 kg. Mean body mass recovery was 3.2 kg. Body mass recovery was always significantly lower than the change in gross mass. This is in agreement with the observed mass loss tendency throughout the breeding season for this species. Mass recovery was analyzed using allometric law, converting both loss in body mass and total egg mass to energy. Using mean turtle body mass, we performed three scenarios for the metabolic maintenance rate of the Hawksbill Turtle during the nesting period. The energy that the turtles expended in egg laying was estimated at 1,183 kJ N d21. The daily net mass loss for the most realistic scenario converted into energy was 4,213 kJ N d21. The total daily energy consumption (maintenance plus egg production) was similar to the daily energy from mass loss. This theoretical treatment suggests that, under this scenario, there is no reason for significant extra energy intake during the oviposition period.