Why do we find dead things intriguing? News stories featuring stranded whales, dolphins and porpoises (cetaceans) seem to be hugely popular, with some people even creating websites solely dedicated to documenting the process of whale decomposition. Take the recent stranding of a blue whale on the shores of a small town in Newfoundland, for example. The story has made international headlines, and the whale even has its own blog. While these stories may be a chance to catch an up-close glimpse of a rarely seen marine animal, the true story seems to be going untold. As fascinating as the mysterious lives of cetaceans are, some of the most incredible biological processes begin after life ends.
Why do whales die?
Cetaceans generally live long lives. The estimated life expectancy of a killer whale is 50-80 years, while larger baleen whales like humpback, fin, or blue whales may live 80-90 years. The longest lived cetacean is thought to be the bowhead whale, with researchers estimating they can live over 100 years. In 2007 a bowhead whale was found with a whaling harpoon embedded in its skin dating back to 1879, suggesting the whale was 115-130 years old.
There are a number of ways that whales can meet the end of their lives. So called natural deaths, due to old age, for example, are thought to occur but little is known about such events. Human activity-related causes of death like entanglement, ship strike, pollution, all pose very serious threats to cetaceans and combined cause hundreds of thousands of deaths per year.
There are also a number of infectious diseases that can have fatal effects on cetaceans, as can bacterial, viral, and fungal infections. Non-infectious diseases such as arthritis have also been observed in cetaceans and may eventually lead to death. In many cases, diseases can cause animals to become slow and weak, making them susceptible to predators or unable to properly feed before succumbing to disease.
Almost all cetaceans carry a healthy load of parasites on them – and usually, this is not a problem. But if an individual’s health becomes compromised, these parasite loads can grow to a level that is unmanageable. Studies have revealed parasitism to be the leading cause of stranding in cetaceans.
Where does a dead whale go?
A dead cetacean may end up on a shoreline or beach, or may float in the ocean for a period of time before sinking to the sea floor.
After death, if the carcass ends up on a beach, it plays an important role in its surrounding terrestrial ecosystem, often immediately becoming prey to a number of scavengers and omnivorous species, including seabirds, wolves and bears. In the ocean, sharks, seabirds and fish may prey on a floating whale carcass. If humans intervene, several courses of action can be taken. In some cases, the carcass is buried at the site of stranding to allow for underground decomposition (resulting in a much less smelly beach!). Other times, the carcass is towed out to sea and left in a remote area to eventually sink to the ocean floor.
Another option is to bring the cetacean to a highly-trained scientific team to perform a post-mortem examination called a necropsy. Information from necropsies is incredibly important, and allows researchers access to tissues and material that would otherwise be extremely difficult or impossible to obtain. Many studies that have lead to a greater understanding of cetaceans would not be possible without data collected from necropsies.
What should I do if I find a dead whale?
In British Columbia, if you find a sick, distressed, injured, or dead cetacean or sea turtle it is important to report it to Fisheries and Oceans Canada (DFO) via the Marine Mammal Incident Reporting Hotline by calling 1.800.465.4336. The faster you act, the more quickly trained experts can arrive onsite and take necessary action to help the situation. By reporting these incidents you can help researchers understand why and how these animals are affected by the potentially fatal threats they face.
But what happens next? Find out what can happen to a whale’s body after it dies in part 2 of ‘What Happens when a Whale Dies?’, coming soon!
REFERENCES:
Perrin, W. F., Wursig, B., & J. G. M. Thewissen (Eds.). (2002). Encyclopedia of Marine Mammals. San Diego, USA: Academic Press. – See more at: http://reffor.us/index.php#sthash.LIAqA6h2.dpuf
Caitlin BirdsallIf a cetacean’s health becomes compromised, normally innocuous populations of whale lice (pictured) and barnacles living on the animals skin can become unmanageable.
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