BEHAVIOR:
Hedgehogs are nocturnal. They usually start their nightly activities such
as foraging as the sun goes down. In the wild hedgehogs may hibernate
or estivate (engage in torpor) depending on the weather (2). In colder
climates the hedgehogs hibernate and in the warmer climates they tend
to estivate (2). During hibernation the heart rate of the hedgehog will
drop almost ninety percent to save energy (2). Hibernation periods may
last from a few weeks to six months depending on the severity of the winter
(2).The primary defense mechanism of the hedgehog is rolling into a tight
ball and protruding it’s quills. The hedgehog is able to form a
ball by means of longitudinal orbicularis and panniculus carnosus muscles
around the body (1). These muscles pull the skin around the sides and
down over the feet and head (1). The hedgehog’s spines can be moved
individually by a complex layer of muscles beneath the skin (2). The hedgehog
erects it’s spines for protection from potential predators. Also
when the hedgehog feels threatened it may hiss or make clicking sounds
(2). An interesting behavior exhibited by the hedgehog is called self-annointing.
Objects or food with a strong scent may elicit the hedgehog to foam at
the mouth (2). The hedgehog will then spread this saliva onto it’s
spines (2). The exact reason for this behavior is unknown but there are
a few speculations. Some believe that the purpose is part of the hedgehog’s
mating ritual and the saliva may act as a scent to attract mates (2).
Others believe that this behavior is an addition to the animal’s
defense strategies (2). This “self- anointing” may be a part
of an effort to blend in with the scent of the surroundings (1).
REPRODUCTION:
Hedgehogs reach sexual maturity almost immediately after being weaned,
when they are still little hoglets. However, breeding may be stressful
for females if it occurs prior to 6 months of age. The gestation period
is about 35 days. Hedgehogs are polyestrus, meaning they may have multiple
litters per year, but in nature a female’s peak breeding times will
be in summer. During these periods the days are longer and the weather
is warmer therefore providing the sow with adequate nutrients supplies.
The female hedgehog is an induced ovulate, therefore simply being in the
presence of a male, during her estrus phase, will cause her eggs to be
dropped. If the female is not in estrus she will forcefully refuse the
males advances, which tend to be very persistent. Studies have shown that
repeated mating, within 24 hours of each, can cause the sow to have larger
litter sizes. However there is a limit at which the repeated mating will
cause litter fitness to decrease.(2)When the female finally is ready to
mate the defensive spines will lay flat on her back so that the male can
mount her. The male will hold unto the spines on her neck during the 2-3
minute copulation. period. Mating usually occurs at night, since hedgehogs
are nocturnal. After the 35-day gestation period a litter of 1 to 10 hoglets
may be born, although the average size is 4-5 per litter. The most serious
concern with larger litters is the higher post-natal death due to lack
of sustenance and attention. In captivity, it has been found, that sows
are very edgy around the time of their delivery. If a new mother is disturbed
she may eat the entire litter of hoglets. Also a sow may confuse one or
more of the babies for an afterbirth and consume them to reabsorb nutrition.
(2)When the babies are born there is a thin membrane which covers their
small white spines. This membrane will fall off within a couple of hours
and the hoglets spines will grow quickly and get darker in color. After
3-weeks the babies will begin to stray from their mothers side. Hedgehogs
are solitary animals; therefore the male will not be present during the
birth and growth period.(2)
ADDITIONAL RESEARCH:
The hedgehog species, Erinaceus europaeus is primarily found in England.
Their primary habitat seems to be along the edges of mowed playing fields,
which are found closer populated areas, or pasture areas, in which the
grass is longer and uncut. The study showed the hedgehog population was
most concentrated in playing field areas rather than pasture areas, 3.9+/-0.8
animals per field and 0.7+/- 0.2 animals per field, respectively. These
results do not correlate with the food and shelter availability, since
the tall grass of the pastureland would tend to supply a hedgehog with
more of both of these resources. However, researchers found that the population
densities inversely coordinated with the badger populations. It was concluded
that 39% of the difference in population could be due to the mortality
rate due to an increase in predators found in the pastureland as well
as isolation of hedgehogs from one another in the pasture environment.
After reading the methods of this paper I also question whether the population
counts were entirely accurate, perhaps the hedgehogs were able to hide
more effectively in the pasture area to escape being counted.(3)
Bibliography:1. Wrobel,
D. The Hedgehog. New York, New York: Howell Book House: 1997.
2. Kelsey-Wood D. African Pygmy Hedgehogs As Your Pet. New Jersey: TFH
Publications: 1995.
3. Micol T., Doncaster C.P., Mackinlay L.A. (1994) Correlates of local
variation in the abundance of hedgehogs Erinaceus europaeus. Journal of
Animal Ecology, 63, 851-860.
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