ISRAEL JOURNAL OF
VETERINARY MEDICINE
REPRODUCTIVE PROCESSES IN CAMELS (Camelus dromedarius)
Yagil R.
Faculty of Heal Sciences, Ben-Gurion University of the Negev, Beersheva
Introduction
A review on camel reproduction is not only a question of presenting new data
associated with a specific subject, but is a move away from anecdotal data taken from
nomadic camel herders (1) with their uncertain husbandry methods, via the model
camel farm (2) where the scientists were also the farmers, to high-tech scientific
laboratories (3).
As with all mammals, camel reproduction is adapted to its specific behavioral,
anatomical, physiological and endocrinological peculiarities. The camelids inhabit the
most extreme climates on the globe and their process of multiplication is determined
by the availability of food and protection for the newborn, consequently their
reproduction is governed by these factors. Camelids are found high in the Andes
mountains of South America (New World camelids), in the frozen Gobi desert in Asia
(Bactrian camels), and in the hot deserts of Africa and Middle East (Dromedaries).
This review will deal with the reproductive performance of the dromedary, the onehumped, hot-desert camel.
As mammals are characterized by milk secretion lactation is an integral part of the
reproductive cycle, and this will be discussed in another article.
Anatomy:
Note: all measurements will be affected by age, season, size and weight.
Male
Testes (4,5): They are found lying horizontally in the perineal region. In young males
they are barely visible in the non-breeding season. In older males they are small and
located almost completely between the legs. A faint median raphe divides the two
testes. Between the ages of 6-10 years, its length averages 9cm, breadth 5cm,
thickness 4.3cm and weight is 92grams. The right testicle is slightly smaller. In the rut
season the testes become enlarged and protrude.
Penis (5): A cylindrical organ directed posteriorally. It is possible that this position
prevents contact between the organ and the hot desert sand when the male squats,
keeping the penal area above the sand. There are three groups of penal muscles:
anterior, posterior and lateral. The contractions and relaxation of these muscles pull
the penis forward during the breeding processes. The glans penis is curved along its
ventral plane, giving it a hooked appearance.
It is noteworthy that the diameter of the penis decreases from its root towards the thin
tapered glans penis. During erection the differences in diameter give the impression of
opening of an old-fashioned telescope.
Female
In general the female genital tract is more similar to that of a mare than of a cow. The
sizes are determined by the age of the animal. Externally the two uterine horns are
joined but there is a definite median septum (6). The left horn is well developed while
the right one is rudimentary. There is a short cervical canal and the mucosal folds are
arranged in 3-4 rows. The cervix tends to protrude into the vagina, creating a dorsal
and ventrical blind sac. The vagina is about 31 cm long. The vulva is about 8cm long,
and a suburethral diverticulum with the urethral orifice above is in its ventral floor.
The sizes of the ovaries are determined by the age, size, health and stage of female
cycle. Follicles on the left ovary are generally larger than those of the right one.
When palpated rectally the ovaries can be found close to the cervix.
Behaviour:
Male
The Dulaa is a palatal flap that is extruded on the side of the mouth during the mating
season (5). It is incorrectly assumed that this protrusion is the tongue. The flap is
formed under the influence of testosterone, so the more virile the male, the longer is
its dulaa which protrudes further in a ball-like structure. The male normally takes a
deep breath and when the air is expelled it pushes the dulaa out of the mouth, the
nostrils quiver and there is a typical sound of “bloo, bloo, bloo” and a large secretion
of saliva. After a few seconds the dulaa collapses and the sac is withdrawn into the
mouth. The importance of the dulaa is that its formation is correlated to the amounts
of testosterone in the blood; the size is an indication for the females of the male's
virility. Towards the end of the season the typical sound is made but no dulaa appears.
The poll glands are situated on the back of neck between ears. They secrete a copious,
acrid-smelling secretion, which flows down the back of neck, marking the skin with a
dark color. The males rub their necks on any solid object, thus marking their territory.
