E= energy needed to sustain an individual (basic cost of living without territoriality)

P= productivity of the environment, a= fraction of P that a non territorial animal can obtain

E smaller than aP (if the animal is to maintain itself-reproduce, respiration, etc)

T= energetic cost of defending territory -Territorial will occur only if the benefit (units of energy) exceed the cost T of being territorial,

b= fraction of P that can be obtained by defending a territory