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The Three W’s of Animal Identification - What, When & Why

What? Past vs. Present ID Methods

Identifying individual research animals like mice is a critical aspect of many medical research programs because it allows researchers to accurately track and monitor the behavior and health of individual animals. There are several methods that have been traditionally used to identify mice, including tattoos, ear notches, ear tags, and toe removal. However, these rudimentary approaches have several disadvantages that make them unsuitable for modern research methodologies. Injectable radio-frequency identification (RFID) tags have emerged as a superior alternative for identifying laboratory mice, providing many benefits over traditional methods.


Identifying each research animal with a unique alphanumeric code is considered to be the best practice for all laboratory animals and is required in certain research scenarios. This identification is as critical to the overall management and welfare of the animals as it is for the success of the scientific research that relies on them. Animals should be tagged with a unique identifier as soon as you receive them in your laboratory. For toe removal and tattoos, it is usually done on very young mice in the first days of life. Injectable RFID tags are also usable when animals are very young, typically 9-12 days. When you identify your new mice as soon as they are received into your laboratory or as soon as they are old enough, you can be sure to maximize the effectiveness and value of the identification program.


When comparing animal identification methods, it is important to consider accuracy, animal welfare, costs and convenience.


Injectable RFID tags provide increased accuracy in animal identification which can result in increased accuracy in your studies. Unlike tattoos, ear tags and ear notches which 1) provide only tens to hundreds of potential unique identifiers, 2) can be difficult to read, or 3) can fade or fall out over time, RFID tags provide a virtually limitless supply of unique and permanent identifiers. This allows researchers to track individual animals over the course of their lives and ensures that they are correctly identified and attributed to the correct data. Furthermore, RFID tags can be read quickly without handling the animal, allowing researchers to quickly and easily identify and track multiple animals at once.

Animal Welfare

Another key component not to be overlooked is the ID method’s effect on animal welfare. Injectable RFID tags are minimally invasive. Tattoos, ear notches, ear tags, and toe removal all require physical alterations to the animal and can cause discomfort, pain, or even bleeding.

In contrast, RFID tags are simply biocompatible glass encapsulated microchips that are inserted under the skin. The procedure is quick and relatively painless. Quality of animal life after application is also important. While long term consequences of these various ID methods are understudied, RFID tags are not known to cause long term pain or distress for the animals.

Ear tags are often not a good choice because other animals may chew on them, making them unreadable. They can also become caught on other things in the cage, and they can even be ripped out of the ear when snagged or chewed by other animals. This leads to discomfort, aberrant behaviors, and injuries.

Animal welfare is also an issue when misidentification requires sacrificing animals without capturing any scientific value. Keeping the 3 Rs in mind (Replacement, Reduction and Refinement), we want to be sure that we avoid such mistakes whenever possible in order to reduce the number of animals used in studies while maximizing the scientific research gained from each animal’s life.

Cost Savings

Injectable RFID tags are also more cost-effective than traditional methods. Because they only require a quick injection under the skin to apply, they are a fast and easy animal identification method. This time savings can result in significant cost savings. And because the unique ID numbers associated with injectable RFID tags positively identifies each animal, you will avoid costly mistakes during studies that could result from misidentifying animals. By scanning each animal before any procedure or data collection, you can quickly confirm that the correct animal has been selected, improving the speed and accuracy. Avoiding repeated procedures or entire studies saves thousands of dollars.

Identifying animals by scanning their RFID tag can also result in labor savings as compared to manual visual identification. Consider this example of a study that requires you to weigh 100 animals 10 times during the study and consider that 30 similar studies are happening across the institution that year. With manual identification and documentation it takes 208 hours per year to weigh those animals (25 seconds per animal) and costs $5,008 per year ($24.04/hour salary). But with RFID based methods it takes just 42 hours per year to weigh the same animals (5 seconds per animal) and costs only $1,002 per year. That’s an 80% cost savings on this simple task!

In conclusion, injectable RFID tags provide a superior alternative to traditional methods for identifying laboratory animals such as mice. They are less invasive, significantly more accurate, cost-effective, convenient, and more humane, making them the preferred method for many researchers. The use of animal identification allows researchers to accurately track and monitor the behavior and health of individual mice, helping to advance our understanding of these important laboratory animals, while also setting the foundation for accurate billing and documentation within your organization.


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