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.

Antiquity and fundamental processes of the antler cycle in Cervidae (Mammalia)

The origins of the regenerative nature of antlers, being branched and deciduous apophyseal appendages of frontal bones of cervid artiodactyls, have long been associated with permanent evolutionary precursors. In this study, we provide novel insight into growth modes of evolutionary early antlers. We analysed a total of 34 early antlers affiliated to ten species, including the oldest known, dating from the early and middle Miocene (approx. 18 to 12 million years old) of Europe. Our findings provide empirical data from the fossil record to demonstrate that growth patterns and a regular cycle of necrosis, abscission and regeneration are consistent with data from modern antlers. The diverse histological analyses indicate that primary processes and mechanisms of the modern antler cycle were not gradually acquired during evolution, but were fundamental from the earliest record of antler evolution and, hence, explanations why deer shed antlers have to be rooted in basic histogenetic mechanisms. The previous interpretation that proximal circular protuberances, burrs, are the categorical traits for ephemerality is refuted.

Antiquity and fundamental processes of the antler cycle in Cervidae (Mammalia)

The origins of the regenerative nature of antlers, being branched and deciduous apophyseal appendages of frontal bones of cervid artiodactyls, have long been associated with permanent evolutionary precursors. In this study, we provide novel insight into growth modes of evolutionary early antlers. We analysed a total of 34 early antlers affiliated to ten species, including the oldest known, dating from the early and middle Miocene (approx. 19 to 12 million years old) of Europe. Our findings provide empirical data from the fossil record to demonstrate that growth patterns and a regular cycle of necrosis, abscission and regeneration are consistent with data from modern antlers. The diverse histological analyses indicate that primary processes and mechanisms of the modern antler cycle were not gradually acquired during evolution, but were fundamental from the earliest record of antler evolution and, hence, explanations why deer shed antlers have to be rooted in basic histogenetic mechanisms.

The Antler Cycle and Fecal Testosterone of Male Sambar Deer Rusa unicolor unicolor at the Horton Plains National Park in Sri Lanka

This study is aimed at evaluating the relationship between endogenous testosterone levels and antler development in male sambar deer (Rusa unicolor unicolor) inhabiting the Horton Plains National Park, Sri Lanka. Seven antler growth stages of sambar were documented based on phenotypic observations for the first time in Sri Lanka as (a) cast, (b) growing 1—single spike, (c) growing 2—antler fork into a Y as the second tine appears, (d) growing 3—velvet begins to harden as the third tine appears, (e) growth completed—velvet shedding begins, (f) hard antler, and (g) casting. Fecal samples were collected every month for a period of eighteen months from male sambar deer in different stages of the antler growth cycle, feeding in the wet patana grasslands of the park, and the fecal testosterone level was estimated by radioimmunoassay. Ten animals were randomly selected from each antler stage for the experiment. The results disclose that the highest concentrations of testosterone were recorded in the hard antler stage. Velvet shedding was preceded by an increase in the testosterone level, and it is the sudden drop in the testosterone concentration which triggers the antler casting. The casting stage corresponded with the lowest mean testosterone concentration. Although the study was able to conclude a clear relationship between the fecal testosterone levels of the male sambar deer in the Horton Plains National Park and their antler stages, there is no clear seasonality for the antler cycle.

Nutrition of antler growth in deer

Stags are susceptible to the effects of nutrition at several stages during their lives and during the antler cycle. Nutrition during the in utero, post-natal (suckling) and yearling stages influences the size of spike antlers, and, generally, there is a close relationship between bodyweight and antler weight in stags aged up to 5 years. While antler size is not greatly affected by nutrition during the growth of immature (velvet) antler, it is influenced by body size and condition at casting, i.e. at the beginning of new antler growth. Antler growth appears to have a high priority for nutrients, especially energy, protein and calcium. Antler growth in adult stags is little affected by diet protein concentrations over 7%, but supplements of protected protein or methionine may improve antler growth. Substantial amounts of calcium and phosphorus are sequestered in antlers as they become mineralised, and calcium is withdrawn from the skeleton in support of this. Feeding programs to obtain good antler growth involve recognising the periods when juvenile stags are susceptible to under-nutrition, and providing sufficient nutrients to re-establish adequate body condition in adult stags between the end of the rut and antler casting.

Relationships between rank-related behaviour, antler cycle timing and antler growth in deer: behavioural aspects

In this review we offer a synthesis of a 30-year-long investigation focussed on the relationship between dominance rank-related behaviour and the timing and growth of antlers in deer. Our studies related primarily to red and fallow deer. We present evidence to suggest that dominance-related behaviour in male deer is strong enough to influence both antler cycle timing and antler growth. In a study on captive red deer we observed that the males of higher rank cast their antlers first and also tended to shed the velvet earlier. In a subsequent series of studies on the same species we found evidence that social position and related agonistic activity of males during the period of antler growth influence antler size and branching. Changes in behaviour related to rank modified antler growth. For example, fallow deer bucks gaining higher rank through fighting other bucks exhibited enhanced growth of that part of the antler that was growing at that particular time. That substantially altered the entire antler growth. Understanding the relationship between rank, agonistic behaviour and hormone levels is crucial for the interpretation of previous results that showed a link between dominance rank and antler growth in deer.