Intro To Rats

The brown rat- Rattus norvegicus- is a common and ubiquitous rodent on its home planet of Earth. The largest of the mouse-like rodents, individuals can grow up to 30cm in body length, with males being larger than females. Despite its Latin name the species originated in Asia but rapidly spread worldwide, now residing on all continents except Antarctica. The key to their success was the spread of another global species: Homo sapiens. Rats quickly learnt that humans are wasteful of food and built excellent dwellings to hide in, so wherever humans settled the rats were not far behind.

Physical Capabilities

Rats have generally poor eyesight, limited to a few metres at best. They do however possess excellent hearing and olfactory abilities. Rats can hear ultrasound and communicate with each other using squeaks too high for humans to hear; audible (to human) squeaks are rare and usually made as a sign of annoyance or pain (as a note, whenever you see rats in a film, the squeaking is always dubbed on). A full 1% of a rat’s DNA is dedicated to smell, which they use for finding food, identifying family, and communicating with each other.

Although quadrupedal in nature, a rat’s forelimbs are noticeably slighter than their rear ones. This allows them to comfortably sit upright, freeing up their dextrous front paws. This position is generally assumed when a rat is eating, allowing them to manipulate objects in their ‘hands’. They can also stand upright on their hind legs, usually to get a better look/sniff at something of interest. 

Rats are excellent swimmers and are naturals in the water. With partially webbed feet and the ability to hold their breath, rats will happily dive underwater in search of food, including molluscs and fish.

Rats are well known for their acrobatic skills, able to scramble up vertical surfaces, balance on thin edges, and squeeze through tiny gaps. There are few places a determined rat cannot get to! One of the important tools of their balancing acts are their large tails, which can be swung about to change their centre of gravity in the same manner as a tightrope walker using a pole. The tail is also plays an important part in thermoregulation.

A notable trait of rats is their intelligence. They are incredibly clever animals, able to figure out solutions to problems and learn from each other. They can also recognise individual human faces and voices, quickly learn new tricks, and memorise routines. Rats have a well-earned reputation for being wily creatures, and their surprising intelligence has been a major contributor to their success. As many owners will attest, some pet rats even seem to enjoy trying to outwit their human keepers!

Rats are non-aggressive (except to their prey), and prefer to flee or hide rather than fight. A cornered rat however is capable of remarkable bravery and will charge (or even bite) a far more powerful threat; this is usually a distraction, with the intention of surprising the attacker long enough for the rat to makes its escape.

Feeding And Nutrition

Rats are gourmands and can and will eat nearly everything they can get their little goblin hands on. In the wild their diet is mainly grains, but they will also happily eat shoots, fruit, eggs, vegetables and meat. Even non-food products such as leather and rubber can be devoured. Rats have little dietary restrictions and a high resistance to poison, meaning that they can eat nearly anything, even food toxic to other animals (such as chocolate). One of the few foods they cannot eat though is grass- they simply do not have the system to digest it.

The key to their culinary success is their teeth and jaws. With strong teeth and incredibly powerful jaw muscles rats can gnaw through most materials, including hard ones like concrete. This means that there is little food that can stand up to an assault from rats; shells and bones are quickly gnawed open for the goodies within. The gnawing motion also reduces food to small particles before being swallowed, so unlike dogs, cats and humans, there is no chance of splintered bones being stuck in the throat. The two halves of the lower jawbone are not fused, meaning that both sides (and the attached teeth) can move independently of each other. Generally this ability is used to help a rat manipulate and chew oddly-shaped food, but in a fight or hunt it allows them to splay their teeth to inflict more damage (giving rat bites their characteristic ‘V’ shape).

Although rats are generally viewed as prey animals, they are also active predators. They will happily attack and kill insects and other small animals, such as chicks or mice. Needless to say, if you have wild rats living in your house, then you certainly won’t have wild mice!

Curiously, rodents cannot vomit. This makes them exceptionally cautious when trying new food, as there is no way of getting bad food out of the stomach once it’s in there. Fortunately with their high toxin resistance rats are quite adept at avoiding food poisoning, so when faced with a novel food rats will have a little nibble then wait to see how they feel.

Lifestyle

Rats are extremely sociable animals- indeed, it is cruel to keep just one rat by itself. Rats live in groups called ‘mischiefs’ (ask anyone who’s ever owned pet rats, they’ll tell you why). Within a mischief there is a strict pecking order, with the alpha rat at the top and the rest of the group in hierarchical order. There are no equals within a mischief- every rat knows if they are dominant or subordinate to another rat; a hierarchy which is formed by squabbles and dominance behaviours such as shoving and boxing. Once everyone has established their place a mischief will function quite peacefully, with no challenges to the structure unless something like a death drastically changes things.

Contrary to popular belief rats are extremely clean animals and hate being dirty. They will spend around a quarter of their waking time grooming themselves. They also enjoy grooming each other as a sign of friendship. Dominant rats may often pin a subordinate down and give them a good ‘power groom’, just to reinforce who is boss (“I like you enough to groom you, but don’t forget who’s the strongest”).

Rats are caring and empathetic and will often take care of sick packmates by bringing them food and cuddling up to them for comfort. If a friend is in distress (such as being trapped) they will investigate and attempt to help. Some individuals also appear to be aware of the concept of death and will show both surprise and distress at the passing of a loved one.

Rats breed very quickly; individuals reach sexual maturity within five weeks, with females able to produce around 5 litters a year. Rats are good mothers and provide excellent care to their babies, who are born blind and helpless (known as ‘eepers’ due to the squeaking sound their make to alert their mother). Litters are generally around 7-8 in number, though higher and lower numbers are not uncommon.

As any rat owner will tell you, each rat has its own unique personality; they can be bold, shy, curious, brave, timid, naughty, mellow, grumpy, cheeky…they are as varied as humans. Consequently, they have a wide range of behaviours and easily adapt to new situations, making them incredibly successful creatures with a lot of evolutionary potential, as we shall see in this project.