What is the appropriate timescale for measuring costs of reproduction in a'capital breeder' such as the aspic viper?

Before we can quantify the degree to which reproductive activities constitu te a cost (i.e., depress an organism's probable future reproductive output) , we need to determine the timescale over which such costs are paid. This i s straightforward for species that acquire and expend resources simultaneou sly (income breeders), but more problematical for organisms that gather res ources over a long period and then expend them in a brief reproductive phas e (capital breeders). Most snakes are capital breeders; for example, female aspic vipers (Vipera aspis) in central western France exhibit a 2- to 3-ye ar reproductive cycle, with females amassing energy reserves for one or mor e years prior to the year in which they become pregnant. We use long-term m ark-recapture data on free-living vipers to quantify the appropriate timesc ale for studies of reproductive costs. Annual survival rates of female vipe rs varied significantly during their cycle, such that estimates of survival costs based only on years when the females were 'reproductive' (i.e., prod uced offspring) substantially underestimated the true costs of reproduction . High mortality in the year after reproducing was apparently linked to rep roductive output; low energy reserves (poor body condition) after parturiti on were associated with low survival rates in the following year. Thus, mea sures of cost need to consider the timescale over which resources are gathe red as well as that over which they are expended in reproductive activities . Also, the timescale of measurement needs to continue long enough into the post-reproductive period to detect delayed effects of reproductive 'decisi ons'.