What is this vent for?

Kinda weird thing, but the fan in that vent just come on for the first time for me very recently. It was the second day after it started getting cold, too; 6 months of 90+ degree weather and the fan never came on, yet as soon as it hits the fourties, boom. Its LOUD too. Damn. You have to have your A/C on full blast with all the vents open to cover the sound. It stayed on for about 10 minutes.

 

Cool pic! Now I know what those vents are for.

 

In Australian Prius the battery is cooled by deadly brown and tiger snakes, after all snakes are cold blooded. The vent allows small marsupial hopping mice to enter the cooling chamber achieving population control of the abundant little hopping mouse and feeding the snakes. How green is that?

 

The sound deadening material is used to make the duct not just a little of it.

 

Oh, I was thinking of that little square patch on the inner wall of the right rear panel.