Marshmallow was one of my pet rats who unfortunately has since passed away.

In the Chinese calendar, 2020 is the Year of the Rat, and today, April 4, is World Rat Day, so what better day to celebrate how an intelligent, social four-legged furry mammal has hugely contributed to our understanding of the world and especially ourselves.

Ratsand miceare staples in basic science research about human physiology and psychology. Although they are not a perfect analogue to humans, rats and mice both are among the most important animal models available to study human disease, effects of environmental exposures and interventions to address both.

What is World Rat Day?

April 4 became World Rat Day in 2002 when a group of rat breeders, pet owners and fans decided to assign a day to celebrate rats as wonderful pets. As a completely biased owner of a dozen pet rats and an occasional rat rescue foster mom, I completely agree with their lovely companionship as pets, but I also recognize their value in scientific research.

But Are They Pets or Research Animals?

Theyre bothand they are definitely pests too. Few New Yorkers probably have a love for rats because they genuinely cause problems as theyve been taking over that city and others, such as leaving droppings that can carry disease and chewing through wires and other materials.

Its important to distinguish between pet rats that have been explicitly bred (and even shown!) for centuries to be pets and the pests, including those that mayor may nothave contributed to spread of the plague, which remains an open question. Both Rattus rattus, the black rat, associated with the plague, and Rattus norvegicus, the brown rat kept as pets and used in research, can be pests, but pet rats, known as fancy rats, have been bred for centuries apart from wild rats, just as lab animals are special bred for different purposes.

Im not unaware of the contradiction in loving ratswhich have very clear personalities of their ownas pets and in recognizing that they have no choice regarding their sacrifice in lab experiments, after which they are usually euthanized. But Im also aware of the extremely strict guidelines that govern how lab animals are housed and cared for. As a member of too many rat pet owning and breeding online groups (though Im not a breeder), I can tell you that lab rats are cared for far better than many under the care of pet owners (and unfortunately some breeders as well).

I always explained to students that we will be respectful, because these were living things, and just as they helped advance knowledge in their life, so they would do after their death, New Zealand biology teacher Madeleine Ware told me regarding her students use of ex-lab rats in their dissections.

Rats have short lifespans, 2-3 years as pets and shorter in the wild, and every scientist I know who uses rodents in their work takes their wellbeing during those short lives seriously.

Further, what we learn from research involving rats and other lab animals benefits more than humansthe larger body of scientific knowledge gained from those experiments has been applied to caring for animals across the spectrum in veterinary medicine and in understanding our worlds ecosystems better so that we can make better decisions in environmental stewardship of the planet and all its life.

Didnt Rats Cause the Plague?

Rats have long been blamed for spreading the plague in the Middle Ages, but recent research has called their culpability into question. Even if they werent the main culprit, I don't think rats are quite off the hook yet, Dr. David Orton, of the Department of Archaeology at the University of York in England, told me.

We can be fairly confident rats weren't a crucial factor in all cases, since they just don't seem to have been sufficiently ubiquitous in all the places they should have been for the rat-flea-human model to stack up: the far north of Europe in the Black Death, western Europe during the Justinianic plague, rural settlements, etc., Dr. Orton said. But at the same time, we know that the model works, in the sense that rats plus fleas do transmit plague. And we also know that rats were common in at least the bigger and better connected settlements during both pandemics. How much a role rats played, like so much else in science, remains an open question.

Rats Contributions to Research

Rats contributions to science are far less controversial. Rats rose to prominence as research animals largely due to the Wistar Institutecurrently working on a COVID-19 vaccineand its development of the Wistar albino strain, according to scientists Jacqueline Phillips, Alison Hogan and Erin Lynch in The Conversation. At the time of that article, 117 albino strains of the lab rat had been developed, each with different characteristics suited to different types of research.

Some of the most important biomedical research of today relies on rats:

Scout and Cleo were rescued from an accidental litter. I fostered them from DFW Rat Rescue and then ... [+] adopted them.

Why Rats Instead of Mice?

The mouse is undoubtedly far more widely used in medical research than the rat, but the rat has been catching up in the past decade or so as technology has allowed it. Millions of years of evolution separate the rat and mouse, as a 2009 paper notes, and the rat offers many advantages over the mouse and other organisms.

Rats are larger and easier to handle, and its also easier to do repeated blood draws from rats. Their physiology may also more closely mimic human physiology in many cases, write scientists Philip M. Iannaccone and Howard J. Jacob.

They note that rats are particularly important in studying cardiovascular disease, such as stroke and high blood pressure, because their physiology is a little closer to humans and is more easily tracked. Rats are also among the most important animals for studying human reproductive and endocrine systems, especially effects of environmental exposures, such as endocrine disruptors and toxic chemicals.

In models of diabetes, the rat model behaves more like the human disease in important ways, including the ability of environmental agents (e.g. toxins, stress, diet and vaccination) to modify the disease, scientists Philip M. Iannaccone and Howard J. Jacob write in that paper. The rat models of breast cancer are superior to those in the mouse insofar as they are hormone responsive with histopathology and have premalignant stages that more closely resemble the human disease.

Rats are also substantially more intelligent than mice and have easily observed behaviors that correspond, to varying degrees, with human behaviors and experiences, such as compassion, fear, cooperation, care-taking, and various types of pro-social and anti-social behavior. They have very clear personalitiesas any rat owner can tell youand these characteristics make them valuable in a wide range of behavioral, cognitive, learning and neuroscience research.

When I worked with rats, training them in the water maze, I had one who was the carer, Professor Catherina Becker of the University of Edinburgh told me. Every time I put a rat back, he would come and start cleaning and drying off the wet arrival. They really do have pronounced characters.

Can Rats Help Us Treat or Prevent COVID-19?

We dont yet know which animal models will be best for understanding COVID-19 or a possible vaccine for it. Scientists are in a mad rush to identify the best animal candidates, which means the disease acts in the animal as much as possible as it does in humans.

But even if the rat isnt ultimately involved directly in developing and testing therapeutic drugs or vaccines for COVID-19, the research will be built on existing knowledge that involved rats. Whatever we find to treat or, hopefully, to prevent COVID-19, at least some of our gratitude should go toward the rat.

Davis was one of my favorite rats and recently left behind his brothers Martin and Sinatra.

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Its World Rat Day In The Year Of The Rat: Gratitude For Rats Role In Biomedical Advances - Forbes