Uniqueness of limit cycles in predator–prey system: the role of weight functions ✩

We consider a Gause type model of interactions between predator and prey populations. Using the ideas of Cheng and Liou we give a sufficient condition for uniqueness of the limit cycle, which is more general than their condition. That is, we include a kind of weight function in the condition. It was motivated by a result due to Hwang, where the prey isocline plays a role of weight function. Moreover, we show that the interval where the condition from Hwang’s result is to be fulfilled can be narrowed.  2002 Elsevier Science (USA). All rights reserved.