Feeder rodents are rodents that are fed to pet reptiles, mainly snakes. After many years of consolidation and growth, feeder rodent farming has turned into an invisible form of factory farming. Indeed, we estimate there are 200-650 million feeder rodents produced globally each year.

In 2019, saulius wrote an article estimating the total number of feeder mice, and bringing attention to some of their welfare issues. Here, we build on salius’ work through additional research, including conversations with members of the feeder rodent industry. We provide a new estimate of the size and scope of the industry, an overview of how feeder rodents are farmed, the market structure of the global feeder rodent trade, the major customers and farming operations, and welfare considerations based on our interviews and a site visit to a small rodent farm. Finally, we discuss two concrete ways to help the hundreds of millions of rodents farmed each year: public pressure campaigns against zoos, and creating sausages that could serve as an alternative to whole animal feeding.

Industry Overview

Feeder Rodent Population

We estimate that there are 200-650 million feeder rodents produced globally each year. Of these rodents, we estimate 150-500 million are mice and 28-120 million are rats. There is also a small amount of guinea pigs farmed each year, fed to the largest of snakes, birds of prey, and felines, but we expect this number is very low relative to the total number of rodents. This estimate is congruent with salius’ previous estimates of 85 million to 2.1 billion. The estimate also aligns with a report in the Independent which pegged the number at 167 million feeder rodents sold in the US in 1999, which was well before the large Chinese farms entered the market, though it is unclear how the author reached his conclusion. 

Rodent Farming

Rodents are farmed in tubs that are placed in rodent racks. Depending on the size of the operation, each tub will include male and female breeders in a ratio of roughly 4 to 6 females to each male, and some number of litters of baby rodents. In larger operations, it is not uncommon for one tub to have 10 male, 60 female breeders, and many baby rodents. Each tub is typically lined with liquid absorbent bedding, usually wood shavings or paper strips. Rodent food is generally supplied in the form of formulated pellets that sit on wiring on top of the tub opening, and water is provided either via gravity-fed bottles or automated watering systems that run throughout the rack. 

Each mouse will generally have 5-10 litters per year and around 3-20 children per litter. Rats can have up to 8 litters per year and average 8 children per litter. These ranges can vary widely based on environmental conditions and evolved changes to the breeding line. Some operations will selectively breed for higher litter size or other desired traits and will cull breeder females when they become unproductive. Children are “pulled” or “harvested” from the tubs, often pre-wean, and killed. Weaned children are often placed in a separate tub where they grow to the desired size before being killed. Farming large numbers of rodents can thus be quite concentrated, with small buildings able to produce millions of rodents per year. For example, the photo below shows Mice Direct’s mouse farm in Georgia, which you can also see a video of here.

Replacement breeders are taken directly from the colony. The rodent population is therefore self-propagating, meaning that genetics are not as heavily optimized as they are in other areas of animal agriculture. Colonies of rodents can collapse occasionally, typically as a result of disease. In these circumstances, which one industry professional told us can happen every 2-3 years, replacement breeders would be purchased live from another operation.

Slaughter

Slaughter methods depend on the age of the rodent and the size of the farming operation. Feeder mice and rats are exempt from the Animal Welfare Act and are thus, according to an industry document, not subject to any sort of welfare regulations. The American Zoo Association, which accredits most of the major zoos in the US, states that feeder animal vendors should adhere to AVMA standards (see here, especially page 60-62). The large feeder rodent producers claim to kill via regulated flow CO₂ inhalation. After slaughter, rodents are generally put in zip-locked bags and frozen before being distributed.

Mice and rat neonates, referred to in the industry as “pinkies” can take 30 minutes to 1 hour to die from CO₂ inhalation, and so AVMA standards allow alternative methods like live freezing of mice and rats that are under 10 days of age. Flash freezing with liquid N₂ is also an AVMA acceptable euthanasia method for rats and mice under 5 days. Standard practice is to freeze live neonates, which comprise a significant portion of total feeder rodent sales.

There aren’t good ways to enforce that these approved methods are being used. For example, in our visit to a small rodent breeder, they killed rodents by violently hitting them against the sides of their cage.

