While black bears can grow very large, they average only around 135kg or so (about 300 pounds), and while capable of killing or injuring humans, in general they do NOT attack humans, except perhaps over food (and unlike the brown and polar bear, human is not really considered fair game for black bears). While they have been hunted themselves for food and sport, black bears have the closest thing to a live-and-let-live relationship with humans as one finds within the bear kingdom. Exceptionally intelligent and dexterous, they can open latches and lids and unscrew the tops of jars; tests have found they learn some things faster than chimpanzees.
It is because of their intelligence and temperament that black bears end up as trained animal acts, circus performers, and mascots more than any other type of bear (Smoky, Yogi, and Winnie were all modeled after black bears). They are also relatively easy to hunt and trap (rather than hunt and kill) compared to other bears.
For a fantasy game like D&D, who doesn’t want a trained attack bear?
B/X doesn’t give stats and prices for trained animals, though one CAN retain the services of an animal trainer (500gp per month, Cook/Marsh Expert set page X21). Now while some wealthy adventurers might decide it’s worth the cost to hire a "Bear Master" to wrangle their furry mercenaries, most adventuring parties are just looking for a single bruiser that knows the command “Kill!” Let’s talk about BOTH.
Animal trainers cost 500gp per month, specialize in a particular type of animal, and can handle up to 6 animals at a time providing on-going training (as well as, I presume, feed and care). There’s no mention of whether or not animals need to be purchased separately or not…I would figure that in a large enough (or strange enough) fantasy city, one could find a bear master with a string of black bears ready for adventure. While the 500gp per month covers the price of the handler’s services, one has to consider the cost of the animals.
A black bear eats 30+ pounds of food per day, and one that it is in captivity is not out hunting/grazing, rations will need to be provided for it. Even considering a poorer quality of rations than the average adventurer consumes, I’d still budget 50gp per month per bear for food (standard rations are 5gp/week x52 weeks /12 months x4 times the normal weight, then reduced for quality). A bear master (if available) will already possess 1D6 black bears in his care; in addition to the bear master’s fee, the employer must pay the food costs of all bears in the handler’s care (the bear master will not voluntarily part from any of his bears). Fees of course are subject to market demand.
The bear master himself is a normal man, albeit one with maximum hit points (4) from his rough and tumble lifestyle. He will try to avoid combat if at also possible, but will direct his bears to fight for him (or as his employer commands).
Purchasing an additional wild bear for the bear master is a matter of finding a bounty hunter or trapper skilled in the live acquisition of large game (perhaps for the local gladiatorial games). Such an animal would 400-800gps depending on size and scarcity, and would require at least one month’s work with the bear master to learn even the simplest commands. A young black bear would be worth 2 to 5 times that amount (D4+1), both because of their extra trainability, and the danger involved of confronting an angry mother bear in its den!
A young black bear can be trained for domestication from an early age. Sold in adulthood, such an animal requires no bear master but costs 2000-4000gp, again depending on size and scarcity. For the character wishing a “pet bear” without hiring an animal trainer, this is the only option other than using magic.
A black bear trained from an early age and purchased as an adult will be only moderately useful to its new owner, knowing the commands “attack,” “stop,” “come,” and “stay.” Regular feeding and care will eventually ingratiate the bear to its master (in 2D6 weeks); prior to that, the owner will need to make a Reaction roll every time a command is given (Charisma modifiers apply as usual). The DM can further modify the reaction rolled based on circumstance as normal (a half-starved bear is more likely to “attack,” but less likely to “come” unless food is being offered).
PC adventurers are NOT animal trainers, and no PC can ever own/handle more than one bear at a time. Such a “pet” counts against the maximum number of retainers a PC can have (based on Charisma). However, a bear companion can become a loyal and lifelong friend. Bears never gain XP or grow in “level;” they heal at the same rate as adventurers (D3 hit points per day, though bed rest is NOT required and light activity does not interfere with healing), and can be affected by curing and blessing spells. As a domestic creature, the owner WILL need to provide it with sustenance at the standard 50gp per month rate (see above).
Black bears are excellent climbers and very fast (25-30mph at a dash…fast enough to chase down that pesky goblin running for help!). They cannot wear armor (at least, nothing that would improve their AC; they can still be “decorated”). With regular food and activity, a domesticated bear will spend much less time in hibernation (if any time at all), though they will still be lethargic during certain months.