Excessive hunting and habitat
fragmentation greatly reduced chinchilla populations in the wild and today it?s
almost extinct in the wild. Understanding basic reproductive physiological
function is essential for a successful conservation program, yet these characteristics
are unknown or poorly studied in this species. Our objective was to
characterize the natural fluctuations in ovarian endocrine activity in female
chinchillas thorough the sexual cycle, using urinary biomarkers of ovarian
function. Urine samples were collected from 9 females, 3 times per week for a
period of 4 months during the active reproductive season. Vaginal opening was
also recorded as an external sign of oestrus. Each sample was analyzed for
creatinine (crt, Sigma #C3613), pregnanediol glucuronides and estrone
conjugates (PdG R13904, EC R522-2,
C. Munro) using EIA. A longitudinal profile was obtained
for each hormone and female, using an iterative process to calculate baseline
and peak hormonal levels. Baseline and peak levels for EC and PdG were (ng/mg
crt) 7.9 ± 0.7, 28.1 ± 4.4 and 890.5 ± 189.3, 2272.0 ± 246.6, respectively. The
length of the natural sexual cycle in the female chinchilla was determined as
34.8 ± 4.4 days (range 16.8-49) for EC and 32.1 ± 3.6 days (range 18.7-56) for
PdG. Maximal EC concentrations used as an indicator of oestrus length lasted
6.7 ± 0.9 days (range 4.7-11). Follicular and luteal phases were 3.9 ± 0.4 and
7.1 ± 0.6 days, respectively. A total of 3.9 ± 0.3 and 3.7 ± 0.3 sexual cycles
were detected throughout the study period using PdG and EC assessments. Vaginal
opening was not synchronous with elevations in hormones above baseline levels
and therefore, can not be used as a reliable indicator of oestrus. It?s clear
that urinary endocrine analysis is a valuable tool in the efforts to elucidate
the reproductive physiology of the endangered chinchilla.