Actually, not really. Fuzzy rats have already started to ossify their bones together.. In comparison Adult mice have thinner bones because they aren't built to take the eventual weight like a rat would be. Besides the fact... depending on diet..and how many siblings the rat pup has, they can be a bigger and better meal for an animal than an adult mouse. They also hold more fat and more vitamins from mother's milk than an adult mouse.
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Lucien
1.1 Columbian Redtail Boa (BCI)(Sutekh and Isis)
2.2 Leopard geckos (2 Blizzards (Caine and Goliath), 1 het Blizzard (Lilith) and 1 Tangerine Albino (Tequila Sunrise ...Tiki for short))
0.1 Savannah Monitor (Kiros)
13 rats
1 Gerbil
2 Dogs (Loki and Storm)
2 cats (Sahara and Hercules)