--> PICTURES

Classification / Natural History
Biology
Behavior
Feeding
Housing
Taming
Diseases
Links




CLASSIFICATION
phyllum : chordata
class : mammalia
order : rodentia
suborder: sciurognathi
family : muridae
subfamily: murinae
subspecies : Rattus rattus rattus
common name : black rat, ship rat.
other subspecies : Rattus rattus alexandrinus (Alexandria black rat), Rattus rattus brevicaudatus (Sawah rat), Rattus rattus diardii (Malayan black rat), Rattus rattus frugivorous (fruit rat).

NATURAL HISTORY
origin : the origin of the order of rodents is almost unknown, the oldest fossils - dating from Eocene (52 M.a) - already showing all its characteristics.

There are 2 theories about the apparition of rats in Europe :
- on Sambon point of view (1924) representations of this rodent in greck and roman paintings show that the black rat could has been in Europe for a long time.
- the second theorie (the most common) asserts that rattus rattus - coming from south-east Asian - has been introduced in Europe during crusades (XI-XIII centuries) ; in France this subspecies has been supplanted by Rattus norvegicus from the XVIII century (the first introduction has occured by english boats in 1730).

The 2 communities seem to alternately be dominant in an environment ; for example in Switzerland where Rattus rattus rattus have reappeared after having been expelled by R. norvegicus and having drove them back.

The rat's fear mainly comes from his role in the epidemics of plague which have ravaged human populations during the last centuries, and collective memory is very imprinted of this fear ; actually the black rat has been the main source of these epidemics cause he is very sensitive to this infection but the real danger was the flea which is the carrier of the disease from rats to humans.




BIOLOGY
The black rat is nocturnal but has some activity during the day.
In the wild R. rattus lives in dry zone, climbs well and can nest in trees or house roofs.
R. norvegicus prefers wet zones and often lives in sewers.
The norway rat (labs rat) is an albinos mutation of Rattus norvegicus.

adult weight : ~200-300g (Rattus norvegicus : ~300-400g)
body size : 16-21 cm (6.2-8.3") / Rattus norvegicus : 18-25cm (7-9.8")
tail size : 18-26 cm (7-10") / Rattus norvegicus : 16-21cm (6.2-8.3")

body temperature : 37,5-38,5°C (99.5-101.3°F)
cardiac rhythm : 270-350 beat/mn
breath rhythm : 66-114 breath/mn
urinary volume : 5,5 ml/24h/100g

longevity : 3-4 years (Rattus norvegicus : 2-3 years)
sexual maturity : 6-7 weeks
gestation : 21-23 days
litter : 5-10 babies, 3-6 times/year (Rattus norvegicus : 7-12 babies)
weaning : 21 days
sleep periods : 13 hours/24h

senses
smell : + + +
hearing : + + +
touching : + + + (the sensations are transmitted to the brain through the vibrissae)
taste : + +
nocturnal eyesight : +
diurnal eyesight : -
rat tail is an orientation, equilibration and thermic regulation organ.



BEHAVIOR

Social organization
Rats live in a group which is composed by individuals of the same family, having the same collective odor ; a kind of "super-group" without strict hierarchy but in which no intruder is admitted.
Rats can recognize each other by smelling, as each "super-group" has its own odor (a single rat can be attacked by his group if he has lost the collective odor). Individuals and trails are marked with urine.
The successive generations stay in the same colony and all defend their territory against other groups of rats.
Some studies show that R. rattus is more territorial (defends his whole territory) than R. norvegicus (only defends trails surroundings).

Cleaning behavior
It's an important part of the rat's activity : rats clean their ears, feet and nose to regulate their corporal temperature with saliva, and they clean their fur to coat it with a pheromone (which is produced by nostrils glands) that works on social sexual excitation (increasing the attention of the other rats).
Cleaning behavior also has a soothing effect if the rat is suddenly stressed (substitution activity).
Some mutual cleaning behaviors have been observed : it's used in calming aggressiveness - for example two rats (A and B) are playing together : A bites B / B shrieks / then A cleans B's fur.

Feeding behavior
By his omnivorous diet, the rat has always survived during droughts, seasonal insufficiencies and epidemics ; he always finds something to eat but the most important is to know what is eatable and what is poisonous. It must be said that rats can't vomit.
Wild rats are extremely prudent with new food, they wait sometimes several days before to taste it, and when they taste it they only eat a very small amount to evaluate its effects : some studies show that rats are able to associate a taste and its visceral consequences, even if effects appear several hours after ingestion.

If a rat eats a familiar food and at the same time a new food and becomes ill, thereafter he will keep clear of the new food but will continue to eat the familiar one : he learns by the past experience and deducts a classification ; rats seem to classify food in 4 categories :
- new
- familiar but dangerous
- familiar without danger
- familiar and positive

It has been showed that a rat can have a specific appetite in order to regulate a defiency, especially with thiamin (B1 vitamin) : thiamin deficient rats are able to choose foods that contain B1 vitamin ; if a rat only find B1 deficient food he will not consume it, considering it's a kind of slow poison, cause when he eats it, he doesn't feel good.
A rat can also choose nutriment to consume the one that will not increase his deficiency, preferring low carbohydrate aliments (carbohydrate increase thiamin metabolism).



FEEDING
omnivorous but not as much carnivorous than norvegicus.
until 6 months years old food must contains about 20% proteins, 4% fibers et 4% lipids.
adults : 14 % proteins, 6% fibers, 2% lipids.

for an adult :
- rat food (like laboratory food) or a mix of seeds for hamster/mouse
- + human food : a spoon of cooked vegetables (rice, pasta, green beans, carrot...) + yogurt + fish...
avoid fat food / too much salted food.



HOUSING
cage
minimum size : L 50 x W 40 x H 25cm (20"L x 16"W x 10"H)
but rats love to explore, so a bigger cage is the best (for example several floors cage).
see exemples of different cages on the picture page

room temperature : 18-26°C (65-79°F)
hygrometry : 40-70%

substrate
newspaper, wooden chips (beware of the wood dust : it can cause serious respiratory problems). do not use cedar chips (toxic).



TAMING
The rat is very easy to tame : you just have to keep him on you (inside your pullover) for a few minutes (10-20mn) every day and to offer him his favorite food.
Be careful : excess can be dangerous, especially in young rats : they need to sleep a lot during the day.




DISEASES
rats can develop a lot of diseases, repiratory problems, tumors, renal problems... especially when they are more than 1,5-2 years old.
here are some symptoms :
- weight loss
- fur problems : hair fall, bristled or sparse fur
- nasal or ocular secretions
- skin abscess
- respiratory problems
- anorexia - diarrhea, abnormal defecation.




LINKS

Virginia's Rat Page (links to websites : genetics, biology, diseases, information, feeding...) :
http://www.interlog.com/~audiotre/gin.html

Black rats :
http://members.madasafish.com/~cj_whitehound/Rats_Nest/Ship_Rats/Menu.htm