Seasonal shifts in prey availability and low feeding requirements of African egg‐eating snakes (Dasypeltis scabra)

For predators that feed on a restricted set of prey resources, individuals must be able to withstand shortages of their required prey. Additionally, when morphological traits make prey access body size‐dependent, changes in prey availability might disproportionately alter access to those resources for different cohorts within a population. In a 3‐year laboratory study, we housed and fed a colony of African egg‐eating snakes ( Dasypeltis scabra ), an obligate bird egg specialist, to quantify their ingestion ability and annual feeding requirements. Using those data, we estimated monthly trends of the accessibility and availability of bird eggs suitable for consumption by differently sized individuals. We estimate that adult and neonate D. scabra can ingest the eggs of 708 of 728 bird species (98%) and 363 of 728 bird species (50%), respectively. Eggs are widely available during warm spring and summer months, but bird breeding declines during colder winter months, especially for species laying smaller eggs. In the laboratory, snakes showed a seasonal feeding rhythm with high food acceptance coinciding with peaks in monthly bird egg‐laying during the austral spring and summer. Our snakes required food equal to only 61% of initial body mass annually to maintain body condition and consumed on average just 2.4 times more food than maintenance levels, corroborating metabolic studies showing low metabolic rates in Dasypeltis . Our findings suggest that seasonal fluctuations of prey availability are likely the selective pressure that contributed to increased ingestion ability (so that smaller snakes could potentially access larger eggs that are more readily available through cooler months) and reduced metabolic rates in D. scabra , which shaped their low feeding requirements. Thus, while seasonal variation in prey availability does not preclude bird egg specialization within D. scabra , it directly influences when these snakes feed as well as how many eggs they consume annually.