Roof Rat Diet, Food & Treats

What do you feed your roof rats?

A complete formulated lab block is the base of their diet (we use Teklad 2018; we’ve also used Mazuri, either works). Everything else, fresh veg, the occasional treat, is an extra.

What treats can roof rats have?

Small, safe treats make great rewards, pumpkin seeds (pepitas) are a favorite, and ours are happy little rats when they get them. Blueberries and sweet peas are good too. Go very easy on almonds: they’re high in oxalates and dangerous in large amounts. The case that documents the kidney damage is a person who ate about five handfuls a day, not a rat, though rats are the standard laboratory model for this kind of stone.^[1]

Can roof rats eat cheese?

Yes, it’s not their favorite, but a little is fine.

I found an orphaned baby roof rat, what do I feed it?

Give puppy formula made from goat’s milk, for as long as it wants it. It is a better choice here than kitten milk. Softening rat food with a little apple juice or milk makes it more likely to start eating solids. Honestly, a mother raises babies far better than we can, ours are all mom-raised, so if there’s any way to leave it with its mom, do. If you can’t keep it, get it to an exotics vet or a wildlife rescue. (If you must hand-feed: rat milk runs roughly 36–38% protein and 45–48% fat with only ~9–10% lactose ^[2]. Those are proportions of the milk solids, not of whole milk: they add to more than 90%, and milk as fed is mostly water. Rat milk is about 31 to 32 percent solids as it comes out, and these figures come from studies on Norway rats, not roof rats. That makes a high-protein kitten formula look like the obvious match on paper. In practice it is not the safest one. Undissolved protein and undigested carbohydrate both raise the risk of bloat, and bloat is the number one cause of death in rescued babies, ahead of aspiration and then dehydration. Calories from fat are safer than calories from protein or carbohydrate, as long as growth and development are still supported, and the extra fat stores help a baby hold its own temperature. Whey dissolves more easily than casein, so a low-casein formula, or one that redissolves properly, is the safer pick. Pre-dissolved milk avoids the problem altogether but risks waste and spoilage. Goat’s milk is especially good here for its medium-chain fats. Never cow’s milk.)^[3]

What’s a good treat or forage mix for roof rats?

One mix we use, by weight: pepitas 5%, sunflower seeds 5%, organic whole oat groats 20%, organic hulled millet 25%, organic hulled barley 25%, freeze-dried blueberries 5%, freeze-dried garden peas 10%, freeze-dried strawberries 5% (roughly 15% protein, 9% fat, 65% carbohydrate, 14% fiber). Treat it as a forage supplement and bonding treat, not a replacement for the complete lab-block base.

Are roof rats the same as “fruit rats”?

Yes, in Florida they’re sometimes called fruit rats. It’s the same species, Rattus rattus.

Do roof rats need fresh water daily?

Yes, fresh water every day, ideally in a locking dish rather than a bottle. Roof rats love to poke a bottle’s ball valve and will happily flood the whole cage with it.

Is a complete lab block all my roof rats really need?

It’s the safe base of their diet, but I’ve come to think it might not be the whole story. Rats fed only lab blocks are probably missing micronutrients they’d get from a varied, foraged diet. A lot of pets have had this kind of problem before us; cats used to be taurine-deficient until people worked that out.^[4] It’s hard to know exactly what’s missing, so I treat a varied mix of fresh foods and good treats as more than enrichment. It might be essential for their long-term health, not just a nice-to-have.

Related: Care & Husbandry Guide.

Thinking about keeping or breeding roof rats yourself? See Successor Breeders Wanted and What It Takes, or get in touch.

Can rats eat fruit? What fruits are safe for rats to eat?

Rats love fruit, and many fruits are healthy treats. The video below shows some of their favorites, and our Rat Food List has the full list with safe amounts and what to avoid.

What kind of food do you recommend?

We used to feed our rats Envigo Teklad Global Lab Blocks  In Florida that is hard to buy, so we switched to Mazuri Rat Breeder pellets.

If you can get Teklad, then for young, growing rats (up to 1 year) you should feed them the 2018 diet with 18% protein.  Mazuri Rat Breeder is also 18% protein.

If your older male rat is gaining weight, you should consider switching him to a lower protein diet, such as 2014 diet with 14% protein.  This will help him maintain a healthy weight.

You can purchase these products online (Amazon, etc.), from a local Animal Feed Store such as Kissimmee Valley Feed Store, or from us.  There are other good brands, such as Oxbow, but make sure whichever you chose is specific for rats and has the appropriate protein percentage for your rat’s age.

Lab blocks should make up the majority (90%) of your rat’s diet, as they as specially formulated to be healthy, nutritious and rats like the taste.

But, they will get very boring, so it’s OK to give your rats the occasional treat.  Mostly, anything that you would feed a child is also OK, keeping in mind that too much fat, sugar, salt, preservatives, artificial colors and flavors and etc., are just as bad for rats as they are for you!

