The short answer for a Californian kit
A young Californian rabbit needs feeding and supervision built around rapid growth, while an adult Californian needs a routine built around weight control and maintaining habits that are already set. Californians are a large breed, and a kit that fits in two hands becomes a heavy, strong rabbit surprisingly quickly. Almost every care difference in this breed traces back to that growth curve: food portions, pen size, handling technique, and how much mischief an unsupervised youngster can find all shift between the first months and maturity.
Feeding a growing Californian versus a finished one
Growth drives the young Californian's bowl. Kits and juniors do well on alfalfa hay, which is richer in calcium and protein than grass hay, alongside a more generous measure of plain pellets to fuel bone and muscle development. Fresh water should be checked twice daily, because a fast-growing kit drinks more than owners expect and a stuck bottle ball goes unnoticed in a busy pen.
The adult Californian flips that logic. Once growth stops, alfalfa becomes too rich, and the main hay should be a grass hay such as timothy, fed freely, with pellets cut back to a measured daily portion. Californians were developed as a stocky, efficient breed, and adults put on condition easily; an owner who keeps feeding the junior ration ends up with a heavy rabbit whose grooming, hopping, and litter habits all suffer.
Handling, bones, and confidence
Young Californians are wiggly and their bones are comparatively fragile, so handling a kit means short sessions, low heights, and always supporting the hindquarters so a sudden kick cannot twist the spine. These calm repetitions are what produce an adult Californian that tolerates being picked up for health checks.
An adult Californian is calmer but far heavier, and the technique changes rather than the principle. Lifting a full-grown rabbit of this breed is a two-handed job with the weight taken securely against your body, and many adults prefer four paws on the ground with stroking instead.
Space, chewing, and litter habits
A young Californian outgrows housing fast, so buy or build for the adult footprint from the start and use a pen panel setup that can expand. Kits explore mouth-first, which makes chew-proofing most urgent in the young months: cable covers, blocked skirting boards, and a rotation of safe chew sticks and cardboard in the pen. An adult still chews — it is a lifelong rabbit need — but tends to settle into known routes and resting spots, so proofing can focus on that established territory.
Litter training also splits by age. A kit is still learning, so place two litter trays in the young Californian's pen corners with hay in or beside them, expect accidents, and clean stray droppings back into the tray so the scent map builds. Adults usually hold one chosen corner reliably, need only one larger tray, and regress mainly when the tray moves or the routine changes.
Health watch at both ages
For a young Californian, the daily check is appetite and droppings: a kit that stops eating or produces tiny, dry pellets needs a veterinarian promptly, because young rabbits go downhill quickly. For an adult, add weight and mobility to that check — a rabbit that stops jumping into the tray or leaves cecotropes uneaten may be carrying too much weight to move comfortably. Any rabbit of any age that stops eating entirely is an urgent vet call, not a wait-and-see.
Keeping the whole household on the same page matters most during the junior months, when rations and rules change fastest, and KinsLe Family Sharing lets everyone who feeds or handles this Californian work from the same profile and care notes rather than from memory.