warning, spoilers!
I find 24 dogs:
start island - 1
portal to the cubic world - 2
capybara lake - 2
central island - 4
desert stage - 2
fire island - 3
waterfall - 1
flying island - 2
2D world - 2
cave with nosy dogs - 2
boss - 3
sorry, if I'm being too obnoxious. But i want to find all dogs too much!