Live vs Frozen

Rodents can be fed to snakes either live or frozen. If frozen, rodents are first thawed and then put into the enclosure with the reptile. Frozen feeding is much more common, but in some countries like the US, live feeding is still practiced. Live feeding is a topic of considerable and heated debate within the snake owner community, and in some countries like in the UK, appears to be extremely rare. Indeed, most large centralized operations, which exclusively freeze their rodents, discourage live rodent feeding on their websites. Major zoos in the US also do not engage in live feeding unless it is required to stimulate the prey drive of the species. The major concerns around live feeding are the safety of the reptile (live rodents can sometimes fight back and injure snakes), and the welfare of the rodents.

Feeder Rodent Production: Local

Most feeder rodents are produced by one of a small handful of consolidated producers (see below). However, up to one-third of global production consists of smaller producers that distribute locally. 

There are four options for acquiring locally produced rodents: farming your own, buying from a local small rodent farm (example here), buying on a reptile forum or social media platform, or buying a pet mouse or rat from a pet store (which is generally more expensive). As snake keeping is a hobby, there are many people who decide to start small-scale farming of feeder rodents to feed their own reptiles. Many of these hobbyists will end up producing more than they need and will start selling their excess to friends or on reptile forums, facebook, or instagram, and some of these hobbyists will evolve into small local rodent farms. We classify anything produced from these four channels as local production. Some of these locally produced rodents are sold live and some are sold frozen. Nearly all live rodent sales are from local channels since shipping live rodents is more burdensome and costly, especially over long distances.

We spoke with multiple feeder rodent industry professionals to try to understand the breakdown between local and centralized production. The owner of one top distributor of frozen rodents, said that there was no data on this topic, but he would estimate that it could be that up to a third of feeder mice in the US are purchased locally from hobbyist/ local/ and regional farms. Another industry professional said that the number could be less than that, but that there is simply no data. We did find one government report from the UK that corroborated that local production was less than one-third of total feeder rodent purchases. The report states that 80% of the total feeder rodents consumed in the UK were supplied through a few main distributors in 2008.

There are also structural reasons why the number is likely fairly low: snake owners may not live close to a regional or local rodent farm, and given some of these local purchases are live, you can not buy in bulk unless you have your own cages, driving the cost per mouse higher. Forum and social media posts also suggest that many snake owners believe feeding live is dangerous for the snake. Based on our conversations with producers and the structural reasons that disincentivize live and local rodent sales, we estimate that the global upper bound for locally produced feeder rodents would be a third of total production, and it is probably lower.

Feeder Rodent Production: Centralized

Centralized farming operations thus account for over two-thirds of global feeder rodent production. All centralized farming operations produce frozen rodents, and many produce millions of rodents per year. One example of a commercial operation can be seen here. There are centralized farming operations in China, the US, and Europe. Some of these operations are vertically integrated where the company will breed the rodents, distribute to zoos and pet stores, and also manage a direct-to-consumer ecommerce channel. Many of the largest distributors in the US have large farming operations themselves or employ a contract growing model where the distributor owns the brand, but is buying from separately owned large farms. As there are no public rodent breeding companies, it is difficult to know exactly which companies own their own farms vs use a contract farming model. In the US, Canada, and the UK, it is clear that centralized distributors also supply a patchwork of downstream distributors that focus on supplying smaller customers.

Major Distributors and Farming Operations

RodentPro is likely the largest producer in the world by number of rodents. They employ a contract farming model and have a network of farms around Indiana from which they source for wholesale and export. RodentPro, and possibly some of the other US distributors, also buy excess rodents produced by the major lab rodent companies like Charles River, Jackson Labs, and Taconic. They also have a strong ecommerce business, accounting for 42% of the web traffic to major US rodent producers (the next largest being Big Cheese Rodent Factory with 17% and Perfect Prey with 11%).

Global Trade

The estimates of our global feeder rodent production model suggest that the US and China account for around three quarters of global production, producing 43% and 31% of global feeder rodents respectively, though our estimates imply a wide possible range. This is congruent with qualitative assessments from the industry, global import data, and extant information from the farms themselves. European centralized and local production makes up the bulk of the remaining quarter of global production. 

China is a major exporter of rodents, and it is likely that the US exports some of its production as well. Public and complete trade data is available for imports into the US, and so we were able to compile information about frozen rodent shipments from China to the US, but because public shipment data is not available for many European countries and some Asian countries, it is less clear what other markets the three Chinese companies export to and to what markets the US companies export to. One Chinese producer reports exporting to Japan, Europe, and Hong Kong. There is also evidence that US companies export to Europe, and a UK government report that implies that at a minimum three of the main US distributors are exporters to the UK.
 