Things that rats especially love are: unsalted nuts (in moderation as they are fattening), frozen sweet peas (either frozen like ice cream, or defrosted, like pudding!), Cheerios, lightly salted microwavable pork rinds (i.e. Carolina Gold), whole wheat bread, some fruits (apple, pear, grape, melon), yogurt.  Roof Rats absolutely love almonds, which is exactly the danger (see the almond warning on this page)…

There are a few things that you should avoid feeding a rat: almonds (very high in oxalate^[1][5], a binge can be fatal, see the almond warning on this page), avocado skin and pit, raw or dried beans (cook them first), moldy or old peanuts and corn, apple seeds and stone-fruit pits, raw or green potato, and alcohol, caffeine, or carbonated drinks. Feed spinach only occasionally, since it is high in oxalate. Note: citrus flesh and a little chocolate are both fine for rats and are deliberately not on this list, the old warning against them was a myth carried over from cats and dogs.

If you have any questions or are unsure, please feel free to ask us!

Is chocolate safe for rats?

Yes, in small amounts. A little chocolate can act as a mild bronchodilator that may help a rat breathe a bit easier during a respiratory flare-up, but it is not a treatment; see a vet for any respiratory illness. Historical laboratory studies summarized in a 1991 IARC monograph reported an acute oral LD50 of 950 mg/kg in rats and about 300 mg/kg in dogs, and an average dog plasma half-life of 17.5 hours after single oral doses of 15–150 mg/kg^[6]. LD50 is a population-level experimental measure, not a serving size or safe-dose guide. The bronchodilator effect was measured on isolated guinea-pig airway muscle, where theobromine relaxes the muscle less strongly than theophylline^[7]. The only real limit is the fat and sugar, so keep it small. We have a fuller page on whether chocolate is safe for rats.

Are onion, garlic, and xylitol dangerous for rats like they are for dogs?

No. Onion and garlic cause a well-documented hemolytic anemia in dogs and cats, and the same organosulfur compounds can harm rats too, but only at experimental doses much higher than a rat would ever get from food. In food amounts they are not a meaningful danger. Xylitol does not cause the deadly drop in blood sugar in rats that it does in dogs^[8]. There is no reason to seek these out, but they are not the emergency for a rat that they are for a dog.

Why can’t my rat just throw up something bad it ate?

A rat has no vomit reflex at all, so it cannot throw up something that disagrees with it.^[9] That is why choking on a chunk or a small hard seed is a real danger, and why sticky, pasty foods like a glob of peanut butter can lodge in the throat. Cut food small, thin out sticky foods, and watch small seeds.

What is ergothioneine, and should I add it to my rats’ diet?

Ergothioneine is a natural antioxidant that rats can only get from food, since they cannot make it themselves.^[10] Their bodies build a dedicated transporter just to pull it in, then hold onto it for weeks, which usually means the body finds it worth keeping. It collects in the kidney, blood, liver and other hard-working tissues. We suspect it may matter to rats the way taurine turned out to matter to cats, a diet-only nutrient that processed food quietly left out. It is not a medicine and will not cure anything, but it is very safe and easy to add, so we keep it in the diet rather than wait for the science to finish. The full story is on our ergothioneine for rats page.

What foods are high in ergothioneine?

Mushrooms are by far the richest source, especially oyster, king oyster and shiitake, though even common button mushrooms have some. It originally comes from soil microbes, so foods grown in healthy soil, plus a little in organ meats, beans and oats, carry smaller amounts. Cooking does not destroy it. A bit of cooked mushroom chopped into the food a couple of times a week is the simplest way to get it into a rat. More detail is on our ergothioneine for rats page.

Do lab blocks and rat pellets contain ergothioneine?

Almost none. Ergothioneine comes from mushrooms and soil microbes, and the grain-and-soy base of most lab blocks and kibble carries very little of it.^[10][11] That is the gap we care about: a rat fed only pellets is probably getting almost none of a nutrient its body works hard to hold onto. It is one of the main reasons we feed fresh foods on top of the block instead of treating pellets as the whole diet. See ergothioneine for rats for why it may matter.

Do rats need taurine if they already make their own?

Rats can make their own taurine, so this is not like cats, who cannot and go blind without it.^[12][13] What we are doing is topping up an already-okay baseline, not fixing a deficiency. The reason it may still be worth it: a plant-and-grain pellet has almost no ready-made taurine, so adding a little is the only way to build up the tissue stores that support the heart, kidneys and aging muscle.^[14] We keep it at a modest maintenance dose, well below anything that could cause harm. The details are on our taurine for rats page.

Should I give my rat fish oil, or are flax and chia enough?

The real problem with most rat diets is not too little omega-3 on its own, it is far too much omega-6 from seeds and grains, which crowds out the benefit. So the first move is to cut back the heavy omega-6 seeds, then add a plant source like flax or chia. Rats can turn the plant form into the long-chain kind their brain needs, just not very efficiently, so if you want to raise tissue levels reliably a small amount of a ready-made source helps. We have had better luck with algal oil than fish or krill, which our rats often refuse. More on the balance and a practical plan is on our omega-3 for rats page.

What does betaine do for rats, and should I add it?

Betaine is a methyl donor, which means it helps run the quiet background chemistry that keeps the liver, kidneys and DNA maintenance working^[15], and newer work in mice suggests it may carry some of the anti-inflammatory, anti-aging effects of exercise^[16]. Grains carry some betaine, so a pellet diet is not starting from zero^[17], but there is no known roof-rat target, so we cannot say a pellet supplies enough. We add a modest amount to be safe rather than assume, and treat the longevity angle as promising rather than proven. The full picture is on our betaine for rats page.