Hyperallergic published a story on the science and cultural aspects of Egyptian animal mummification, specifically focusing on preservation:
The Conservation Laboratory’s staff often found that the more ostentatious the coffin’s exterior, the more likely the animal within would be nothing but rocks and dirt and maybe a bit of bone. The lion’s share of the animal mummies discovered from ancient Egypt are believed to have been votive offerings, as pet animals were only common among royalty, and animals considered divine and given human-like burials were also rare. The animals were messengers: dead souls who could travel in the afterlife and transport messages to the gods. A crocodile mummy might be offered to Sobek, often depicted with a crocodile head, while the incredible number of ibis mummies in herringbone wrappings or gilded sculptures might have been sent on mortal wings to Thoth, usually shown with as a part-man, part-ibis. A long bronze snake coffin whose slithering body curves up to a sculpted human head was likely a tribute to Atum, and a tiny shrew enshrined it its own metal sarcophagus was possibly a tribute to the sun-god Ra, whom the petite, pointy-nosed mammals served as guardians. A pair of dogs tightly coiled in interlaced linen, doleful eyes painted on their heads, may have been intended for Anubis. Sometimes, mummies of farm and game animals seem to have been sent into the afterlife as food for the deceased.