Contrasting Alternative Hypotheses to Explain Rut‐Induced Hypophagia in Territorial Male Chamois

Abstract

Male ungulates in temperate environments often show a severe reduction in time spent foraging during the mating season. Several hypotheses have been put forward to explain this phenomenon but, so far, no study investigated the proximate mechanisms underlying rut-induced hypophagia in ungulates using alternative mating tactics (AMTs). Between the pre-rut and post-rut of 2011 and 2012, we collected data on activity budgets, parasite burden and androgen levels of territorial and non-territorial male Alpine chamois Rupicapra r. rupicapra in the Gran Paradiso National Park (Italy). We aimed to investigate whether AMTs showed similar reduction in time spent foraging during the mating period and to test the predictions underlying alternative hypotheses that may explain rut-induced hypophagia. Only territorial males showed a significant reduction in time spent foraging during the rut; the lack of correlation between proportion of time spent foraging and androgen metabolites or parasite burden did not fully support the physiological and the parasite hypotheses, while the foraging constraint, the energy-saving and the physical rest hypotheses could not be discounted. Territorial males decreased the time spent lying down from the pre-rut to the rut, but not their foraging-to-lying-down ratio. During the mating period, we found negative correlations between time spent foraging or lying down and time spent rutting. Our data suggest that territorial males' behaviour is more consistent with the foraging constraint hypothesis than with the energy-saving hypothesis previously suggested. Yet, during the rut territorial males did not maximise their foraging time, and the optimisation of their energy balance could rather depend upon feeding on relatively high-quality plants. This suggestion -possibly named 'forage quality hypothesis' -now requires further investigations. This work showed that alternative mating behaviours may underlie different patterns of foraging strategies: we suggest that tests of alternative hypotheses to explain rut-induced hypophagia within ungulate populations should not ignore the occurrence of AMTs.

The use of block counts, mark‐resight and distance sampling to estimate population size of a mountain‐dwelling ungulate

“…2b). For practical reasons, surveys took place between 4 p.m. and 8 p.m., but male chamois do not show significant differences in activity rhythms between morning and afternoon (Corlatti and Bassano 2014). Observations were conducted with the aid of proper optical instruments (binoculars Zeiss and Swarovski 8/10 9 40 and a spotting scope Swarovski 20-60 9 65): all occurrences of marked and unmarked adult males (i.e., C2 years of age) were noted down, and every spotted animal was georeferenced (Table 1).…”

Heterothermy in large mammals: inevitable or implemented?

“…The authors (Grigg et al ., ) speculated that the lowered minimum body core temperature of the male camels in rut reflected a strategic hypothermia that would allow rutting males to store more heat during fights before they reached a critical maximum body core temperature, thereby increasing their reproductive success. Alternatively, the high energetic cost of the rut combined with reduced foraging time, common in ungulates as a result of high vigilance and territoriality during the rut (Corlatti & Bassano, ), may have lowered energy reserves and resulted in a reallocation of energy use away from less essential functions, including the maintenance of body core temperature. However, more empirical evidence is required to confirm the link between energy use and the maintenance of homeothermy in large mammals.…”

Capital-income breeding in wild boar: a comparison between two sexes

“…The mating system and, specifically, the degree of polygyny may act as a further push-factor in positioning male ungulates along the capital-income continuum 6 . Indeed, higher levels of intra-sexual male competition for mating opportunities are likely to enhance the reproductive demands of polygynous males and, concomitantly, their tendency to adopt feeding reduction 7 , 8 and suppression 9 , 10 during the rut, inevitably forcing them to rely on a stored capital of reserves. Moreover, in order to maximize their lifetime reproductive success, individuals can occupy different positions along the capital-income breeding continuum throughout their life cycles 5 .…”