Ecological Archives E095-087-A1
J. Martínez-Padilla, L. Pérez-Rodríguez, F. Mougeot, S. C. Ludwig, S. M. Redpath. 2014. Experimentally elevated levels of testosterone at independence reduce fitness in a territorial bird. Ecology 95:1033–1044. http://dx.doi.org/10.1890/12-1905.1
Appendix A. Experimental design, fitness estimations, and parameter estimations.
Fig. A1. Chronogram of the experiment expanded. Average and range of dates of captures throughout the experiment.
Table A1. Sample sizes (number of males) for the three levels of testosterone treatments and three levels of parasite treatments. Note that since we did not find any difference in parasite loads between P1- and P2-treated birds, these two groups were pooled for subsequent analyses, which contrasted males that were not challenged (P0) with those challenged with parasites (P1* and P2).
Final treatment |
Testosterone treatment |
Parasite treatment |
Sample size |
T0P0 |
Sham implanted birds |
No parasite challenge |
35 |
T0P1* |
Sham implanted birds |
Parasite challenge |
12 |
T0P2 |
Sham implanted birds |
Parasite challenge |
23 |
T1P0 |
Intermediate levels of testosterone |
No parasite challenge |
27 |
T1P1* |
Intermediate levels of testosterone |
Parasite challenge |
12 |
T1P2 |
Intermediate levels of testosterone |
Parasite challenge |
11 |
T2P0 |
Intermediate levels of testosterone |
No parasite challenge |
41 |
T2P1* |
Intermediate levels of testosterone |
Parasite challenge |
11 |
T2P2 |
Intermediate levels of testosterone |
Parasite challenge |
23 |
Short-term effects of testosterone implants on testosterone levels
In a previous and partially unpublished experiment, we explored how testosterone levels changed in a short time period (i.e., 1 day) following implant. We captured male Red Grouse, implanted them with the same tube length (T-treated, n = 5) as we used in our manuscript for high-testosterone treated birds (T2-males) and other birds remained as control (n = 4). We recaptured them one day later. On both recaptures we took a blood sample to measure circulating levels of testosterone. We determined testosterone levels before and after manipulation for control and testosterone-treated birds. In the short-term, we found that testosterone-treated males increased circulating levels of testosterone more than control males (T-treated: From 0.53±0.78 to 2.75±0.69; Control birds, from 0.83±0.58 to 0.73±0.57, F1,6 = 14.83, p = 0.009). Also, testosterone-treated birds in the short-term reached similar testosterone levels than the high-testosterone treated males one month later (our manuscript, from 0.38±0.41 to 3.24±0.48). A statistical analysis comparing increases of T-treated birds one day after implanting (unpublished data shown before) and one month after implanting (main study) indicated no significant difference between groups (GLMM, individual as random factor, interaction treatment -one day vs. one month- and time -before and after treatment-, F1,38 = 0.98, p = 0.329).