Cavalier King Charles Spaniel vs Jack Russell Terrier

This is a "Velcro dog" in the truest sense. They were bred to warm laps in drafty castles and have not lost this biological imperative. They cannot be left alone for standard workdays (8+ hours). Isolation leads to profound distress, destructive chewing, and incessant whining or barking.

While they are toys, they are still spaniels. They retain a prey drive that can be triggered by birds, squirrels, or butterflies. This "arrested" predatory sequence means they may suddenly bolt into traffic if not leashed, despite generally good recall.

Hardwired to hunt vermin and bolt foxes. Poses a lethal threat to hamsters, guinea pigs, rabbits, and birds. Most cannot be trusted with cats unless raised together from puppyhood.

Notorious for intolerance toward dogs of the same sex. Can coexist peacefully for years, then a sudden vicious fight requiring permanent separation. Typically manifests at 18-24 months.

When under-stimulated, will dismantle gardens or bark incessantly at falling leaves. This is the breed's work ethic manifesting without a job to do.

Can climb chain-link fences, dig under walls, and squeeze through impossibly small gaps. Standard backyard fencing is often insufficient containment.