This spoiler on pets was written by Eva Myers, with helpful contributions from Jules Bean and Tina Hall. For general information on acquiring pets and the different types of tame monster, see my spoiler on how to acquire pets in Nethack and Slash'EM. If you have any comments, additions or corrections, please feel free to email me.
A pet has two important properties: its tameness, which is a general measure of how resistant it is to going wild, and its apport, which measures how well trained it is to fetch. A pet hatched from a non-dragon egg in the hero's inventory starts with a tameness of 20 (dragons hatched from eggs only have a tameness of 5). In Slash'EM, pets summoned by invoking artifacts (the Hand of Vecna, the Candle of Eternal Flame or the Storm Whistle) start with a tameness of 30, and minions and spell beings start with a tameness of 10. Otherwise, pets start off with a tameness of 10 if they are a domestic animal (dog, cat or horse) and 5 if not, and an apport of 10. If a pet which rises from the dead comes back tame, its tameness and apport will remain unchanged.
The higher your pet's apport is, the better it is at stealing from shops. A pet with high apport has a greater tendency to pick up and drop objects, and also favours dropping objects close to the hero over dropping them anywhere else. Apport is reduced by 1 each time the pet drops an object, and can be increased by rewarding the pet with food it likes (tripe or meatballs for a cat or dog, apples or carrots for a horse) as soon as possible after it has dropped something. The reward must be a treat (corpses do not count) and the hero must have picked it up at some point, but it is not necessary to throw the treat to the pet. When the hero rewards the pet, its apport is increased by
200 / (dropdist + time since pet dropped something)
where ``dropdist'' is the distance from you to your pet last time it dropped something. Thus the best-case scenario is when your pet drops an item at your feet and you reward it immediately, in which case its apport goes up by 100. In practice, when your pet's apport is very low, it is generally quicker to reward it as soon as possible after it drops an item anywhere. This will raise its apport and hence its tendency to drop items at your feet, and you can reward it again when it does so.
A pet's tameness is changed in the following circumstances. If its tameness falls to zero, it will no longer be tame, but will remain peaceful unless otherwise stated.
In Slash'EM, the following types of pet can rebel (spontaneously turn hostile): migo drone, migo warrior, assassin bug, death dog, rabid wolf, shadow wolf, displacer beast, hellcat, gremlin, gargoyle, winged gargoyle, dwarf thief, deep one, deeper one, deepest one, mind flayer, master mind flayer, dretch, rutterkin, nupperibo, blood imp, all kobolds, quickling, all orcs, mangler, harpy, byakhee, nightgaunt, forest centaur, mountain centaur, deep dragon, red dragon, white dragon, orange dragon, black dragon, blue dragon, stalker, gnome thief, Ruggo the Gnome King, all gnolls, the Largest Giant, Father Dagon, Mother Hydra, all liches, all ogres, shoggoth, giant shoggoth, disenchanter, all trolls, all vampires, ghoul mages, ghoul queens, gugs, gibberlings, grimlocks, drow, mugger, gypsy, all demons except water demons, erinys and sandestins. This will only happen when the pet has at least as many HP as you do and is three or fewer squares away. Pets with high tameness or which haven't been abused much are less likely to rebel. Abusing your pet is likely to trigger a rebellion, but there is also a small chance that the pet will rebel at any time.
Tameness affects your chance of successfully saddling or riding a steed, but does not have any other effect on a pet's behaviour.
The foods that a pet will eat can be divided into three categories:
Almost all monsters can be classfied as carnivorous, herbivorous, omnivorous, metallivorous or non-eating:
Carnivores:
Giant ants, giant ticks, giant fleas, soldier ants, fire ants, snow ants, giant beetles, giant lice, spitting beetles, assassin bugs, killer beetles, all d, all f, all mimics, all piercers, giant badgers, scrampers, squealers, manglers, all rats, all s, all t, all w except larvae, echnidae, platypuses, all B except vampire bats, byakhees and nightgaunts, all D, all H except titans, the Cyclops, Lord Surtur, Father Dagon and Mother Hydra, (vorpal) jabberwocks, black naga hatchlings, black nagas, all ogres, disenchanters, all snakes, all trolls, all U, vampires, vampire lords, vampire mages, Vlad the Impaler, all Y except monkeys, (ordinary) apes and sasquatches, ghouls, ghasts, gugs, piranhas, giant eels, sharks, electric eels, kraken, all ``:'' except salamanders, all evil food, all evil coins.
Herbivores:
Chickens, cockatoos, parrots, lambs, sheep, goats, cows, bulls, mumakil, titanotheres, baluchitheria, mastodons, Jumbo the Elephant, juggernauts, catoblepases, (rabid) rabbits, woodchucks, all u except Pegasus, koalas, wombats, wallabies, wallaroos, kangaroos, the Grand Master, Master Kaen, abbots, monks.
Omnivores:
Migo drones, migo warriors, migo queens, gelatinous cubes, chickatrices, cockatrices, pyrolisks, hobbits, dwarves, bugbears, dwarf lords, dwarf kings, dwarf thieves, (master) mind flayers, deep ones, deeper ones, deepest ones, clear jellies, yellow jellies, orange jellies, rancid jellies, all kobolds, all orcs, rothes, leocrottas, wumpuses, Tasmanian devils, vampire bats, byakhees, nightgaunts, all centaurs, disgusting molds, black molds, all G, titans, all nagas except black nagas and black naga hatchlings, all P, all Q, monkeys, apes, sasquatches, all ``@'' except the Grand Master, Master Kaen, monks and abbots, the Cyclops, Lord Surtur, Father Dagon, Mother Hydra.
Metallivores:
Rock moles, (giant) shoggoths, rust monsters, xorns.
Non-eating:
Killer bees, tsetse flies, queen bees, yellow jackets, black wasps, giant wasps, all b except gelatinous cubes, all e, all g, gnolls, duergars, all i, blue jellies, spotted jellies, ochre jellies, all l, all nymphs, Pegasus, all v, larvae, all x, all y, all A, all E, all F except disgusting molds and black molds, all Kops, all liches, all mummies, fire vampires, star vampires, all W, all Z except ghouls, ghasts and gugs, all golems, shadows, ghosts, shades, all ``&'', jellyfish, giant crabs, salamanders, Count Dracula.
Pets will never eat anything which will do them harm. For example, they will not eat acidic or poisonous corpses unless they have acid or poison resistance. (Pets have resistances solely by virtue of their species - unlike the hero, they do not gain resistances from eating.)
In Nethack 3.4.1, starving pets find a few more types of food acceptable. Starving carnivores will eat fruits and vegetables, but not vegan corpses. Starving herbivores will eat "people food" other than tins, but not tripe, meat, meaty corpses or eggs.
In Slash'EM only:
When you chat with a pet or any other monster, there are many possible responses, depending on the type of monster. This section covers only the responses which will give you diagnostic information about your pet.
(In Slash'EM, barking spiders and werespiders also do this.)