Sometimes people act surprised when I mention animals in relation to eternity. That shouldn’t seem strange if you’ve read Isaiah’s prophecy (Chapters 11 and 65 are good places to start) and if you understand the Bible’s teaching about the world to come.
Eternity is not a spiritual state as in non-corporeal; it is “the new heavens and new earth” just as John described in his visions. When Paul talks about the “spiritual body” in 1 Cor. 15, he is referring to a body made by the Spirit. Our resurrection bodies will be like the body of our risen Lord whose resurrection body was a physical body (Luke 24:42-43; John 20:27). Why have a physical body if there is no physical realm to inhabit?
The redemption of Creation and the making of a New Creation involves all of Creation, not just humanity. After God originally created the world and the pants and animals, he looked at creation and said that it was good. Our Lord says that the Father knows every sparrow that falls, he feeds the birds, and he clothes the flowers. Why would God do this if he did not take some delight in this?
This is how gracious our God is: he will redeem not only us, but all of his creation; he will leave nothing corrupted by sin or degradation. The One sits on the throne says, “Behold, I make all things new” (Rev. 21:5) and that means everything!