The scale of the whale: using video-tag data to evaluate sea-surface ice concentration from the perspective of individual Antarctic minke whales

Abstract

Background Advances in biologging technology allow researchers access to previously unobservable behavioral states and movement patterns of marine animals. To relate behaviors with environmental variables, features must be evaluated at scales relevant to the animal or behavior. Remotely sensed environmental data, collected via satellites, often suffers from the effects of cloud cover and lacks the spatial or temporal resolution to adequately link with individual animal behaviors or behavioral bouts. This study establishes a new method for remotely and continuously quantifying surface ice concentration (SIC) at a scale relevant to individual whales using on-animal tag video data. Results Motion-sensing and video-recording suction cup tags were deployed on 7 Antarctic minke whales (Balaenoptera bonaerensis) around the Antarctic Peninsula in February and March of 2018. To compare the scale of camera-tag observations with satellite imagery, the area of view was simulated using camera-tag parameters. For expected conditions, we found the visible area maximum to be ~ 100m2 which indicates that observations occur at an equivalent or finer scale than a single pixel of high-resolution visible spectrum satellite imagery. SIC was classified into one of six bins (0%, 1–20%, 21–40%, 41–60%, 61–80%, 81–100%) by two independent observers for the initial and final surfacing between dives. In the event of a disagreement, a third independent observer was introduced, and the median of the three observer’s values was used. Initial results (n = 6) show that Antarctic minke whales in the coastal bays of the Antarctic Peninsula spend 52% of their time in open water, and only 15% of their time in water with SIC greater than 20%. Over time, we find significant variation in observed SIC, indicating that Antarctic minke occupy an extremely dynamic environment. Sentinel-2 satellite-based approaches of sea ice assessment were not possible because of persistent cloud cover during the study period. Conclusion Tag-video offers a means to evaluate ice concentration at spatial and temporal scales relevant to the individual. Combined with information on underwater behavior, our ability to quantify SIC continuously at the scale of the animal will improve upon current remote sensing methods to understand the link between animal behavior and these dynamic environmental variables.

Spatiotemporal Overlap of Baleen Whales and Krill Fisheries in the Western Antarctic Peninsula Region

“…However, waters off the Western Antarctic Peninsula are comparatively ice-free (Ducklow et al, 2013), and becoming more so (Turner et al, 2016). Minke whale abundance off the Western Antarctic Peninsula is lower than in surveyed areas in the Weddell Sea (Herr et al, 2019) and minke whales tracked off the Western Antarctic Peninsula spent a great deal of time in open water (sea ice concentration <20%) with few locations in dense sea ice (>20% concentration) (Linsky et al, 2020). Minke whales thus have a facultative rather than obligate link with sea ice.…”

Tools for integrating inertial sensor data with video bio-loggers, including estimation of animal orientation, motion, and position

“…This process also allows for some flexibility, depending on the research question, to iteratively adjust the track to account for obvious errors (such as going over land). For instance, in an environment adjacent to a complex shoreline, an animal's movement in a track that parallels the contours of a shoreline may be able to be used as an approximate anchor point for the track (e.g., [50]).…”

Exfoliating Whales–Sandy Bottom Contact Behaviour of Humpback Whales

“…These tags were deployed on various species (O. orca, Balaenoptera musculus, B. bonaerensis) [27][28][29] and with different archival loggers attached (temperature, velocity, depth, sound, cameras) using poles or cross bows for deployment. For example, CATS tags were used to study suckling rates for humpback whale calves for the first time [30,31] and deployed to document minke whales in Antarctica (B. bonaerensis) [32]. They allow the assessment of type, time, and frequencies of behaviour, along with body angles, body accelerations, depth, and location.…”