Comments on "Critical Study on the Absorbing Phase Transition in a   Four-State Predator-Prey Model in One Dimension"
  In a recent article [arXiv:1108.5127] Park has shown that the four-state predator-prey model studied earlier in [J. Stat. Mech, L05001 (2011)] belongs to Directed Percolation (DP) universality class. It was claimed that predator density is not a reasonable order parameter, as there are many absorbing states; a suitably chosen order parameter shows DP critical behavior. In this article, we argue that the configuration that does not have any predator is the only dynamically accessible absorbing configuration, and the predator density too settles to DP critical exponents after a long transient. 
P. K. Mohanty, Rakesh Chatterjee and Abhik Basu
cond-mat.stat-mech