Lab rats have been staples of scientific research for over 150 years. With their friendly dispositions, small size, and short lifespans, they make ideal test subjects. But have you ever wondered why lab rats are almost always white?

As it turns out, there are several scientific reasons behind the predominance of white lab rats.

If you’re short on time, here’s a quick answer: Lab rats used in research are most often albino strains, which lack pigment and appear white. Their lack of pigment allows researchers to easily spot physiological changes during experiments.

Additionally, white coats make the rats easy to tell apart and observe. Read on for more details on the history and science behind white lab rats.

History of Lab Rats in Research

Lab rats have played a crucial role in scientific research for over a century. Understanding the history of their use can provide valuable insights into why they are predominantly white in color today.

Early Use of Rats in 19th Century

The use of rats in scientific experiments can be traced back to the 19th century. Researchers recognized the advantages of using rats due to their small size, short lifespan, and ability to reproduce quickly. These characteristics made them ideal for studying a wide range of biological processes.

During this period, rats with various coat colors were used, including brown, black, and even spotted varieties. However, as research expanded and standardized protocols were established, albino strains of rats emerged as the preferred choice due to their genetic uniformity.

Albino rats have a lack of pigmentation, making them easier to study and observe anatomical changes.

Emergence of Albino Strains in Early 20th Century

In the early 20th century, the emergence of albino strains of rats became more prevalent in scientific research. Albino rats, characterized by their white fur and red eyes, were easier to breed and maintain in controlled laboratory conditions.

Their genetic uniformity allowed researchers to minimize the variations between individual rats, ensuring more reliable and reproducible results.

Albino strains, such as the Sprague Dawley and Wistar rats, quickly gained popularity due to their docile nature and ease of handling. These strains became the cornerstone of many experiments, leading to a significant increase in their use in scientific research.

Rat Fancying Hobby Provided Lab Animals

Interestingly, the rise of rat fancying as a hobby in the early 20th century also contributed to the availability of lab rats. Rat fanciers selectively bred rats for various traits, including coat color and temperament.

These hobbyists inadvertently provided a steady supply of rats for scientific research, including the albino strains that were in high demand.

The hobbyist breeders played a crucial role in maintaining and refining the albino strains, ensuring their genetic quality and suitability for laboratory use. This collaboration between hobbyists and researchers helped establish a standardized rat model for scientific experiments.

Rise of Popular Strains Like Wistar and Sprague Dawley Rats

Over time, certain strains of lab rats, such as the Wistar and Sprague Dawley rats, became widely recognized and trusted in the scientific community. These strains were carefully bred and selected for specific traits, including their white coat color.

The Wistar rat, developed at the Wistar Institute in Philadelphia, and the Sprague Dawley rat, developed at the Sprague Dawley Farms, gained popularity due to their adaptability and widespread use in a variety of research fields.

These strains have become the gold standard for many types of experiments, contributing to the predominance of white lab rats in research today.

Advantages of Using Albino Rats in Research

Lack of Pigment Allows for Observation of Physiological Changes

One of the main advantages of using albino rats in research is their lack of pigmentation. Albino rats have a genetic mutation that prevents the production of melanin, the pigment responsible for coloration in animals.

This lack of pigment makes it easier for researchers to observe any physiological changes in the rats during experiments. For example, if a rat’s skin turns red or its eyes become bloodshot, it would be much more noticeable on a white coat compared to a colored one.

This allows researchers to quickly identify and monitor any changes that may occur.

White Coats Make Rats Easy to Identify and Monitor

Another advantage of using albino rats is that their white coats make them easy to identify and monitor. Unlike rats with colored coats, which can vary in shades and patterns, albino rats have a uniform and distinct appearance.

This makes it easier for researchers to keep track of individual rats and ensure accurate data collection. Additionally, the contrast between the white fur and any potential markings or lesions on the rat’s body makes it easier to spot any abnormalities that may arise during the course of the experiment.

Less Interaction Between Coat Color Genetics and Experiment Variables

When conducting experiments, researchers aim to control as many variables as possible to obtain accurate and reliable results. By using albino rats, researchers can minimize the potential interaction between coat color genetics and the experiment variables.

