Williams R.,University of British Columbia |
Gero S.,Dalhousie University |
Bejder L.,Murdoch University |
Calambokidis J.,Cascadia Research Collective |
And 4 more authors.
Conservation Letters | Year: 2011
Evaluating impacts of human activities on marine ecosystems is difficult when effects occur out of plain sight. Oil spill severity is often measured by the number of marine birds and mammals killed, but only a small fraction of carcasses are recovered. The Deepwater Horizon/BP oil spill in the Gulf of Mexico was the largest in the U.S. history, but some reports implied modest environmental impacts, in part because of a relatively low number (101) of observed marine mammal mortalities. We estimate historical carcass-detection rates for 14 cetacean species in the northern Gulf of Mexico that have estimates of abundance, survival rates, and stranding records. This preliminary analysis suggests that carcasses are recovered, on an average, from only 2% (range: 0-6.2%) of cetacean deaths. Thus, the true death toll could be 50 times the number of carcasses recovered, given no additional information. We discuss caveats to this estimate, but present it as a counterpoint to illustrate the magnitude of misrepresentation implicit in presenting observed carcass counts without similar qualification. We urge methodological development to develop appropriate multipliers. Analytical methods are required to account explicitly for low probability of carcass recovery from cryptic mortality events (e.g., oil spills, ship strikes, bycatch in unmonitored fisheries and acoustic trauma). © 2011 Wiley Periodicals, Inc.
News Article | November 16, 2016
It takes a village to raise a whale. Rather than sticking exclusively to their mothers’ side, baby pilot whales in the north Atlantic take turns swimming next to other adults – including both females and males. Pilot whales are social creatures. They are thought to live in multigenerational family units of about two to four dozen individuals, says Joana Augusto at Dalhousie University in Halifax, Canada. Those units often gather in larger groups that stay together for up to a few weeks, allowing whales to travel, feed, rest and socialise together. And while anecdotal evidence suggests calves sometimes accompany members of the gang that aren’t their mothers, nobody had systematically studied the behaviour in pilot whales before, Augusto says. “People have noticed that the calves didn’t really stay with the same adults,” she says. “We would see the babies just go from one individual to the other and then jump back.” To see if this behaviour is common among the population of more than 3000 long-finned pilot whales that spend the summer off Cape Breton Island in Nova Scotia, Canada, Augusto and her colleagues tagged along on a whale-watching boat. From the vessel, the researchers photographed and identified specific whales based on physical marks such as nicks in their dorsal fins, scars and pigmentation patterns. During more than 600 whale encounters over three years, the team spotted 356 identifiable calves, about one fourth of which sometimes stuck close to an adult that wasn’t their mother. One baby took turns swimming beside five grown-up companions. Using a foam-tipped dart and a crossbow, the scientists collected DNA samples from 75 adult whales to determine their sex. Only five of those adults were identified as non-maternal calf companions — and of those, four were male. That was a surprise, Augusto says. It is unclear why a male might let a baby stay by his side, but one possibility is that he is showing off in front of the females. “It’s a way to advertise that they’re a good mate, basically,” Augusto says. The scientists didn’t notice the adults altering their behaviour when they had a young companion. That could enable the calf to observe the complex social conventions of their community, Augusto says. “The calf might be learning from experiences with different individuals of how they should be behaving socially,” she says. Shared parenting is something you would expect in a species with such strong social bonds, says Robin Baird at the Cascadia Research Collective in Olympia, Washington state. Bottlenose dolphins and killer whales sometimes escort others’ calves, for example, and sperm whales and belugas even nurse others’ babies, strengthening the social ties of the group, or perhaps signalling to other adults that the babysitters are pulling their weight in the community. It will be interesting to gather more details on the nature of the interactions between pilot whale calves and adults, Baird says, like how long they spend side by side, and the age of the adult male companions. If the males are relatively young, for example, they may be seeking playmates rather than pupils. Still, Baird says, it is highly likely that calves are soaking up social understanding during the encounters. “Calves are gregarious,” he says. “Calves are motivated to interact with other individuals when their mom’s not right around them.” Read more: Post-menopausal orcas’ wisdom helps family survive; Orcas are first non-humans whose evolution is driven by culture
Chilean Blue Whales as a Case Study to Illustrate Methods to Estimate Abundance and Evaluate Conservation Status of Rare Species [Ballenas Azules Chilenas como Caso de Estudio para Ilustrar Métodos para Estimas la Abundancia y Evaluar el Estatus de Conservación de Especies Raras]
Williams R.,University of Washington |
Hedley S.L.,University of St. Andrews |
Branch T.A.,University of Washington |
Bravington M.V.,CSIRO |
And 3 more authors.
