Mam,
According to my knowledge, I would like to submit the following :
For Lord Ganesha, Mouse is the Vahana. i.e. why
"Mooshika Vahana Modhaka Hastha - Sloka
Ga stands for intellect i.e. Buddhi and
Na stands for Vijnana i.e. Wisdom
The Universe is sustained by Ganas (Gods) and Lord Ganapathi
is the Master of all that. i.e. why, We first pray Lord Ganesha
before doing anything, so that things materialise without any vignam
i.e. trouble.
Mooshika - it indicates the ignorance of darkness
Normally the mouse moves only in the darkness. Hence, we can say
that it removes our ignorance and dispels the darkness, leading a bright
path to us to do good things after praying HIM.
We have Nandhi before Lord Shiva
We have Tortoise before Shirdi Sai Baba
We have Simha (Lion) before Kali
Balasubramanian
Ambattur