Elephants and their reproductive cycles are complex. They have large reproductive tracts, long pregnancies, produce large calves that require a long developmental period and reproduce infrequently with the inter-calf interval as long as 5 years.
Male Reproductive System |
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Unusual for mammals, the testicles of elephants are located within the body, close to the kidneys. The male’s reproductive tract is about 2 meters long. Male elephants, called bulls, begin producing sperm between 10 and 15 years of age, sometimes even earlier in zoos. In the wild, only the older, larger bulls gain access to the females, however younger breeders are known in zoos. Adult bulls go through periodic episodes of elevated testosterone and heightened aggressive states called musth. Musth bulls can be recognized by the large amounts of thick fluid draining from the temporal glands located just behind the eyes. Many bulls continually dribble urine and show damp patches on their hind legs. Musth bulls show several unique behaviors including: ear-waving to spread the musth scent, a musth rumble (or low frequency vocalization announcing his presence to cycling females), a musth walk with head and ears held high above their shoulders as a visual display to other bulls and aggression towards everything in its path. All of these make the musth bull a formidable opponent. Although we don’t fully understand the complex behavioral function of musth, musth bulls are frequently successful suitors for cycling cows. Female Reproductive System |
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The reproductive system of the female elephant has been better understood in the last 30 years through the combination of studies using necropsy, hormonal assays and ultrasonic investigations. A cycling female, or cow, may vocalize and show greater interest and enthusiasm for bulls. Bulls will test the cow’s readiness to breed by performing a flemen behavior, which uses his trunk to bring urine samples to the veromonasal receptors in the roof of the mouth. These sensory receptors send chemical signals to the elephant’s brain telling him if the female is ready to breed. Courtship may last from 1 hour to 4 days where the bull will stay near the cow and guard her from other bulls while he occasionally mates with her. After 1 to 3 days, the cow will no longer be receptive to breeding or be capable of conceiving. Typically, wild cows will begin reproducing at 12-14 years of age, sometimes earlier in zoos. The interval between calves can be about 5 years but this is highly variable based on the availability of food, the presence of a suckling calf and the age of the cow.| Photos by Dr. Thomas Bernd Hildebrandt, Institute for Zoo and Wildlife Research |
Female Elephant Estrous Cycle |
Ongoing endocrine research has allowed elephant facilities to develop the capacity to monitor and predict elephant reproductive events, including ovulation, conception and parturition. Continuous hormone monitoring and ultrasonography are the only ways to conclusively determine the level of reproductive activity. This can easily be accomplished by measuring the concentration of progestins in urine or blood samples collected on a weekly basis and regular ultrasonic exams. In general terms, the estrous cycle of the Asian and African elephant is 15 to 16 weeks, comprised of an 8 to 11 week luteal phase and a shorter interluteal (follicular) period of 4 to 6 weeks. |
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Figure Caption: Patterns of serum progestogen (black) and leuteinizing hormone (LH; red) during two successive ovarian cycles followed by pregnancy (grey) and birth. Two surges of LH in each cycle (19 to 21 days apart) allow for accurate timing of ovulation on the 2nd LH surge (asterixes) for artificial insemination (AI) or breeding (gestation month = 0). At the end of gestation progestogen concentrations fall to baseline prior to the onset of labor and birth. |
Photo by Dr. Catharine Wheaton |
Ultrasonography of Developing Calf |
Advances in ultrasonography allow detection and monitoring of elephant pregnancy. Early development can be monitored transrectally but as the fetus develops, it drops out of reach of the probes. Later in gestation, fetal movement and parts of the fetus can be detected by transabdominal ultrasound. Ultrasound exams are also important for monitoring the birth process. |  |
This ultrasound image shows a developing elephant calf at 99 days. |
| Photo by Dr. Michele Miller and Dr. Don Neiffer |
Elephant Birth |
Once the cow becomes pregnant, she has a long wait before the calf is born. The length of pregnancy, or gestation time, can vary between 21-23 months. The following images take you through the stages of one Asian elephant birth. |
 | #1 First, a bulge appears underneath the tail as the calf’s legs, either front or back, move over the mother’s hip girdle into the vestibule. |
#2 In this birth the water did not break until the calf was fully delivered. Notice the fluid-filled amniotic sac emerging from the vestibule. |  |
 | #3 As the calf exits the vestibule, it is forced forward under the belly of the mother. The amniotic fluid in this case forms a ball under the calf’s legs. |
#4 The mother is squatting and pushing and the calf has almost fully exited under her belly. |  |
 | #5 The calf is fully delivered and on impact with the ground the amniotic sac breaks spilling large quantities of birth fluid onto the floor. |
#6 In this birth, the calf struggled to stand almost immediately. During his examination by the medical and animal care team, the calf is kept in reach of the mother and is toweled off ready to be with his mother again. |  |
 | #7 The calf, identified as a male weighing about 300 lbs, stood within a few minutes. Nursing occurred within a few hours after birth. |
| Photos by Dr. Susan Mainka |
The sequence of this birth from bulge to birth was 7 hours. Every birth is different and each phase can take widely varying amounts of time. This particular birth was a first time mother at age 11 and the calf was quite large, probably contributing to the long birth process. Many births are much shorter in duration. |
Advances in Medical Technology |
Advances in assisted reproduction in elephant facilities have been especially valuable for overcoming the logistical problems facing elephants that are often housed long distances apart. Artificial insemination (AI) is a viable alternative to natural breeding in cases where the female’s chances of being bred naturally are limited. AI applied to elephant populations can have many positive effects, such as increasing the genetic diversity, increasing the number of elephants that can be reproductively active, reduce the need to transport, and reduce the need to disrupt established female social groups. AI may also be a tool in the future for introducing new genetics into a population without having to remove elephants from their range countries through the use of semen collected from wild bulls.
Source: http://www.elephanttag.org/
