Pet Wiki

Double Rex Rat

Rattus norvegicus domestica

Also called Homozygous rex rat, Patchwork rex, Patchwork rat

VarietyShort profile

From Produced wherever two Rex rats are mated; the Rex coat itself was developed in England in 1976.123

At a glance the quick version

Weight, male0.45 to 0.65 kg4
Weight, female0.35 to 0.45 kg4
Length20 to 25 cm5
Lifespan1.5 to 3 years64
Sizesmall

General figures for the domestic rat species from the MSD Veterinary Manual; club standards set no separate weight for this coat type, which shares the standard fancy rat body.

Unusual, ever-changing patchwork look
Curly whiskers like its Rex parents
The same sociable, people-friendly nature as other fancy rats
136

Coat and looks how to spot one

Sparse, patchy rex coat (two copies of the rex gene)

A double rex carries the rex gene twice, which gives a thin, uneven coat. Over its life the fur grows in and moults away in changing patches, and at times the rat may wear a very short, even coat all over. The whiskers are curly and shorter than a smooth rat's.13

Personality what they are like

The coat genes do not change personality, so a double rex is as curious, affectionate and trainable as any well-handled fancy rat.36

Daily activity how busy a day looks

As lively as any fancy rat. Most active around dusk and through the night, it needs daily supervised time out of the cage, things to climb and forage for, and short play or training sessions.67

Grooming and care the hands-on bits

No brushing is needed. Because the coat thins and regrows in patches, keepers should expect its look to change from month to month; this is normal for the type. A warm, draught-free room and plenty of soft nesting material help a thin-coated rat stay comfortable.17

Home where they are happiest

The largest multi-level rat cage you can fit, with shelves, ropes, ladders, hammocks and hideouts, dust-free bedding such as shredded paper, placed in a quiet room around 19-23 C away from direct sun and draughts.74

Food basics what goes in the bowl

A complete rat nugget or pellet as the daily staple, with small portions of vegetables, a little fruit, grains and cooked egg counted into the ration. Keep sugary or fatty bits for training rewards, scatter some food to encourage foraging, and provide fresh water from a bottle at all times.8

Company who they like around

A very sociable animal that should share its home with at least one other rat, in a same-sex pair or small group or a neutered mixed pair, and enjoys daily time with its people.63

The story where it all began

Once the dominant Rex coat reached fanciers from 1976 onwards, breeders found that pairing two Rex rats could give some babies two copies of the gene. These became known as double rex or patchwork rats, and AFRMA documents them as genetically sound animals with a typical lifespan.213

Fun facts for the dinner table

  1. 1

    Double rex rats can moult and regrow their coat in different patches several times in one lifetime.3

  2. 2

    Genetically a double rex is written ReRe, while an ordinary Rex is Rere.1

  3. 3

    Some double rexes go through phases of a very short, even coat when they moult.1

Recognised by the official bits

American Fancy Rat and Mouse Association (AFRMA)
Not one of AFRMA's seven standardised varieties; AFRMA explains it as the homozygous (ReRe) form of the Rex coat.1

The care rhythm a typical week and year

A typical home-care rhythm for a Double Rex Rat. A starting point, not a vet's advice.

Treats they will love homemade and simple

Hamster and Gerbil Fresh Veggie and Herb Mix

A simple, safe daily supplement that provides essential vitamins, hydration and enrichment for hamsters and gerbils.

You need

  • 1 small piece of carrot (about the size of a pea)
  • 1 small piece of broccoli (about the size of a pea)
  • 1 small piece of cucumber (about the size of a pea)
  • 1 small piece of apple (without seeds, about the size of a pea)
  • 1 small leaf of basil or parsley

How

  1. Wash all fresh ingredients thoroughly.
  2. Cut the carrot, broccoli, cucumber and apple into pieces no larger than a pea.
  3. Tear the herb leaf into tiny pieces.
  4. Mix all ingredients together in a small bowl.
  5. Offer a total of 1.5 to 4.5 teaspoons of this mix per day, depending on the size of your pet.

How much: 1.5 to 4.5 teaspoons per day for hamsters and gerbils

Recipe from Oxbow Animal Health

Rat-Friendly Veggie and Egg Treat

Rats are omnivores and enjoy a varied diet. This treat provides protein and enrichment, and encourages natural foraging behaviour.

You need

  • 1 small slice of carrot (about 1cm thick)
  • 1 small floret of broccoli
  • 1 small slice of cucumber (about 1cm thick)
  • 1 small slice of apple (without seeds, about 1cm thick)
  • 1 small piece of cooked egg (about the size of a pea)

How

  1. Wash all fresh ingredients thoroughly.
  2. Cut carrot, broccoli, cucumber and apple into small pieces (about 1cm cubes).
  3. Cook an egg until hard-boiled, then cool and peel. Take a small piece about the size of a pea.
  4. Mix all ingredients together in a small bowl.
  5. Offer this as part of your rat’s daily food allowance, not in addition to it.

