Evidence of resource partitioning between humpback and minke whales around the western Antarctic Peninsula

Author Posting. © The Author(s), 2009. This is the author's version of the work. It is posted here by permission of John Wiley & Sons for personal use, not for redistribution. The definitive version was published in Marine Mammal Science 25 (2009): 402-415, doi:10.1111/j.1748-7692.2008.00263.x.For closely related sympatric species to coexist, they must differ to some degree in their ecological requirements or niches (e.g., diets) to avoid inter-specific competition. Baleen whales in the Antarctic feed primarily on krill, and the large sympatric pre-whaling community suggests resource partitioning among these species or a non-limiting prey resource. In order to examine ecological differences between sympatric humpback and minke whales around the Western Antarctic Peninsula, we made measurements of the physical environment, observations of whale distribution, and concurrent acoustic measurements of krill aggregations. Mantel’s tests and Classification and regression tree models indicate both similarities and differences in the spatial associations between humpback and minke whales, environmental features, and prey. The data suggest (1) similarities (proximity to shore) and differences (prey abundance versus deep water temperatures) in horizontal spatial distribution patterns, (2) unambiguous vertical resource partitioning with minke whales associating with deeper krill aggregations across a range of spatial scales, and (3) that interference competition between these two species is unlikely. These results add to the paucity of ecological knowledge relating baleen whales and their prey in the Antarctic and should be considered in conservation and management efforts for Southern Ocean cetaceans and ecosystems.This research was supported by the International Whaling Commission, the Duke University Marine Laboratory, NSF US Antarctic Program Grant OPP-9910307 as part of the Southern Ocean GLOBEC project, and a Fulbright Scholarship and Office of Naval Research Grant N00014-03-1-0212 (to G. Lawson)

Validation of a blubber-based endocrine pregnancy test for humpback whales

Baleen whales have few identifiable external indicators of pregnancy state, making it challenging to study essential aspects of their biology and population dynamics. Pregnancy status in other marine mammals has been determined by measuring progesterone concentrations from a variety of sample matrices, but logistical constraints have limited such studies in free-swimming baleen whales. We use an extensive blubber sample archive and associated calving history data to retrospectively identify samples that correspond to pregnant females and develop a progesterone-based pregnancy test for humpback whales. The lowest pregnant blubber progesterone concentration was 54.97 ng g−1, and the mean for the known-pregnant group was 198.74 ± 180.65 ng g−1. Conversely, females known to be below the minimum age of sexual maturity (juvenile females) had an overall low mean progesterone concentration (0.59 ± 0.25 ng g−1), well below the known-pregnant range. Of the mature females that did not return with a calf (n = 11), three fell within the known-pregnant range (320.79 ± 209.34 ng g−1), while the levels for the remaining eight were two orders of magnitude below the lowest known-pregnant level (1.63 ± 1.15 ng g−1). The proportion of females that did not return with a calf but had values similar to known-pregnant females are consistent with rates of calf mortality, but other potential explanations were considered. Our findings support a validated blubber endocrine assignment of pregnancy corroborated with field life history information, a first for any baleen whale species. The progesterone values we measured were similar to those found in different pregnancy states of other cetaceans and support using blubber biopsy samples for assigning pregnancy in humpback whales. This method can be applied to existing archives or new samples to better study life history and population demography broadly across species and populations

Humpback Whale Song and Foraging Behavior on an Antarctic Feeding Ground

The article of record as published may be located at http://dx.doi.org/10.1371/journal.pone.0051214Reports of humpback whale (Megaptera novaeangliae) song chorusing occuring outside the breeding grounds are becoming more common, but song structure and underwater behavior of individual singers on feeding grounds and migration routes remain unknown. Here, ten humpback whales in the Western Antarctic Peninsula were tagged in May 2010 with non-invasive, suction-cup attached tags to study foraging ecology and acoustic behavior. Background song was identified on all ten records, but additionally, acoustic records of two whales showed intense and continuous singing, with a level of organization and structure approaching that of typical breeding ground song. The songs, produced either by the tagged animalsor close associates, shared phrase types and theme structure with one another, and some song bouts lasted close to an hour. Dive behavior of tagged animals during the time of sound production showed song occurring during periods of active diving, sometimes to depths greater than 100 m. One tag record also contained song in the presence of feeding lunges identified from the behavioral sensors, indicating that mating displays occur in areas worthy of foraging. These data show behavioral flexibility as the humpbacks manage competing needs to continue to feed and prepare for the breeding season during late fall. This may also signify an ability to engage in breeding activities outside of the traditional, warm water breeding ground locations.This material is based upon work supported by the National Science Foundation under Grant No. ANT-07-39483. The authors also greatefully acknowledge funding support from the F.V. Hunt Fellowship of the Acoustical Society of America

Common and Antarctic Minke Whales: Conservation Status and Future Research Directions

