Effect of age and body condition score on reproductive organ size and sperm parameters in captive male African lion (Panthera leo): Suggesting a prime breeding age

Sexual maturity and body condition are interconnected in many mammals. For non-domestic felids held in human care, the effect of body condition on male fertility has not been studied, although obesity is a recognized problem for many species such as the African lion (Panthera leo) under captive conditions.

Here, we assessed body weight, body condition via body condition score (BCS), reproductive organ appearance and size by ultrasonography and semen parameters as a function of age in a large population of captive male lions housed in different facilities in South Africa. Of 59 individuals (age range 2.5–10 years), we rated 21 (36 %) of the males (≥ 4 years) as highly obese (BCS 8–9). Semen collection via urethral catheter was successful in 49 males (83.0 %). Sperm were found in 44 males (74.6 %) across all age groups. Sperm motility and detailed sperm morphology was assessed in 42 and 18 lions, respectively.

As expected, body weight and reproductive organ size increased with age, but only the testis size increased in proportion to BCS. Although our data are unbalanced, as older animals (already after five years of age) were more often obese, they suggest an optimum age and body condition for potential fertility with adequate physical maturity in male lions. Physical maturity appeared to be reached between the ages of three and five years, which is later than sexual maturity in male lions.

Lions that far exceeded the normal body weight range and had a BCS of 8 or 9 had lower semen quantity and quality. Therefore, male lions in captivity are in prime breeding condition when physical maturity is combined with a BCS < 8.

Our data contribute towards interpretation of fertility assessments in managed breeding programs for lions. Ultrasonographic appearance of the reproductive organs, BCS and semen parameters can help to identify and select breeding males.