Reproduction, Growth and Development in Captive Beluga (Delphinapterus leucas)

Abstract

Recent success propagating captive beluga has resulted from combined efforts by North American zoos and aquariums to manage disparate collections as a single population. This success has provided a tremendous opportunity to increase our understanding of beluga reproductive biology. Blood samples were collected on a weekly to biweekly basis from 23 female and 12 male beluga, ranging in age from 2-15 years, for analysis of serum progesterone (P) and testosterone (T), respectively. Peri-parturient observational data, including food intake, duration and signs of labor, and nursing patterns were collected from 15 days prepartum to 30 days postpartum during 21 births. Total body lengths and weights were collected from 10 captive-born beluga. For female beluga, the mean (7SD) age, body length, and weight at first conceptions were 9.172.8 years, 318.079.1 cm, and 519784 kg. Thirty-five luteal phases and 13 conceptions were detected from January-June, and 70% of luteal phases and 80% conceptions occurred from March-May. The mean luteal phase and total estrous cycle lengths were 30.076.5 days and 48.074.6 days, respectively. For male beluga, the mean age that males sired their first calf was 13.372.6 years. Compared to younger males (o8 years of age, 0.95 ng/ml), levels of T secretion in older males (48 years of age, 5.0 ng/ml) were elevated significantly only during the interval from January-April. Highest T concentrations (6.274.9 ng/ml) were recorded from January-March, whereas nadir concentrations (1.171.0 ng/ml) were detected from August-September. The mean gestation length was 475.0720.4 days (n ¼ 9). For parturition, the mean time from the first appearance of fluke or rostrum to delivery, delivery to placental passage, and delivery to nursing were 4.472.9 hr, 7.671.8 hr, and 43745 hr, respectively. All cows had decreased food intake on the day of delivery, with 44% having zero intake. Peak 24-hr nursing activity occurred 3.972.7 days post-partum. Growth (i.e., body weight and length) as a function of age were well described by the Gompertz model (r 2 ¼ 0.91, 0.93). Based on the model, growth in body weight and length were significantly greater in males compared to females. Predicted birth weight (88.9 kg) was similar for both sexes, however, and male calves were predicted to be shorter (154.3 cm) than female calves (160.7 cm). The results provide the first descriptions of captive beluga reproductive physiology, including endocrinology, peri-parturient behavior, growth, and reproductive maturity. This knowledge is important for helping to maintain genetically diverse, self-sustaining populations of captive beluga whales.

Socio-sexual and probable mating behavior of Cook Inlet beluga whales, Delphinapterus leucas, observed from an aircraft

“…However, these behaviors closely resemble the specifi c behavioral events of previously observed beluga whales courting and mating in captivity (Hill et al, 2015). The seasonality of these apparent courting and mating behaviors in CIBW correspond with reported spring mating seasons for the Arctic populations (Burns and Seaman 6 ) as well as captive belugas (Robeck et al, 2005).…”

“…Among captive beluga whales, Robeck et al (2005) ly spring, peaking in March (Robeck et al, 2005). These combined studies suggest that breeding should peak seasonally among CIBW as well, although there are no reported behavioral, hormonal, or reproductive data to support this, in part because aerial surveys and sampling of whales rarely occur in March in Cook Inlet (Shelden et al, 2015).…”

Seasonality, estrous cycle characterization, estrus synchronization, semen cryopreservation, and artificial insemination in the Pacific white-sided dolphin (Lagenorhynchus obliquidens)

“…However, sperm production remains unchanged for both these species (Robeck & O'Brien 2004, Robeck & Monfort 2006. The beluga, which has a defined and repeatable reproductive seasonality, undergoes estrus activity from March to June (Robeck et al 2005a). A male beluga exhibited periods of peak serum T (October-April) and sperm production (January-June).…”

“…For each individual female, P concentrations that exceeded 3 ng/ml and were at least 2.0 times the mean non-pregnant P concentration for that particular individual were considered presumptive evidence of luteal activity (Robeck et al 2005a). When a sample below this threshold was serially adjacent to a sample above the threshold, the beginning or end of a luteal phase was defined as median point between these two samples.…”

“…This approach also maximizes the global genetic exchange of gametes among ex situ populations, but semen cryopreservation methods must be optimized for AI to reach its full potential as a management tool. Methods for semen cryopreservation have been developed for three cetacean species, the bottlenose dolphin, the killer whale, and the beluga (Seager et al 1981, Schroeder & Keller 1990, Robeck & O'Brien 2004, 2005a, 2005b, O'Brien & Robeck 2006. Despite their accessibility in captivity, no information is available concerning semen production or cryopreservation in the Pacific white-sided dolphin.…”