Premium
Annual variability in dentin δ 15 N and δ 13 C reveal sex differences in weaning age and feeding habits in Risso's dolphins ( Grampus griseus )
Author(s) -
Evacitas Florence Chan,
Kao WenYuan,
Worthy Graham A. J.,
Chou LienSiang
Publication year - 2017
Publication title -
marine mammal science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.723
H-Index - 78
eISSN - 1748-7692
pISSN - 0824-0469
DOI - 10.1111/mms.12396
Subject(s) - weaning , biology , delphinus delphis , sex ratio , ontogeny , zoology , sexual maturity , ecology , demography , endocrinology , population , sociology
Teeth of odontocetes accumulate annual dentinal growth layer groups ( GLG s) that record isotope ratios, which reflect the time of their synthesis. Collectively, they provide lifetime records of individual feeding patterns from which life history traits can be inferred. We subsampled the prenatal dentin and postnatal GLG s in Risso's dolphins ( Grampus griseus) ( n = 65) that stranded or were collected as bycatch in Taiwan (1994–2014) and analyzed them for δ 15 N and δ 13 C. Age‐specific δ 15 N and δ 13 C values were corrected for effects of calendar year, stranding site, C/N, and sex. δ 15 N values were higher in prenatal layers (14.94‰ ± 0.74‰) than in adult female GLG s (12.58‰ ± 0.20‰), suggesting fetal enrichment during gestation. Decreasing δ 15 N values in early GLG s suggested changes in dietary protein sources during transition to complete weaning. Weaning age was earlier in males (1.09 yr) than in females (1.81 yr). Significant differences in δ 15 N values between weaned males and females suggest potential sexual segregation in feeding habits. δ 13 C values increased from the prenatal to the 4th GLG by ~1.0‰, indicative of a diet shift from 13 C‐depleted milk to prey items. Our results provide novel insights into the sex‐specific ontogenetic changes in feeding patterns and some life history traits of Risso's dolphins.