AnimalsMammals
Rats laugh when you tickle them.
The sound is far above human hearing, and they come back for more of it.
Source
This fact is written from the English Wikipedia article it links to, so you can check every word in one tap. Fact Drop rates that source 4 out of 5 for credibility, and the rating travels with the fact on the back of its card in the app.
More animal facts
Animal facts are the ones people repeat at dinner. Sharks are older than trees, a headless chicken lived for eighteen months, and vampire bats remember who fed them. Every fact here links to the reference it came from.
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