Cougars can be almost as large as jaguars , but are less muscular and not as powerfully built ; where their ranges overlap , the cougar tend to be smaller on average . Besides the jaguar , the cougar is on average larger than all felids apart from lions and tigers . Despite its size , it is not typically classified among the " big cats " , as it cannot roar , lacking the specialized larynx and hyoid apparatus of Panthera . Compared to " big cats " , cougars are often silent with minimal communication through vocalizations outside of the mother @-@ offspring relationship . Cougars sometimes voice low @-@ pitched hisses , growls , and purrs , as well as chirps and whistles , many of which are comparable to those of domestic cats . They are well known for their screams , as referenced in some of their common names , although these screams are often misinterpreted to be the calls of other animals .