TY - JOUR
T1 - A simple rule reduces costs of extragroup parasitism in a communally breeding bird
AU - Riehl, Christina Pauline
N1 - Funding Information:
This study was supported by graduate research fellowships from the Smithsonian Tropical Research Institute and the National Science Foundation, as well as by additional funding from the Max Planck Institute of Ornithology (Department of Migration and Immuno-Ecology), the American Ornithologists' Union, the American Museum of Natural History, and the Program of Latin American Studies at Princeton University. Research was approved by the Animal Care and Use Committees of Princeton University and the Smithsonian Tropical Research Institute. Microsatellite genotyping was carried out with the assistance of the Cornell Laboratory of Ornithology and the Naos Island Laboratory of the Smithsonian Tropical Research Institute. L. Jara and W. Webber provided valuable field assistance, and M.C. Wikelski contributed advice and assistance on all aspects of the project.
PY - 2010/10/26
Y1 - 2010/10/26
N2 - How do cooperatively breeding groups resist invasion by parasitic "cheaters," which dump their eggs in the communal nest but provide no parental care [1,2]? Here I show that Greater Anis (Crotophaga major), Neotropical cuckoos that nest in social groups containing several breeding females [3], use a simple rule based on the timing of laying to recognize and reject eggs laid by extragroup parasites. I experimentally confirmed that Greater Anis cannot recognize parasitic eggs based on the appearance of host egg phenotypes or on the number of eggs in the clutch. However, they can discriminate between freshly laid eggs and those that have already been incubated, and they accordingly eject asynchronous eggs. This mechanism is reliable in naturally parasitized nests, because group members typically lay their eggs in tight synchrony, whereas the majority of parasitic eggs are laid several days later. Rejection of asynchronous eggs therefore provides a rare empirical example of a complex, group-level behavior that arises through relatively simple "rules of thumb" without requiring advanced cognitive mechanisms such as learning, counting, or individual recognition.
AB - How do cooperatively breeding groups resist invasion by parasitic "cheaters," which dump their eggs in the communal nest but provide no parental care [1,2]? Here I show that Greater Anis (Crotophaga major), Neotropical cuckoos that nest in social groups containing several breeding females [3], use a simple rule based on the timing of laying to recognize and reject eggs laid by extragroup parasites. I experimentally confirmed that Greater Anis cannot recognize parasitic eggs based on the appearance of host egg phenotypes or on the number of eggs in the clutch. However, they can discriminate between freshly laid eggs and those that have already been incubated, and they accordingly eject asynchronous eggs. This mechanism is reliable in naturally parasitized nests, because group members typically lay their eggs in tight synchrony, whereas the majority of parasitic eggs are laid several days later. Rejection of asynchronous eggs therefore provides a rare empirical example of a complex, group-level behavior that arises through relatively simple "rules of thumb" without requiring advanced cognitive mechanisms such as learning, counting, or individual recognition.
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U2 - 10.1016/j.cub.2010.09.005
DO - 10.1016/j.cub.2010.09.005
M3 - Article
C2 - 20888229
AN - SCOPUS:78049297852
SN - 0960-9822
VL - 20
SP - 1830
EP - 1833
JO - Current Biology
JF - Current Biology
IS - 20
ER -