Full title: Finnish wildlife photographer Lassi Rautianen documented the surprising friendship between a male brown bear and a female grey wolf. The pair was seen hunting together, walking together and sharing with each other.
Oh, ok, I understand. No. It's not a sign of submission. Tail down is usually just when they have nothing to say (relaxed), or when they are trying not to be seen (hunting, or hiding).
Generally though, it doesn't mean anything without context.
Second last pic looks like a greeting (non threatening pose), last pic is scared. They clearly spotted the photographer. Female wolves are especially skittish around humans.