This is because they act as wild games, as long as they are part of the winning combination, they bring the x3 multiplier. This means that for your balance, the biggest victory for a walrus (usually 3,333 credits) can be a bigger 9,999 credits. To move from a casual player to an experienced explorer, you need to trigger 8 free games by finding three or more scatter symbols.
When you finish the job (and do a good job), you need to sit down and hope to appear wild during this time. Seeing that the field already has its multiplier, the spoils of your snow journey can become very large.