Isnt the answer to the various animals obvious. Like any other adventurer or colonist, Vikings would have had needs that could have been met by animals, all of which would have been assets of wealth in the homeland.
1. Horse-transportation and war
2. Pig—Makin’ bacon, hmm, hmm, good.
3. Dog —used in war since Roman times in Europe and of course a small cuddly toy for miladies boudoir hut.
I’m pretty sure bacon has been the main driver of civilization.