Maternal traits and ecological conditions shape mother-offspring association in a capital breeding mammal

Aditi Mary Jacob , Madison Pfau, Molly H.F. McEntee, A. Marm Kilpatrick, Allison Payne, Patrick Robinson, Daniel Costa, Roxanne Beltran 

Maternal investment is central to life history theory and population dynamics. However, variation in maternal behaviors mediating investment, and the drivers and consequences of such variation, remain poorly understood. Using 30 years of data from 565 northern elephant seals (Mirounga angustirostris), we evaluated the intrinsic and extrinsic factors influencing mother-offspring association, calculated as the proportion of days a female was observed near a pup during lactation. Offspring weaning mass increased with mother-offspring association, linking variation in this behavioral metric to offspring quality. Despite high mother-offspring association across the population, association increased with maternal age until 8 years and pupping experience until five previous pups, declining thereafter, and decreased with local seal density and extreme wave and tide events. These findings highlight behavioral variation as a potential mechanism through which maternal state and ecological conditions shape offspring quality, such that even small behavioral deviations can have profound consequences for reproductive performance.