Looking to live forever? Common frogs might have a lesson to provide, at least if you are an ectotherm. Namely, as reported in paper to appear in Oecologia soon, there is a strikingly linear and tight positive correlation between mean age and the latitude of origin in these creatures. Frogs in southern Sweden complete their hectic lives in 2-3 years, whereas the northern ones enjoy – or endure – lifespans about four times longer. Most of this in hibernation though: as shown in the enclosed picture, the number active active days is reduced from 209 days in south to only 98 days in north. Hence, while the frogs in north are chronologically older than those in south, physiologically (e.g. in terms of energy burnt), they might strike about the same note as the their southern conspecifics.
Whatever the ultimate explanation for the differences in lifespan along the latitudinal gradient (reduced predation rate in north is the prime suspect), it is striking that the life history within a single species can vary this much over the relatively short geographic distances covered by this study. Consider two frogs born in the same year in south and north: once the frog born in south is about die, the northern conspecific has not yet matured sexually.
Hjernquist M.B., F. Söderman, K.I. Jönsson, G. Herczeg, A. Laurila & J. Merilä (2012) Seasonality determines patterns of growth and age structure over a geographic gradient in an ectothermic vertebrate. Oecologia, in press.
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A recent meta-analysis of longevity in amphibians finds no evidence for latitudinal patterns: “This potentially makes it impossible to find a latitudinal longevity cline”. A statement which in stark contrast with the pattern seen in figure above.
http://onlinelibrary.wiley.com/doi/10.1111/j.1095-8312.2012.01876.x/full
From the appendix of the paper, the reported maximum longevity for R. temporaria is 8.2 years. That is somewhat less than the 18 years reported in previous blog post (Polar frogs).
Sexual differences in age at first reproduction can explain “female-biased sex ratios in the subarctic common frogs” (Alho JS, Herczeg G, Merila J (2008))
The maximal age of 18 years is cool! I revealed the same ages in subarctic Bufo bufo only!