SUMMARY: Gestation has been calculated to last about 35 +/- 4 days; occasional records indicate the possibility of pregnancies lasting more than 40 days; this may be related to adverse environmental conditions triggering a period of torpor during (early) pregnancy. Hedgehog embryos are evenly distributed between the two horns of the uterus and post-implantation losses appear to be low.
Many matings do not end in a successful pregnancy.
Mating often does not occur with the first oestrus cycle of the breeding season and several cycles of pseudopregnancy (2 or 3) may typically occur before conception is achieved. Whilst levels of fertility at the beginning of the breeding season may be variable, the adaptive significance of the apparent level of infertility is unclear.
Studies of the reproductive tract of female hedgehogs have shown that mating often does not result in pregnancy; it appears to be usual for several cycles of oestrus, pseudopregnancy and return to oestrus to occur before a successful pregnancy.
The degree of intraspecific variation for estimates of the gestation period for Erinaceus europaeus exceeds quoted interspecific variation within the Erinaceinae (Erinaceidae - Hedgehogs, moonrats (Family)).
Gestation length is estimated to range between 35+/-4 days, although outlier observations in excess of 40 days exist in the literature.
Minimum probably 34-35 days and maximum probably 39 days: Females gave birth up to 37 days after capture and at a minimum of 36 days after being placed in a breeding pen with a male.
Estimated gestation length is 31-35 days. The shortest time between introduction of a female to a breeding pen with a male and subsequent parturition was 31-32 days.
Gestation period is approximately 34 days (B260.6.w6, B261) with variation of up to 4-5 days (B260.6.w6); 31-35 days.(B142, B147); 31-37 days.(B144); 35 days.
Variation in estimates of gestation period may be due to incomplete data sets.
Although no supporting evidence is available, it has been postulated that in response to adverse environmental factors (e.g. cold ambient temperature and reduced food availability), a sow may undergo a period of torpor that could delay gestation.
Hedgehog embryos are able to migrate between the two uterine horns prior to implantation which ensures even distribution.
Studies of the reproductive tract of female hedgehogs have shown that the number of embryos is the same in each uterine horn, or one horn contains only one more embryo than the other.
The chorioallantoic placenta of the hedgehog is typical of that for the Insectivora - Insectivores (Order) and is discoidal and haemochorial in anatomical design.
Pregnancy diagnosis by abdominal palpation is reported to be impossible in the conscious sow. However if the hedgehog is under general anaesthesia, palpation and differentiation of a gravid uterus from a full urinary bladder may be possible with considerable experience and care, through refection of the latter organ.
Despite multiple matings, many sows do not become pregnant, and "a fair proportion may escape becoming pregnant altogether."
Death and resorption of fetuses following implantation appears to be uncommon: only four of a total of 42 pregnant females in one study contained such fetuses, with loss of the whole litter in two cases (four and two fetuses respectively) and of a single fetus from the litter in two other females. The percentage mortality of embryos from 53 pregnancies was 3.3% (8/242).
Mon Jun 11, 2012 4:47 pm
