Comparative diving patterns of two minke whales (Balaenoptera acutorostrata) and two fin whales (Balaenoptera physalus) in Northern Norway

Abstract Background Common minke whales ( Balaenoptera acutorostrata ) and fin whales ( Balaenoptera physalus ) are important and abundant top predators in the North Atlantic marine ecosystem. Despite this, information on their diving behavior in this area is scarce. Such knowledge is essential for understanding their role in the marine ecosystem, both as top predators on fish and large zooplankton, and as fertilizers of nutrients to phytoplankton through their excretions. To study their diving behavior in this area, we satellite-tagged two minke whales and two fin whales at the coast of Northern Norway. Results The whales were tracked for 5–11 days, displaying both area-restricted search (assumed feeding) and transit behavior, as quantified by first passage time analyses. Minke whale dives lasted 2.0–11.8 min (mean ± sd, minke 1: 4.5 ± 1.3 min; minke 2: 4.4 ± 1.1 min) and reached depths of 20–250 m (minke 1: 62.9 ± 40.8 m; minke 2: 128.7 ± 66.8 m). Fin whale dives were significantly longer, lasting 2.4–25 min (fin 1: 6.6 ± 1.8 min; fin 2: 9.6 ± 3.1 min), but the dive depths were within the same depth range as the minke whales, reaching depths of 20–275 m (fin 1: 129.8 ± 23.0 m; fin 2: 98.9 ± 58 m). While foraging simultaneously during summer in a large and deep fjord, both species showed similar depth preferences (mainly 120–160 m), possibly targeting the same resources. However, the fin whale exhibited significantly longer dives (6.5 ± 1.6 min) compared to the minke whale (4.4 ± 1.1 min). For both species, square-shaped dives were significantly more common during assumed feeding, while V-shaped dives were more frequently observed during transit. Conclusions Despite the limited sample size and deployment duration, this study provides valuable insight into the currently limited understanding of the diving behavior of minke and fin whales in high-latitude feeding grounds of the North Atlantic.