dinosaur life span

The dinosaur age lasted tens of millions of years. But how many generations does this represent? In short, are there any estimates as to the average life span of a dinosaur? I understand that some sea turtles are estimated to be hundreds of years old, and that there are trees thousands of years old. So, is it possible that some types of dinosaurs lived to be thousands, or even tens of thousands, of years old? Thanks, MzF

New Scientist, 18 November 2000 (no. 2265):

'[John C.] George had access to the frozen remains of 48 bowheads killed between 1978 and 1996. He thawed out the eyes, removed the lenses and sent them to [Jeff] Bada ... Four of the whales were more than 100 years old, and one was 211.' There is a margin of error of up to 25 years, but that makes the animal as likely to have been 236 when it met its premature death as 186, and that still exceeds the age range you provide. The source the article's writer cites in the piece is 'Age and growth estimates of bowhead whales (Balaena mysticetus) via aspartic acid racemization', John C. George et. al., Canadian Journal of Zoology, vol. 77, p. 571 (1999).

The most recent

That's the one, but since all the animals used for the study were the victim of hunters neither a natural maximum age for the species nor any clear idea of how close to the average any of the dead specimens was is possible. There are more numerous accounts of hunt victims being found with aged harpoons in them, which date at least to the mid-1800s but could be far older since the technique used to produce them hadn't changed for centuries. Animals which became targets of harpoons 150 years ago would have been mature specimens if not necessarily especially old, and were still going until killed by the hunters who found them, so ages over 150 would seem to be rather more common than the analysis of bowhead remains implies.

I am not

Not a doctot, I'm afraid, hence my references from popular science magazines rather than more detailed journals.

Animals with a

Another popular science reference, I'm afraid - from a documentary about a Romanian species. It spends by far the majority of its time in a torpor, which probably explains the extended lifespan if the programme was indeed accurate. On the other hand, even a third of that is impressive in bats.

So it is; I've no idea where 't' came from.

The 'r' comes from

They are, but there does seem to be a correlation between similarly-sized animals (say, between many frogs, lizards and rodents up to around a foot in length) which adopt the r-strategy - in this case between six and seven years is the normal maximum. It's not a scientifically noteworthy observation, but might give some pointers regarding probable upper and lower maximum age ranges for comparably-sized extinct animals when their behaviour is understood well enough to judge whether they favour r or K strategies.

Philip Bowles

Hello,

Mr. Bowles, thanks for the clarification on the bowhead age. As I noted, I had the abstract available electronically, but we do not get the Canadian Journal of Zoology, so I did not see the article.

Based on my reading of bat literature (which is fairly extensive), I would suspect that the documentary was not accurate in its age estimate for the bat. There are numerous species with recorded ages of 25-30 years in the wild and several species with captive specimens in the 20-30 year range. The greatest verified age for a European bat that I have seen is 30 years for the Greater Horseshoe Bat (Rhinolophus ferrumequinum) (Schrober and Grimmberger, 1997).

In terms of lifespan of small rodents. I think you would find that a six to seven year life span in most small rodents would be akin to a 150 year life span for a human. Most species of small rodents probably max out somewhere closer to 4 years (with real expectation in the wild less than 2 years). I can't comment on similar sized frogs.

Reference cited Schrober W and Grimmberger E (W Charlton, trans.). 1997 The Bats of Europe and North America. Neptune, NJ: T.F.H. Publications, Inc.

Rick Toomey Illinois State Museum