169 BEHAVIORAL ASPECTS OF ESTRUS IN THE COMMON ELAND ANTELOPE, TAUROTRAGUS ORYX

Abstract

Knowledge of the estrous cycle and behavior is important in managing captive breeding programs. However, such information is negligible in spiral-horned antelopes, including the eland. In the present study, conducted between September 2007 and March 2008, we sought to characterize mounting activity and courtship behavior in a group of eight adult eland females. Estrus was induced in groups of four females by treatment with 25 mg PGF₂ ∝ (IM, Lutalyse^®, Pharmacia and Upjohn Company, Kalamazoo, MI, USA) administered after 7 days of daily oral progestin (5 mL of 2.2% altrenogest, DPT Laboratories, San Antonio, TX, USA) or 11 days after an initial treatment of PGF₂ ∝ (25 mg). The eight females received each treatment in a crossover design. Females were induced and monitored during the induced and subsequent natural estrus for 34 to 38 days. Observations for estrus behavior were initially assisted by using Estrotect^™ heat detector patches (Rockyway, Inc., www.estrotect.com). Since January 2008, the HeatWatch^® electronic heat detection system (CowChips, Denver, CO, USA) and an androgenized eland female were used to assist with heat detection. For androgenization, 8 pellets of Synovex-H^® (Fort Dodge Animal Health, Fort Dodge, IA) comprising a total dose of 1600 mg testosterone propionate and 160 mg estradiol benzoate were implanted (SC) on the convex side of the ear. To confirm mounting activity detected by Estrotect^™ or HeatWatch^®, eland behavior was recorded continuously using an 8-channel real time DVR. Chi-square analysis was used to test the association between time of day (day or night) and the frequency of standing to be mounted. The cycle length (n = 6 females) was the time interval (d) between the first mounts at the induced and natural estrus. The time of mounts was determined for a total of 52 mounts. More than half of the mounts (n = 32 or 61.5%) occurred between 6 pm and 6 am (night); however, there was no association between the number of mounts and time of the day (p = 0.886). Analysis of mounts by quarters of the day showed that mounts were evenly distributed between early afternoon (noon to 6 pm: 29%), late afternoon (6 pm to midnight: 33%) and early morning (midnight to 6 am: 29%) but were less frequent during late morning, between 6 am and noon (10%) possibly due to interference by human activities. The number of mounts observed per female ranged from 1 to 20. Mounts lasted for 2 seconds or less. The duration of estrus ranged from 2.1 to 29.0 hours. Typical courtship behaviors included prolonged head butting, flehmen response and following the female in estrus before mounting. The average length of the estrous cycle, based on mounting activities, was 19.3 d (range: 17–24). Although further studies are required in herds with eland males, the present results suggest that estrus detection for captive breeding or application of reproductive technologies in the eland should be spread around different times of the day and night. We have also demonstrated that an electronic mount detection system can be applied to assist with determination of estrus in the eland.