World's Largest Rat: Are They Kept As Pets Or Considered Pests?

Anusuya Mukherjee
Oct 11, 2023 By Anusuya Mukherjee
Originally Published on Nov 19, 2021
Closeup young vole mouse
Age: 3-18
Read time: 8.3 Min

Rats belong to the rodent family and there are 56 known species of rats living all over the world.

Animals, like cats and rats, have been represented in cartoons for a long time. It is quite natural for an animal, like a cat, to chase a rodent out of an apartment.

One of the most common found species in the world is the black rats and brown rats. These rats are said to have originated in Asia but are now found all around the world with the exception of Antarctica. In the search for the world's largest rat, it is believed that the Sumatran bamboo rat is discovered as the world's largest rat or the biggest rodent ever known to survive in history. It is also called the giant rat. The search of many species in history has the name 'large rat' replaced with a 'giant rat'.

This giant rat is about 20 in (50 cm) in length, a size similar to some common cats! But the rodent has a smaller length of the nose and smaller length of the tail than compared to the world's other giant rat or rodent family named the Gambian pouched rat.  Talking about a US giant rodent, a South American giant rat named the Coypu was discovered years ago in the US. Coypu is Native to the States, mainly South America since they thrive in warm environments. The species of a black rat can be found among them. Such a black rat is also called the Rattus Rattus. Animals tend to prey on such a rodent. In case any animal senses the sign of a rodent in the wildlife, the rat cannot escape with its tiny foot and skull. After reading about the world's largest rat species, also check out can rats eat bananas and are rats nocturnal?

What is the largest rat ever recorded?

Currently, there are 56 existing species of rats all around the world. But scientists have found several pieces of evidence which point towards the existence of a giant species of rats that weigh a lot, which is now Extinct. On the islands of Papua New Guinea, scientists excavated the skeleton of a species of rat that died years ago and is now Extinct.

These rats are said to belong to the Coryphomis genus and are suspected to weigh about 13 lb (5.9 kg) in their adult size. This species is now Extinct but the distant relatives of this species are found roaming on the islands of Papua New Guinea.

In terms of rats that are alive and thriving today, the largest rat species are Sumatran Bamboo rats. These species of rats are mainly found in China, but also in Sumatra. These rats can grow up to 20 in (50 cm) in height and the heaviest rat recorded in this species is known to have been 8.8 lb (3.99 kg). Sumatran Bamboo rats have brown or gray coats and mostly live below the ground in the burrow system. These rats live by eating the roots of various plants so they do not have to come above the ground unless absolutely necessary.

How big is an average sewer rat?

Rats tend to live in any conditions and can live on small amounts of food and water every day. They start breeding pretty quickly, at an age of about three to five months, and birth a litter of about 10 to 15 rats at a time. These rodents can eat anything which they can find, from leftovers to plant and fruit waste, even cardboard, and paper.

Due to the availability of food and the abundance of places where rats can find it, sewers are an optimum place for rats breeding and infesting. Rats who live in sewers can grow to weigh up to 2 lb (0.9 kg). This study was conducted by a student of Fordham University, Matthew Combs where the size of the largest rat he could catch from the sewers of New York City weighed up to 1.48 lb (0.675 kg). The research concluded that the average size of sewer rats in the New York City of the US was half a pound. The researcher claimed that though there is a myth that rats can grow according to the amount of food they consume, there are some physiological limits to which the rats can grow. He concluded the research by finding that however much the rats eat, most sewer rats cannot surpass the weight of 2 lb (0.9 kg).

How big do NYC rats get?

As reported in the Huffington Post in a 2016 article, a student of Fordham University conducted experiments to calculate the average size of rats in the sewers of NYC. The main aim of the research was to find out how these rodents colonize the sewers and other parts of NYC.

As mentioned above, concluding from the experiments, the researcher, Matthew Combs concluded that the average size of the rats in NYC was half a pound, but this size can grow up to two pounds for a fully grown adult rat. The largest rat which was caught by the researcher weighed 1.5 lb (675 g). That's almost the size of two medium-sized human hands.

How did the biggest rats get so big?

