How old is a rat in human years?

Childhood and puberty

Compared to humans, rats have a brief, accelerated childhood. Rats develop rapidly during infancy and become sexually mature at about 6 weeks of age. Humans, on the other hand, develop slowly and don't hit puberty until about age 12-13 years (range: 8 to 16 years).

Adolescence and adulthood

Rats become sexually mature at age 6 weeks, but reach social maturity several months later at about 5 to 6 months of age (Adams and Boice 1983). In adulthood, each rat month is roughly equivalent to 2.5 human years (Ruth 1935).

Female rats enter menopause between ages 15 and 18 months (Durbin 1966), while humans enter menopause between 48 and 55 years (eMedicine).

Life expectancy

Domestic rats live about 2 to 3.5 years (Pass and Freeth 1993). In a survey of pet rat lifespans in the UK, the average lifespan was 21.6 months, and 95% percent had died by age 3 years (Clark 2004). In contrast, wild rats living in the wild tend to live for less than one year: 95% of wild rats die before age 1 year (Davis 1948).

The worldwide human life expectancy of humans is 66.7 years, but life expectancy varies a great deal between different countries. Human lifespan tends to correlate with economic development: people in the top 55 most developed nations have an average lifespan of 77.1 years, while people in the 33 least developed countries have an average lifespan of 49.4 years. In 2003, Japan had the highest life expectancy of 81.3 years, while Zambia had the lowest of 33.4 years (HD reports).

The rat's age in human years...so if we 6 rat weels times ...not thats not right..start again...if we have

Why are rat testicles so big?

The first sight of a male rat can be a shock to the uninitiated. Those testicles, giant pillow-like things hanging behind the rump, seem to take up one's entire field of vision. Rat testicles -- also known as torpedoes and goolies -- give rise to a lot of humor and embarrasssment.

So, why are rat testicles so large?

A species' sexual anatomy is related to its mating system -- who mates with whom. In species in which many males mate with one female when she is in heat, sperm from all these males is deposited in the female's reproductive tract in a short span of time. A male that deposits more sperm under these conditions will have a higher chance of fertilizing the female's eggs, and hence siring offspring. Males with larger testicles produce more sperm, and therefore have an advantage in such a sperm competition scenario. This is called sperm competition theory, because sperm from different males duke it out inside the female's reproductive tract.

Rats have just such a mating system in which multiple males mate with one female, especially at higher population densities. When a female rat comes into heat, she may be mated by multiple males in a short span of time. The male with the biggest testicles will produce the most sperm, which means he'll have a higher chance of fertilizing some of her eggs.

In contrast, species in which just one male mates with a female during her estrus don't have sperm competition, because the sperm racing to fertilize the female's eggs belong to a single male. There is no need to produce a lot of sperm, so males of such species can afford to have small testicles.

This relationship between testicle size and sperm competition holds true across the animal kingdom, and has been found in mammals (primates, sheep, rodents etc.), birds, amphibians, fish and insects. In fact, testicle size is considered an excellent predictor of a species' mating system. Species in which multiple males mate with a female in a short span of time encounter sperm competition and have large testicles relative to their body size. Species in which just one male mates with a female encounter no sperm competition and have relatively small testicles.

What about the testicles of humans and our close relatives, the gorilla and the chimpanzee? Gorillas are large 400 pound animals, but their testicles are tiny, a little over 1 oz together. Gorillas live in small groups in which one male mates with multiple females -- no sperm competition, hence the small testicles. Chimpanzees are much smaller animals, tipping the scales at 100 pounds, but they have large testicles weighing about 4 ounces together. Not surprisingly, chimpanzees live in groups with multiple males and females, and when a female comes into heat she may mate with several males in one day. This means lots of sperm competition, hence the large testicles.

Humans fall between gorillas and chimpanzees, with a body size around 150-200 pounds, and testicles that weigh about 1.5 ounces. Human testicles are neither especially large nor especially small. This indicates that humans have a mating system that was neither as promiscuous as that of the chimpanzee, nor as exclusive as that of the gorilla. Therefore, sperm competition probably played a small role in the evolution of our sexual anatomy and behavior.

That rat's got balls...

Are rats right-handed?

Yes. Just like in people, the majority of rats are right-handed, or "right-pawed."

Paw preference in rats was first recognized in 1930, when Tsai gave rats a small glass bottle of wheat germ. The opening of the glass bottle was so small that a rat could insert only one paw at a time. Tsai watched each of 105 rats grab food out of the container 250 times. A little over half of the rats (52%) used their right paws to grasp food out of the container 75-100% of the time, making them right-handed. About a third (31%) preferred to use their left paws, and a small number (17%) showed no paw-preference, making them ambidextrous (Tsai and Maurer, 1930).

More recent studies have found an even higher percentage of right-handed rats. In general, all these studies agree that most rats are right-handed, a smaller number are left-handed, and a few are ambidextrous.

Are left-handed rats more creative?