Birthdate, mass and survival in mountain goat kids: effects of maternal characteristics and forage quality

In temperate environments, early-born ungulates may enjoy a longer growth p eriod before winter, and so attain a higher body mass and an increased prob ability of survival compared to late-born ones. We assessed the effects of maternal characteristics, forage quality and population density on kid birt hdate, mass and survival in a population of marked mountain goats (Oreamnos americanus) in Alberta. The duration and timing of the birth season were s imilar in all years. Births were highly synchronised: 80% of kids were born . within 2 weeks of the first birth. Maternal age, maternal social rank and density did not affect kid birthdate or mass. Previous breeding experience was not related to kid birthdate, but kids born to pluriparous mothers wer e heavier during summer than kids born to primiparous mothers. Male and fem ale kids had similar mass and accumulated mass linearly during summer. Earl y-born kids were heavier than late-born kids. Faecal crude protein (FCP) in late spring and maternal mass were positively related to kid mass. Surviva l to weaning appeared higher for males (90%) than for females (78%), but su rvival to 1 year was 65% for both sexes. FCP in late spring, density, birth date and mass did not affect kid survival to weaning in either sex. Surviva l to 1 year increased with FCP in late spring for females, but not for male s. Survival to I year was independent of birthdate for both sexes,;but heav y females survived better than light ones. Multiple logistic regression rev ealed a positive effect of mass on survival to 1 year when the sexes were p ooled. Our results suggest that mountain goats are constrained to give birt h in a short birth season synchronised with forage productivity.