INVESTIGADORES
CRESPO enrique Alberto
artículos
Título:
Ontogenic dietary changes in South American sea lions (Otaria flavescens).
Autor/es:
DRAGO, M., L. CARDONA, E.A. CRESPO & A. AGUILAR.
Revista:
JOURNAL OF ZOOLOGY (1987)
Editorial:
WILEY-BLACKWELL PUBLISHING, INC
Referencias:
Año: 2009 vol. 279 p. 251 - 261
ISSN:
0952-8369
Resumen:
Stable isotopes of carbon and nitrogen in the skull bones of South American sea
lions Otaria flavescens from the Chubut province (Argentina) were analysed to
determine whether their feeding habits change during ontogeny. The stable isotope
analysis showed that d13C steadily increased in males and females with their
developmental stage (young, first adult, adult and senile), except in senile males
whose d13C decreased to a value close to that of first adults. Pairwise comparison
of bone stable isotope ratio in each developmental stage revealed differences
between males and females only for the d13C values relative to first adults and
adults. Overall, results indicate that the contribution of benthic prey items to the
diet of both sexes increases with the developmental stage, except in senile males,
and that first adult and adult males have a more benthic diet than females at the
same developmental stage. No differences exist between males and females at
younger and older developmental stages. With respect to d15N, the only difference
was in young female skulls, which were more enriched than those of any other
group. Consequently, the trophic level of sea lions is roughly the same throughout
life, independent of the developmental stage and sex, except for young females.
The growth curve analysis revealed statistically significant differences in the
condylobasal length of the skull between the sea lions in both sexes of the young
stage and those of the other three developmental stages considered here but not
among the individuals of the three later stages. This result indicates that the dietary
differences between individuals in the young stage and those in the successive
stages is likely due to differences in body size, whereas dietary differences among
individuals of the later three stages might be dueOtaria flavescens from the Chubut province (Argentina) were analysed to
determine whether their feeding habits change during ontogeny. The stable isotope
analysis showed that d13C steadily increased in males and females with their
developmental stage (young, first adult, adult and senile), except in senile males
whose d13C decreased to a value close to that of first adults. Pairwise comparison
of bone stable isotope ratio in each developmental stage revealed differences
between males and females only for the d13C values relative to first adults and
adults. Overall, results indicate that the contribution of benthic prey items to the
diet of both sexes increases with the developmental stage, except in senile males,
and that first adult and adult males have a more benthic diet than females at the
same developmental stage. No differences exist between males and females at
younger and older developmental stages. With respect to d15N, the only difference
was in young female skulls, which were more enriched than those of any other
group. Consequently, the trophic level of sea lions is roughly the same throughout
life, independent of the developmental stage and sex, except for young females.
The growth curve analysis revealed statistically significant differences in the
condylobasal length of the skull between the sea lions in both sexes of the young
stage and those of the other three developmental stages considered here but not
among the individuals of the three later stages. This result indicates that the dietary
differences between individuals in the young stage and those in the successive
stages is likely due to differences in body size, whereas dietary differences among
individuals of the later three stages might be dued13C steadily increased in males and females with their
developmental stage (young, first adult, adult and senile), except in senile males
whose d13C decreased to a value close to that of first adults. Pairwise comparison
of bone stable isotope ratio in each developmental stage revealed differences
between males and females only for the d13C values relative to first adults and
adults. Overall, results indicate that the contribution of benthic prey items to the
diet of both sexes increases with the developmental stage, except in senile males,
and that first adult and adult males have a more benthic diet than females at the
same developmental stage. No differences exist between males and females at
younger and older developmental stages. With respect to d15N, the only difference
was in young female skulls, which were more enriched than those of any other
group. Consequently, the trophic level of sea lions is roughly the same throughout
life, independent of the developmental stage and sex, except for young females.
The growth curve analysis revealed statistically significant differences in the
condylobasal length of the skull between the sea lions in both sexes of the young
stage and those of the other three developmental stages considered here but not
among the individuals of the three later stages. This result indicates that the dietary
differences between individuals in the young stage and those in the successive
stages is likely due to differences in body size, whereas dietary differences among
individuals of the later three stages might be dued13C decreased to a value close to that of first adults. Pairwise comparison
of bone stable isotope ratio in each developmental stage revealed differences
between males and females only for the d13C values relative to first adults and
adults. Overall, results indicate that the contribution of benthic prey items to the
diet of both sexes increases with the developmental stage, except in senile males,
and that first adult and adult males have a more benthic diet than females at the
same developmental stage. No differences exist between males and females at
younger and older developmental stages. With respect to d15N, the only difference
was in young female skulls, which were more enriched than those of any other
group. Consequently, the trophic level of sea lions is roughly the same throughout
life, independent of the developmental stage and sex, except for young females.
The growth curve analysis revealed statistically significant differences in the
condylobasal length of the skull between the sea lions in both sexes of the young
stage and those of the other three developmental stages considered here but not
among the individuals of the three later stages. This result indicates that the dietary
differences between individuals in the young stage and those in the successive
stages is likely due to differences in body size, whereas dietary differences among
individuals of the later three stages might be dued13C values relative to first adults and
adults. Overall, results indicate that the contribution of benthic prey items to the
diet of both sexes increases with the developmental stage, except in senile males,
and that first adult and adult males have a more benthic diet than females at the
same developmental stage. No differences exist between males and females at
younger and older developmental stages. With respect to d15N, the only difference
was in young female skulls, which were more enriched than those of any other
group. Consequently, the trophic level of sea lions is roughly the same throughout
life, independent of the developmental stage and sex, except for young females.
The growth curve analysis revealed statistically significant differences in the
condylobasal length of the skull between the sea lions in both sexes of the young
stage and those of the other three developmental stages considered here but not
among the individuals of the three later stages. This result indicates that the dietary
differences between individuals in the young stage and those in the successive
stages is likely due to differences in body size, whereas dietary differences among
individuals of the later three stages might be dued15N, the only difference
was in young female skulls, which were more enriched than those of any other
group. Consequently, the trophic level of sea lions is roughly the same throughout
life, independent of the developmental stage and sex, except for young females.
The growth curve analysis revealed statistically significant differences in the
condylobasal length of the skull between the sea lions in both sexes of the young
stage and those of the other three developmental stages considered here but not
among the individuals of the three later stages. This result indicates that the dietary
differences between individuals in the young stage and those in the successive
stages is likely due to differences in body size, whereas dietary differences among
individuals of the later three stages might be due