Age at Maturity: Okapis become sexually mature at about two years of age and can continue to reproduce throughout old age, although aged females may encounter health problems with pregnancies and/or deliver weak calves. The youngest female recorded to have bred was 19 months of age. Gestation lengths from earlier data were recorded to range from 414 to 493 days. Average gestation lengths according to current records are 430 to 435 days, based on a total of 34 pregnancies from seven different females at two institutions (Brookfield and SDWAP), with a total range of 415 to 455 days.

Estrous Cycle and Hormone Tracking: The estrous cycle occurs every 13–16 days and estrus (receptivity or heat) lasts 2–5 days throughout the year with no seasonal variation. Signs of estrus vary depending on the female, but may include an increased level of general activity including pacing and licking; a slightly swollen vulva; posturing (lordosis) and stiffened front legs; and increased attention from the male (Flehmen, Laufschlag, and pursuit behaviors). Multiple breedings are common during estrus. Occasionally, breedings will continue into the first five months of pregnancy and this can create some difficulty for the animal care staff in determining accurate conception and subsequent parturition dates.
It can be difficult to detect estrus in females, even if a male is in the same building. Estrus behaviors seem to vary in intensity and duration. Naïve individuals are not as obvious and consistent in displaying sexual behavior as are experienced individuals. It is important for staff to become familiar with the individuals they are caring for since there appears to be considerable individual variation. Urinary and/or fecal hormone analysis can be a useful tool in determining the cycles and periods of estrus of a particular female which can then be compared to observed behaviors to provide more insight as to the particular behaviors associated with estrus in specific animals.

Analysis of urinary and/or fecal hormone metabolites may detect “possible” pregnancies by less than one month after conception (by a persistent elevation of progesterone metabolites at luteal phase levels).
Less than one milliliter of urine or 3-4 fecal pellets per day for 30 days (frozen immediately after collection) are needed to diagnose pregnancy. However, it must be understood that since this method of analysis measures the female’s ovarian steroids and not fetal-specific hormones, false positives can occur, especially in the case of infections or diseases of the reproductive tract which can result in similar hormone profiles. Currently, no fetal-specific hormones have been identified in ungulates in general to provide the basis for diagnostic methods for more accurate measures of pregnancy detection. Confirmation of pregnancy in okapis is possible via urinary or fecal progesterone metabolite measurements after the fifth month of gestation when levels can reach ten times those typically measured during ovarian cycles.

Breeding Behaviors: Some elements of courtship and mating
behaviors are similar to other ungulates: Flehmen, chin-resting,
neck-thrusting, Laufschlag, and mutual circling. Often the male
will vocalize a soft coughing or moaning sound, which is not heard
at any other time. Copulation lasts no more than 10–20 seconds.
Sometimes the ejaculatory thrust is noticeable.
Breeding behavior can vary a great deal depending on the individuals
involved. Males sometimes use their horns to hook and scrape
an uncooperative female. In an effort to avoid male advances, a
female may lie down in total recumbency for a minute or two.
Experience has shown that a male may become aggressive, even
with a familiar female; therefore, all introductions should be
watched closely by experienced staff. Although serious physical
injury is rarely inflicted, psychological damage can be substantial
and may interfere with subsequent reproductive performance and
success over the long term.

Introductions for Breeding: Breedings often occur inside holding
facilities because some institutions plan them during the winter so
that calves will be born in the spring-summer months, and for better
control in the event that the introduction becomes aggressive.
Ample space, good footing, and sufficient height within the interior
enclosures are vital for successful introductions and breedings.
Regardless of where the introductions take place, the animal care
staff should watch the animals closely.

The intended breeding pair should be placed adjacent to one another, or at least within visual access of one another, for some time prior to the actual introduction. This species is solitary in the wild, so individuals would not have prolonged contact with one another outside of a situation where a female is in estrus. It is not important for the female to be in estrus for an introduction to occur. Some adult pairs get along very well regardless of the female’s reproductive state.
Experienced keeper staff should be in the area for the duration of the introduction to closely observe and be prepared to separate the animals if necessary. The female may be cautious or uncooperative in the male’s presence; especially if she is naïve or not in estrus. Her comfort level in the presence of the male should be evaluated carefully. It is important that she is not overly stressed at the introduction, which should end sooner than later if it is determined that tension is increasing between the two animals. Introductions should be continued on a regular basis, especially if the male is behaving in a gentle manner. Sometimes it is easier to assess the female’s reproductive status by watching the male’s behavior towards her than the behavior of the female herself. If no sexual interest or mating has occurred within 90 minutes of pairing, it is not likely to occur and animals can be separated until the next day. If a male is overly aggressive towards a female or if the female appears to regularly become overly stressed in the presence of a male, introductions should occur only during the female’s estrus period in an effort to minimize aggressive/fear behaviors.

Post-partum estrus can occur in okapis, but this varies between individuals. Studbook records indicate that an estrus of 1–2 days following parturition is possible but this occasion for breeding is rarely utilized if the female’s calf is viable since it will likely interfere with cow/calf bonding. (In fact, based on reports on domestic livestock, this period is associated with lower fertility due to the condition of the uterus at that time.)
Lactating females tend to resume cycling within 2-8 months post-partum. Managers often utilize the 6–8 month post-parturition estrus periods to re-breed the female, which does not appear to be problematic for the female or the calf.

Pregnancy can be determined via urinary and fecal hormone analysis (a confident diagnosis can only be expected after five
months of gestation when the measurements rise up to ten-fold higher than those observed during cycling profiles) or transabdominal
ultrasound. If the animals have access to a floor scale, body weights can also be an indicator of pregnancy as well as the
general health of females. Certainly, the later stages of pregnancy especially in experienced females, are more easily recognized by
staff. However, since gestation in okapis is thirteen and a half months long, it takes some time and experience before casual
observations can determine that a particular animal is pregnant; especially in the case of primiparous females. It is more prudent
to have urinary and/or fecal hormone measurements performed to gain more conclusive results (as soon as one month after
breeding with confirmation only after five months of gestation), rather than lose valuable time in case a female has not conceived as expected.

Hormone therapy has been utilized to assist in maintaining pregnancy in females with a history of abortions and also to stimulate estrous cycles for females that do not appear to be cycling on a regular basis and are not conceiving as expected.
Our Reproductive and Veterinary Advisors will have the most up-to-date information on recommended treatment protocols for these situations. Contraception has not been employed with okapis as yet.

Provisions for Parturition and Management of the Female:
Okapis generally exhibit a good level of maternal care. However, the birthing process can be very startling for primiparous females. Females have been known to injure or kill the newborn if in an excited or confused state. It is critical for the female to be in familiar surroundings, without the distraction of other animals or people in the immediate area. If a pregnant female is to be moved to a different stall/area, this should be completed as early in the pregnancy as feasible. This will allow the female time to become comfortable in her new surroundings. Any additional substrate should be added to the interior flooring approximately 3–4 weeks prior to parturition, which will give enough time for the female to become familiar and to avoid the new substrate from becoming too soiled. Adult males should not be housed next to expectant females. Information on vaccinations and other veterinary issues for pregnant females can be found in the health section.

Edited by Terry DeRosa, San Antonio Zoo, Fran Lyon, White Oak Conservation Center and Ann Petric, Okapi SSP Coordinator, Brookfield Zoo Illustration: J. Busch
Updated and adapted for the web, Patrick Immens