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Causes of Live Strandings in Cetaceans
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Causes of Live Strandings in Cetaceans


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  • 1. By Kaitlin Prince
    Spring 2011
    Animal Behavior 4411.001
    Causes of Live Strandings in Cetaceans
  • 2. Outline
    Overview of cetaceans and strandings
    Most susceptible species
    Possible causes
    Geomagnetic disturbances
    Possible reasons for spatial and temporal distribution
  • 3. What are Cetaceans?
    Figure 1: Order: Cetacea
    Whales, dolphins, porpoises
  • 4. 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?
  • 5. 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
  • 6. 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
  • 7. 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)
  • 8. 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)
  • 9. 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
  • 10. 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)
  • 11. 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).
  • 12. 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
  • 13. 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)
  • 14. 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)
  • 15. 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)
  • 16. Figure 3: Spatial Distribution of Strandings in Oregon and Washington between 1930-2002
    Possible Causes for Spatial Distribution
    • Summer migration into shallow waters
    • 17. Increased human traffic
    • 18. Patterns in prey movement
    Entire Slide: (Norman, et. al., 2003)
  • 19. 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.
  • 20. 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.
  • 21. 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.