We can’t be sure whether an exotic cactus from Mexico might be growing in the Queensland outback, but if Bob Katter was a scrub bull, you’d be wary of him, fearing he’d been grazing on mescaline.
I don’t know what this means. I often have trouble translating Aussie into English. The article is about an election, and the fate of the independents. And the lead to the article is the cactus metaphor above.