Conservation Biology | Year: 2011
Often abundance of rare species cannot be estimated with conventional design-based methods, so we illustrate with a population of blue whales (Balaenoptera musculus) a spatial model-based method to estimate abundance. We analyzed data from line-transect surveys of blue whales off the coast of Chile, where the population was hunted to low levels. Field protocols allowed deviation from planned track lines to collect identification photographs and tissue samples for genetic analyses, which resulted in an ad hoc sampling design with increased effort in areas of higher densities. Thus, we used spatial modeling methods to estimate abundance. Spatial models are increasingly being used to analyze data from surveys of marine, aquatic, and terrestrial species, but estimation of uncertainty from such models is often problematic. We developed a new, broadly applicable variance estimator that showed there were likely 303 whales (95% CI 176-625) in the study area. The survey did not span the whales' entire range, so this is a minimum estimate. We estimated current minimum abundance relative to pre-exploitation abundance (i.e., status) with a population dynamics model that incorporated our minimum abundance estimate, likely population growth rates from a meta-analysis of rates of increase in large baleen whales, and two alternative assumptions about historic catches. From this model, we estimated that the population was at a minimum of 9.5% (95% CI 4.9-18.0%) of pre-exploitation levels in 1998 under one catch assumption and 7.2% (CI 3.7-13.7%) of pre-exploitation levels under the other. Thus, although Chilean blue whales are probably still at a small fraction of pre-exploitation abundance, even these minimum abundance estimates demonstrate that their status is better than that of Antarctic blue whales, which are still <1% of pre-exploitation population size. We anticipate our methods will be broadly applicable in aquatic and terrestrial surveys for rarely encountered species, especially when the surveys are intended to maximize encounter rates and estimate abundance. ©2011 Society for Conservation Biology.
Stabeno P.J.,National Oceanic and Atmospheric Administration |
Kachel N.B.,University of Washington |
Moore S.E.,National Oceanic and Atmospheric Administration |
Napp J.M.,National Oceanic and Atmospheric Administration |
And 3 more authors.
Deep-Sea Research Part II: Topical Studies in Oceanography | Year: 2012
The southeastern, middle shelf of the Bering Sea has exhibited extreme variability in sea ice extent, temperature, and the distribution and abundance of species at multiple trophic levels over the past four decades. From 1972-2000, there was high interannual variability of areal extent of sea ice during spring (March-April). In 2000, this shifted to a 5-year (2001-2005) period of low ice extent during spring, which transitioned to a 4-year (2007-2010) period of extensive sea ice. High (low) areal extent of sea ice in spring was associated with cold (warm) water column temperatures for the following 6-7 months. The ocean currents also differed between warm and cold years. During cold years, the monthly-mean currents over the shelf were largely westward, while in warm years the direction of currents was more variable, with northward flow during December-February and relatively weak flow during the remainder of the year. The types and abundance of zooplankton differed sharply between warm and cold years. This was especially true during the prolonged warm period (2001-2005) and cold period (2007-2010), and was less evident during the years of high interannual variability. During the warm period, there was a lack of large copepods and euphausiids over the shelf; however, their populations rebounded during cold period. Small crustacean zooplankton taxa did not appear to vary between and warm and cold years. For both walleye pollock and Pacific cod, year-class strength (recruitment) was low during the prolonged warm period, but improved during the following cold period. Year-class strength did not appear to vary as a function of warm and cold years during the period of high year-to-year variability. Also, recruitment of arrowtooth flounder (a predator of pollock and cod) did not appear influenced by the warm or cold years. Finally, the distribution and relative abundance of fin whales appeared to differ in warm and cold years, with fewer whales on the southeastern, middle shelf during warm years. © 2012 Elsevier Ltd.
