Green’s Dictionary of Slang

a group of young men looking for suitable female company.

1967		Current Sl. II:1 1: Beaver patrol, n. Girl watching.
1975		L. Dills CB Slanguage 9: Beaver Hunt/Patrol: looking for women.
1999		J. Ellroy ‘My Life as a Creep’ in Destination: Morgue! (2004) 128: The Beaver Patrol – USC frat boys fresh from late keggers.