Chinese production has grown significantly in the last decade, with one company, Yukylin, opening its farm in 2014 and is now likely producing 20-40 million rodents per year. Honfer, another of the three Chinese farms, just started exporting to the US in 2021 and is now likely producing 5 to 25 million rodents per year. The three major Chinese exporters are all based in Qingdao. Daren Fucheng has a strategic partnership with Qingdao Agricultural University. Unlike the main US producers, Daren Fucheng and Honfer also both also supply genetically engineered mice to Chinese research laboratories. 

The export data, pulled in September of 2023, implies that Chinese exports to the US grew at a compound annual growth rate of 35% between 2017 and 2023. By estimating the percent of exports that are mice vs rats and estimating the mean weight exported of each species, it appears exports from China to the US are between 23 to 62 million rodents annually as of 2023. 

The large US importers are primarily the major distribution companies and farms. Some of these importers like RodentPro use imports to supplement their own production. Others, like American Rodent Supply, which has imported 307,000 kg in the last 8 years, have no production facilities of their own. Companies like Layne Labs and Big Cheese Rodent Factory are likely to be supplementing their own domestic production with these imports.

Costs

The cheapest pricing we could find was from one of the three Chinese farms and wholesalers. This pricing requires ordering a minimum of 100,000 animals, and likely more because it assumes that you would be filling up a refrigerated shipping container. We heard from one smaller farm in the US that the main input into costs is labor, but it is possible on a large scale commercial farm or in markets with cheaper labor costs that feed and bedding also become important constituents of total cost.

 US ecommerce costs are more expensive than this: on RodentPro.com pinky mice are sold for $0.34 each, and jumbo mice are sold for $0.99 each. To purchase frozen rodents online, the customer has to purchase enough to justify the substantial cost of being shipped on dry ice. Customers will therefore usually have freezers where they can store the reptile food. If a customer wants to purchase from a local store prices are even higher. One local reptile store we visited sold pinkie mice for $1.30 each and adult mice for $1.80 each. At PetCo, a large national pet store, pinky mice were sold for $2.16 each and large mice for $4.75 each

Customers

Globally, the vast majority of feeder rodents are being fed to pet snakes in private homes, pet stores, and reptile breeding facilities. We estimate that there are 7 to 11 million pet snakes in the world, a number that has increased significantly in the last few years over Covid. A US survey from the American Pet Products Association found that the number of reptile owning households grew 33% from 2020 to 2023, and has doubled since 2012. We believe that zoos and wildlife rehab centers for birds of prey are the only other major customers for feeder rodents, and we estimate that they comprise between 2% and 20% of total farmed feeder rodent consumption. We found no evidence that carnivorous animal farms, whether crocodilian or snake, represent a significant portion of farmed feeder rodent sales, instead relying on formulated diets composed of animal agriculture byproducts and some vegetable protein.

Welfare Considerations

In their 2019 article, saulius highlights many of the welfare concerns that we also encountered during our research for this paper including lack of space, shelter, daylight and activities, along with the fact that these rodents generally live in their feces and are sometimes fed live to snakes. A PETA investigation into what we would classify as a small local farm also highlighted the disturbing conditions that these rodents face, including ineffective and cruel euthanasia methods and drowning. Some other welfare concerns are listed below.

Infanticide

Infanticide and cannibalism can be common in mice and other rodents. There also may be some evidence that increases in stress can induce higher rates of matricide or infanticide. During our visit to a rodent farm, the farmer said that it was “very common” to pull out a tub and find that there had been a “rampage” where a mother killed children. It was also common, he told us, for female mice to kill pups that were not their own, and for adult males to engage in aggressive behavior towards each other. Rodents that are wounded from these encounters, but not killed, may have to wait days or up to a week to be found by the farmers, and when found either euthanized or, as we witnessed at this farm when a bloody mouse was found in a tub, thrown into a bucket to be discarded alive.

Injury and Disease

A few of the breeders that we talked to expressed that they purposefully let disease and viruses run through their colonies because it developed a hardier and more effective breeding line. One farmer we spoke with said that some of these diseases, like mange or ringworm, can cause open wounds for the rodents. Treatment of disease is extremely rare given that any individual rodent has little economic value. Any rodent with physical disfigurations from disease or fighting that would exclude it from being sold is therefore discarded rather than treated. 

