Multiple mechanisms of egg recognition in a cuckoo host

摘要

The cognitive mechanisms behind egg rejection behavior have received increasing attention in recent years helping to understand the evolution of anti-parasite behavior by hosts. Here, we tested egg discrimination mechanisms of yellow-bellied prinia (Prinia flaviventris) in relation to different stages of egg laying (pre-egg laying, one host egg, and multi-host egg stages) and different extent of foreign egg mimicry (poor and high mimicry). We found that the prinia showed variation in egg rejection not only toward foreign eggs differing in mimicry but also among different stages of egg laying and within the same stage of laying. Prinias rejected 100 % of poorly mimetic foreign eggs in the pre-egg-laying stage, and 78.9 and 100 % in the one-host-egg and multi-host-egg stages, respectively. In contrast, they only rejected 38 % of highly mimetic eggs during the pre-egg-laying stage and accepted all at other stages. Multiple mechanisms, including a memory-based template through inheritance or learning, onset of laying, and direct comparison, may have evolved in the yellow-bellied prinia. The mechanisms depend on the mimicry of foreign eggs and the egg-laying stages tested. Innate or long-term memory template from previous breeding attempts may also be used in egg discrimination by hosts while observational learning or experience enhancement is involved in template formation, in which the first laying eggs may play a key role. However, discrimination during the pre-egg-laying stage may be a response toward foreign objects rather than parasitic eggs in this host species. These findings highlight the complexity of the multiple cognitive mechanisms involved in anti-parasite behavior.