Age-Related Alterations in Testicular Histoarchitecture of Yangzhou Goose Ganders

The age of maturity and seasonality are vital characteristics in the production of seasonal breeders like Yangzhou ganders. Ancestors of the current geese breeds were wild geese that adapted their breeding season, according to the season having plenty of food and suitable weather conditions to reproduce and raise their chicks to combat harsh environmental conditions. The present study aimed to elucidate histological changes in testicular histoarchitecture of Yangzhou goose ganders. Testis samples were collected from Yangzhou ganders during premature, transition and mature states. Testicular regression was accessed by observing changes in the number of spermatocytes, spermatogonia, elongated spermatids, round spermatids, width of seminiferous tubules, epithelial height, luminal tubular diameter and Johnsen’s score. The results depicted a positive correlation between age and number of spermatogonia, primary spermatocytes, spermatids, and epithelial height. Thus, testicular histoarchitecture works usually on the balance between Sertoli and other germ cells. Further, our results conclude that breeding seasonality and age of sexual maturity also affect spermatogenesis efficiency in Yangzhou ganders.

Breeding seasonality of Chital (Axis axis) in the Hetauda Valley of Nepal

Breeding seasonality of Axis axis differs from place to place mainly due to the difference in vegetation and climate. In Nepal, although Chital is found all over the lower Terai region, studies on breeding seasonality are limited. In this study, we observed the annual cycle of antler renewal and casting, monthly changes in frequency of bellowing call and ratio of new born fawn to adult and sub-adult females from October 2016 to March 2019. Seasonal peak of proportion of hard-antlered males was found in June and seasonal peak of bellowing call frequency was found in May. Seasonal peak of fawning occurred in December, January and February, at the beginning of dry season before monsoon, probably to coincide with the energy demanding late lactation season with excessive food available in rainy season. From antler cycle, bellowing call frequency and fawning frequency data, peak breeding season was identified as May-June. This information can be crucial in nutritional management, herd composition, and translocation period determination for in-situ and ex-situ species management programs.

Local timing of rainfall predicts the timing of moult within a single locality and the progress of moult among localities that vary in the onset of the wet season in a year-round breeding tropical songbird

Rainfall seasonality is likely an important cue for timing key annual cycle events like moult in birds living in seasonally arid environments, but its precise effect is difficult to establish because seasonal rainfall may affect other covarying annual events such as breeding in the same way. In central Nigeria, however, Common Bulbuls Pycnonotus barbatus moult in the wet season but only show weak breeding seasonality. This suggests that moult is more sensitive to rainfall than breeding, but a similar outcome is possible if moult is simply periodic. We tested the relationship between rainfall and moult in Common Bulbuls at a single location over 18 years: on average moult started 5th May (± 41 days: 25th March–15th June), being on average later than the onset of the rains which is usually mid-April. The likelihood of finding a moulting Common bulbul was best predicted by rainfall 9–15 weeks before moult was scored. We then tested the generality of this across populations: the progress of moult should, therefore, correlate with the average timing of the wet season along a spatial environmental gradient where the rains start at different times each year south-to-north of Nigeria. To test this, we modelled moult progress just before the rains across 15 localities 6°–13° N as a function of the onset of the wet season among localities. As predicted, moult progressed further in localities with earlier wet seasons, confirming that the onset of moult is timed to the onset of the wet season in each locality despite weak breeding seasonality in the Common Bulbul. This strategy may evolve to maintain optimal annual cycle routine in seasonal environments where breeding is prone to unpredictable local perturbations like nest predation. It may, however, be less obvious in temperate systems where all annual cycle stages are seasonally constrained, but it may help with explaining the high frequency of breeding–moult overlaps in tropical birds.

Do female dingo–dog hybrids breed like dingoes or dogs?

Hybridisation between animals that breed once (e.g. dingoes) and twice (e.g. domestic dogs) annually may produce offspring that breed either way. This question was investigated by determining the breeding seasonality of female dingo–dog hybrids in south-east Queensland, Australia, through evaluating macroscopic and histological features of 71 female reproductive tracts. All animals were sourced from urban areas where levels of hybridisation are generally high. Most animals trapped in summer were pups less than 6 months of age. A peak of uterus diameter and weight coincided with a peak of corpus luteum in winter. The follicular phase was characterised by growing follicles, ~1–3 mm wide, in late summer and autumn. Only two of the animals (1.4%) showed out-of-season reproductive cycles: one was found with corpus luteum in summer and another in autumn. Our data clearly show that hybrids have a single annual breeding season in winter, exhibiting the same breeding seasonality as dingoes. Our findings are similar to those found in the New Guinea singing dog. Future studies should be conducted to understand and exploit the mechanism and drivers of the breeding seasonality of dingo–dog hybrids to develop more effective management of their populations.