Our time with rats as our Animal of the Month is drawing to a close on this last day of July. We hope that you not only enjoyed the fun and fascinating facts we posted about rats throughout the month, but that perhaps we also managed to change some hearts and minds about these incredibly misunderstood rodents. If you happened to miss any of our posts on “X” (a.k.a.) and/or Threads during the month, you can find a summary right here that you can reference any time. Did you know?:

• While there are more than 50 species of rats, our Animal of the Month will be focusing on just one – the wild brown rat (Rattus norvegicus). Nearly all rats kept in captivity are descendants of this species.
• Even though the brown rat is also known as the Norway rat, this species does not originate from Norway; but rather, from northern China.
• The reason brown rats are known as Norway rats stems from the belief that in the 18th century they landed in England on ships arriving from Norway.
• But some archaeological digs have uncovered brown rat remains dating back to the 14th century in places such as Tarquinia, Italy. This suggests brown rats were in Europe much earlier than initially believed.
• International trade and shipping have helped rats populate almost every corner of the globe. They can be found almost everywhere humans live.
• Going back to their origins in northern China, wild brown rats lived in forests and brushy landscapes.
• But rats are highly adaptable and, with their expansion around the globe, have adjusted to living in almost every type of environment with the exception of tundra, polar ice and desert.
• Because rats can be found in the vast majority of places where humans live, they have a “commensal” relationship with humans.
• This means rats take advantage of human shelter and food and benefit from living close to humans without creating a reciprocal benefit or causing direct harm.
• Antarctica is the only continent where rats are not found because not only is it too cold for them to survive outside, but there also isn’t enough of a permanent human presence there from which they can benefit.
• Rats are medium-sized generally slender rodents that grow to an adult size of about 40 cms (15.7 inches) in length from nose to tail. Females are typically a bit smaller than males.
• Rats have heads that narrow to a pointed snout which has fairly long whiskers. They have large round eyes relative to their head size and rounded ears.
• As their name suggests, brown rats naturally have a coat of short brown dense fur over most of their bodies. The underside of their bodies is usually a lighter colour, such as tan or grey.
• Selective breeding has resulted in domesticated brown rats with a wide variety of coats, colours, coat patterns and even eye colour.
• One of the rats’ most distinctive physical features is their long slender tails, which are slightly shorter than their body length.
• Did you know that rats can regulate their body temperature through their long tails?
• The tail has blood vessels which can control the amount of blood that flows to the rat’s tail. Heat from the blood radiates out through the tail, so higher blood flow keeps them cool while less blood helps them stay warm.
• Rats also use their tails to help keep their balance while travelling along fences, ropes or other narrow surfaces.
• Rats are both crepuscular and nocturnal animals, meaning they are most active at dusk, dawn and at night. They sleep in burrows during the day.
• Rat eyes are very sensitive to sunlight and other bright light. Even though rats can see in the dark, their eyesight is actually pretty poor. But other senses make up for the rat’s terrible eyesight.
• Rats have excellent hearing. Compared to humans, who have a hearing range of 20 Hz (hertz) to 20 kHz (kilohertz), rats can hear at a frequency of between 250 Hz and 80 kHz (approximately).
• Rats can hear sounds that we can’t. These sounds are called “ultrasonic,” which is defined as sounds which are at a high enough frequency that they are inaudible to human ears.
• Rats communicate to each other with ultrasonic sounds. Their excellent hearing also helps them pinpoint the location of both food sources and approaching predators.
• Rats also have an excellent sense of smell, which also helps them locate food and predators. Their sensitive noses will also help lead them to potential mates.
• To make up for their poor eyesight, rats rely heavily on their sense of touch to navigate their surroundings and identify objects. And they do this not with their paws, but with their whiskers!
• Rats use their whiskers much like we use our hands. They can even move each of their whiskers individually, just like we can move our fingers individually.
• In order to help them identify an object and determine its characteristics (e.g. size, texture, shape, etc.), rats will rapidly brush their whiskers against the object. This behaviour is called “whisking.”
