Probably Stolen Rat Ranching Guide: Getting Rats, Breeding, Disease, Genetics and When to Butcher

To ranch rats in Probably Stolen, start with a male and a female in an Animal Cage with a Livestock Feed Dispenser. Every night each rat eats, grows and tries to mate. A rat with average genes reaches 400 g on night 10, which is one Raw Meat (Standard) worth 159. Keep their Immunity high, keep the cage clean and under 55% full, and never let a rat eat rat meat. The calculator below shows how heavy a rat with your stats gets each night and when to butcher it.

How do you start raising rats?

There are three ways to get rats.

1. Rat Wrangler start. 600 cash, a worn Animal Cage with a Livestock Feed Dispenser, six rats (a male and a female aged 5, 3 and 1 day), a Meat Cleaver, a Blue Labeler, a Marking Pen, six Nutrifruits and a Livestock Immunity Serum with 2 uses left. Every starting rat has exactly average genes. It also unlocks the We Have Rats! achievement straight away.
2. Ranching in Wild's Network. 750 on Mark Up. You get the same cage, dispenser, six rats and tools (no serum), plus three Peat and six Nutrifruits. These rats have random genes, so some will be better and some worse than average.
3. Mouse Trap. Put a Processed Cheese in a Mouse Trap and it catches a wild rat on 50% of nights. The rat is 3–7 days old, male or female at even odds, with random genes. A missed night eats the cheese 25% of the time. An empty trap catches something on only 1% of nights. Dr. Jackson has a Mouse Trap in only 5% of restocks, so grab one when you see it.

With Ranching bought or the Rat Wrangler start, the Retired Rat Rancher comes every Friday. He sells the equipment and a 5-day-old pair of rats for 120 each; his full stock is listed further down.

You need at least one male and one female. Any container works as a pen. The Animal Cage is better because it has slots for a feed dispenser and an Auto Butcher, and rats loose in the store wander between the counter, the back storage and the display case.

What do a rat's stats mean?

Hover over a rat to see its card. Line by line:

• Header: Male or Female, its stage (Infant, Juvenile, Adolescent, Adult, Elder) and species. Rename rats with the Blue Labeler to keep a cage organised.
• Age: days (weight in g). Weight is what you butcher.
• Health. Disease takes 25% of Max Health a night. A rat dies at 0 health.
• Hunger. Stored calories, 0 to 500. A rat loses its Hunger Rate every night and eats when it is below 375.
• Fertility (only once it is Mature). Its chance to conceive when mating, shown as current % and base % when something is lowering it.
• Growth Rate. Multiplies how many grams it gains each night. Average 1.
• Expected Litter Size. How many pups a female has. Average 3. It only matters on females, but males pass it on.
• Immunity. How often it gets sick, heals, and resists Prion Disease. Average 30.
• Max Health. Average 100.
• Longevity. Multiplies its lifespan (14 days at 1). Average 1.
• Hunger Rate. Calories burned each night. Average 65; lower is better.

Status tags under the stats include Pregnant, Starving, Diseased, Prion Disease, Neutered, Miscarried, Scratch Mark (killed by a cage mate), Mature, Strong Immunity (50 or more), Immunocompromised (below 25) and Overcrowding with its level.

A number in brackets after a stat, like 1.2 (1.0), means a serum or Prion Disease is changing it: the first number is what counts now, the second is the rat's own value.

How fast do rats grow?

Rats gain weight fast until day 4, slowly until day 10, then shrink. At Growth Rate 1 and fully fed, a rat weighs about 80 g after its first night, 305 g at day 4 and 407 g at day 10, its heaviest. Butcher at 400 g or just after; waiting only loses weight.

Growth needs food. Below 400 Hunger a rat grows less, down to half at 0 Hunger, and a Starving rat loses half its normal gain instead.iGain is multiplied by 1 − (400 − Hunger) ÷ 400 × 0.5, and rounded to whole grams. Weight never drops below a quarter of its stage's weight.

From age 14 × Longevity, every night a rat has a 75% chance to die of old age, so an average rat almost never sees day 17. Rats with Longevity above 1 keep losing 17 g a night until that day; rats at Longevity 1 or below stop changing weight at day 14.

How do you feed rats?

Each night a rat first loses its Hunger Rate, then eats if it is below 375 (75%):

1. From the Livestock Feed Dispenser, if one is in the cage's dispenser slot or sitting in the cage. It tops the rat up to the dispenser's target, 85% (425) by default.
2. Then one loose food item in the cage, if the rat is still below 375. A rat eats exactly one item a night, whatever its size, and anything above 500 is wasted. Peat is canned, so rats ignore it unless it goes through the dispenser.

A newborn starts at 125 Hunger, so a cage without a dispenser needs food every night. With an average Hunger Rate of 65, a rat burns about 650 calories by day 10.

