Biomedical Engineering Reference
In-Depth Information
reproduction is limited in pubescent animals and there is
potential value in additional social experience for breeders
with their natal group, as described below.
Female marmosets display no overt signs of ovulation.
Copulations may occur at any point during the cycle and
during pregnancy, although there is an increase in sexual
activity during the female's ovulatory period. Average
gestation length is 143
e
144 days (
Hearn, 1986; Jaquish
et al., 1995
). Lactation lasts for 65
e
90 days and infants
begin to take solid food at around 30 days of age and are
completely weaned from milk at around 80
e
100 days of
age. As opposed to most nonhuman primates, callitrichids
do not display any meaningful delays in ovulation associ-
ated with lactation. Marmoset females typically ovulate
9
e
11 days following parturition.
Marmosets are typically housed for breeding as mated
pairs. Aggression between males and females is relatively
uncommon, and establishing breeding pairs is straightfor-
ward. Marmosets are cooperative breeders
e
group
members including the breeding male and older offspring
in the group participate in the care of dependent offspring,
including transport and provisioning the infants with solid
food once weaning begins. Therefore, it is preferable for
the breeding female to remain not only with her mate but
also with her older offspring. There is some suggestion that
callitrichids
e
particularly tamarins
e
display more adept
parenting skills if they were previously exposed to and
participated in the care of younger siblings (
Tardif et al.,
1984; Tardif, 1997
). Generally, older offspring will not
reproduce as long as the original mated pair remains intact.
Daughters are often reproductively suppressed and do not
ovulate (
French, 1997; Saltzman et al., 1997a,b
), and
mothers and daughters generally will not accept copulation
attempts from sons/brothers.
Therefore, “nuclear” marmoset families are a stable
housing condition as long as the original breeding pair
remains intact, i.e. there is generally no need to remove
older offspring from the group unless cage size requires it.
Once the reproductive male or female dies or is removed
from the group, the group may become unstable as new
breeders are placed in the cage. Marmoset groups will
sometimes include two breeding females if an unrelated
male is present, but this configuration often leads to high
infant mortality, especially due to infanticide (
Rothe and
Koenig, 1991; Saltzman et al., 2004, 2008
).
Marmosets and tamarins are the only anthropoid
nonhuman primates that routinely produce litters. In the
wild, marmosets typically produce litters of 2, but in
captivity they may produce litters up to 5, and triplets are
often the most common litter size. Ovulation number and
litter size are related to maternal condition, with a higher
average maternal weight for larger litters than for smaller
litters (
Tardif and Jaquish, 1997
). Females will not
routinely rear more than two litters at a time, and it is thus
reasonable to have plans in place for the handling of
supernumerary offspring. Infants may be hand-reared for
short periods (around 3 weeks) and successfully reintro-
duced into either their original group or into an experienced
group that has had visual and olfactory exposure to the
infant while it was being hand-reared. Supernumerary
infants may also be hand-reared by rotating a different
infant out of the group each day (
Ziegler et al., 1981
).
Infants may also be cross-fostered to families with only one
infant of a similar age.
The reproductive potential of marmosets is often cited
as 4.0
e
4.5 young/year or up to 80 offspring in a lifetime.
However, because marmosets have relatively high infant
mortality and relatively short life spans, these figures likely
represent maxima rather than averages. A recent exami-
nation of reproductive output in a population of around
400 dams found an average yearly production of weaned
offspring of around 2.3 and a lifetime production of 7.75.
So, while the pace of marmoset reproduction is clearly
faster than in larger-bodied Old World monkeys (e.g. 2.3
versus 0.44 young/year for provisioned macaques)
(
Fedigan et al., 1986
), it is considerably less than the oft
reported maximum.
PREGNANCY MANAGEMENT
Detection of Ovarian Cycle Phase
Ovulation in most nonhuman primates occurs with few, if
any, behavioral or externally perceptible cues, yet the
ability to predict ovulation is essential to many reproduc-
tive and developmental studies. This section provides
information on the methods commonly used to assess
cyclical ovarian change in nonhuman primates, including
ovulation and menses.
Monitoring female reproduction by cyclical changes in
vaginal cytology (e.g. changes in vaginal epithelial corni-
fication), such as is done in rodents, is not commonly used
in assessing monkeys but has been evaluated for those
nonhuman primates with no or limited menstrual flow,
primarily prosimians and New World monkeys (
Travis and
Holmes, 1974; Hendrickx and Newman, 1978; Stolzenberg
et al., 1979; Dukelow, 1983; Nagle and Denari, 1983; Izard
and Rasmussen, 1985; Gluckman et al., 2004
).
In contrast to prosimians and New World species,
ovarian cyclicity is easily determined in the higher
nonhuman primates due to an overt menses. In almost all
breeding colonies, monitoring menses is done in one of two
ways: (1) visual examination of the external genitalia for
fresh blood, or (2) use of vaginal swabs to detect menstrual
blood. Vaginal swabs or smears are taken by placing
a cotton-tipped swab into the vaginal canal, preferably in
the anterior fornix, and then visually examining the swab
for the presence of blood. In some instances it may be