News Article | August 8, 2016
Rescuers on Sunday morning were hoping to save a baby humpback whale that got stranded just 20 feet from West Seattle shore, but efforts failed and the young one perished, reports say. The 30-foot juvenile humpback whale (Megaptera novaeangliae) was found trapped in the shallows near West Seattle's Fauntleroy Ferry dock in the wee hours of the morning on August 7. That day, hundreds of people flocked to the ferry terminal and attempted to help in rescuing the stranded animal, according to a report from King5 News. Unfortunately, efforts were in vain. A spokesperson from the National Oceanic and Atmospheric Administration (NOAA) says that the baby humpback whale died hours later. Lynne Barre, a member of NOAA's Protected Resources Division in Seattle, says the humpback whale was first reported at 8 a.m. during high tide. Rescuers from NOAA, the West Seattle Seal Sitters, the Cascadia Research Collective and others came to the shore shortly afterward to save the whale and keep the crowds away. Cascadia stranding coordinator Jessie Huggins and others went into the waist-deep waters to place wet blankets on the sickly animal to regulate its temperature and keep it hydrated. As the tide went out, however, the baby whale slowly perished, says Huggins. Scientists have yet to determine the cause of the animal's death, but tissue samples have been taken. The young one's carcass was covered with "whale lice," an indication of poor health, investigators say. Meanwhile, Huggins says officials were unlikely to decide whether to tow the mammal to another place for a full necropsy or the tissue samples taken would suffice for an investigation. "There are lots of logistics involved in doing an examination," says Huggins. Barre says it is not uncommon to see humpback whales in Puget Sound because the population has grown over the past few years. Even so, NOAA's National Marine Fisheries Service recommends that some segments of the whale population in the Northwest Pacific should be listed as threatened. Barre says sightings of humpback whales have become less unusual than they used to be, but it is still unusual to find live whales get stranded. In June, a 35-foot humpback whale was found dead in the Bremerton ferry, but a full necropsy did not help disclose the reason for its death. In 2010, another dead whale was towed from the shores of West Seattle. Scientists still have no conclusive explanation the cause of death. Troubled humpback whales also turn up in other parts of the United States. In November last year, marine experts tried to free a humpback whale that was stuck in a commercial fishing line. © 2016 Tech Times, All rights reserved. Do not reproduce without permission.
Schorr G.S.,Cascadia Research Collective |
Falcone E.A.,Cascadia Research Collective |
Moretti D.J.,Naval Undersea Warfare Center |
Andrews R.D.,University of Alaska Fairbanks |
Andrews R.D.,Alaska SeaLife Center
PLoS ONE | Year: 2014
Cuvier's beaked whales (Ziphius cavirostris) are known as extreme divers, though behavioral data from this difficult-to-study species have been limited. They are also the species most often stranded in association with Mid-Frequency Active (MFA) sonar use, a relationship that remains poorly understood. We used satellite-linked tags to record the diving behavior and locations of eight Ziphius off the Southern California coast for periods up to three months. The effort resulted in 3732 hr of dive data with associated regional movements - the first dataset of its kind for any beaked whale - and included dives to 2992 m depth and lasting 137.5 min, both new mammalian dive records. Deep dives had a group mean depth of 1401 m (s.d. = 137.8, n = 1142) and duration of 67.4 min (s.d. = 6.9). The group mean time between deep dives was 102.3 min (s.d. = 30.8, n = 783). While the previously described stereotypic pattern of deep and shallow dives was apparent, there was considerable inter- and intra-individual variability in most parameters. There was significant diel behavioral variation, including increased time near the surface and decreased shallow diving at night. However, maximum depth and the proportion of time spent on deep dives (presumed foraging), varied little from day to night. Surprisingly, tagged whales were present within an MFA sonar training range for 38% of days locations were received, and though comprehensive records of sonar use during tag deployments were not available, we discuss the effects frequent acoustic disturbance may have had on the observed behaviors. These data better characterize the true behavioral range of this species, and suggest caution should be exercised when drawing conclusions about behavior using short-term datasets.
Potvin J.,Saint Louis University |
Goldbogen J.A.,Cascadia Research Collective |
Shadwick R.E.,University of British Columbia
PLoS ONE | Year: 2012
Bulk-filter feeding is an energetically efficient strategy for resource acquisition and assimilation, and facilitates the maintenance of extreme body size as exemplified by baleen whales (Mysticeti) and multiple lineages of bony and cartilaginous fishes. Among mysticetes, rorqual whales (Balaenopteridae) exhibit an intermittent ram filter feeding mode, lunge feeding, which requires the abandonment of body-streamlining in favor of a high-drag, mouth-open configuration aimed at engulfing a very large amount of prey-laden water. Particularly while lunge feeding on krill (the most widespread prey preference among rorquals), the effort required during engulfment involve short bouts of high-intensity muscle activity that demand high metabolic output. We used computational modeling together with morphological and kinematic data on humpback (Megaptera noveaangliae), fin (Balaenoptera physalus), blue (Balaenoptera musculus) and minke (Balaenoptera acutorostrata) whales to estimate engulfment power output in comparison with standard metrics of metabolic rate. The simulations reveal that engulfment metabolism increases across the full body size of the larger rorqual species to nearly 50 times the basal metabolic rate of terrestrial mammals of the same body mass. Moreover, they suggest that the metabolism of the largest body sizes runs with significant oxygen deficits during mouth opening, namely, 20% over maximum VO2at the size of the largest blue whales, thus requiring significant contributions from anaerobic catabolism during a lunge and significant recovery after a lunge. Our analyses show that engulfment metabolism is also significantly lower for smaller adults, typically one-tenth to one-half VO2/max. These results not only point to a physiological limit on maximum body size in this lineage, but also have major implications for the ontogeny of extant rorquals as well as the evolutionary pathways used by ancestral toothed whales to transition from hunting individual prey items to filter feeding on prey aggregations. © 2012 Potvin et al.