Minke whales comprise some of the most widely distributed species of baleen whales, some populations of which are still regularly targeted by commercial whaling. Here, we review the conservation status of common (Balaenoptera acutorostrata) and Antarctic (Balaenoptera bonaerensis) minke whale populations, against the backdrop of ongoing whaling operations and other anthropogenic threats, including climate change, entanglement in fishing gear, ship strikes, and noise pollution. Although some coastal minke whale populations have been studied in detail, others, which inhabit remote and ecologically sensitive locations, such as the Antarctic ice shelf, are among the least understood populations of marine mammals. The unresolved taxonomy of dwarf minke whales further highlights some of the existing knowledge gaps concerning these species. Due to their relatively small size and elusive behaviors, large uncertainties exist for almost all minke whale populations with respect to behavior, migratory routes and winter distributions, hindering effective conservation and management. However, recent advances in research technology, such as passive acoustic monitoring (PAM), unmanned aerial systems (UAS), multisensor recording tags, and machine learning assisted photo-identification, are increasingly being applied to study minke whales and their habitat, and are starting to open new windows into their life history and ecology. In future research, these non- and less-invasive methods should be integrated in larger-scale comparative studies aiming to better understand minke whale behavior, ecological interactions and their varying habitats to drive and support effective species conservation

Temporal and regional variability in the skin microbiome of humpback whales along the Western Antarctic Peninsula

© The Author(s), 2018. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Applied and Environmental Microbiology 84 (2018): e02574-17, doi:10.1128/AEM.02574-17.The skin is the first line of defense between an animal and its environment, and disruptions in skin-associated microorganisms can be linked to an animal's health and nutritional state. To better understand the skin microbiome of large whales, high-throughput sequencing of partial small subunit ribosomal RNA genes was used to study the skin-associated bacteria of 89 seemingly healthy humpback whales (Megaptera novaeangliae) sampled along the Western Antarctic Peninsula (WAP) during early (2010) and late (2013) austral summers. Six core genera of bacteria were present in 93% or more of all humpback skin samples. A shift was observed in the average relative abundance of these core genera over time, with the emergence of four additional core genera corresponding to a decrease in water temperature, possibly caused by seasonal or foraging related changes in skin biochemistry that influenced microbial growth, or other temporal-related factors. The skin microbiome differed between whales sampled at several regional locations along the WAP, suggesting that environmental factors or population may also influence the whale skin microbiome. Overall, the skin microbiome of humpback whales appears to provide insight into animal and environmental-related factors and may serve as a useful indicator for animal health or ecosystem alterations.This project was supported by 67 donors to the “Whale Bacterial Buddies” crowdfunded project supported by WHOI, the Edna Bailey Sussman Fund, and the Michael K. Orbach Enrichment Fund awarded to K. C. Bierlich

Hydrodynamic properties of fin whale flippers predict maximum rolling performance

Maneuverability is one of the most important and least understood aspects of animal locomotion. The hydrofoil-like flippers of cetaceans are thought to function as control surfaces that effect maneuvers, but quantitative tests of this hypothesis have been lacking. Here, we constructed a simple hydrodynamic model to predict the longitudinal-axis roll performance of fin whales, and we tested its predictions against kinematic data recorded by on-board movement sensors from 27 free-swimming fin whales. We found that for a given swimming speed and roll excursion, the roll velocity of fin whales calculated from our field data agrees well with that predicted by our hydrodynamic model. Although fluke and body torsion may further influence performance, our results indicate that lift generated by the flippers is sufficient to drive most of the longitudinal-axis rolls used by fin whales for feeding and maneuvering

Context-dependent lateralized feeding strategies in blue whales.

Lateralized behaviors benefit individuals by increasing task efficiency in foraging and anti-predator behaviors [1-4]. The conventional lateralization paradigm suggests individuals are left or right lateralized, although the direction of this laterality can vary for different tasks (e.g. foraging or predator inspection/avoidance). By fitting tri-axial movement sensors to blue whales (Balaenoptera musculus), and by recording the direction and size of their rolls during lunge feeding events, we show how these animals differ from such a paradigm. The strength and direction of individuals' lateralization were related to where and how the whales were feeding in the water column. Smaller rolls (≤180°) predominantly occurred at depth (>70 m), with whales being more likely to rotate clockwise around their longest axis (right lateralized). Larger rolls (>180°), conversely, occurred more often at shallower depths (<70 m) and were more likely to be performed anti-clockwise (left lateralized). More acrobatic rolls are typically used to target small, less dense krill patches near the water's surface [5,6], and we posit that the specialization of lateralized feeding strategies may enhance foraging efficiency in environments with heterogeneous prey distributions

Feeding performance by sympatric blue and fin whales exploiting a common prey resource

A major focus in macroecology is to understand the mechanisms that drive differences in habitat, morphology, and behavior in closely related species (Brown 1995). Within this paradigm, energy use and prey acquisition play a fundamental role in affecting behavior, especially with respect to foraging patterns and predator‐prey interactions. Because resources may occur in discrete regions and are often limited, sympatric organisms that feed in similar ways partition resources, when they are limited, both to avoid competition and maximize energy gain (Pianka 1974, Schoener 1983). Baleen whales (Mysticeti) comprise more than a dozen species that have evolved a bulk‐filter feeding strategy that enables the efficient exploitation of low trophic level oceanic resources. Although mysticetes are opportunistic predators that feed on diverse prey types, from schooling fish to small copepods, many sympatric baleen whale species, including blue (Balaenoptera musculus) and fin whales (Balaenoptera physalus), target the similar resources. What remains unknown, however, is whether resources are partitioned when baleen whales and prey overlap in both time and space.This is the publisher’s final pdf. The article is copyrighted by the Society for Marine Mammalogy and published by John Wiley & Sons Ltd. It can be found at: http://onlinelibrary.wiley.com/journal/10.1111/%28ISSN%291748-769