A novel approach to analysing observer-based attendance patterns data, using lactating Subantarctic fur seals from Marion Island

• Published in: Antarctic Science
• Main Authors: Wege, Mia, Nevoux, Marie, de Bruyn, P. J. N., Bester, M.
• Other Authors: Mammal Research Institute, Department of Zoology and Entomology Pretoria, University of Pretoria South Africa -University of Pretoria South Africa, Écologie et santé des écosystèmes (ESE), Institut National de la Recherche Agronomique (INRA)-AGROCAMPUS OUEST
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2014
• Subjects: Arctocephalus tropicalis; detection probability; pup sex; seasonal effects; transition probability; [SDV]Life Sciences [q-bio]; Antarctic Science; Marion Island
• Online Access: https://hal.science/hal-01210218; https://doi.org/10.1017/S0954102014000716

Observer-based studies often underestimate key ecological parameters. Here a fresh approach was used to analyse six years (2006–11) of attendance cycles to estimate foraging trip lengths of a lactating flipper-tagged otariid: subantarctic fur seals at Marion Island. Multi-state mark-recapture models were used to calculate detection failures of females, correct estimates accordingly, and investigate the effects of year, season, pup sex and the presence of a telemetry device on attendance cycle parameters. There were no differences between corrected and uncorrected attendance data. This is attributed to the high capture probability across all seasons (range: 83–98%). This illustrates that observer-based studies are useful to augment telemetry studies. Only season and pup sex had a significant impact on female provisioning rates. In winter, foraging trip durations were longer (t-value=25.22, P<0.0001) and attendance durations shorter (t-value=-2.15, P=0.01) than during summer. Females with female pups spent a higher proportion of their time on land (χ2=6.6, P<0.05). Male pups have higher growth demands and are larger which suggests they can deplete female milk-stores faster.