A Long-Term Experimental Study Demonstrates the Costs of Begging That Were Not Found over the Short Term Soler Cruz, Manuel Ruiz-Raya, Francisco Carra, Laura G. Medina-Molina, Eloy Ibáñez Álamo, Juan Diego Martín-Gálvez, David Acoustic signals Animal signaling and communication Clutches Evolutionary immunology Immune physiology Immune response Immunocompetence Larvae Parent–offspring conflict theory predicts that begging behaviour could escalate continuously over evolutionary time if it is not prevented by costliness of begging displays. Three main potential physiological costs have been proposed: growth, immunological and metabolic costs. However, empirical evidence on this subject remains elusive because published results are often contradictory. In this study, we test for the existence of these three potential physiological costs of begging in house sparrow (Passer domesticus) nestlings by stimulating a group of nestlings to beg for longer and another group for shorter periods than in natural conditions. All nestlings were fed with the same quantity of food. Our study involves a long-term experimental treatment for begging studies (five consecutive days). Long-term studies frequently provide clearer results than short-term studies and, sometimes, relevant information not reported by the latter ones. Our long-term experiment shows (i) a clear effect on the immune response even since the first measurement (6 hours), but it was higher during the second (long-term) than during the first (short-term) test; (ii) evidence of a growth cost of begging in house sparrow nestlings not previously found by other studies; (iii) body condition was affected by our experimental manipulation only after 48 hour; (iv) a metabolic cost of begging never previously shown in any species, and (v) for the first time, it has shown a simultaneous effect of the three potential physiological costs of begging: immunocompetence, growth, and metabolism. This implies first, that a multilevel trade-off can occur between begging and all physiological costs and, second, that a lack of support in a short-term experiment for the existence of a tested cost of begging does not mean absence of that cost, because it can be found in a long-term experiment. 2014-12-01T08:21:53Z 2014-12-01T08:21:53Z 2014 journal article Soler, M.; et al. A Long-Term Experimental Study Demonstrates the Costs of Begging That Were Not Found over the Short Term. Plos One, 9(11): e111929 (2014). [http://hdl.handle.net/10481/33945] 1932-6203 http://hdl.handle.net/10481/33945 10.1371/journal.pone.0111929 eng http://creativecommons.org/licenses/by-nc-nd/3.0/ open access Creative Commons Attribution-NonCommercial-NoDerivs 3.0 License Public Library of Science (PLOS)