Wade Paul R.

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Wade
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Paul R.
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  • Article
    Baleen whales are not important as prey for killer whales Orcinus orca in high-latitude regions
    (Inter-Research, 2007-10-25) Mehta, Amee V. ; Allen, Judith M. ; Constantine, Rochelle ; Garrigue, Claire ; Jann, Beatrice ; Jenner, Curt ; Marx, Marilyn K. ; Matkin, Craig O. ; Mattila, David K. ; Minton, Gianna ; Mizroch, Sally A. ; Olavarría, Carlos ; Robbins, Jooke ; Russell, Kirsty G. ; Seton, Rosemary E. ; Steiger, Gretchen H. ; Víkingsson, Gísli A. ; Wade, Paul R. ; Witteveen, Briana H. ; Clapham, Phillip J.
    Certain populations of killer whales Orcinus orca feed primarily or exclusively on marine mammals. However, whether or not baleen whales represent an important prey source for killer whales is debatable. A hypothesis by Springer et al. (2003) suggested that overexploitation of large whales by industrial whaling forced killer whales to prey-switch from baleen whales to pinnipeds and sea otters, resulting in population declines for these smaller marine mammals in the North Pacific and southern Bering Sea. This prey-switching hypothesis is in part contingent upon the idea that killer whales commonly attack mysticetes while they are in these high-latitude areas. In this study, we used photographic and sighting data from long-term studies of baleen whales in 24 regions worldwide to determine the proportion of whales that bear scars (rake marks) from killer whale attacks, and to examine the timing of scar acquisition. The results of this study show that there is considerable geographic variation in the proportion of whales with rake marks, ranging from 0% to >40% in different regions. In every region, the great majority of the scars seen were present on the whales’ bodies when the animals were first sighted. Less than 7% (9 of 132) of scarred humpback whales with multi-year sighting histories acquired new scars after the first sighting. This suggests that most killer whale attacks on baleen whales target young animals, probably calves on their first migration from low-latitude breeding and calving areas to high-latitude feeding grounds. Overall, our results imply that adult baleen whales are not an important prey source for killer whales in high latitudes, and therefore that one of the primary assumptions underlying the Springer et al. (2003) prey-switching hypothesis (and its purported link to industrial whaling) is invalid.
  • Article
    Space use patterns of the endangered North Pacific right whale Eubalaena japonica in the Bering Sea
    (Inter-Research, 2015-07-21) Zerbini, Alexandre N. ; Baumgartner, Mark F. ; Kennedy, Amy S. ; Rone, Brenda K. ; Wade, Paul R. ; Clapham, Phillip J.
    Understanding habitat use of critically endangered North Pacific right whales (NPRWs, Eubalaena japonica) is important to better evaluate the potential effects of anthropogenic activities and climate change on this species. Satellite transmitters were deployed on individual right whales in 2004, 2008 and 2009 to investigate whether their space-use patterns in the Southeastern Bering Sea (SEBS) were influenced by environmental conditions and to assess habitat use in areas of human interest. Whales were monitored for an average of 40 d (range 29-58 d) between July and October, a period in which they inhabited the SEBS shelf. Individuals tagged in 2008-2009 (cold years) remained in the middle shelf domain, travelled at a slower rate and showed a spatially more restricted habitat use than a whale tagged in 2004 (a warm year). Monte Carlo tests suggested that NPRWs associated with the cold pool (remnant winter water in the bottom layer of the middle shelf domain) during cold years, which is likely due to higher copepod abundance and reduced competition with other copepod predators within the cold pool. Telemetry data indicated that a Critical Habitat designated by the US National Marine Fisheries Service encompasses the main feeding range of NPRWs in the Bering Sea. Two whales briefly visited the North Aleutian Basin, an area previously considered for oil and gas development. Small sample sizes precluded conclusive comparisons of space-use patterns among years with significantly different temperature regimes, but we hypothesize that habitat use in the SEBS varies with these regimes because of concomitant changes in the abundance of the whales primary copepod prey. Long-term evaluation of space-use patterns of NPRWs is required to further understand their habits in the feeding grounds in light of global warming and the potential for increased anthropogenic activities.
  • Article
    Beluga whale (Delphinapterus leucas) acoustic foraging behavior and applications for long term monitoring
    (Public Library of Science, 2021-11-30) Castellote, Manuel ; Mooney, T. Aran ; Andrews, Russel ; DeRuiter, Stacy L. ; Lee, Wu-Jung ; Ferguson, Megan ; Wade, Paul R.
