Temporal and ontogenetic variation in trophic ecology of crabeater seal (Lobodon carcinophaga) from the east Antarctic Peninsula

JULIETA CEBUHAR; JAVIER NEGRETE; EDUARDO SECCHI; SILVINA BOTTA

Hobart

Conferencia; 9th SCAR OPEN SCIENCE CONFERENCE; 2020

Scientific Committee on Antarctic Research

We analysed stable isotopic composition in dentine Growth Layers Groups (GLGs) in canines from mummified (~100 yr) seals from Marambio Island. GAMMs (General Aditive Mixed Models) were run to understand the ontogenetic variation in δ¹⁵N and δ¹³C values. Additionally, we analysed whisker segments of mummified and actual crabeater seals to estimate their isotopic niche area. Yearlings showed wider isotopic niche area, higher δ¹⁵N and lower δ¹³C than subadults and adults. The latter showed no differences in isotopic values. GAMMs showed significant effects of GLGs in the isotopic values, with an increase in δ¹³C from GLG-1 to GLG-5/6 and a decrease in δ¹⁵N from GLG-1 to GLG-3. Higher δ¹⁵N in yearlings may be influenced by lactation as well as tissue catabolism during the post-weaning fast. After 5-6 years (sexual maturity) values tend to stabilize. These trends probably reflect differences in the foraging pattern of younger individuals or the effect of high growth rate on isotopic discrimination values between prey and predator tissues. Actual seals showed wider isotopic niche areas and higher δ¹⁵N than mummified seals. No significant differences were found for δ¹³C. Changes in baseline could explain these δ¹⁵N differences. We provide novel information on the trophic ecology of crabeaters from the eastern Antarctic Peninsula.