Sobral prison warden Wellington Picanco tells the G1 news website the geese make a lot of noise when they sense "strange movements."
He says the geese roaming the prison grounds also will help alert guards to the outbreak of violence among rival gangs at the overcrowded facility.
The prison was built to hold 153 inmates. It currently holds 255.
Calls to the prison for more details went unanswered.
(Copyright 2011 by The Associated Press. All Rights Reserved.)