An empirical test of evolutionary theories for reproductive senescence and reproductive effort in the garter snake Thamnophis elegans

Some of you may have seen this article before (it's not a new a bit of research) but I just stumbled across it looking for something else.

Basically, it shows variations in clutch sizes and reproductive success in different populations of T. elegans. Not surprisingly, the larger the female the larger the clutch, however there was no change in the ratio of live births to stillborn and jellies. The authors ask a question as to why there had been no evolutionary driver to make reproduction more efficient in older snakes.