Premise: A pack rat or packrat, also called a woodrat, can be any of the species in the rodent genus "Neotoma". Pack rats have a rat-like appearance with long tails, large ears and large black eyes. Compared to deer mice, harvest mice and grasshopper mice, pack rats are noticeably larger and are usually somewhat larger than cotton rats.
Hypothesis: pack rats are noticeably larger and are usually somewhat larger than cotton rats but loved by many as pets