Laboratory examination of the poll gland secretions revealed similar concentrations of
androgens as in the blood (5). Histological examination confirms that the poll glands
are of endocrinological origin (7).
Urination: Another peculiarity of the male in rut is spreading its legs, placing its tail
between them, urinating on it and then swishes it over its back. (4, 8, 9), It is likely
that pheromones in the urine attract the females.
Aggressiveness: When the males exhibit all the above signs they become very
aggressive towards other males and can attack humans, even their owners (6, 9).
It is noteworthy that male elephants in the musth exhibit similar behavioral signs to
those of the camel (10).
Female: In the breeding season the female is receptive to the male for 3-4 days at a
time, followed by about 10 days of quiet. This corresponds with the fluctuations in
sex hormones in blood (11). When in rut the female approaches the male, presents her
hind parts and urinates constantly and flaps her tail up and down in quick, short
movements (4, 9).
Physiology:
The rut is confined to the cooler and wetter seasons, corresponding to the availability
of food when the calf is born (11). In Israel this period is between end of December
and end of April. At the equator the reproductive cycle can be all year round but
particularly in the heavy rain season (4). When camels are kept corralled and have
ample amounts of food, this period is extended by as much as 2 months (7, 12).
Male: In nomadic herds the male become sexually mature at about 5 years old (1), but
this age declines when herds are better controlled (7)
Female: Females become mature at 4 years and remain fertile for over 20 years. This
age is reduced as the husbandry practices improve and if the animals are kept in feed
lots (12).
Inter-calf period: This is definitely dependent on husbandry practices. In nomadic
herds the period is normally once very two years, but this is because the lactating
females are separated from the herd in order to be close to humans. Therefore they,
only mate in the following season (one year hence). As she-camels can have estrus
25-40 days after parturition they can give birth once a year (7, 12). The herders'
misconception of selection led to “negative selection” for milk production in bringing
poor milkers to the male soon after parturition, whereas good milkers gave birth once
every two years (12).
Sexual cycle: Follicles take about 6 days to develop. The Graafian follicle can remain
from 5 to 19 days and then regress over another 7 days. There is an estradiol peak
every 7 days. The cycle is dependent on mating so there is an induced ovulation.
Ovulation occurs 36 hours after mating (13,14). The corpeus luteum (CL) is flabby at
the beginning of a pregnancy but becomes hard eventually. There can be as many as
three CL in an ovary.
Endocrinology:
In females, an estradiol cycle is found only if there is no ovulation (13, 14). After
copulation there can be a short-lived rise in progesterone. When the females are
pregnant the progesterone levels rise to above 2ng/ml (9,15) In males there are
elevated testosterone levels in the rut period.
Courting and mating:
In the rut period, males continually sniff about the females. When a female is “in
heat” the male shows Flehmen and becomes excited (4, 5) . The male starts to push on
the female to bring her down, which normally results in the female running away. The
male gives chase, biting at her sides, back, legs, hump, or even genitalia. This often
leads to severe wounds requiring surgery. When she eventually stands still, the male
places his neck on hers and forces her to squat.
Then the male straddles the female, moves up to the hump and then begins to slide
down until he eventually squats on the female, his front legs closely holding her, his
full force on his tibiae (back legs).
Now the penis is pulled forward, the tip appears and it “feels around” for the vulva.
When it is located the full length is inserted, one part after another. The male makes
constant shuffling movements to push in further. He sits gazing into the distance,
saliva trickling out of his mouth and a constant vibration of his nostrils. The female
normally does not lie quiet but bellows and constantly bites his neck.
Mating can last up to 40 minutes and pulsations can be seen on the penis. When the
male is finished he often just falls over on his side before standing up.Males can mate
eight females in a day.
Semen: The semen is jelly-like and opaque (16, 17). The sperm are almost motionless.
In the female genital tract the sperm become motile, an important fact since ovulation
occurs only 36 hours after mating. If this is not known, examination of semen can
mislead the observer in assuming the sperm are dead and the male is infertile.
