Rattus rattus vs. Rattus norvegicus: Key Differences and Identification Guide

Rattus rattus (black rat)

As global citizens, we share our habitats with a vast array of wildlife, including the much-maligned rat. Two species in particular, Rattus rattus (commonly known as the black rat or ship rat) and Rattus norvegicus (known as the brown rat or Norway rat), have adapted exceptionally well to human environments. In fact, they are among the most successful mammalian species living on Earth today. However, to the untrained eye, these rodents may appear virtually identical. This article will offer a comparative analysis of these two species, focusing on key differences and providing an identification guide to distinguish between them.

Body: The Physical Differences

Rattus rattus and Rattus norvegicus, despite their superficial similarities, exhibit several distinct physical differences. The black rat typically measures around 16 to 24 cm long, not including its tail, which can add an additional 17 to 24 cm. It usually weighs between 75 and 230 grams. On the other hand, the brown rat is considerably larger, with a body length ranging from 20 to 25 cm, a tail measuring about 18 to 21 cm, and a weight that can reach up to 500 grams.

Additionally, their appearances diverge. Rattus rattus, as the name implies, has a black or dark brown fur, with a lighter belly. It possesses a slender body with a pointed snout and large, prominent ears. Comparatively, Rattus norvegicus has a more robust body, sporting a brown or grey coat, and a blunt snout. Its ears are smaller and its tail, shorter than its body, distinguishes it from the black rat whose tail is longer than its body length.

Habitat and Behavior

Another key difference between these two species lies in their preferred habitats and behavioural tendencies. The black rat is an excellent climber, often found in the upper parts of buildings, trees, or other elevated structures. They have a preference for warmer climates, and their nests are typically located off the ground.

The brown rat, conversely, is less adept at climbing, but excels in digging. They often create extensive burrow systems and prefer cooler environments. They tend to nest at ground level, often in cellars, under sidewalks, or in other concealed locations close to food sources.

Dietary Habits

Rattus rattus and Rattus norvegicus have different dietary preferences as well. Black rats primarily eat plants, including fruits, seeds, and stems, although they can also consume insects and other small animals when necessary. The brown rat is more omnivorous, and while it can also eat plant material, it has a broader diet that includes meat, fish, and various types of waste.


In terms of reproduction, the black rat typically breeds throughout the year in warmer climates, with a peak in spring and autumn. The gestation period lasts about 21 to 29 days, and a female can produce 3 to 6 litters per year, each with up to 10 offspring.

The brown rat also breeds year-round, but is more prolific in cooler climates. It has a gestation period of around 21 to 24 days and produces larger litters, with an average of 7 to 8 pups, but as many as 14 in some instances.

Impact on Humans

Both species have substantial impacts on human populations. Due to their close proximity to humans, they’re often considered pests. The black rat, historically, is infamous for its role in spreading the bubonic plague during the Middle Ages. Today, both species can still spread diseases, contaminate food, and cause structural damage to buildings.


While Rattus rattus and Rattus norvegicus may seem similar at a glance, these two rat species exhibit significant differences in their physical characteristics, behaviours, and interactions with their environments. Understanding these differences is crucial for proper identification and control measures. As both species continue to coexist with us, it’s essential to maintain an informed understanding of these resilient rodents.

While they may not be universally adored, these rats offer a compelling testament to the remarkable adaptability and diversity of life on our shared planet. Despite their reputation, rats are an integral part of our world’s ecosystems and have more to offer than meets the eye.

Remember, while it’s fascinating to observe wildlife, always prioritize safety and health by keeping a respectful distance, especially with known pest species. For any rat-related problems, always seek advice from a pest control professional.

The Bubonic Plague and Rattus rattus

Historically, Rattus rattus has been implicated as the primary vector for the bubonic plague, also known as the Black Death, which ravaged Europe during the Middle Ages. This pandemic, which resulted in the deaths of an estimated 75-200 million people from 1347 to 1351, was triggered by the bacterium Yersinia pestis. It’s worth noting that Rattus rattus themselves were not the direct transmitters of this disease to humans. 

Instead, they served as hosts to the fleas (primarily Xenopsylla cheopis, the rat flea) that carried this deadly bacteria. The bacterium would infect and block the flea’s digestive system. When the flea bit the rat, it regurgitated the bacterium into the rat’s bloodstream, causing infection. When the black rat population declined during plague outbreaks, these infected fleas would seek new hosts, including humans, thus transmitting the disease. 

The commensal nature of Rattus rattus, living closely alongside human populations, further facilitated the spread of the disease, demonstrating the indirect, yet crucial, role these rodents played in this historical pandemic.

Rat Control and Extermination Services

Dealing with a rat infestation can be a stressful and challenging task for homeowners and businesses alike. Fortunately, professional rat control and extermination services are available to handle such situations effectively and humanely. These experts possess the knowledge, experience, and tools necessary to assess the severity of the infestation, identify the species (such as Rattus rattus or Rattus norvegicus), and pinpoint entry points within your property.

They implement targeted strategies that may involve trapping, baiting, and exclusion techniques, all designed to effectively manage the rat population. Additionally, they also provide advice on preventative measures to inhibit future infestations. This can include sealing potential entry points and addressing environmental factors that may attract rats, such as food and water sources. Engaging a professional service not only ensures the immediate issue is handled but also promotes a safer, healthier environment in the long run. It’s crucial to act promptly when a rat problem is suspected to prevent potential health risks and damage to property.

Karin HarndenKarin Harnden
17:14 05 May 24
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20:26 20 Feb 24
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