Assessment of reproductive status and ovulation in female brown kiwi (Apteryx mantelli) using fecal steroids and ovarian follicle size

Abstract

Despite being listed as endangered on the IUCN (World Conservation Union) red list [BirdLife International 2005], and intense conservation efforts on its behalf, little is known about the reproductive physiology of the brown kiwi (Apteryx mantelli). This study therefore was undertaken to describe ovarian function in brown kiwi using noninvasive methods that can be utilized in the field. This study describes a simple method for extraction and detection of steroid metabolites in brown kiwi feces by enzyme-linked immunosorbent assay (ELISA). Average fecal steroid hormone metabolite concentrations were derived from 10 egg-lay cycles in 2 hens. Testosterone began to increase between 23 and 18 days before oviposition (-23d to -18d) and remained elevated until just before oviposition. Estradiol rose from -28d to -13d and remained elevated until 12 days after oviposition. Progesterone exhibited an increase of short duration from -8d to +7d with a peak at -3d. Ovarian follicle growth rate was determined by serial ultrasound measurements of follicles in three habituated female kiwi. Follicle growth rate was described by the formula y = 132.54e0.0569x (y = follicle diameter, x = days before oviposition). Follicles ranged in size from 10 to 76 mm. Day of ovulation was estimated using egg yolk size, follicle growth curve, and day of oviposition. This yielded an ovulation-oviposition cycle length of 7-10 days, significantly shorter than the only other estimate of 16-17 days derived using body weights of a single kiwi hen. The correlation of fecal steroid hormone concentrations with follicle growth provides new insight into the reproductive physiology of the female brown kiwi. © 2005 Wiley-Liss, Inc.