Here are some comments and a reference on the lifespan post. LIFE SPAN. Someone asked me if there was some sort of equation to predict life span. One current equation is: Lifespan = 11.8(body size in Kg) So ferrets, which average about .68 kG (1.5 lbs) for both males and females would be expected from the equation to live: Lifespan = 11.8 (.68) = 8.024 years. Understand, this is the *median* or average lifespan, and depending on the species, the distribution of deaths will follow a normal distribution curve (bell curve). In other words, when you add up all the age-at-deaths you can find for ferrets, they should be close to 8 years for males and females combined, but will include many that are much sooner or later than the expected value. This equation is for mammals in captivity; wild animals can be expected to average 1/3 to 1/2 of the predicted value. Brilliant readers who plug in human weights will discover we live about 4 times longer than expected, and the reason is still controversial. One idea is that in most mammals, the brain size is roughly correlated to body size, but in humans the brain size is markedly higher, but that doesn't actually offer an explaination, nor does it explain marsupial lifespans, who follow the body mass rule. Its still a mystery and is most likely related to the prolonged juvenilization of humans. One person wrote to say my final joke was in bad taste (What is a few years for people is a lifespan for ferrets). It was meant to be a pun, referring to "psychological time," which addresses the perception of time by individual species. This is a very complex issue, one which I feel has a lot of arguments left unproven, but it basically says those mammals that have shorter lifespans will PERCIEVE their alloted time similarly to those with longer life spans. In other words, a ferret may only live 8 years, but it will percieve its lifespan as roughly equal to that of a dog or a horse, even though the actual time is shorter. This is based on physiological efects of rapid metabolism, heartrates and respiration rates, and how the brain percieves time. Think of how the human eye sees things. The human brain visually sees time is slices of about 1/30 sec. each, which is why a movie running at 60 frames per second is seen as unbroken movement. Some studies have shown smaller mammals would see the movies as a series of still frames, because their brains see time in shorter segments. (This is one explaination why smaller mammals can react to movement much faster than humans can) The argument is those brains percieve time in tiny segments, which, when normalized to the human perspective, would add up to a human lifespan (or what it should be without us being such a nasty exception). So psychological time basically says the perception of time is relative to the species, but is correlated to metabolic and weight relationships. There are many good references on this subject, but I recommend for basic understanding: Knut Schmidt-Nielsen 1984 "Scaling: Why is Animal Size So Important?" Cambridge University Press. Bob C and 20 MO Furbutz [Posted in FML issue 2162]