I knew that cats could understand when humans sign to them, since my cat knows the sign for "fish" and the sign for "beg". But, this is the first time I have seen a cat making actual sign language.
That is neat!
To this day I will swear on all I hold Holy that my little cat Tunafish (1978 - 1994) would say clearly in English, with her meows, her two favorite things.
She'd sit by her bowl and the vocalization would be "Me eat?"
She'd sit by the patio door and the vocalization would be "Me out?"
Adorable! I'm not surprised...