Some dogs show very little evidence of pain, while others become irritable. This irritability might make them a touch snappy, or introspective. Decreased mobility also affects how the pet may react to stressful events. Your dog might once have been quite happy to travel in your car but as they age, they become more fearful and less able to cope with journeys. Age related changes in dogs include circling, tremors, stiffness or weakness, inappropriate vocalization, compulsive behaviours, and changes in sleep patterns, house training, interest in food, attention and activity, and awareness of surroundings.