Factors potentially driving inter-population variation in senescence rates.

Creek temperatures were measured during the breeding period via hand-held thermometers or data loggers. Values are the average and SE across days (N). Migration distances were measured as the shortest straight-line water distance from the mouth of each focal creek to the ocean. Migration elevation gain was measured as meters above sea level for the lake into which the focal creek drains [44]. Predation rate represents the average of the yearly percent of breeding salmon killed by bears. The standard error represents the among year variation in the percent of salmon killed by bears. Predator selectivity for salmon showing little senescence represents the average (± SE) of the predicted predation rate across the first full three days in-stream (i.e., the average of the first three points presented in Figure 2).