Pregnancy:
It is assumed that the fertility rate in camels is low but this is normally due to the
practice of bringing the male only once to the female. As it is not certain at what stage
of the estradiol cycle the female is in, it is better for the male to mate the female once
a day for a few days (16,17).
When a female is pregnant, she will show it by lifting and curving her tail when a
male advances. The male then moves off looking for another, receptive, female. This
is the method used by nomads to determine pregnancy in she-camels. Modern
methods for pregnancy diagnosis include ultrasound (17), a bioassay with mice (18),
or radioimmunoassay for progesterone (13).
As mentioned, calving once every two years is a managerial problem and not an
endocrinological one (9, 19).
Gestation:
The length of pregnancy averages 1 year (308-440 days) but will be affected by the
herders who determine the date that it conceives.
Parturition:
The signs of parturition begin a few hours prior to the appearance of the calf (12). The
mother becomes agitated, gazes into the distance and moves away from other camels.
Corralled camels can even attempt to break out.The first outer signs are the relaxation
of the sacrosciatic ligaments, creating grooves on either side of the tail. The vulva
becomes markedly swollen. When the cervix is fully dilated, in about 3-5 hours, the
birth process begins. The female can remain standing, lie on her side or alternate
between standing and lying.
The long front legs are the first to appear, followed by the head and shoulders. The
rear portion is then rapidly ejected. The entire process normally lasts about 25
minutes. The placenta can be discarded immediately but normally only after an hour.
In some camels at the beginning of the birth process, the mother raises a leg and
suckles herself, a “natural” way to raise oxytocin secretion, and hence uterine
contractions.
As soon as the calf is out the mother stands,and in so doing,sever the umbilical cord.
female camels do not clean the calf or eat the placenta but are very protective
mothers.
There are no reports of twins although aborted pregnancies can expel two foeti.
The placenta is similar to that of a horse, it is diffuse and smooth, with no cotyledons.
There is an extra fetal membrane which is epidermal in origin which completely
encloses the fetus (18).
The weight of the calf varies between 25 kg to 52 kg. Males are slightly heavier.
The calves normally stand after 30 minutes, but one hour is also normal. After another
hour the calf starts looking for the teats, often helped by the mother.
When the commercial value of camels became apparent, modern reproductive
interventions were introduced. The commercialization varied from racing camels in
the Emirates (14, 17) to improving lactation performance in Israel (16).
Artificial insemination: is practiced in camelids. The peculiarities of the male and
female reproductive processes must be taken into account. A modified bull vagina is
used to collect semen. About 320 x 106 spermatoids are inseminated into the uterus
24hrs after GnRH treatment. The recipient must be induced to ovulate for a pregnancy
(20).
The techniques of embryo transfers were developed for raising better racing camels in
the Emirates (17) but also for increasing milk potential for starving Africa (16). In the
Emirates the technique was developed in modern facilities with excellent equipment.
In Israel the technique was developed in simple facilities, suitable for African
conditions. In the well-equipped laboratories scanners were used to determine ovarian
activity while in the other case reliance was placed on knowledge of the female cycle
and using progesterone ear implants to bring the cycles to a starting point, before
initiating hormonal treatment to get poly-ovaries. The females are mated at least twice
on consecutive days or 48 hrs apart. Embryos were collected by transcervical uterine
flushing 7 days after ovulation. Embryos were drawn into straws for later transfers.
Recipients were treated with GnRH and 6 days after ovulation the embryos were
transferred intrauterinely into the left, better developed, uterine horn.
Lactation:
This is an important part of reproduction because without milk there will be no
“future generation”. The female starts producing small amounts of colostrum soon
after parturition. The colostrum is pure white but very sticky (6).
It is common practice that if a calf dies, camel herders will either remove the skin and
put it on a child, or tie the hind part of the calf around the mother’s flank as the shecamel will turn to smell her calf before “dropping” milk. No other calf will be allowed
to suckle.
Acknowledgements:
The author is grateful to the Benny Slome Charitable Foundation for financial and
morale support.
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