Phenology of harbor seal pupping and the influence of weather on pup counts, investigated by UAV

• Published in: Marine Mammal Science
• Main Authors: Segan Freddo, Samanta, Teilmann, Jonas, van Beest, Floris, Galatius, Anders
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2023
• Subjects: Phoca vitulina; behavior; breeding; phantom drone; phenology; survey; weather variables; harbor seal
• Online Access: https://pure.au.dk/portal/en/publications/b89117d4-5726-4d20-b08f-b4121b314bf4; https://doi.org/10.1111/mms.13020; https://pure.au.dk/ws/files/314432901/Marine_Mammal_Science_2023_Seganfreddo_Phenology_of_harbor_seal_pupping_and_the_influence_of_weather_on_pup_counts_.pdf

Surveys of harbor seals to assess pup production in Denmark are conducted at the assumed breeding season peak between 9 and 15 hr at winds 95% of pups are born at two haul-out sites situated 4 km apart. Drone sur- veys of these two haul-outs were conducted throughout the breeding seasons during 2017–2019. The effects of weather conditions and timing of surveys on counts were analyzed by generalized additive mixed models. The best- performing model included date and wind speed. Pup counts grew from the onset of the observation period and were predicted to peak on June 22. Wind speed had a linear relationship with pup counts and > 50% more pups were counted at 5 m/s than at 1 m/s. To achieve representative pup counts careful consideration of survey conditions and possibly correction for these effects are necessary.