I was today years old when I discovered, on a whim, that wolves will follow you by swimming. So, with a stack of stamina potions, and treading water, you don't need a longship to transport wolves small distances. You can walk along the shoreline to the place where you want to bring them and then swim to the nearby continent/island where you want to breed them. With a halfway-decent swim skill, you can relocate an entire colony of wolves to nearby islands. You don't even need to use the "cart boat." This opens up great opportunities!
UPDATE!
Operation "Wolf Swim" is a success! And, there are 2-star wolf cubs all along the route where I stopped to get rested buff. I was taking five with me, and they had deer and boar to eat along the way. I was able to swim the channel with three stamina potions and eyescream, onion soup, and turnip stew for stamina foods. Now I have five 2-star wolves in a pen near the Elder altar.
Source: https://www.reddit.com/r/valheim/comments/10rqxpd/well_ill_be/
