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| Mating |
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Pinnipeds often come ashore or
haul out on ice to breed, often
travelling long distances from their
feeding grounds to suitable mating
grounds with a high level of reproductive
synchrony. Almost all pinnipeds
are polygynous, i.e. males breed
with up to several dozen females
in a season. Males of many species,
(e.g. elephant seals and Northern
fur seals) aggressively defend groups
of specific females, referred to
as harems. Males of other species
(e.g. most sea lions) defend territories
on reproductive rookeries while
females move freely between them.
Some form of competition, either
for females or territories, some
of which can be violent, is an integral
part of the male breeding strategy
among most pinnipeds. Otariids,
which are generally more land-adapted,
tend to form major aggregations
in the summer months on beaches
or rocky outcrops. Consequently,
their reproductive behavior is easier
to observe and well studied. Walruses
and many phocids, on the other hand,
tend to form smaller aggregations,
often in remote locations or on
ice, and copulate in the water.
Their reproductive behavior is therefore
generally less well known.
Females have a postpartum oestrus
allowing them to mate soon after
giving birth. Subsequent implantation
of the embryo is delayed (embryonic
diapause) thus removing the need
to come ashore (haul-out) twice,
once to give birth and again later
to mate. After giving birth mothers
suckle their young for a variable
length of time. Amongst the phocids,
lactation varies from 4 to 50 days,
whereas the otarids may lactate
from 4 to 36 months. This reflects
the fact that phocid feeding grounds
tend to be a long way off-shore
so lactation is associated with
maternal fasting. To compensate
for the short lactation period,
the fat content of phocid milk is
higher than in any other species
of marine mammal (45 – 60%
fat). After lactation most female
phocids make extensive migratory
movements to feeding grounds for
intensive foraging to recoup depleted
energy reserves. On the other hand,
otarid feeding grounds are generally
closer to shore and females go on
foraging trips to maintain lactation.
Fat content of otarid milk is lower
than that of the phocids owing to
the protracted lactatory period
(typically 25 – 50%). Protracted
nursing also leads to the formation
of social bonds.
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Seals come out of the water for mating and
breeding. Some seals have been known to return
to the same beaches each breeding season. Seals
have been known to form herd which can number
into the thousands. Within these herds are large
male bulls, female cows, and young seals, called
pups. A male seal will defend his territory
by large gestures and displays. They do this
to warn other males to stay away from their
females. The bigger and stronger males will
have larger harems (mates) and have more cubs.
After the pups are born, the females take care
of them while the males move on.
Seals have one pup a year. Pups are usually
born with a thick coat of fur to keep them warm.
This coat is shed after a month or so and underneath
is a sleek adult coat. The seal pup grows very
quickly because its mother's milk is forty-five
to fifty percent fat. A cow's milk contains
only four percent fat and human milk has only
two percent fat. Baby seals use the milk to
make blubber which they need to servive the
cold weather. After only a few weeks, young
seals are ready to swim and feed themselves.
Durning the mating and breeding season, the
male and female don't eat. This is six weeks
with no food! The reason they can stay alive
for this period is because of their blubber.
They draw fat from this layer for nutrition.
Males spend most of their days chasing down
females to mate with because the male with the
most mates and pups is considered the alfa male.
SEXUAL MATURITY
1. Most male harbor seals become sexually mature
when they reach a weight of about 75 kg (165
lb.), at three to seven years. Most females
become mature when they reach about 50 kg (110
lb.), at three to six years.
MATING ACTIVITY
1. Mating season varies among the subspecies
but generally occurs in late spring through
fall, when females come into estrus ("heat"
or "season") usually about six weeks
after their pups are born. Females remain in
estrus for one to nine weeks.
2. Harbor seals usually return to the same breeding
grounds every year.
3. Prior to the pupping season, males and females
exhibit pre-mating activity such as rolling,
bubble-blowing, and mouthing each other's necks.
This pre-mating behavior ends with the beginning
of the pupping season.
4. During the mating season, male harbor seals
exhibit underwater vocal displays during short
dives, which are probably associated with mating.
These displays take place near haul-out sites,
foraging areas, and travel routes between the
two areas and also increase during times that
females are more likely to be in the water.
5. After the pupping season, males initiate
true mating behavior by chasing, neck- and flipper-biting,
and embracing. When approached, females respond
by growling, head-thrusting, and flipper-waving.
Copulation usually takes place in the water.
6. A male harbor seal may mate with several
females.
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| Features of Seal |
Seals have been known to dive as deep as 4,100 metres (13,450 feet) and can remain submerged for up to an hour. Grey and common seals, however typically dive to a maximum depth of around 200 metres (655 feet), for periods of up to 15 minutes, although they can go deeper and for longer. |
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