There are frequent Salmonella outbreaks tied to feeder rodents, and there is at least one instance in the academic literature of a large-scale cull of feeder mice due to Lymphocytic Choriomeningitis Virus (LCMV), likely on a RodentPro farm. Some of the breeders we talked to purposefully kept “dirty” colonies, meaning there were minimal biosecurity measures in place. One operator of a small breeder farm said that he purposefully allowed wild mice or rats to interbreed with his colonies to increase the natural disease resistance of his rodents. In his words, “no one cares if the mice have a sniffly nose every so often.” 

Slaughter Methods

There are no regulations that govern euthanasia for feeder rodents. Some of the larger operations may be governed by AVMA standards if they choose to sell to zoos which have an AZA accreditation. However, it seems unlikely that purchasing zoos inspect the feeder rodent facility before they purchase, and there is no evidence that the AZA certifies feeder rodent operations. 

Regardless, we estimate that 15-33% of feeder rodent production is local, on small distributed farms or hobbyists’ basements. These small farms and individuals are not supplying zoos and thus have no commercial need to adhere to AVMA standards. It does appear that some of these rodents are euthanized using CO₂ inhalation, but many of these will not be killed in CO₂ chambers that are filled with a regulated flow. According to the AVMA, unregulated flow of CO₂ can be painful for the rodent if the flow rate is too high or can cause distressing shortness of breath if too low. Our visit to a small rodent breeder, described below, demonstrates that AVMA guidelines are not always followed.

Our visit to a breeder

We visited one small local reptile store with a rodent breeding operation in a back room, likely with over 1,000 rodents that were used to feed the reptiles in the store, and which were sold live to customers. We were very surprised about how open the store was to sharing details about their operation. Given that feeder rodents have not received much attention from animal activists, it’s possible that feeder rodent producers are generally less guarded, although some of the large producers we talked to definitely were concerned about increased attention leading to regulation. The door to the breeding room was kept open and was visible to customers as they walked in. The main operator of the breeding room seemed eager to show off his breeding system, and gave us a tour when we expressed interest. During this tour, we witnessed some disturbing cruelty:

• Each plastic bin containing rodents was partially transparent. In the corner of many bins, under the litter bed there were what seemed to be partial or full carcasses of dead rodents that had not been removed, and which had been gradually pushed into the corners.
• When the operator opened the first mouse bin, there was a dead bloody mouse, who was likely attacked by another mouse in the bin. The unphased operator picked the mouse carcass up and tossed it casually into the large trash bin in the center of the room.
• While the operator was talking to us, an owner of the store came to take around ten rats to be fed to the reptiles in the store. Making no effort to conceal his actions in front of strangers, he picked each rat up by the tail and swung their body against a metal beam on the bin rack in order to kill them. He then tossed each mouse into a small plastic container, where we noticed some were not fully dead, but just injured or knocked out.
• The operator bragged that he had selectively bred his rats to be more docile so that they wouldn’t bite him. To demonstrate this, he picked up multiple large rats and handled them roughly, holding them close to his face and petting them aggressively to demonstrate that they would not bite him.

Paths to Impact

We have identified two interventions that we believe could help feeder rodents.

Public pressure campaigns against zoos

Mirroring the success of corporate campaigns in encouraging egg producers to convert to cage-free production, it may be effective to target downstream purchasers of bulk frozen rodents to enforce welfare standards on their suppliers. AZA accredited zoos in the US seem like the best target for this. Since many zoos are publicly owned, some of their frozen rodent purchase orders are publicly visible (see for example Springfield 2017, 2021, Cleveland 2017, Miami 2016, Boise 2023, and Norfolk 2023). Since zoos purchase in bulk, they generally use the larger rodent producers such as RodentPro. Zoos could account for up to 20% of frozen rodent consumption, so may be able to effectively pressure their suppliers to implement basic welfare standards and comply with third party audits. Additionally, supporters of zoos may care about animal welfare, making zoos good targets for public pressure campaigns. We’re not sure what the desired outcome should be, but there could be welfare standards from lab rodents bred for experimentation that could be easily ported over to feeder mice. Alternatively, zoos could be pressured to use alternative products, like the ones discussed below.

Alternatives to whole animal feeding

Mirroring the success of alternative proteins as a method to help animals, it’s possible that in the future alternative methods of feeding could become more common, such as through sausages. There’s many examples in the academic literature of snakes being fed homemade sausages instead of whole rodents (e.g. here and here). Additionally, there’s a company called Reptilinks that does this (feeding example here). 

