For every successful attempt at domestication, as is the case for some wolves, cows and horses, there were a few attempts that were complete failures. Certain wild animals just can’t be tamed due to aggression while others just avoid humans how ever they can, making it difficult to form a bond with them. Below are five animals that we seriously failed to domesticate.

1. Hippopotamuses 

What made anyone think they could tame such a wild and aggressive animal? Hippos are known for taking the lives of over two thousand people every year—that’s more than lions, leopards, elephants, rhinoceroses and buffaloes combined. Despite their size, they’re incredibly fast and have very large teeth that can end a life in mere seconds. This was the case of a South African farmer named Marius Els who he was trying to domesticate one he named Humphrey.

2. Moose

A few centuries ago, King Karl XI of Sweden decided that horses weren’t ferocious enough in battle. Instead, he wanted an animal that would send his enemies fleeing in terror upon first sight. So he settled on the moose. However, this was a very bad idea for a number of reasons. First of all, moose are very aggressive animals, so approaching them alone was a huge risk, especially during mating season. There were other attempts to harvest them for meat but that too was unsuccessful.

3. Elephants

Elephants, although they have been captured and tamed for the past 3,000 years, are not classified as domestic animals because they have not been selectively bred. They’re still wild animals, regardless of whether they’ve been living in captivity their entire lives. And being the wild animals they are, elephants are still prone to moments of unpredictability that unfortunately leads to a rampage. Elephants in the wild are even more prone to this and there have been several incidents of elephants attacking people, especially when threatened.

4. Great White Sharks

It’s impossible to keep a great white shark in a tank. This is because they don’t last long in these environments and typically die within a few days of captivity. The longest one has lasted in a tank is just 16 days. These sharks also resort to bashing their head against the aquarium’s glass walls, and continue to do so until it dies or is freed. Another reason they don’t fare well in captivity is because sharks require lots of water to both swim in and breathe. Let’s not forget about their aggressive nature and they also need their prey to be alive, otherwise they won’t eat it.

5. Zebra

Zebras and horses, along with donkeys, are part of the Equidae family. So there should be no problem domesticating them, right? Wrong! Zebras are extremely aggressive and avoid humans because they live in hostile environments with predators such as crocodiles, leopards, lions and hyenas. They’re really fast too and are difficult to catch. And if someone does manage to catch one, they won’t be able to ride them for too long. The zebras will start fighting back and will kick and bite, all in an attempt to escape captivity.