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 Parasites Pollution Age Geomagnetic disturbances Sonar Possible reasons for spatial and temporal distribution Conclusion References
What are Cetaceans? Figure 1: Order: Cetacea Animalia Chordata Mammalia Cetacea Whales, dolphins, porpoises (http://www.politicsandcurrentaffairs.co.uk/Forum/world-events/67461-whaling-commission-head-says-japan-must-compromise.html)
Basic Information Complications 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) Dehydration 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. Parasites Pollution Age Geomagnetic disturbances Sonar 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. Disease Parasites Old age Injury 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 Bacteria 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 Trash/debris 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
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.