The Bible is somewhat silent on the subject of animal immortality and this may be because man, in his arrogance, might feel if there’s an afterlife for an animal there’s nothing he needs to do to be saved himself. I struggled with this since I was a small child and prayed through tears many times that God would let me be with my beloved pets in eternity. The first verse I was inspired by was Romans 8:22-23. “…the whole creation has been groaning . ..” I was impressed that meant not just humans but all created living beings. The more I prayed the more confidence I felt that this is true. Since then, I feel God has led me to many more verses and publications that support this hope .