A platypus has to make some sort of vocalisation, and the nature of the vocalisation depends upon the shape and structure of its voice box. Growling just happens to be the noise made by young platypuses, or males engaged in territorial behaviour.
No. America does not have platypuses. Platypuses are endemic to eastern Australia.
No. Kangaroos do not growl.
Platypuses is the correct spelling.
Yes, tulips do growl, but their growl is so soft that you can't hear them.
Growled is the past tense of growl.
You spelled the word growl correctly. The large dog had a deep growl, but the small dog had a high-pitched growl.
Platypuses were not invented. They were discovered by someone.
Platypuses are found only in Australia.
Are PLATYPUSES born alive?
Platypuses are considered carnivores.
Platypuses are nocturnal. They come out at night.
Platypuses have dense fur.