As a marine biology student, you often get two different reactions when you tell people what you study. It's either a weird look and a question about 'how can fish be that interesting?', or you get people looking surprised and impressed and saying how interesting that must be. Well, I attended an event that gives that same response all on its own. Last month me and my friends went to watch a dolphin post-mortem. Yep - an actual dolphin dissection.
The event was a joint venture run by the National Marine Aquarium and the Zoological Society of London as part of the monthly adult only NMA|Lates series of events. The post-mortem was part of the work done for the Cetacean Strandings Investigation Programme, which was started in 1990. Around 600 porpoises, dolphins and whales become stranded around the UK coast each year, and this programme ensures that these strandings are recorded and post-mortems completed to identify the reason why the animal died. Since 1990 they have collected data on over 13,000 individual cetacean strandings and carried out 3,600 post-mortem examinations. This helps us to understand the biggest threats to cetaceans and how we can potentially alter our actions to help protect these beautiful creatures. It also provides information about their growth, feeding and about how they lived.
The dolphin we saw had been found on a beach in Worthing 2 weeks previously. There was no visible harm to it, no scars, wounds or fishing net entanglement (which is actually the most common reason for a cetacean's death).
The post-mortem starts with the basics of measuring the animal. Then using a very sharp scalpel, sections of the blubber are cut away. The thickness of the blubber can tell a lot about how healthy the animal is. Measurements and samples of the blubber are taken; last year the team published a paper showing how a pollutant (PCBs) which has been banned in the EU for over 30 years are still found in high levels in the blubber of dolphins.
One of the worst things for me was when they had to cut through the ribs. They cut through them one by one and the sound just went straight through me. With full access to the organs underneath though things got really interesting. The team did say that the dolphin was quite large and did not look underfed but there was still a sad surprise waiting. This dolphin was actually pregnant when it died, the baby was only about 2 months away from being born. The unborn dolphin was removed from the womb and laid out along with the organs one by one.
You would think that after being dead for 2 weeks, and not being frozen, the animal would be really disgusting and stink but I was actually surprised it wasn't as bad as I was expecting. Perhaps the fact that I was sat a few metres away helped. The lovely staff of the National Marine Aquarium were prepared though with sick bags on hand, just in case.
An interesting fact that I learnt was that dolphins actually have three stomachs. Our dolphin's stomach was cut open to reveal a belly full of fish. All the fish were pointed downwards into the stomach, this is the easiest way rather than going against the scales. The stomach also had a whole squid inside, so clearly finding food wasn't a problem for this dolphin.
I found the kidneys particularly fascinating. Instead of two whole ones like we have, dolphins have a more efficient design of lots of tiny almost bubble shaped ones. All the different organs were inspected for damage, malfunction or any deformities, samples of the different cell types were also taken and stored. These samples go towards an impressive collection that will be used by many different science studies for years to come.
The dissection ended with the opening up of the skull to take samples from the brain. Here simply a saw is used to cut through the bone. The sound of this was as bad as when they had to cut through the ribs. The brain was interesting to see as well and not nearly as gruesome as when the eye was removed. That was certainly a sight I could have done without.
Sadly there was no clear reason as to why this dolphin in particular died. The samples taken will be sent off for further testing to try and give a clearer picture of the condition of the dolphin and try and identify why it died.
This whole event was captivating for everyone who was there. Many people thought it was disgusting that I went to watch this, but the work done for this project is invaluable both for us scientists and for the cetaceans. We need to understand them and why these strandings occur to help prevent them when we can. Being able to experience that was a real privilege and the understanding we all gained will stay with us forever.
If you would like to watch a recorded dissection or learn more about the Cetacean Strandings Investigation Programme there are some links provided below.