Coat color genetics can sometimes influence certain physiological traits or behaviors, which could confound the results of the study. By using rats with a uniform white coat, researchers can reduce the impact of coat color genetics on the experiment and focus solely on the variables they are investigating.

Early Familiarity and Availability Allowed Strains to Dominate

The dominance of albino rat strains in research can also be attributed to their early familiarity and availability. Albino rats were one of the first rat strains to be bred specifically for research purposes, and they quickly became the standard choice due to their ease of handling and breeding.

Over time, researchers became more accustomed to working with albino rats, and specialized breeding programs were established to ensure a consistent supply. This familiarity and availability have contributed to the dominance of albino rat strains in research laboratories worldwide.

Commonly Used Albino Rat Strains

Sprague Dawley Rats

Sprague Dawley rats are one of the most commonly used albino rat strains in scientific research. They are known for their docile nature, making them ideal for handling and experiments. Sprague Dawley rats are extensively used in a wide range of research areas, including toxicology, pharmacology, and behavioral studies.

These rats have a white coat due to a mutation in the gene responsible for pigmentation.

Wistar Rats

Wistar rats are another popular albino rat strain used in research. They were developed at the Wistar Institute in Pennsylvania in the early 20th century. These rats are known for their calm temperament and are widely used in studies related to neuroscience, physiology, and toxicology.

Their white coat is also a result of a mutation in the pigmentation gene.

Long-Evans Rats

Long-Evans rats are a strain of pigmented rats commonly used in research. However, they also have an albino variant that is occasionally used in specific experiments. These rats have a longer lifespan compared to other strains, making them suitable for long-term studies.

The albino Long-Evans rats have a white coat due to the absence of melanin pigment.

Fischer 344 Rats

Fischer 344 rats, also known as F344 rats, are a popular strain used in aging research, cancer studies, and toxicology. These rats have a white coat color due to a mutation in the TYR gene, which is responsible for the production of melanin.

Their albino variant is used in various experiments to study different diseases and their treatments.

Lewis Rats

Lewis rats are another commonly used strain in scientific research. They are known for their high susceptibility to autoimmune diseases like rheumatoid arthritis and multiple sclerosis. The albino variant of Lewis rats is used in immunology and transplantation studies.

Their white coat is a result of a mutation in the pigmentation gene.

Other Less Common Strains

In addition to the widely used albino rat strains mentioned above, there are several other less common strains with white coat colors. These include ACI rats, BN rats, and SD rats. While their usage may not be as widespread as the more popular strains, they still have their specific applications in various research fields.

For more detailed information about albino rat strains and their usage in scientific research, you can visit or

Rat Coat Colors and Patterns Beyond Albino

While lab rats are typically known for their white fur, there are actually several different coat colors and patterns that can be found in rats. These variations in color and pattern are a result of genetic mutations that affect the production of pigments in the rat’s fur.

In this article, we will explore some of the different coat colors and patterns that can be found in rats beyond the typical albino phenotype.

Agouti (Wild Type)

The agouti coat color is considered the “wild type” in rats and is the most common coat color found in wild rat populations. Rats with agouti fur have a banded pattern of fur, with alternating bands of dark and light fur.

This pattern helps the rat blend into its natural environment, providing camouflage and protection from predators. The agouti coat color is often seen in pet rats as well, and it can vary in shades from light to dark.

Black (Non-Agouti)

Rats with a black coat color have a mutation in the agouti gene, resulting in the absence of banding in their fur. Instead, their fur is uniformly black throughout their body. This non-agouti mutation is responsible for the black coat color seen in many lab rats.

Black rats are often used in scientific research because their uniform color makes it easier to observe and track specific traits or mutations.

Himalayan Pattern

The Himalayan pattern is characterized by a light-colored body with darker points on the nose, ears, feet, and tail. This pattern is similar to the coloration seen in Himalayan cats. The Himalayan pattern in rats is caused by a temperature-sensitive mutation, where the pigmentation is more pronounced in cooler areas of the body.

