[Jonty30]

I was reading that these rats can grow as big as 250lbs.

[Does so]

To demonstrate the killing-power of piranha, one was spooked into the water--then shot. Movies of the aftermath eventually showed a large capybyra skeleton.

OTOH, if the capybyra is as smart as the squirrel (another member of the rodent family) at your birdfeeder, there's much to worry about if they get "loose".

Another "rodent" is the beaver, who recently bit a fisherman in Belarus, who died of his wound.