Question: What is the biggest deep sea animal?

James Bell answered on 19 Jun 2014:

Well that depends if you mean animals that spend all their time in the deep sea (in which case it would probably be a colossal squid – the biggest squid we know of that can maybe grow up to 14m long!) or animals that spend some of their time in the deep sea (in which case it would be a sperm whale – which is a very big animal indeed and can weigh up 50 or 60 tons – that’s the same as 10-12 male african elephants)

Most animals in the deep sea don’t grow very big and this is because most of the deep sea is quite limited by how much food there is – there are no plants and only very limited areas where when organic matter is made so most places rely on food that sinks down from near the surface. It’s estimated that only about 1% of the food made by plants in surface waters ever makes it into the deep sea, and it gets less and less the deeper you go. In the deep north pacific (about 5000m and a long way from land), this food falls at rates of only a few mm every 1000 years, so the animals have to be very small to live off such a tiny amount of food