The Livestock Feed Dispenser (300) holds up to 40,000 kcal. Drop food into its storage and press Start to blend it into stored calories, or toggle it on to Auto Blend everything you put in. The slider sets how full it feeds rats, from 0% to 100% in 5% steps. Empty throws out every stored calorie, which is how you get rid of rat meat that went in by mistake. A live rat dropped into the dispenser is killed, butchered and blended.

Food per credit, for buying feed:

Pilk and Bei's Premium Vanilla Icecream are the cheapest calories you can buy, then Puice and Peat. Nutrifruit from your own Hydroponic System costs nothing but the seed.

Why should you never feed rats rat meat?

Every cut from a butchered rat is marked as rat. A rat that eats rat meat gets Prion Disease with a chance of 100 minus its Immunity, so an average rat with 30 Immunity catches it 70% of the time. Meat from a rat that already had Prion Disease infects every time.

It happens whether the meat is loose in the cage or blended into the dispenser: any feed drawn from a dispenser holding rat meat counts. Press Empty on the dispenser if rat meat went in.

Prion Disease is permanent: Growth Rate, Immunity and Longevity drop by 20%. The lower Immunity is what kills, because a rat below 25 loses health every night instead of healing. Raw meat bought from traders is not rat meat, and no other meat causes it.

Why do rats get sick and die?

Immunity decides almost everything about a rat's health:

• Getting sick: below 50 Immunity a rat may fall sick on its own each night, from 25% at 0 down to 5% just under 50. At 50 or more it never falls sick on its own.
• Healing: every night a rat heals by (Immunity − 25) ÷ 25 × 30% of its Max Health, at most 30%. Below 25 Immunity this turns negative and the rat slowly bleeds out even when healthy.
• Being sick: a Diseased rat loses 25% of its Max Health a night and recovers with a chance equal to its Immunity. Its Fertility drops by 75% while sick.

A dirty cage also makes rats sick. Feces and dead rats covering 25% of the cage give each rat about a 2% chance a night (15% of the time it rolls 15%); 35% or more gives about 12%. Each level of Overcrowding adds 20% to that roll once the cage is dirty. Rats drop feces on any night they gain 30 g or more.iUnder 25% covered: no hygiene risk. 25–34%: 15% chance of a 15% roll. 35% or more: 35% chance of a 35% roll. Overcrowding adds 20 points per level to the roll, even when the 15% or 35% part misses.

Clean the cage every morning, or put a Cleaner Robot (250) in it. It collects feces every night into its own storage until full. Upgrade it with Electronic Parts (Common) and it burns what it collects. It does not pick up dead rats. Feces are worth nothing.

Starvation is fast: a rat at 0 Hunger becomes Starving, and if it is still at 0 the next night it dies. A pregnant Starving rat miscarries 75% of the time.

How many rats fit in a cage?

The Animal Cage is 10 cells wide and 3 rows tall. A rat takes 2 cells under 180 g, 3 cells at 180–599 g, 6 at 600–999 g and 8 at 1,000 g or more. Dead rats count; feces, the dispenser and the Auto Butcher do not.

• Overcrowding 1 (over 55% full): every rat loses 20% Fertility.
• Overcrowding 2 (over 70%): also, each night every rat has a 5% chance to kill the lightest rat smaller than itself. The victim gets a Scratch Mark.
• Overcrowding 3 (over 90%): the chance is 15%, and Fertility is down 60%.

Overcrowding does not take health directly. It kills small rats and makes a dirty cage sicker. Expand the cage before the next litter is born: each Metal Ingot adds a row, up to 8 rows, and 20 durability.

Every night a cage loses durability equal to its live rats' cells ÷ 4. A cage starts at 100. Use Scrap Metal on it to restore half its maximum. Below 20 durability each rat has a 5% to 25% chance a night to break out into the store.

How do rats breed?

Rats can mate from 3 days old (Adolescent). Each night every rat that is not Starving, Pregnant or Neutered mates with up to three rats of the other sex in the same container. Each mating succeeds with the lower Fertility of the two: a 60% male with a 40% female gives 40%.

Fertility starts at about 50 and drops:

• Hunger below 200: up to −40% at 0 Hunger.
• Elder (from 11 × Longevity days): −15%.
• Diseased: −75%.
• Overcrowding: −20% per level.

A pregnant female gives birth after 3 nights. The litter is her Expected Litter Size: the whole part, plus one more with a chance equal to the fraction, then one fewer, the same or one more at random, and never less than 1.iExpected Litter Size 3.4 gives 3 pups 60% of the time and 4 pups 40% of the time, then −1, 0 or +1 at even odds: 2 to 5 pups. Pups start at 5 g with 125 Hunger and inherit genes from both parents.

To stop a rat breeding, use a Surgery Toolset on it: it neuters the rat for good, or makes a pregnant female miscarry. Keep breeders and growers in separate cages so you only breed your best rats.

When should you butcher a rat?

