Cetacean Strandings & Collections
Studying marine mammal life history using dead animals
SWFSC responds to dead marine mammal strandings along the approximately 80 miles (125km) of coastline in San Diego, whereas Sea World responds to live marine mammal strandings in the area. Both organizations are members of the West Coast Marine Mammal Stranding Network, which is part of the broader national Marine Mammal Health and Stranding Response Program
In San Diego County, marine mammal strandings are typically of single animals. Twenty-one different cetacean species have stranded along our beaches, although the most common to strand are long-beaked common dolphins, bottlenose dolphins, short-beaked common dolphins, and gray whales. The greatest number of strandings occur from March through June. Necropsies reveal the most common cause of death in stranded San Diego County cetaceans to be trauma, infectious disease, and domoic acid toxicosis. Several modalities are used to investigate strandings, which include radiology (computed tomography and magnetic resonance imaging), histopathology, microbiology, and occasionally gas analysis.
Stranding investigations and fishery observer programs provide researchers valuable data which are otherwise unobtainable. These programs have provided much of the data we have about cetacean species living off California and in the eastern tropical Pacific. By examining marine mammal carcasses, we can learn about a species’ life history , occurrence, population structure, disease prevalence, and anthropogenic causes of mortality. Tissue samples and skeletal material collected from these animals are archived at SWFSC and museums, respectively. This tissue archive of samples and associated data about individual animals has facilitated technique development, incorporation of photogrammetric data into life history studies, and retrospective studies.
Life History Data
Life history studies describe the reproductive and survival characteristics of a species, including
- How long individuals live
- Age at which they become sexually mature and first reproduce
- How often they breed
- How long they nurse their young
- Where they forage
- What they eat
Combining this data for many individuals of a species enables us to understand the lives of marine mammals and their growth rate potential, which is a critical factor in developing plans for effective management and conservation. Current life history studies at SWFSC are focused on short-beaked common dolphins, long-beaked common dolphins, and bottlenose dolphins that live offshore of California.