Cats don’t like to leave their familiar territory. Unlike dogs, they are not always reassured by the presence of their owner. In a new environment, such as the car, cats are unable to predict what might happen, and this can make them anxious.
Cats may also be more sensitive to the movement of the car – their sense of balance is very acute, so the motion may not be pleasant to them, and they may not feel in control of the situation. The car will also sound and smell very strange.
Cats that experience car travel as young kittens, during the period between 2 and 7 weeks of age when they are most receptive to learning new things, tend to tolerate it much better.