Use any blade on a living rat to kill it, then on the body to cut it: the Meat Cleaver, Kitchen Knife, Box Cutter and every other knife work. The cut depends on weight:

400 g is the threshold that matters: it is one Raw Meat (Standard), worth 159, against 125 for a 399 g rat. A Diseased rat is cut as if it weighed 25% less, so cure it or wait before butchering.

The Auto Butcher (400) goes in the cage's butcher slot and does it every night, into a 10 × 10 tray. Its Harvest setting is Off by default; set it to Weight (400 g and up by default), Age (10 days and up) or Carcasses only. Cull sick and Cull prion carriers are on by default. Keep breeders keeps the youngest unneutered rats of each sex, up to 10, and Spare pregnant skips pregnant females. Rats you renamed or marked with the Marking Pen are never butchered.

After 100 rats butchered, you are given a Skinning Knife the next time you open the store. It shows how many animals you have butchered.

How do serums work?

The Retired Rat Rancher sells two serums, 100 each, 10 uses per bottle. Select the bottle and click a rat.

• Livestock Steroid Serum: Growth Rate +20%, Immunity −40%, Hunger Rate +25%.
• Livestock Immunity Serum: Immunity +75%, Hunger Rate +25%.

One dose lasts 4 nights, and the last night still counts. Another dose of the same serum while it is active does not stack: it adds 4 more nights. The two serums can be combined.

The Steroid Serum is risky on its own: an average rat with 30 Immunity drops to 18, below the 25 where it starts losing health. Combined with the Immunity Serum the same rat sits at about 40. The Immunity Serum alone lifts an average rat to 52, safe from falling sick on its own. Use it on a sick breeder or a low-Immunity rat you want to keep.

How does rat genetics work?

Every gene has two values, called alleles. The stat a rat shows is the average of the two. A pup gets one allele from its mother and one from its father, each picked at random, so two rats with the same stat can pass on very different genes.

Wild rats and Ranching rats get alleles between half and one and a half times the average, most of them close to the middle. Each allele a pup inherits has a 15% chance to mutate by up to ±8%, sometimes ±24%. The further a gene already is from average, the smaller and more likely to pull back the change, so records take many generations.

The Gene Scanner (500) shows both alleles next to each stat, for as long as it is switched on and you own it. Allele values more than 5% better than average are green, more than 5% worse are red. For Hunger Rate, lower is green.

How to improve a colony:

1. Remove weak Immunity first. Neuter or butcher any rat below 25 Immunity, and any that shows a red Immunity allele, before it breeds. A sick colony loses rats faster than good genes can add them.
2. Breed pairs with green alleles in the same genes. A pup gets one allele from each parent, so if both parents carry a high allele for Growth Rate, a quarter of pups get two.
3. Keep the best and cull the rest. Leave only your two best breeders in the breeding cage, move pups to a growing cage, and replace breeders before they turn Elder at 11 days and lose Fertility.

The Retired Rat Rancher also has a chance each week of a 500-credit rat with Growth Rate or Expected Litter Size boosted 25–50%. Community breeders report rats with Growth Rate above 3, Immunity above 65 and weights over 1,500 g after many generations.

What does the Retired Rat Rancher sell?

He comes every Friday once you have Ranching or the Rat Wrangler start, plus the day after you buy Ranching. These are base values; he adds 15% on Mark Up, 30% on Thin Margins and 45% on Red Ink.

Item	Base value
Animal Cage	250
Livestock Feed Dispenser	300
Auto Butcher	400
Cleaner Robot	250
Gene Scanner	500
Livestock Steroid Serum	100
Livestock Immunity Serum	100
Meat Cleaver	65
Blue Labeler	50
Marking Pen	50
Wire Cutter	40
A male and a female rat, 5 days old	120 each
Each of four bred rats (a male or female with better Growth Rate or Expected Litter Size), 25% chance each	500

He does not sell Mouse Traps, Processed Cheese or the Surgery Toolset. Wire Cutters are for clearing debris, not for rats. Dr. Jackson also stocks the Auto Butcher once you have Ranching, and the Gene Scanner.

Where do you sell rat meat?

Live rats are worth nothing and no customer buys them, so profit comes from meat. Every customer who buys food takes the cuts, and Raw Meat (Standard) also counts as a luxury item for upper-level buyers. Butcher in step with your buyers: meat only sells as fast as food customers come in.

One average rat raised to day 10 eats about 950 kcal, about 25 credits of Pilk, and yields meat worth 174: about 149 profit before haggling. A rat with Growth Rate 1.3 reaches 400 g by day 5. See money making to compare it with other production lines.

Daily routine

1. Morning. Clean feces and dead rats out of the cage. Check for Diseased, Starving and Immunocompromised rats.
2. Check space. Count cells before litters are born. Expand with a Metal Ingot or move pups to a second cage before 55%.
3. Check the cage. Repair with Scrap Metal before durability falls below 20.
4. Fill the dispenser. Keep a few thousand kcal stored. Never put rat meat in it.
5. Butcher. Anything past 400 g, or let the Auto Butcher do it.