Senescence and costs of reproduction in the life history of a small precocial species

Species following a fast life history are expected to express fitness costs mainly as increased mortality while slow-lived species should suffer fertility costs. Because observational studies have limited power to disentangle intrinsic and extrinsic factors influencing senescence, we manipulated reproductive effort experimentally in the cavy (Cavia aperea) which produces extremely precocial young. We created two experimental groups: One was allowed to reproduce continuously (CR), the other intermittently (IR) by removing males at regular intervals. We predicted that the CR-females should senesce (and die) earlier and produce either fewer and/or smaller, slower growing offspring per litter than those of the IR group. CR-females had 16% more litters during three years than IR-females. CR-females increased mass and body condition more steeply and both remained higher until the experiment ended. Female survival showed no group difference. Reproductive senescence in litter size, litter mass ...