Pyenson N.D.,Smithsonian Institution |
Goldbogen J.A.,Cascadia Research Collective |
Shadwick R.E.,University of British Columbia
Biological Journal of the Linnean Society | Year: 2013
Rorqual whales (crown Balaenopteridae) are unique among aquatic vertebrates in their ability to lunge feed. During a single lunge, rorquals rapidly engulf a large volume of prey-laden water at high speed, which they then filter to capture suspended prey. Engulfment biomechanics are mostly governed by the coordinated opening and closing of the mandibles at large gape angles, which differentially exposes the floor of the oral cavity to oncoming flow. The mouth area in rorquals is delimited by unfused bony mandibles that form kinetic linkages to each other and with the skull. The relative scale and morphology of these skeletal elements have profound consequences for the energetic efficiency of foraging in these gigantic predators. Here, we performed a morphometric study of rorqual mandibles using a data set derived from a survey of museum specimens. Across adult specimens of extant balaenopterids, mandibles range in size from ∼1-6m in length, and at their upper limit they represent the single largest osteological element of any vertebrate, living or extinct. Our analyses determined that rorqual mandibles exhibit positive allometry, whereby the relative size of these mandibles becomes greater with increasing body size. These robust scaling relationships allowed us to predict mandible length for fragmentary remains (e.g. incomplete and/or fossil specimens), as we demonstrated for two partial mandibles from the latest Miocene of California, USA, and for mandibles from previously described fossil balaenopterids. Furthermore, we showed the allometry of mandible length to body size in extant mysticetes, which hints at fundamental developmental constraints in mysticetes despite their ecomorphological differences in feeding styles. Lastly, we outlined how our findings can be used to test hypotheses about the antiquity and evolution of lunge feeding. © 2012 The Linnean Society of London.
Faerber M.M.,University of Wales |
Baird R.W.,Cascadia Research Collective
Marine Mammal Science | Year: 2010
Anthropogenic activities must be monitored to determine effects on marine mammal species, but the difficulty lies in how to measure impact. Mass strandings of beaked whales have occurred in association with naval exercises, with two species most affected, Cuvier's (Ziphius cavirostris) and Blainville's (Mesoplodon densirostris) beaked whales. Six such events have occurred in the Canary Islands but there have been no reported mass strandings in Hawai'i. We assess the hypothesis that factors that influence the likelihood of strandings occurring and/or being detected differ between the Canary and main Hawaiian Islands, such that beaked whale stranding/detection probabilities will be lower in Hawai'i. On an archipelago-wide basis, nearshore bathymetric comparisons indicate that the Canaries have a greater proportion and a total greater amount of appropriate beaked whale habitat closer to shore, with a steeper slope. Hawaiian shorelines are more dominated by steep cliffs, human population density is much lower, and human population per kilometer of shoreline is 53% lower than in the Canaries. All of these factors suggest that there is a higher probability of a carcass washing onshore and being detected in the Canary Islands. It cannot be concluded that the lack of mass strandings in Hawai'i is evidence of no impact. © 2010 by the Society for Marine Mammalogy.
Goldbogen J.A.,Cascadia Research Collective
Proceedings. Biological sciences / The Royal Society | Year: 2013
Mid-frequency military (1-10 kHz) sonars have been associated with lethal mass strandings of deep-diving toothed whales, but the effects on endangered baleen whale species are virtually unknown. Here, we used controlled exposure experiments with simulated military sonar and other mid-frequency sounds to measure behavioural responses of tagged blue whales (Balaenoptera musculus) in feeding areas within the Southern California Bight. Despite using source levels orders of magnitude below some operational military systems, our results demonstrate that mid-frequency sound can significantly affect blue whale behaviour, especially during deep feeding modes. When a response occurred, behavioural changes varied widely from cessation of deep feeding to increased swimming speed and directed travel away from the sound source. The variability of these behavioural responses was largely influenced by a complex interaction of behavioural state, the type of mid-frequency sound and received sound level. Sonar-induced disruption of feeding and displacement from high-quality prey patches could have significant and previously undocumented impacts on baleen whale foraging ecology, individual fitness and population health.