I raised a chicken and really think that they are pretty brainless- so I say squid.
Now cow vs octopus- octopus wins hands down.
We went to Sea World in San Diego and got to see the back rooms ( I have a naturalist friend who writes scientific papers for Sea World) One of the other workers told me this story:
Sea World had a tankful of very large and expensive saltwater tropical
fish. They were having problems with fish disappearing – and these were
pricey fish, so naturally they were worried. This pattern continued for a
while – every so often a fish would disappear without a trace from the
tank. No remains, no nothing.
They concluded that one of the aquarium
staff was stealing the fish after hours and selling them to pet stores or
maybe private buyers. But they had no way of figuring out who, and they
didn’t want to levy random accusations, so they decided to set up a hidden
camera to catch the thief in the act.
A few days later the culprit was revealed. Opposite that saltwater tank
was another saltwater tank, wherein lived an octopus. This fellow would
wait until it was late at night, crawl up the glass and out of his tank,
open up the latch to the cover, down across the room to the fish tank, open the top, crawl in, catch a fish, bring it back to his tank and eat it there.
Seriously- could a Cow pull that off?