Code and data from: Silver spoons, reproduction, and growth catch-up in eastern grey kangaroos

Early growth and environmental conditions can shape life-history
trajectories. Long-lived iteroparous species with indeterminate growth
face growth-reproduction trade-offs for most of their lives. Poor early
conditions can delay primiparity and restrict growth, potentially
compensated for by faster growth later in life, at the cost of reduced
reproduction. We explored the variation in age at primiparity and early
reproduction in eastern grey kangaroos, based upon 13 years of monitoring
about 100 known-age females. We then examined associations between early
reproduction, later reproduction, lifetime growth. We used a modified von
Bertalanffy growth function to model the indeterminate growth of females
and to test the effects of early reproduction on lifetime growth.
Favorable environmental conditions, large size, and condition as a
subadult led to earlier reproduction and higher reproductive success at
ages 3-5. As females aged, size and condition had diminishing effects on
reproductive success. Females with greater early-adulthood reproduction
had slightly higher reproduction later in life. We did not detect a growth
cost of early reproduction. Large females in good condition favored early
reproduction over growth, while those with poor early growth exhibited
growth catch-up at the cost of reproduction both early and later in life.
As reported for other long-lived iteroparous species with indeterminate
growth, female kangaroos prioritize growth over reproduction for much of
their lifespan. Eastern grey kangaroos show heterogeneity in early growth
and reproductive strategies. Early primiparity and reproduction are
constrained by body condition, size, and environmental conditions when
females are pre-reproductive subadults.