Author(s)

Brenda Natasha Mejía-Guarnizo^1,2*, Carlos Julio Polo-Silva^2,3, Guiomar Aminta Jauregui-Romero^2,4, Antonio Delgado-Huertas⁵

¹Centro de Investigaciones en Ciencias Marinas (CICIMAR-IPN), La Paz, México.
²Marine Biology Program, Faculty of Natural Sciences and Engineering, Jorge Tadeo Lozano University, Santa Marta, Colombia.
³Sharky Management and Consulting, Oldsmar, FL, USA.
⁴Programa de Conservación de Tortugas y Mamíferos Marinos (ProCTMM), Santa Marta, Colombia.
⁵Instituto Andaluz de Ciencias de la Tierra (CSIC-UGR), Armilla, Spain.

Stable isotope analysis is a widely used method for gathering ecological insights into the diet and feeding habitats of various species. While captive studies often limit lethal sampling and differ from wild conditions, they offer valuable insights into inherent isotopic variations among individuals, which are often assumed to reflect differences between natural populations. In the Sea Turtle Conservation Program, loggerhead turtle hatchlings from different nests were fed. Necropsies were conducted on turtles that died during this period, obtaining bone fragments for analysis. We evaluated the isotopic variation of carbon (δ¹³C) and nitrogen (δ¹⁵N) in bone tissue across six turtle nests (n = 66 samples) and assessed differences in Straight Carapace Length (SCL, n = 71 samples). Using SIBER and nicheROVER in R, we calculated niche width and overlap, while the simmr package determined primary prey assimilation. Despite feeding the hatchlings the same prey, we observed variations in nitrogen isotope assimilation between nests. Nests 4 and 6 had a niche width >1.8‰, indicating consistent consumption frequencies across all prey and >70% niche overlap with other nests. In contrast, nests 1 and 2 showed a narrower niche width (<0.3‰) and minimal overlap, suggesting specialization on specific prey. Comparing SCL, no significant diet differences were found between groups, nor a correlation between SCL and isotopes. The mixture model results indicated that Mugil sp. constituted the primary diet component (>40%) across all groups. This study demonstrates how factors like competition or prey preference can influence the assimilation of diet, even when the source remains constant (inherent variation).

Stable Isotopes, Caretta caretta, Head-Starting, Nests, Straight Carapace Length

Mejía-Guarnizo, B. , Polo-Silva, C. , Jauregui-Romero, G. and Delgado-Huertas, A. (2024) Loggerhead Sea Turtles Hand-Reared in Captivity: Isotopic Insights into Their Inherent Dietary Variation. Open Journal of Ecology, 14, 435-454. doi: 10.4236/oje.2024.145026.