We’ve heard that there are some challenges with feeding snakes sausages as opposed to whole animals. Firstly, snakes can be very picky eaters, and sausages won’t always trigger their predatory instinct. That said, we’ve heard this can be a problem for all feeding methods, and it’s not clear how much worse this is for sausages compared to other methods. Reptilinks recommends getting around this by applying mouse or chicken essential oils to the casing of the sausage. Secondly, we’ve heard that snakes can sometimes “attack” their prey before eating, sometimes causing the sausage casing to rupture. However, this seems like a solvable problem with some product development. 

On snake owner forums, and in discussions with snake owners, it seems like Reptilinks has a lukewarm reputation. Some other problems we’ve heard about include:

• Many consumers think Reptilinks is more expensive than whole animal feeding. However, Reptilinks claims that their products are more calorie dense, meaning that snakes need to be fed less often.
• Many snake owners worry about the health of their snakes on a sausage-based diet. There seems to be a belief in the snake owning community that complete snake nutrition must include things like bone, connective tissue, and organs. To counter this worry, Reptilinks claims that their sausages include “whole prey,” and are “rigorously lab tested by the Ohio Department of Agriculture.”

Despite Reptilinks’ reputation, it seems to us like the status quo of whole animal feeding should in theory be extremely unpleasant for most people. Often, snake owners will keep frozen rodents in their main freezer, where they also keep food for human consumption. When feeding, snake owners need to thaw each rodent out in warm water before feeding. If the snake doesn’t eat the rodent right away, some snake owners will dangle the rodent by the tail in front of the snake for up to 15 minutes. Others may cut the rodent’s carcass open to make it more appealing to the snake. It seems implausible on its face that consumers would elect to keep doing this if there were more pleasant options available.

That said, in all of our conversations, snake owners seem to get used to this process very quickly, and aren’t actively looking for alternatives. In some cases, there is a sense among experienced snake owners that if you don’t have the stomach to go through the feeding process, you have no business owning snakes. Therefore, it may be more effective for a sausage product to be marketed towards new snake owners that haven’t yet gotten used to the standard feeding methods.

It seems like there are ways that Reptilinks’ products could be improved. They use very expensive ingredients, possibly to combat the worry about snake health. However, a sausage that used primarily contained byproducts of animal agriculture could be substantially cheaper. Additionally, Reptilinks sausages are stored frozen and shipped on dry ice, significantly adding to the cost. In theory, it should be possible to create a shelf-stable sausage product that would be significantly cheaper to ship. It’s also possible that sausages stored at room temp could be packaged in an oily or liquidy environment (like cat food or tuna) leading to more prominent volatiles which could help with the feeding challenges.

It’s likely that sausages would need to be filled with animal products, at least in the beginning. If these animal products were mainly byproducts, or products from larger animals like cows, this would likely still be a huge win for animal welfare. However, one snake expert we spoke with pointed out that our scientific knowledge of snake nutrition is underdeveloped, and it’s possible a healthy snake's diets could involve a substantial amount of plant-based materials. One piece of evidence in favor of this is that farmed crocodile diets can involve up to 100% soy protein, in order to keep costs down. This could be an important area of further research.

Urgency

Now might be a particularly good time to prioritize the welfare of feeder rodents, given the overlap with in-ovo sexing, which is becoming more common in Europe. In countries where day-old male chicks are primarily culled via gassing rather than maceration, their bodies remain intact, allowing them to be sold as feed for snakes, birds of prey, and other animals that generally eat whole animals. 

The UK government’s Animal Welfare Committee recently issued an opinion endorsing the use of in-ovo sexing as an alternative to male chick culling. However, it also noted that if the UK banned male culling as some countries in the EU have, this might increase demand for imported rodents. According to the report, 70% of the male layer chicks killed in Great Britain go to two large wholesalers that then freeze them and sell them as animal food. 60% of these chicks go to feed raptors in a variety of settings, 30% to zoos that use them to feed a range of species, and 5% to reptiles kept as pets. Many of the paths to impact noted here for pet snakes could also be used in theory for rodents that are fed to raptors and other birds of prey. 

If you’re interested in possibly working on either of these interventions, please don’t hesitate to send me a direct message here on the forum!