Older mothers follow conservative strategies under predator pressure: The adaptive role of maternal glucocorticoids in yellow-bellied marmots

► We performed a study on yellow-bellied marmots under the stress of predation. ► We investigated whether stress during pregnancy affected the offspring. ► We found that predators had both direct and indirect effect on marmot pups. ► The effect depended on the age of the mother. ► Older mothers were conservative and probably increased their own fitness.