• Check out this Science Bytes video from PBS to learn more about how similar rat whiskers are to human hands along with research being done on rat whiskers.
• The Summer Olympics started on July 26th in Paris, which is known as The City of Light. But did you know that Paris is a city of rats too?
• When it comes to cities with rat populations, Paris ranks fourth in the world behind New York City, London, England and Deshnoke, India. Paris has 2.1 million people and about 6 million rats inhabiting the city.
• Last year the City of Paris launched a new initiative with several partners, including the Pasteur Institute and Sorbonne University, called “Project Armageddon” to manage its rat population.
• While it may sound ominous, “Project Armageddon” is actually aimed at educating people about rats to dispel myths and misconceptions about them so Parisians can live more harmoniously with them.
• Rats are very social animals and need to be with other rats in order to live happier and healthier lives. Rats living alone will likely become lonely, depressed and anxious.
• It has long been known that rats have the ability to calm each other down by releasing pheromones, which are chemical signals released by one animal to be communicated to another.
• But in 2023, researchers from the University of Tokyo managed to isolate and identify the pheromone by sedating calm rats and using water to absorb pheromones from their necks.
• The researchers found that the main pheromone released by the calm rats was 2-methylbutyric acid (2-MB). It should come as no surprise that 2-MB is also found in the aromas of wine and cheese.
• The researchers then presented the lab rats with two small identical chambers – one laced with 2-MB and one without. They found that the rats were comfortable exploring the chamber with the pheromone.
• This experiment was repeated twice outside the laboratory with wild rats and the same results were achieved.
• Rats are naturally neophobic, meaning they are fearful of new things such as unfamiliar food, objects and situations. The researchers observed that the presence of 2-MB reduced the rats’ neophobia.
• The researchers are hopeful this can help develop more humane urban rat control by using 2-MB to lure rats into live traps and keeping them calm while they are being relocated.
• You may remember “Pizza Rat,” who was filmed dragging a piece of pizza down the steps into a New York City subway station. The Pizza Rat video fed into the myth that rats will eat anything and everything.
• While rats don’t literally eat anything and everything, they do have a diet made up of a huge range of foods. This adaptability has helped them achieve major success in establishing populations around the world.
• One German study of a rat’s stomach found evidence of 4,000 different items that the rat consumed. Most of those items were made up of plant matter.
• Rats are omnivores, meaning they both plants and animal matter. Rats living in urban areas are known for feasting on a wide variety of different foods discarded by humans.
• In addition to discarded human food scraps, rats not kept in captivity will eat things such as grain, seeds, fruits, flowers, eggs, chicks, small lizards and other small rodents.
• Rats are naturally great swimmers and those living near bodies of water have been known to catch and eat fish.
• When we think of pollinators, most often birds, bats and insects come to mind. But new and emerging research is encouraging us to think about rats as pollinators too.
• One Colombian study found that rats in the city of Duitama were eating the petals of the feijoa plants (Feijoa sellowiana), which are normally mainly pollinated by birds. But in Duitama, bird presence and activity are low.
• The researchers found that as the rats spent hours moving through and eating the petals of the feijoa plants, they came in contact with the plants’ reproductive parts.
• The researchers suggest that the rats could actually be the most prominent pollinator of the feijoa plant in urban settings where birds are not as active.
• Meanwhile in New Zealand, researchers caught an invasive black rat (Rattus rattus) on a wildlife camera seemingly drinking nectar from mountain flax plants (Phormium colensoi) in a wetland area.
• The researchers observed the rat drinking nectar from multiple flax plants without destroying the flowers.
• The researchers believe that the flax pollen stuck to the rat’s fur and was carried to other flowers much in the same way that the pollen sticks to and is carried by a bird’s plumage.

This is the fourth time we have featured rats as our Animal of the Month. We invite you to revisit our previous blog posts from June 2015, June 2018 and January 2020 to see what we posted the first three times around.