摘要：Spring and summer–autumn nutrition are the prime determinants of reproductive investment in most largeherbivore populations, though winter severity is known to affect reproductive rates in some situations. To evaluate the effects of a long-term decline in winter habitat quality, a diet shift away from sagebrush (Artemisia spp.) during winter, and differential habitat selection during spring–autumn on pronghorn (Antilocapra americana) reproduction, we assessed female and fawn condition, maternal investment, and early fawn survival in migrant and nonmigrant portions of the Yellowstone pronghorn population in Montana and Wyoming during 1999–2001. Mean female mass at capture in late winter (46.81 kg, SE = 0.66), pregnancy rate (0.94, SE = 0.03), date of birthing (median = 1 June), litter size (1.90, SE = 0.07), ratio of litter mass to maternal mass (0.134, SE = 0.005), fawn mass at birth (3.08 kg, SE = 0.07), and fawn survival to August (0.15, SE = 0.04) were within the ranges reported for populations elsewhere, and birth dates were uncorrelated with female mass and indexed condition the preceding winter. However, fawn age at death (median = 7 days) was correlated with indexed fawn condition at birth, and indexed fawn condition and age at death were significantly greater for migrants occupying higher-elevation interior areas during the summer than for nonmigrants occupying the winter range year-round. Winter habitat conditions did not appear to substantially limit reproductive rates in this population during the study period. Our data suggest that spring and possibly summer nutrition may be higher for migrants than for nonmigrants, resulting in higher perinatal mass in migrant fawns and reduced neonatal mortality.La nutrición durante la primavera y durante el verano-otoño primaveral y veraniega–otoñal son losconstituye el principales determinante principals de la inversión reproductiva en la mayoría de poblaciones de herbívoros grandes, aunque la severidad del invierno afecta las tasas reproductivas en algunas situaciones. Para evaluar los efectos de un descenso de largo plazo en la calidad del hábitat invernal, de una dieta con menos artemisa (Artemisia spp.) durante el invierno, y de diferencias en la selección del hábitat durante primavera–otoño sobreen la reproducción del berrendo (Antilocapra americana), nosotros examinamos la condición de las hembras y cervatos, la inversión maternal y la supervivencia temprana de cervatos en grupos migratorios y no migratorios de la población de berrendos Yellowstone en Montana y Wyoming, EE.U.AU. durante 1999–2001. El peso promedio de las hembras al tiempo de captura a finales del invierno (46.81
