鬼天竺鼠

Compound of 鬼(おに) (oni, “ghost”) + 天竺鼠(てんじくねずみ) (tenjikunezumi, “guinea pig”)

鬼(おに)天(てん)竺(じく)鼠(ねずみ) or 鬼天竺鼠(オニテンジクネズミ) • (onitenjikunezumi) 

1. capybara (Hydrochoerus hydrochaeris)

   Synonym: カピバラ (capibara)

As with many terms that name organisms, this term is often spelled in katakana, especially in biological contexts (where katakana is customary).