Animal of the Week March 31, 2014 — How deep is your dive?

This week's animal of the week is a record-holding mammal, able to dive deeper or longer than any other. As reported in PLOS One, Ziphius curvirostris (Cuvier's beaked whale) can dive almost 3 km in depth remaining submerged for over 2 hours.

When George Cuvier first described this species, he thought it was an extinct species, but now they are known to be found around the world in all oceans except the high polar regions. The beaked whales are a widespread group of cetaceans, and despite there being quite a few species that are probably not uncommon, their open-ocean deep-diving habits mean they are poorly known—all but a few species having escaped the attention of the whaling industry, whence a lot of our knowledge of whales comes (not that that makes whaling a good thing). The northern bottlenose whale, one of which popped up the Thames to die back in early 2006, is also a species of beaked whale.

Beaked whales are named for their mouth, which notably protrudes from their head. They typically have only one pair of teeth and in many species these only erupt through the gums in the males—in older Cuvier's males these tusks protrude from the jaw, and combat between males are likely the cause of the parallel striations seen on the skin of many male whales. They hunt by sucking up squid and small fish on their forays into the deep ocean. To aid their impressive diving feats they have a very high proportion of myoglobin (the equivalent of haemoglobin that permeates muscle tissue), which keeps their muscle well oxygenated on deep dives, they are able to collapse the air cavities in their bodies on diving, and they have a very waxy blubber.

The previous record holder for mammal deep diving was an elephant seal that dove not quite as far for not quite as long—such is the nature of records. It's possible that other beaked whales and sperm whales dive even deeper, but until we know better, we salute you Cuvier's beaked whale. Great diving!

Animal of the Week March 16, 2014 -- first butterfly of the year

I'm a simple and predictable man. Just as I will let out a yelp of glee at the first bee of the season, the first sighting of a butterfly each year, usually a few weeks later, also elicits a broad grin. And that first butterfly is invariably this week's animal Gonepteryx rhamni (brimstone)—spotted this weekend in NW5.

The brimstone is somewhat unusual among UK butterfly species in that it hibernates as an adult, rather than migrating here from warmer climes, or overwintering as a pupa as many other butterflies do. This habit means it is often the first butterfly one sees in the year.

The brimstone is almost unmistakable. Other yellow butterflies, such as the rarer clouded yellows have substantial black markings on their wings and don't have the same, odd, geometrical wingshape of the brimstone.

The name brimstone obviously comes from their colour (related to sulphur, also known as brimstone, and yellow in colour). But oddly enough, one theory for the origin of the word butterfly is that it originated with the brimstone—ie, the butter-coloured fly.

However, a lot of other old words for butterfly in Germanic languages derive from a mediaeval belief that butterflies were witches in disguise that would steal unguarded milk, cream or butter; and this may be the true origin of the word. These words have been replaced with other terms related to Latin Papilio, but the German word for butterfly schmetterling is thought to derive from smetana, the Czech word for cream, and the belief that butterflies were milk-thieving witches.