Willow Ptarmigan (Lagopus lagopus) Science Article 1
1) Recent experiments on cyclic red grouse populations discovered that aggressiveness, induced by testosterone implants, depressed population density for more than a year after the implants were exhausted. 2) This confirms the observation, also made in previous studies of this territorial species, that aggressiveness can determine population density. Additionally, it hints at a form of social memory that sustains the effect of episodes of high aggressiveness after their cause has ceased to exist. […].
Jason Matthiopoulos, Robert Moss, Francois Mougeot, Xavier Lambin and Steve M. Redpath, Journal of Animal Ecology 2003 72, 1083-1096