Investigating Marine Mammal Health

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In our first blog from the field, we would like to take the time to introduce ourselves and give you an idea of what we do.

Dr Carly Holyoake is a Veterinarian with a background in conservation medicine and epidemiology and Dr Nahiid Stephens a Veterinary Pathologist. Together, we work as a team to investigate cetacean stranding deaths, feeding back the information gained to the rest of MUCRU and our stakeholders to contribute to the body of knowledge on cetacean health and population management.

So – what happens? We are contacted if a cetacean strands. If it dies and it is retrievable – and not in a significant state of decomposition – then we carry out a post-mortem examination at Murdoch University. This is a process that doesn’t just end at the end of the exam – as we take numerous samples for various researchers (e.g. genetics, aging, stable isotopes and prey species investigations, contaminants, heavy metals).

Sometimes, there is no obvious answer from the post-mortem – but we can still gain a lot of knowledge about the individual and the context in which it has lived (e.g. environment, nutritional status, presence of disease). It can take weeks to months to get the subsequent testing completed in many instances – and often data doesn’t make sense until we see an emerging pattern! Essentially we are collecting background information on disease, including new diseases, and changes in existing disease trends.

However, sometimes we get almost immediate answers about why individuals die. And, with the onset of spring and the likelihood of increased recreational fishing activity in the coming months, we’d like to share with you a particular case which brings home how important it is to manage waste.

In 2009 we carried out a post-mortem on “Cruiser”, a young female Bunbury bottlenose dolphin calf. She had a long history (about a year’s duration – several attempts to free her were not successful) of a fishing line entanglement around her beak. She was in emaciated body condition and we found that the line was wrapped several times around the beak so tight she could hardly open her mouth – and scar tissue had grown over it in places (see photo).

This would have prevented her from hunting and feeding. She also had developed pneumonia – more than likely because her malnourished state had resulted in a reduction in the function of her immune system. Also, the way the line was embedded meant her problems with feeding might have predisposed her to developing pneumonia through aspiration. Sadly, the line was embedded so deep it would have been impossible to remove had she survived.

So please remember to take everything home with you and dispose of it responsibly.

We liaise with MUCRU team members on a daily basis, and our investigations are a multidisciplinary effort with a close collaboration with the Department of Environment and Conservation. We also often get interesting photos from the field for advice on injuries and lesions – more on that next blog!

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