This pattern is often seen in fancy rats and can come in various color combinations, such as Siamese and Burmese.

Hooded Rats

Hooded rats have a distinct pattern where their head and shoulders are a different color than the rest of their body. The head and shoulders are typically white or a lighter color, while the rest of the body is a darker color. This pattern resembles a hood or cape, hence the name.

Hooded rats are popular as pets due to their unique and eye-catching appearance.

Dumbo and Rex Variations

In addition to different coat colors and patterns, there are also variations in the physical characteristics of rats. Dumbo rats, for example, have a unique mutation that gives them larger, rounder ears that are positioned lower on their heads. This gives them a distinctive and adorable appearance.

Rex rats, on the other hand, have curly or wavy fur due to a mutation in the hair follicles. These variations in physical traits add to the diversity and charm of pet rats.

Understanding the different coat colors and patterns in rats can not only be fascinating but also provide valuable insights into genetics and heredity. Whether you prefer the classic agouti or the striking black, there’s no denying the beauty and diversity found in the world of rat coat colors.

Are There Drawbacks to Using Only White Rats?

While white lab rats are widely used in scientific research, there are certain drawbacks to relying solely on this particular color of rats. These drawbacks primarily stem from the lack of coat color variety and the physiological differences associated with albinism.

Lack of Coat Color Variety Can Reduce Genetic Diversity

Using only white rats limits the genetic diversity of the rat population used in research. Coat color in rats is determined by a variety of genes, and different coat colors can be associated with different genetic traits and susceptibility to diseases.

By using rats of only one color, researchers may miss out on important variations in genetic makeup that could impact the results of their experiments.

According to a study published in the Journal of Experimental Biology, genetic diversity is crucial for research involving rats as it allows for a better understanding of the genetic factors underlying certain diseases and behaviors. Using only white rats may limit the generalizability of research findings and make it more difficult to extrapolate the results to other populations or species.

Albino Rats Have Poorer Eyesight Than Pigmented Rats

Albino rats, which are commonly white lab rats, have a genetic condition that affects their eyesight. Their eyes lack pigment, making them more sensitive to bright lights and reducing their visual acuity.

This can pose challenges in experiments that require visual acuity, such as maze tests or visual discrimination tasks.

Research conducted at the University of Maryland School of Medicine found that albino rats exhibited poorer visual acuity and greater sensitivity to bright light compared to pigmented rats. This suggests that using only white rats may introduce confounding factors in experiments that rely on visual stimuli or require precise visual discrimination.

Bright Light Sensitivity May Impact Some Behavioral Tests

Due to their lack of pigmentation, white lab rats are more sensitive to bright light. This sensitivity can impact certain behavioral tests that involve exposure to bright light or require the rats to navigate in well-lit environments.

The rats may experience stress or discomfort, which can affect their performance and behavior in these tests.

According to a study published in the Journal of Neuroscience Methods, bright light sensitivity can influence the outcomes of behavioral tests, such as open-field tests or light-dark box tests. It is important for researchers to consider the potential impact of bright light sensitivity when interpreting the results of these experiments.

Trend Toward More Diversity in Lab Rats

In recent years, there has been a growing recognition of the importance of genetic diversity in research animals. As a result, there is a trend toward using more diverse strains of rats in scientific studies.

This includes using rats with different coat colors, as well as rats with specific genetic traits or disease susceptibilities.

Organizations such as the National Institutes of Health (NIH) and the International Mouse Phenotyping Consortium (IMPC) have emphasized the need for increased genetic diversity in lab animals to improve the translation of research findings to human health. By using a more diverse range of rat strains, researchers can gain a more comprehensive understanding of the genetic factors influencing various diseases and behaviors.


For over a century, white albino rats have been the norm in scientific laboratories around the world. Their lack of pigment provides important advantages for researchers observing physiological changes during experiments.

Additionally, their distinctive white coats make them easy to identify and monitor compared to rats with fur patterns and colors. However, some scientists argue for increased diversity in lab rats to improve genetic variation.

While they may not be the only game in town anymore, the ubiquitous white rat has secured its place in the history of science.

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