Sample chapter

Take the largest oil tanker currently in operation in the world and empty it of oil. Now gather together a bunch of hippos (the regular-sized ones, not the pygmy ones) and pack them into the empty space as tightly as you can. How many do you think you could fit into the tanker?

A. 1,000

B. 5,000

C. 10,000

D. 30,000

E. 50,000

F. 250,000

G. 500,000

H. 1,000,000

The answer

F: 250,000

Let’s start with the easy part – the tanker. The largest oil tankers in the world are the two TI Class supertankers built in 2002–3 by Daewoo Shipbuilding and Marine, currently named the TI Oceania and the TI Europe (not the most exciting names, we know). Their two sister ships, the TI Asia and the TI Africa, no longer operate as tankers, having been converted into floating storage and offloading vessels – essentially massive oil-processing and storage platforms.

These ships can carry 503,409,900 litres (132,986,826 US gallons) of oil, more than three million barrels, and fully laden they weigh more than half a million tonnes. They are not the largest oil tankers ever constructed – that record is held by the ship named The Seawise Giant when it launched in 1979, which weighed almost 650,000 tonnes when full. Having survived being set on fire, sunk and refloated during the Iran–Iraq war in 1988, it too has now become a floating offshore platform. Nor are they the longest ships on the seas – despite being an astonishing 380 metres long; the Barzan container ship which launched in 2015 is 400 metres long. The Titanic was a mere tiddler in comparison at 269 metres, and long weighing a mere 50,000 tonnes. Yup, when full these tankers weigh the same as ten Titanics. 

Now to the hippos. Hippos are big. Sure, not oil tanker big, but they are the third largest living land animal, and weigh around 1,500 kg – one and a half tonnes.

How much space will one take up in an oil tanker, though? A hippo has a volume of around two cubic metres, or two thousand litres. If you get them to tuck their legs in, you can stack them together pretty well. That means with a capacity of 503,490,900 litres you can fit around 250,000 hippos into the largest oil tanker in the world.

Today, hippos can only be found in the wild in Africa, with one exception, which we shall come on to shortly. In the past, however, they were much more widely spread – 30,000 years ago you could have found them happily roaming around in Europe, even in the UK. They also spread far across Asia into India and Indonesia. That exception? Ah yes. In the 1980s the Colombian drug lord Pablo Escobar built a private zoo at his ranch near Medellín (if you have watched the TV series Narcos you will have seen a re-creation of it. When Escobar was killed in 1993, the animals from his zoo were rehoused, apart from the hippos, which were deemed to be too difficult and dangerous to handle. So they were left on the estate, where they continued to happily munch vegetation and breed. As their numbers increased, so did the amount of land they needed to feed from, and so they spread. There are now estimated to be between 50 and 70 hippos living in the region, and, if left unchecked, this number is likely to double in the next ten years.

Hippos may appear to be slow, ungainly beasts, but they are exceptionally graceful swimmers and remarkably fast on land. They can run at 30 kph (19 mph). They are also very dangerous – they kill more humans (around 500 per year) than any other large land animal. Lions and tigers and bears, oh my, but also, oh not nearly as deadly as these river-horses (that’s what ‘hippopotamus’ means in Greek).

Of the dozens of species of hippo that have existed, only two remain today. For our calculation we have been using what one might think of as the “regular” hippo. As our question suggests, though, there are also pygmy hippos. Now pygmy is a relative term, when the standard-sized beast is so large – these miniature versions can still weigh in at 275 kg (over 600 pounds) and be almost 6 feet (183 cm) long. Now, you are probably wondering how many pygmy hippos will fit into an oil tanker? Don’t worry, we have done the math for you, and the answer is 1,710,000.

Are there enough hippos in the world to fill an oil tanker though? Sadly, no there are not. It is estimated that between 125,000 and 150,000 hippos remain in the wild. For pygmy hippos the situation is even more dire; it has been estimated that fewer than 3,000 of these beasts remain in the wild. Not enough to even fill 1% of our oil tanker.

We would, therefore, rather that you didn’t attempt to check our calculations by actually getting hold of an oil tanker and filling it with hippos.

To find out all the other questions and explanations, get the book!