Rats are rodents who can live in almost every climatic condition except for extreme cold which can be found on the continent of Antarctica. These rodents thrive on almost every type of food as they are omnivorous animals.

Rats are animals that can eat waste food, plants, fruits, flowers, and garbage, and their diet also includes foods like paper and cardboard. The rats which live in forests tend to be a lot bigger than city rats because of their habitat.

In forests, there are no humans to step on them or kill them, hence their population lives safely inside the forests. In the case of city rats, compared to wild rats, they have a lot of access to sources of food due to human habitation. Humans are the largest producers of waste and the heaps of garbage collected every day in the cities serve as a primary source of food for these rodents.

Brown and black laboratory mouse

Are they more dangerous?

Contrary to popular belief that large rats are more dangerous, the fact is known that big rats are no more dangerous than smaller ones. Though huge and giant rats may look scarier because of their size, they are mostly harmless in the case of making direct human contact.

Rats tend to flee away from humans and keep to their underground places unless they find an extremely tempting source of food in your home or a warm and comfortable place to stay.

Rats may not directly harm you physically unless you get in their way, but they are the carriers of the most deadly viruses and diseases. Rats carry diseases like Salmonella, E Coli, rat-bite fever, and various viruses like the Hantavirus. Rats have also been proved to be the major spreaders of the bubonic plague. Hence, even though the differences in their size are not a threat per se, the diseases and viruses which the rats are capable of spreading are far more dangerous than their size.

Where are they found?

Rats are found in almost all parts of the world except Antarctica, as it is too cold there for the rats to survive. Rats are said to be native to the continent of Asia but have spread worldwide from there.

Rats are scavengers and opportunistic survivors, hence the most common species like black rats and brown rats tend to live within human civilization where they can live off the waste which humans create.

Since the 19th century, many people have also started keeping rats as pets. Several species of black rats as well as giant pouched rats are on the top list of pet rats. These rats are safe to keep as pets like any dog or cat, because of generations of selective breeding. These pet rodents also exhibit different behaviors than their wild counterparts and can also be taught certain behaviors and habits by positive reinforcement.

Rats are also primarily used in various lab experiments. Rats have been experimented on for several years now and they have helped us understand a lot about genetics, diseases, and several other medical fields which include testing of drugs and cosmetics. Experimenting on rats has caused several scientific breakthroughs and helped mankind in the health and medicine section.

Are they considered pests?

Apart from a very few rats which are pets, most of the rats which we come across fall under the category of pests. There are several reasons why rats are considered pests. One of the first and foremost reasons is that rats are carriers of several viruses and diseases like Salmonella, E Coli, and the Seoul Hantavirus. Rat bites are also infectious and can cause illness apart from spreading these diseases.

These fatal diseases can be caused by not just rat bites, but food or water which has been eaten or drunk by the rat. Their saliva carries these harmful pathogens which can affect the human body. Even rat feces or dead bodies of rats can cause various infections, hence it is advised to not touch any of these without proper protection, like gloves.

Apart from that, as rats are rodents, they like to burrow into places that need not specifically be mud and earth. Rats can burrow into your furniture and chew away at several things like your walls and wires, which causes a lot of damage to the furniture and the interior. Rats tend to chew wires and plastic because their teeth find these substances like plastic and rubber very good for their teeth. This habit of rats can destroy electrical appliances beyond repair. Hence, rats are considered pests in most parts of the world.

Here at Kidadl, we have carefully created lots of interesting family-friendly facts for everyone to enjoy! If you liked our suggestions for the world's largest rat then why not take a look at are rats good pets, or bosavi woolly rats facts?

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Written by Anusuya Mukherjee

Bachelor of Arts and Law specializing in Political Science and Intellectual Property Rights

Anusuya Mukherjee picture

Anusuya MukherjeeBachelor of Arts and Law specializing in Political Science and Intellectual Property Rights

With a wealth of international experience spanning Europe, Africa, North America, and the Middle East, Anusuya brings a unique perspective to her work as a Content Assistant and Content Updating Coordinator. She holds a law degree from India and has practiced law in India and Kuwait. Anusuya is a fan of rap music and enjoys a good cup of coffee in her free time. Currently, she is working on her novel, "Mr. Ivory Merchant".

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