    Cook Inlet, Alaska, is home to an endangered and declining population of 279 belugas (Delphinapterus leucas). Recovery efforts highlight a paucity of basic ecological knowledge, impeding the correct assessment of threats and the development of recovery actions. In particular, information on diet and foraging habitat is very limited for this population. Passive acoustic monitoring has proven to be an efficient approach to monitor beluga distribution and seasonal occurrence. Identifying acoustic foraging behavior could help address the current gap in information on diet and foraging habitat. To address this conservation challenge, eight belugas from a comparative, healthy population in Bristol Bay, Alaska, were instrumented with a multi-sensor tag (DTAG), a satellite tag, and a stomach temperature transmitter in August 2014 and May 2016. DTAG deployments provided 129.6 hours of data including foraging and social behavioral states. A total of 68 echolocation click trains ending in terminal buzzes were identified during successful prey chasing and capture, as well as during social interactions. Of these, 37 click trains were successfully processed to measure inter-click intervals (ICI) and ICI trend in their buzzing section. Terminal buzzes with short ICI (minimum ICI <8.98 ms) and consistently decreasing ICI trend (ICI increment range <1.49 ms) were exclusively associated with feeding behavior. This dual metric was applied to acoustic data from one acoustic mooring within the Cook Inlet beluga critical habitat as an example of the application of detecting feeding in long-term passive acoustic monitoring data. This approach allowed description of the relationship between beluga presence, feeding occurrence, and the timing of spawning runs by different species of anadromous fish. Results reflected a clear preference for the Susitna River delta during eulachon (Thaleichthys pacificus), Chinook (Oncorhynchus tshawytscha), pink (Oncorhynchus gorbuscha), and coho (Oncorhynchus kisutch) salmon spawning run periods, with increased feeding occurrence at the peak of the Chinook and pink salmon runs.
  • Article
    Killer whales and marine mammal trends in the North Pacific : a re-examination of evidence for sequential megafauna collapse and the prey-switching hypothesis
    (Blackwell, 2007-10-26) Wade, Paul R. ; Burkanov, Vladimir N. ; Dahlheim, Marilyn E. ; Friday, Nancy A. ; Fritz, Lowell W. ; Loughlin, Thomas R. ; Mizroch, Sally A. ; Muto, Marcia M. ; Rice, Dale W. ; Barrett-Lennard, Lance G. ; Black, Nancy A. ; Burdin, Alexander M. ; Calambokidis, John ; Cerchio, Salvatore ; Ford, John K. B. ; Jacobsen, Jeff K. ; Matkin, Craig O. ; Matkin, Dena R. ; Mehta, Amee V. ; Small, Robert J. ; Straley, Janice M. ; McCluskey, Shannon M. ; VanBlaricom, Glenn R.
    Springer et al. (2003) contend that sequential declines occurred in North Pacific populations of harbor and fur seals, Steller sea lions, and sea otters. They hypothesize that these were due to increased predation by killer whales, when industrial whaling's removal of large whales as a supposed primary food source precipitated a prey switch. Using a regional approach, we reexamined whale catch data, killer whale predation observations, and the current biomass and trends of potential prey, and found little support for the prey-switching hypothesis. Large whale biomass in the Bering Sea did not decline as much as suggested by Springer et al., and much of the reduction occurred 50–100 yr ago, well before the declines of pinnipeds and sea otters began; thus, the need to switch prey starting in the 1970s is doubtful. With the sole exception that the sea otter decline followed the decline of pinnipeds, the reported declines were not in fact sequential. Given this, it is unlikely that a sequential megafaunal collapse from whales to sea otters occurred. The spatial and temporal patterns of pinniped and sea otter population trends are more complex than Springer et al. suggest, and are often inconsistent with their hypothesis. Populations remained stable or increased in many areas, despite extensive historical whaling and high killer whale abundance. Furthermore, observed killer whale predation has largely involved pinnipeds and small cetaceans; there is little evidence that large whales were ever a major prey item in high latitudes. Small cetaceans (ignored by Springer et al.) were likely abundant throughout the period. Overall, we suggest that the Springer et al. hypothesis represents a misleading and simplistic view of events and trophic relationships within this complex marine ecosystem.