with the presence
of two distinct peaks of estradiol. Larkin (2000) reported
that almost half of all fecal estrogen peaks observed in her
study were followed by basal values of fecal progestins, also
indicating the existence of two different peaks in Florida
manatees. That author proposed that these peaks may be
important for mating behavior and male attraction. Likewise,
the occurrence of two peaks of estradiol during the
ovarian cycle of the Amazonian manatee may have physiological
and ecological significance in the reproductive
strategy of this species.
The cause of the acyclic hormonal pattern observed
in female Ti-060 is unknown, as this female demonstrated
a cyclic pattern in the previous year. Larkin
(2000) and Horikoshi (2004) also observed acyclic patterns
in some of the individual Florida manatees studied.
According to these authors, environmental influences,
such as a lack of social interaction, may have caused
the irregularity or absence of estrous cycles among
the Florida manatees analyzed. Another important point
is the relationship between stress and reproduction.
The inhibitory effects of stress on reproductive functions
are widely known; however, the mechanisms of
interaction between the hypothalamus–pituitary–adrenal