Dogs have specifically been breeding to perform these tasks, while dolphins just can do it "out of the box". Also i suspect killer whales would out do dolphins in many tasks, especially those requiring social intelligence and language. Maybe elephants wouldn't do much worse either, but they were probably too difficult to study because of their size.
Dogs have been bred to perform these tasks, but they've also evolved to become dependent on humans. If humans had never entered the situation, who knows where the intelligence of other animals would be.
I think wolves and foxes give us a good picture of what dogs would be like without human intervention.
I assume that's removing primates from the running where there are probably a dozen species to mention.
and octopus?
Problem for octopi are that they are not social animals, so their intelligence consists mostly from problem solving.
sounds almost like me :)
actually they can communicate by changing colors as I understand it
I don't know if there is any truth to this, but I have heard that octopus have a "different" sort of intelligence than we are used to. It's more innate to them, so they are capable of learning much less but they have some very advanced "pre-baked" capabilities.
Most of what I've seen is that they have fairly amazing learning ability when it comes to problem solving, and also when it comes to applying observations of other octopi solving problems (e.g., an octopus can figure out how to work mechanical things that pose barriers to food, and one octopus can watch another octopus work such an mechanism once to learn how to do it themselves.)
Crows as well. One radio report I recall discussed how they not only recognize human faces but can inform others about individuals that threaten them. The researcher who was featured has to wear a mask when he is performing experiments or else he risks being attacked by other birds while walking around campus...