Specimen of the Week: Week Eighty-Two
By Emma-Louise Nicholls, on 6 May 2013
The sun is here!! Wow, I had genuinely forgotten what being warm outdoors felt like. Other than the sweaty sort of warmth that comes from running for buses. Being rather more reptilian than the average Homo sapiens I am very much a hot weather person. My DNA decided at an early stage of my life to go against the grain of our hominid evolutionary path, the result of which is that I am a shockingly inefficient endotherm. Over the years I have spent any moment I am able, out of the UK, inserting myself wherever possible into a country with greater levels of UV. One of my favourite placements was at the Florida Museum of Natural History where I worked on a shark exhibition. Whilst there I saw and fell head over heels in love with a certain species that unquestionably warrants the use of words such as ‘beautiful’, ‘awe-inspiring’ and ‘breath taking’. We happen to have a foetus of this species in the collection, which makes for a good excuse to tell you all about this magnificent animal. This week’s Specimen of the Week is…
**The Killer Whale Foetus**
1) The killer whale, rumour has it, is a name coined by fishermen in ye olde days that witnessed them killing whales, and subsequently named it ‘killer whale’. In the modern day however, many conservationists feel that the name ‘killer whale’ gives the animal negative connotations and prefer to use the name orca. This doesn’t seem unreasonable and so our specimen shall henceforth be known as the orca foetus.
2) It is reported by some, for whom I do not vouch, that the orca is the most geographically widespread mammal after humans. I would expect say, rats and mice, to have something to squeak about that, for example. Orca are found throughout the world’s oceans, and in semi enclosed areas such as the Gulf of Mexico, the Gulf of California, the Red Sea and the Arabian Gulf. Bizarrely not minding cooler waters, they inhabit areas from the poles to the equator.
3) Despite being somewhat ubiquitous, orcas are sadly endangered. The culprit is of course us. Above and beyond direct affects such as hunting, we also are really quite prolific at destorying oceanic habitats and even, sadly, ramming them with boats. Collisions with boats is common in the world of aquatic animals, and many whales, dolphins and sharks (for example) show scarring due to propeller blades. Many more, aren’t that lucky.
4) Orca hunt using echolocation, a bit like a monochromatic overgrown wingless bat. If you like. Although, as with most mammals, they will pick and choose what they eat depending on what comes along at the time, orca mostly prefer other mammals such as seals, sea lions and dolphins. It is the only cetacean (whales and dolphins) to routinely do so. They are also noteworthy in the cetacean world for their comparative fin ratio. Whilst researching for this blog I had a ‘holy baloney’ moment when I read that the dorsal fin of a male orca can grow up to an extremely impressive 1.8 metres in height. That is taller than me darn it! Perhaps needless to say, that is the largest dorsal fin of any cetacean. Respect.
5) Although orca will begin to be sexually useful at the age of 15, they will continue to grow until their 21st birthday. Give or take. Whilst there is no set breeding season, within the northern hemisphere calves tend to be born between October and March, whereas in the Southern hemisphere it appears to be year round. The beautiful monochromatic appearance of the orca becomes more distinctive with age, as the white areas of a calf’s body tend to be slightly orange in colour. One of the reasons that hunting is an issue for orca populations is because females will only give birth once every 3 to 8 years and births in females over the age of forty have never been recorded, severely limiting the number of children a female orca can have in her lifetime. For the remaining 50 or so years of their lives, the female orcas assume a grand-parental role in which they pass on experience, and influence the behaviour of the younger individuals within their pod.
Emma-Louise Nicholls is the Museum Assistant at the Grant Museum of Zoology