'Opens' in the Bible

"I'm taking the descendants of Levi for myself from among the Israelis in place of every first-born who opens the womb. The descendants of Levi belong to me

But if the LORD creates something new, so that the ground opens its mouth and swallows them and everything that belongs to them and they all descend directly to Sheol while still alive, then you'll know that these men have spurned the LORD."

Everything that opens the womb, any living thing that they bring to the LORD whether from human beings or animals are for you. Just be sure that you redeem the firstborn of people and the firstborn of unclean animals.