Age, seasonality, and correlates of aggression in female Apennine chamois

Abstract

Intrinsic and environmental stressors, such as age and seasonality, may influence social behavior and endocrine levels in gregarious foragers, but little is known about how season and age affect both behavioral and physiological responses. We evaluated seasonal/age variation of aggression and vigilance, and seasonal/age variation of endocrine levels (fecal cortisol and testosterone metabolites), in a gregarious herbivore, the Apennine chamois Rupicapra pyrenaica ornata. We examined a period of decreasing resource abundance and maternal care from July to October, a key period for nursing, weaning, and early growth of offspring. Aggression rate, vigilance, and cortisol levels decreased throughout July-October, while aggression intensity showed the reverse. Aggression intensity peaked when chamois were on the most nutritious vegetation patches. Dominance increased with age, and prime-aged females (4-8 years old) showed higher cortisol and testosterone levels and were involved in aggressive interactions more often than subadult or older females. Our findings suggest that, in early summer, when nursing effort is the greatest, selection of nutritious food patches leads to frequent encounters between female chamois, enhancing aggression rate, vigilance, and endogenous stress response. The progressive decrease in food abundance throughout July-October triggers competition for scarce resources and increased intensity of aggression. Most likely, the energetic demands of lactation and offspring guarding were key determinants of behavioral and physiological stress of female chamois. Our results suggest a multi-factorial compromise between reproductive state and stress levels, in a group-living species. Significance statementThe cost of motherhood: in female chamois, aggression, vigilance, and stress peak during lactation, despite abundant food resources. In females, aggression and dominance increase with age. A multi-factorial compromise between reproductive stage and stress may be necessary in a group-living animal. We suggest that motherhood is a stressful event for female chamois.

Progesterone and Cortisol Levels in Blood and Hair of Wild Pregnant Red Deer (Cervus Elaphus) Hinds

“…Our results show, as expected, highly variable plasma CORT levels ranging from 0.38 to 2.97 ng/mL. This is likely to be imputed to several "acute" factors and the variability of this hormone pattern itself [22,34]. On the other hand, hair CORT levels are the reflection of the continuous incorporation of the hormone into the hair shaft [15], and thus less influenced by acute stressors.…”

“…Blood cortisol levels change quickly throughout the day and are therefore relatively unreliable, but quantification in matrices such as feces and hair seems to be a good indicator of chronic stress, potentially also related to the reproductive status of the animal [16,23]. Moreover, cortisol, in all matrices, shows high seasonality variations in red deer [33] as in other wild ungulates [34].…”

To scan or not to scan? Occurrence of the group‐size effect in a seasonally nongregarious forager

“…Furthermore, in family groups, i.e., when offspring were present, females increased vigilance. We suggest that, in adult females, maternal effort is the major determinant of vigilance, in agreement with previous studies on the same species (San José et al, ; Tuner, ) and other ungulates (red deer Cervus elaphus : Childress & Lung, ; Alpine ibex Capra ibex : Toïgo, ; mouflon Ovis aries : Benoist, Garel, Cugnasse, & Blanchard, ; white‐tailed deer Odocoileus virginianus : Lashley et al, ; Southern chamois Rupicapra pyrenaica : Fattorini, Lovari et al, ; fallow deer: Pecorella et al, ). Differences in vigilance between sex and age classes seem also to agree with the predicted increase in both scan frequency and duration in response to a greater predation risk (sensu Sirot & Pays, ) perceived by a certain sex/age class, as females with fawns should be the wariest individuals in a group.…”

“…As animals face different trade‐offs according to the biological stage of the annual cycle (e.g., reproductive seasons and availability of food), vigilance effort could also be expected to show seasonal variation (birds: e.g., Reboreda & Fernandez, ; mammals: e.g., Favreau, Goldizen, Fritz, & Pays, ). For example, reproducers may maintain the highest vigilance until fledging/weaning of offspring (birds: e.g., Seddon & Nudds, ; mammals: e.g., Fattorini, Lovari et al, ). Conversely, vigilance of breeding individuals may peak during the mating season, when it serves to monitor competitors (birds: e.g., Jenkins, ; mammals: e.g., Cameron & Du Toit, ).…”

Male aggressiveness in a polygynous ungulate varies with social and ecological context

“…Ecological factors such as seasonal changes in temperature, diurnal rhythms and distribution of food resources can all influence the development of aggressive interactions (Briffa & Sneddon, 2010;Fattorini, et al, 2018). Theory suggests two alternative relationships between aggressiveness and forage resources.…”