What animal(s) symbolize a braggart/self centered character in literature?

The most common symbol of the braggart in European literature is the rooster, often named or personified as Chanticleer. The rooster’s crowing provides a good analogy for the voice of a person bragging, as shown by the common metaphorical use of "crow" for "brag."
At least as far back as the Middle Ages, a bragging rooster appears in French folk tales, such as the 13th-century Reynaud the Fox stories. The Grimm Brothers also included Chanticleer stories. In modern times, Edmond Rostand’s 1910 drama Chanticler (in French) features this boastful rooster.
Perhaps its most well-known incarnation in English is “The Nun’s Priest’s Tale,” which Geoffrey Chaucer includes in The Canterbury Tales. In this version, Chanticleer the rooster is not only boastful but also vain, and these flaws set him up to be fooled by the fox.
Another braggart animal is the donkey or ass, also based on the sound it makes,
https://www.britannica.com/art/Chanticleer-literary-character