Maternally-derived anti-helminth antibodies predict offspring survival in a wild mammal

The transfer of antibodies from mother to offspring provides crucial protection against infection to offspring during early life. However, few studies have tested the consequences of variation in maternal antibody transfer for offspring fitness in the wild. Further, separating out the immunoprotective effects of antibodies from their association with nutritional resources provided by the mother is difficult. Here, we measured plasma levels of total and parasite-specific antibody levels in neonatal (<10 days old) wild Soay sheep over 25 years to quantify variation in maternal antibody transfer and test its association with offspring survival. Maternal antibody transfer was predicted by maternal age and previous antibody responses, and was consistent within mothers across years. Neonatal total IgG antibody levels were positively related to early growth, suggesting they reflected nutritional transfer. Neonatal parasite-specific IgG levels positively predicted first year offspring surviv...