Best way to switch from mice to rats

[Pythonfriend]

or you could do it the frankenstein way. connect a frozen-thawed mouse and a frozen-thawed rat with a surgical suture using bio-degradeable thread.

just kidding, would be too much work.

but then.... when someone has a 3000 grams chronic mouser female that needs 10 mice per week and all else fails....

but seriously, first thing to do: just try. creativity is only needed when that fails.