I visit Canada at least once a year.
The guaranteed minimum questions are:
- Where are you headed?
- How long are you staying?
- What are you bringing with you?
Sometimes this is all I get asked, but I've been grilled with dozens of questions before too. And I've been pulled aside for a random vehicle search two out of the past five times I've gone... so I definitely would declare it.
It's a good sign that the US customs agent didn't give any hassle bringing it in... in my experience crossing into the US is often more scrutinized, even for a US citizen. But then again I'm not sure how Canadian import laws differ.