Stranding and post-mortem investigation of a Dwarf Sperm Whale

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Dwarf sperm whale strands in Jurien Bay:

On the 31st of March 2016 a Dwarf Sperm Whale (Kogia sima) was reported live stranded in Jurien Bay to Paul Jennings, Jurien Marine Park Coordinator and Chris Phillips, District Wildlife Officer, Department of Parks and Wildlife. Despite efforts to refloat it to free it, it restranded and its condition deteriorated, hence the decision was made to euthanase it on humane grounds (Image 1).

Dwarf sperm whale stranded in Jurien Bay, Western Australia.

Image 1. Dwarf sperm whale stranded in Jurien Bay, Western Australia. Taken in the field immediately following euthanasia (photo courtesy: DPaW DWO Chris Phillips).

Wildlife Officer Phillips very kindly transported the carcase to Murdoch University, where a post-mortem examination was carried out on 1st April by veterinary pathologist Dr Nahiid Stephens. This was a very valuable opportunity – relatively little is known about this species and most existing information comes from the study of stranded individuals.

 

Preliminary post mortem summary:

Morphometric measurements and a genetics sample (to confirm species and characterise any regional genetic differences) were taken; the individual was in good to excellent body condition. Changes present within the reproductive tract confirmed the individual to be a sexually mature adult female; a small amount of milk  was present in the mammary glands, and so it may have been separated prior to stranding from a dependent juvenile/calf. A heavy gastric burden of Anisakis sp. nematodes was present; however no overt cause of stranding was identified on gross post-mortem examination. C1 and C2 stomachs also contained numerous squid beaks and otoliths, indicating recent feeding; fragments of translucent orange material that broke up easily with gentle handling were also present (Image 2), they are believed to be semi-digested portions of crustacean exoskeletons.

 

Kogia image 2

Image 2. Orange material from C1/C2 stomach compartments – presumed crustacean exoskeleton (photo courtesy of Murdoch University PhD candidate Elitza Germanov).

Further histopathological investigation continues, including detailed examination of the heart to rule out cardiomyopathy and myocardial degeneration as a potential cause of stranding, as has been reported in Kogia sima and Kogia breviceps (latter = Pygmy Sperm Whale) from the coastal US Atlantic Ocean and the Gulf of Mexico (Bossart et al 2007). MUCRU and Dr Stephens would like to thank DPaW and in particular DWO Chris Phillips for their efforts to allow us this rare opportunity to study this individual.

For more information about Murdoch University’s Marine Mammal Health Project, click HERE.

This blog was written by Dr Nahiid Stephens. Please contact Dr Stephens should you have any questions.

 

 

 

Reference: Bossart GD, Hensley G, Goldstein JD, Kroell K, Manire CA, Defran RH, Reif JS. ‘Cardiomyopathy and Myocardial Degeneration in Stranded Pygmy (Kogia breviceps) and Dwarf (Kogia sima) Sperm Whales.’ Aquatic Mammals. 2007, 33(2): 214-222.

 

 

Lars Bejder PhD
Lars Bejder PhD
Professor Lars Bejder PhD is the Research Leader of the Murdoch University Cetacean Research Unit.
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