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Causes of Live Strandings in Cetaceans

Causes of Live Strandings in Cetaceans






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    Causes of Live Strandings in Cetaceans Causes of Live Strandings in Cetaceans Presentation Transcript

    • By Kaitlin Prince
      Spring 2011
      Animal Behavior 4411.001
      Causes of Live Strandings in Cetaceans
    • Outline
      Overview of cetaceans and strandings
      Most susceptible species
      Possible causes
      Geomagnetic disturbances
      Possible reasons for spatial and temporal distribution
    • What are Cetaceans?
      Figure 1: Order: Cetacea
      Whales, dolphins, porpoises
    • Basic Information
      Strandings are when cetaceans swim or float into shallow water and become unable to return to deep water.
      Cetaceans can become stranded dead or alive.
      Dead strandings occur due to tides.
      Skin damage and overheating (caused by sun exposure)
      Respiratory distress (caused by body weight not supported by water)
      Drowning (high tide moves in and covers the blowhole)
      What are Strandings?
    • Basic Information
      Possible Causes
      Mass strandings occur when multiple organisms become stranded at once.
      These strandings point to causes that would affect the entire group.
      Geomagnetic disturbances
      Mass Strandings
    • Basic Information
      Possible Causes
      When one organism becomes stranded by itself.
      More common than mass strandings.
      Most likely caused by factors that only affect one individual, rather than the entire group.
      Old age
      Individual Strandings
    • More Susceptible
      Less Susceptible
      Species that live in pods
      Species that spend most of their time away from the shore in deep waters
      Toothed whales
      Beaked whales
      Solitary species
      Species that spend most of their time in shallow waters
      Baleen whales
      Which Species are Most Susceptible?
      Entire Slide: (Norman, Bowlby, Brancato, & Calambokidis, 2003)
    • Possible Causes: Parasites
      Parasites have been found in necropsies of stranded cetaceans in various locations across the world.
      Stranding can be due to multiple parasitic infections, rather than just one.
      Parasites can damage organs, including the brain, which can lead to sickness, stranding and/or death.
      Common parasitic infections
      Trematodes (flatworms or flukes)
      Nematodes (roundworms)
      Entire Slide: (Daily, & Stroud, 1978)
    • Toxic Pollution
      Material Pollution
      47% of bacteria likely originated from fecal matter (Parsons, & Jefferson, 2000)
      Organochlorine compounds (such as PCBs)
      Ingested by eating infected prey (Jarman, Norstrom, Muir, Rosenberg, Simon, Baird, 1996)
      Fishing nets
      Boat propellers
      Possible Causes: Pollution
    • Possible Causes: Age
      Table 1: Juveniles present in strandings in South Australia between 1881-1989
      28% of strandings between were juvenile
      Percent of juveniles varied greatly among species
      Highest percent = Minkewhale
      Possibly caused by lack of experience
      Entire Slide: (Klemper, & Ling, 1991)
    • Possible Causes: Geomagnetic Disturbances
      Cetaceans use weak geomagnetic signals for orientation, navigation and/or piloting (Kirschvink, Dizon, & Westphal, 1986).
      High prevalence of cetacean strandings in areas with local magnetic activity (Kirschvink, et. al., 1986).
      Migratory animals follow lines of magnetic minima and avoid areas of magnetic gradients (Kirschvink, et. al., 1986).
      The pattern of the disturbance is more important than the absolute level (Klinowska, 1986).
    • Determination of Biological Significance
      Open Questions
      Area affected vs. available habitat
      Behavioral disruption
      Long-term exposure
      Trauma due to sound impact or reaction to sound
      Aspect of sonar that is harmful (pressure, frequency, signal usage)
      Gradual interaction or sudden onset
      Possible Causes: Sonar
    • Possible Causes: Sonar cont.
      Greece 1996
      Low to mid-range sonar frequencies
      Cuvier’s beaked whales
      Bahamas 2000
      Mid-range sonar
      Examined specimens showed cerebral ventricular and subarachnoid hemorrhages
      Madeira 2000
      Cuvier’s beaked whales
      Inner ear hemorrhages
      Canary Islands 2002
      Three different Ziphiidae species
      Inner ear hemorrhages and edema
      Entire Slide: (Norman, et. al., 2003)
    • Figure 2: Temporal Distribution of Strandings in Oregon and Washington between 1930-2002
      Figure 3: Temporal Distribution of Strandings in South Australia 1881-1989
      Temporal Distribution of Strandings
      (Norman, et. al., 2003)
      (Klemper, & Ling, 1991)
    • Possible Causes for Temporal Distribution
      Long Term Increases in Stranding Occurrences
      Increased human traffic
      Increased species abundance
      Oceanographic changes
      Speed, sudden changes, pressure, etc.
      Migration patterns
      Changes in observer effect
      Increase in human interest/population/coastline activities
      Changing governmental policies concerning strandings
      Increased possible causes
      Pollution due to human population
      Sonar usage due to military activity
      Temporal Distribution of Strandings cont.
      Entire Slide: (Norman, et. al., 2003)
    • Figure 3: Spatial Distribution of Strandings in Oregon and Washington between 1930-2002
      Possible Causes for Spatial Distribution
      • Summer migration into shallow waters
      • Increased human traffic
      • Patterns in prey movement
      Entire Slide: (Norman, et. al., 2003)
    • Conclusion
      Strandings have many possible causes and each case should be examined to determine the most likely cause.
      Strandings have been increasing over long periods of time either due to increased reporting or increased causes.
      More research is needed to determined which causes are most prevalent and how strandings can be prevented.
    • References
      Daily, M., Stroud, R. Parasites and associatedpathology observed in cetaceans stranded along theOregon coast. J. of Wildlife Diseases. 14, 503. 1978.
      Jarman, W., Norstrom, R., Muir, D., Rosenberg, B., Simon, M., Baird, R. Levels of organochlorine compounds in the blubber of cetaceans from the west coast ofNorth America. J. Marine Pollution Bulletin. 32(5), 426-436. 1996.
      Kirschvink, J., Dizon, A., Westphal, J. Evidence fromstrandings for geomagnetic sensitivity incetaceans. J. Biol. 120, 1-24. 1986.
    • References cont.
      Klemper, C., Ling, J. Whale strandings in south Australia (1881-1989). Transactions of the Royal Society of S. Australia. 115(1), 37-52. 1991.
      Klinowska, M. Cetacean live stranding dates relate togeomagnetic disturbances. J. Aquatic Mammals. 11.3, 109-119. 1985.
      Norman, S., Bowlby, C., Brancato, M., Calambokidis, J. Cetacean strandings in Oregon and Washingtonbetween 1930 and 2002. J. Cetacean Res. Manage. 6(1), 87-99. 2004.
      Parsons, E., Jefferson, T. Post-mortem investigations onstranded dolphins and porpoises from Hong Kongwaters. J. of Wildlife Diseases. 36(2), 342-356. 2000.