How much: A small amount as part of daily food allowance for rats

Recipe from RSPCA

Small Furries Safe Snack Plate

A selection of safe, low-sugar vegetables and herbs that can be offered as occasional treats to hamsters, gerbils, rats and mice.

You need

  • 1 small piece of carrot (about the size of a pea)
  • 1 small piece of broccoli (about the size of a pea)
  • 1 small piece of cucumber (about the size of a pea)
  • 1 small piece of apple (without seeds, about the size of a pea)
  • 1 small leaf of basil or parsley

How

  1. Wash all fresh ingredients thoroughly.
  2. Cut carrot, broccoli, cucumber and apple into pieces no larger than a pea.
  3. Tear the herb leaf into tiny pieces.
  4. Arrange on a small plate or scatter in the cage for foraging enrichment.
  5. Offer only in small amounts alongside their regular pelleted food.

How much: A small amount as an occasional treat for hamsters, gerbils, rats and mice

Recipe from Burgess Pet Care

Not veterinary advice. Check with your vet first if your pet has allergies, a health condition, is on a special diet or is pregnant. Treats should stay a small part of the daily food. Cut to a safe size and supervise. Terms of use

Owner questions the things everyone asks

How often should I feed my Double Rex Rat?

Feed your Double Rex Rat daily with a complete rat nugget or pellet as the staple. Offer small portions of vegetables, fruit, grains, and cooked egg as treats, and scatter some food to encourage foraging. Always provide fresh water from a bottle.8

What should a Double Rex Rat eat, and which foods are dangerous?

A Double Rex Rat's daily staple is a complete rat nugget or pellet. You can add small amounts of vegetables, fruit, grains, and cooked egg. Avoid dangerous foods such as chocolate, caffeine, grapes, raisins, onion, garlic, raw meat, and xylitol. For a full list, check with your vet.89

Should I bathe a Double Rex Rat?

Bathing is not usually needed because rats groom themselves well. If your rat becomes very dirty, ask a vet for safe guidance on how to clean it without causing stress.

Does a Double Rex Rat need brushing?

No brushing is needed for a Double Rex Rat. Its coat naturally thins and regrows in patches, which is normal. Provide plenty of soft nesting material to keep it comfortable.17

How do I look after a Double Rex Rat's nails and teeth?

Furry Diary's starting plan suggests checking your rat's nails every three weeks. Provide safe chew toys and wooden items to help wear down its teeth naturally. For nail trimming, ask a vet for the proper technique. Pet Wiki plan

How much space and exercise does a Double Rex Rat need?

Give your Double Rex Rat the largest multi-level cage you can fit, with shelves, ropes, ladders, and hideouts. It needs daily supervised time out of the cage, at least an hour, to climb and explore. They are most active at dusk and through the night.674

Should a Double Rex Rat live alone or with friends?

Double Rex Rats are very sociable and should live with at least one other rat, in a same-sex pair or small group. They also enjoy daily time with their human family.63

How long does a Double Rex Rat live?

A Double Rex Rat typically lives between 1.5 and 3 years. With good care, regular vet check-ups, and a loving home, you can help it enjoy a full, healthy life.64

Is a Double Rex Rat a good pet for children?

Double Rex Rats are curious, affectionate, and trainable, which can make them wonderful pets for children. They need gentle handling and adult supervision to ensure a positive experience for both the rat and the child.36

How do I hold a Double Rex Rat?

Safe handling varies by the rat's comfort level, so it's best to ask a vet or a good breeder for guidance. In general, support the rat's body fully and let it feel secure in your hands.

Written from the sources on this page, a few checked guides (VCA, ASPCA, RSPCA) and Pet Wiki's own starting care plan. A friendly guide, not a vet's advice.

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Where this comes from

Every fact on this page has a numbered source. Spotted an error? support@petwiki.app.

  1. AFRMA - Rex and Double Rex Rats afrma.orgused for genetics, coat description, whiskers, history
  2. AFRMA - Rex Rats afrma.orgused for rex origin 1976
  3. Fancy rat - Wikipedia en.wikipedia.orgused for patchwork name, coat cycles
  4. MSD Veterinary Manual - Description and Physical Characteristics of Rats msdvetmanual.comused for weight, lifespan
  5. AFRMA Rat Standards afrma.orgused for recognition, body type, body length
  6. RSPCA - Rats rspca.org.ukused for lifespan, temperament, social needs
  7. RSPCA - Rat environment rspca.org.ukused for housing, temperature, enrichment
  8. RSPCA - Rat diet rspca.org.ukused for diet basics
  9. ASPCA: People foods to avoid feeding your pets aspca.orgused for owner questions

Checked 2026-09-30. Text is written in our own words from these sources.