Lyrics: To have you with me I would swim the seven seas?

Questions

The gastric juices of a snake can digest bones and teeth - but not ----------?

Two rats can become the progenitors of 15,000 rats in less than?

Unlike dolphins, porpoises are not very ----------?

The rear portion of the head of a horse is called the ----------?

Unlike most fish, electric eels cannot get enough oxygen from water. Approximately every five minutes, they must surface to breathe, or they will drown. Unlike most fish, they can swim both ----------?