The morphology and parasite burdens of culled free-ranging red jungle fowl (Gallus gallus) from the San Diego Zoo were compared with those of captive roosters used previously in sexual selection experiments, to determine if results obtained with the captive birds were relevant to more natural situations. Zoo roosters had three helminth gut parasites: Ascaridia galli, tapeworms, and Heterakis. Parasite distribution was generally over-dispersed, with most individuals having none or few worms and some having heavy parasite burdens. These levels were comparable to those artificially induced in test roosters. The appearance of the zoo birds was similar to test roosters as well. Higher parasite burdens in the zoo birds was negatively related to hackle feather redness, comb length, and especially testis volume. The latter finding is discussed in light of information about the relationship between testosterone levels, sexual selection, and the immune system. A new analysis of female choice of uninfected controls versus experimentally infected roosters suggests that females prefer a multivariate array of traits perceived as a continuous, rather than categorical, variable.
Bibliographical noteFunding Information:
3) Present address: Department of Ecology, Ethology, Illinois, Urbana, Illinois 61801, U.S.A. 4) We are grateful to the people who assisted with care of the birds and helped run experiments: C. BLANCO-MONTERO, C. COSTIN, D. KELLER, C. KROPEK, S. LIGON,J . MCCONACHIE, M. MELLOY, S. PORTMAN, D. SHIPPERT, A. THORNHILL, N. THORNHILL, and P. THORNHILLA. . RISSERa nd the San Diego Zoo kindly supplied us with jungle fowl, and L. R. McDougald provided Ascaridia galli eggs. The Zoo pathology department was very cooperative in helping us to obtain culled birds. J. T. ROTENBERRY gave useful statistical advice, and S. GARDNER helped identify helminths. This research was funded by NSF grants to R.Th., J.D.L. and M.Z. and received support from D. DUSZYNSKanId the UNM biology department and from P. RISSER.