Non-Breeding Gonadal Testosterone Production of Male and Female Northern Cardinals (Cardinalis cardinalis) Following GnRH Challenge
Yearly, testosterone (T) levels fluctuate as many vertebrates cycle through reproductive and non-reproductive periods. Among many temperate birds, it is well established that levels of T peak as gonads recrudesce for breeding and then fall as gonads regress prior to the non-breeding season. While the tissues producing breeding season T are well studied, the tissues responsible for non-breeding T have received less investigative attention. We examined the ability of male and female Northern Cardinals (Cardinalis cardinalis) to elevate gonadal T following standardized injections of gonadotropin-releasing hormone (GnRH) across three non-breeding seasons. Males and females were capable of significantly elevating gonadal T production following GnRH injections during periods of reproductive quiescence. The magnitude of T elevation varied across the non-breeding season, but not between sexes. To our knowledge, this is the first report of a significant increase in gonadal T production following GnRH injections administered in the non-breeding season. (C) 2011 Elsevier Inc. All rights reserved.
General and Comparative Endocrinology
DeVries, M. S.,
Holbrook, A. L.,
Winters, C. P.,
Jawor, J. M.
(2011). Non-Breeding Gonadal Testosterone Production of Male and Female Northern Cardinals (Cardinalis cardinalis) Following GnRH Challenge. General and Comparative Endocrinology, 174(3), 370-378.
Available at: http://aquila.usm.edu/fac_pubs/8341