Sex- and age-specific migratory strategies of blue whales in the northeast Pacific Ocean

Abstract

Migration is a complex behavior that has evolved in multiple taxonomic groups as a means of accessing productive foraging grounds and environmentally stable areas suitable for reproduction. For migratory whales that forage throughout the year because of their high energetic demands, changes in the abundance of prey in different areas along their migratory route(s) can have serious implications for individual fitness and population viability. Thus, identifying the regions these species use to forage and breed while evaluating their migratory plasticity at the individual level can provide key information for their management and conservation. Serial stable isotope analysis of whale baleen, a continuously growing but metabolically inert tissue, has proven useful in generating individual migratory and foraging records over several years prior to death. We measured carbon (δ13C) and nitrogen (δ15N) isotope values along the length of baleen plates collected from thirteen blue whales of different sex and age classes, representing the largest collection analyzed to date in the northeast Pacific Ocean. Adult females exhibited relatively stable seasonal movements between temperate latitude foraging grounds and subtropical breeding grounds, although two skipped migration one year and subsequently moved to the same subtropical breeding ground near the Costa Rica Dome, potentially to give birth. Adult males exhibited two movement strategies with most remaining at temperate latitudes for 3-4 years before death, while two migrated to subtropical breeding grounds. In contrast, movement patterns in juveniles were erratic. These results are potentially driven by the energetic requirements during pregnancy and nursing in adult females, intra-specific competition among adult males, and inexperience in locating prey in juveniles. We also describe baleen δ15N patterns in recently weaned whales (<16.5m) that reflect switching from the consumption of milk to solid food (krill). In addition, baleen δ13C data suggest that weaned whales continue to use stored nutrients (blubber) acquired during the nursing period long after they are weaned. These results broaden our understanding of habitat selection in this species, highlight the importance of nursing for the critical period after weaning, and indicate that the Costa Rica Dome is an important calving region for this endangered population.

Historical baleen plates indicate that once abundant Antarctic blue and fin whales demonstrated distinct migratory and foraging strategies

“…The individuality and atypical nature of blue whale migration both within and out of the Southern Ocean has been documented by recent papers (Burtenshaw et al., 2004 ; Hucke‐Gaete et al., 2018 ; Lesage et al., 2017 ). In the northern hemisphere, multiple life history strategies and movement patterns have been observed, including residential non‐migratory populations, broad distributions throughout the year, or breeding and feeding in high latitudes through winter months (Blevins et al., 2022 ; Burtenshaw et al., 2004 ; Busquets‐Vass et al., 2017 ; Lesage et al., 2017 ). It is possible that combinations of latitudinal and longitudinal migrations are the cause of the less distinct annual cycles for the blue whales in this study (Table 1 ).…”

“…Mysticete whales with distinct summer and winter foraging areas, such as bowheads and North Atlantic right whales ( Eubalaena glacialis ), generally have consistent and well‐defined δ 13 C and δ 15 N cycles in baleen that are synchronized (Best & Schell, 1996 ; Lysiak et al., 2018 ; Matthews & Ferguson, 2015 ). In contrast, stable isotope studies using baleen of modern North Pacific blue whales have shown inconsistent patterns of annual cycles, possibly reflecting less prey switching across seasons or variation in migration behaviors (Blevins et al., 2022 ; Busquets‐Vass et al., 2017 ). In the present study, no fin whales showed any isotopic correlations between δ 15 N and δ 13 C, but individual blue whales exhibited both positive and negative isotopic synchronicity between carbon and nitrogen cycles, or none at all (Figures A3 and A4 ).…”

“…Carbon data demonstrated regular cycles in only two whales, while nitrogen data demonstrated better-resolved cycles in most individuals, especially in the blue whales. Furthermore, several recent studies have shown relatively consistent δ 15 N values of annual cycles within baleen plates of blue whales and other mysticetes (Blevins et al, 2022;Busquets-Vass et al, 2017;Eisenmann et al, 2016;Silva et al, 2019;Trueman et al, 2019). We detrended each plate's δ 15 N values using a Gaussian low-pass filter to study seasonal trends (Park & Gambéroni, 1995;Pomerleau et al, 2018) then used Fast Fourier Transform (FFT) to calculate peak spectral frequencies to estimate annual cycles (Figure A5).…”

Mixed stock analysis identifies natal origins of green turtles at foraging grounds in southeastern Australia

“…Seasonal migrations between geographically distant breeding and non-breeding grounds are common for threatened marine animals including turtles (Hays, 2008), whales (Mate et al, 2015), seabirds (Pinet et al, 2011), and sharks (Werry et al, 2014). These migratory behaviors can be complex, varying spatiotemporally and by sex and age (Druskat et al, 2019;Blevins et al, 2022). Despite the challenges of tracking migratory species, animal movement data are critical to our understanding of the species' spatial ecology, population structure, vulnerability to anthropogenic threats and ability to adapt to environmental change (Block et al, 2005;McCauley et al, 2015;Paiva et al, 2015).…”

Adaptation of Blue Ocean Strategy in Increasing Business Markets

“…The fastest-moving development of photography, which everyone can follow, is the advancement of cameras on mobile phones (Awladthani, 2023). Smartphones currently present in the community have capabilities that are no less great than the shots of the digital camera itself (Blevins, 2022). With the development of smartphones, users can access social media that can directly take photos, such as Instagram, Facebook, FotoGrid, and so on (Erekson, 2022).…”