97 Social Dominance does not Affect Semen Quality in African Wild Dogs (Lycaon pictus)

Abstract

Sperm banking and AI could benefit conservation of endangered African wild dogs (AWD). However, it is not clear whether their strict dominance hierarchy causes subfertility in subdominant males that typically do not breed. Our study investigated the effect of dominance on male reproductive parameters, including faecal glucocorticoids (fGCM) and androgens (fAM), testis and prostate volume, preputial gland size, semen collection success, and the number, motility, morphology, viability, acrosome integrity (PSA-FITC), and DNA integrity (TUNEL) of spermatozoa collected by electroejaculation. Samples were obtained from n = 12 captive AWD (4 US packs) in the pre-breeding season and n = 28 captive AWD (n = 11 from 4 US packs; n = 17 from 3 Namibian packs) in the breeding season. Male hierarchy was clearly determined by behavioural observations in all but 1 Namibian pack. Data were grouped by dominance status and means were compared by ANOVA or t-test; P ≤ 0.05 was significant. In the pre-breeding season, there was no significant difference in body weight, fGCM, fAM, or prostate and testis volume between dominance groups. Semen was successfully collected from all alphas but only half the subdominants; urine contamination was negatively associated with dominance. Sperm quality was low (17.3 ± 10.2% total motility, 12.8 ± 8.5% progressive motility, 27.4 ± 11.5 × 106 ejaculated spermatozoa, 40.6 ± 9.8% normal morphology, 63.1 ± 5.1% viability, 72.6 ± 5.2% acrosome integrity) with no difference observed in any parameter except progressive motility and normal sperm morphology, which were significantly lower in subdominants (27.7 ± 16.8% v. 0.0 ± 0.0% and 59.8 ± 13.0% v. 21.4 ± 5.7%). From pre-breeding to breeding season, testis and prostate volume increased significantly, particularly in beta and gamma males respectively. Prostate volume was higher in alpha than beta males (16.0 ± 6.4 cm3 v. 5.7 ± 1.4 cm3), but testis volume, body weight, fAM, and fGCM did not differ between dominance groups (12.0 ± 0.9 cm3, 28.5 ± 0.8 kg, 0.51 ± 0.07 µg g−1, and 30.6 ± 2.3 ng/g of dry weight). Semen was successfully collected from 75% of males with reduced urine contamination. Collection success, urine contamination, and preputial gland size were not associated with dominance. Sperm quality improved with significantly greater number, viability, and total motility. However, sperm quality did not differ between dominance groups (47.4 ± 6.7% total motility, 30.5 ± 5.8% progressive motility, 32.3 ± 9.2 × 106 ejaculated spermatozoa, 50.9 ± 5.2% normal morphology, 74.4 ± 4.2% viability, 85.6 ± 3.0% acrosome integrity, and 99.7 ± 0.1% DNA integrity). In conclusion, subdominant males are at higher risk of urine contamination and have lower sperm motility and normal morphology when semen is collected in the pre-breeding season. However, their semen is of similar quality to dominant males in the breeding season, indicating that reproductive suppression of subdominant males is only behavioural. Thus, AWD males of all social ranks in the breeding season are suitable candidates for sperm banking.