Senate dives into dolphin doozy over ban

We don't know what dolphins are thinking - so why ban them from being kept for entertainment?

That's the opinion of One Nation senator Malcolm Roberts, who on Thursday opposed a Greens motion in the upper house calling for an end to the mammals being used for amusement.

"This is yet another example of the arrogance of the Greens to presume they know what dolphins are feeling and thinking," Senator Roberts told parliament.

He used the example of his daughter's horse named Clancy, who behaves like a herd animal.

But with no companion animal, Clancy loves being with humans and doesn't like horses.

"The point of the matter is that we don't know what animals think," Senator Roberts said.

"Dolphins like humans, that's a fact, that's well known, dolphins are attracted to humans."

He said keeping dolphins in captivity for entertainment funded research and supported curing animals hit by boats.

Labor frontbencher Katy Gallagher said she couldn't top Senator Roberts' speech.

But her party voted against the motion because it was a state issue.

The motion was defeated 49 votes to eight.