per ESPN today:
Since the stadium opened in 1927, much of its existence has also been accompanied by the presence of the bats who found shelter in the stadium, often in its upper decks. An estimated 250,000 bats lived in the crevices of Kyle Field and the stadium has long been a "bat-friendly" zone, with signs posted in the old stadium alerting fans to their presence.
The Mexican free-tailed bats, which are the official flying mammal of Texas, were vigilant in controlling insects, with the population eating anywhere from 50 million to 150 million insects a night. The large population of bats was difficult to clean up after, though, with bat guano appearing throughout the stadium and requiring an estimated $150,000 per year in cleanup costs.
How many bats make it back this season to the newly redeveloped Kyle Field, which has undergone a complete renovation in the past two offseasons, is unclear, but it won't be nearly as many as before. During construction of the new Kyle Field, Texas A&M took measures to prevent bats from re-entering the stadium, which led to the mammals taking shelter in other places, like dorms or the campus natatorium, which had to be temporarily shut down this spring after numerous bats made their way in.
http://espn.go.com/college-football/story/_/id/13503957/college-football-stadium-oddities
Go Gophers!!
