Ratablog

How old is your rat?

In human years, that is. Because rats have such short lived lives (2.5 to three years is about average), it's hard to come up with something similar to "one dog year is equal to seven human years." I, personally, have said a five-week old rat is equal to about fifteen human years, a one year old rat is about 30 or 35 in human years, a two-year old rat is about eighty, and a three-year old rat is about 100. Bob and Curly, our two boys who lived more than forty months, would be about 110.

In Volume 21, Issue Six of the journal Nutrition, Dr. Robert Quinn D.V.M. addresses this issue in a non-scientific editorial. In scientific studies, the question is more than academic; as Dr. Quinn explains in his opening paragraph such questions as, "Is an 8-week old rat comparable to a teenager?" and, "Is a newborn mouse a good model for a newborn human?" are often asked after a study has been completed.

Writing in an informal style, Dr. Quinn compares six major lifestages (birth, weaning, puberty, musculoskeletal maturity, reproductive senescence [no longer able to reproduce], and the postsenescence period [average amount of lifespan from senescence to death]) between rats and humans. Even though he lists 13 citations at the end of his editorial, it's obvious to me Dr. Quinn is engaging in a thought experiment rather than a formal scientific study, and his conclusion should be taken with a small grain of salt.

Without going into too much detail, Dr. Quinn's break down of the lifestages is as follows:
Newborn: 13.8 rat days=1 human year
Weaning: 42.4 rat days=1 human year
Puberty: 3.3 rat days=1 human year
Musculoskeletal maturity: 10.5 rat days=1 human year
Reproductive senescence: 11.8 rat days=1 human year
Postsenescence: 17.1 rat days=1 human year

...and at the end, Dr. Quinn averages out the above numbers to determine...
Average: 16.7 rat days=1 human year

The only logical conclusion I can reach from this is we should have a rat birthday party every sixteen or seventeen days. I'm sure the rats would not argue.

Posted by Publius at June 5, 2005 09:55 PM