Bruno Bassano

CLIMATE FORCING AND DENSITY DEPENDENCE IN A MOUNTAIN UNGULATE POPULATION

Population models in ecology are rarely validated by comparing their pre- dictions to long-term observations of changes in population size. We have used a variety of analytical tools to examine a 45-year time series of annual censuses of Alpine ibex (Capra ibex) in the Gran Paradiso National Park in northwestern Italy. This ibex population grew from about 3300 to almost 5000 individuals in the 1980s during a decade of anom- alously mild winters, and then began to decline in the 1990s. By 1997, the population size had returned to previous levels. Adult survival apparently increased and adult sex ratio may have changed to slightly favor males during the increase in population density. Yearly changes in total population were correlated with seasonal average snow depth and population density over the 39 years for which climate data were available. Our results show that the ibex population size was limited by both density dependence and deep snow. A model based on these factors fit to the first 19 years of data was used to forecast subsequent changes in total population based on initial population size and yearly snow depth. The model was able to predict the increase and subsequent decline in total population size over the final 20 years of the study but failed to reproduce population levels after the eruption. Our results suggest that the 1980s episode of population growth was primarily driven by increased adult survival, rather than increased recruitment.

Temperature constraints on foraging behaviour of male Alpine ibex (Capra ibex) in summer

In arctic and alpine environments, warm summer temperatures may force a reduction in foraging time of large herbivores, whose tolerance for heat is lower than for species adapted to warmer weather. We constructed time budgets for marked ibex (Capra ibex) males over two summers to test whether warm temperatures constrained foraging behaviour and forced altitudinal migrations. As daily temperature and solar radiation increased, feeding activity was reduced at midday and evening, but increased in the early morning, probably to anticipate for an expected reduction in foraging later in the day. With increasing temperature and solar radiation, ibex moved to higher elevations where they spent very little time feeding. Changes in forage quality and availability could not explain altitudinal migration. Temperatures above 15–20°C apparently result in heat discomfort in male Alpine ibex. As temperature and solar radiation increased, older and larger ibex spent less time feeding during daylight and showed a steeper decrease in feeding time than younger and smaller ibex. Larger males may be more sensitive to temperature and solar radiation, or may have more flexibility in allocating time to different activities, given their lower relative energetic requirements.

Predation Risk as a Factor Affecting Sexual Segregation in Alpine Ibex

Abstract Alpine ibex (Capra ibex) are polygynous ungulates that exhibit extreme sexual dimorphism and segregation. To test the hypothesis that risk of predation plays a key role in the development of sexual segregation (habitat segregation) in this species, compositions and locations of groups of ibex were recorded from February 2003 to October 2004. Individual fixes of marked adult males and females in the Gran Paradiso National Park in Italy were collected monthly over a 4-year period (January 2000–December 2003). Distances were measured between each location and the nearest refuge area (rocky slopes), and between each location and the nearest source of disturbance (roads and hiking trails). Group size was not related to distances from refuge areas or from sources of disturbance, but sex, age, and weaning played a key role in spatial segregation. During the period of rut, females kept nearer to rocky slopes and further from hiking trails than males. The presence of young also influenced the spatial behavior of females: mothers made use of refuge areas more frequently and of areas near hiking trails less frequently than other females. In contrast, no difference between the spatial behaviors of pregnant and nonpregnant females was recorded in spring. Age played an important role in space use by males, but not by females. Young males (2–5 years) stayed closer to rocks than did middle-aged males (6–11 years), and both stayed closer to rocks than did adult males (>11 years). Adult males stayed closer to hiking trails than middle-aged males; likewise, the latter stayed closer to hiking trails than young males. Males stayed near areas with human presence, likely because of good foraging opportunities. Although our findings do not exclude other explanations, they support the reproductive strategy–predation risk hypothesis. Moreover, predation risk was shown as an important factor leading to both sexual and age segregation in males.

Age‐dependent genetic effects on a secondary sexual trait in male Alpine ibex, Capra ibex

Secondary sexual traits, such as horns in ungulates, may be good indicators of genetic quality because they are costly to develop. Genetic effects on such traits may be revealed by examining correlations between multilocus heterozygosity (MLH) and trait value. Correlations between MLH and fitness traits, termed heterozygosity–fitness correlations (HFC), may reflect inbreeding depression or associative overdominance of neutral microsatellite loci with loci directly affecting fitness traits. We investigated HFCs for horn growth, body mass and faecal counts of nematode eggs in wild Alpine ibex (Capra ibex). We also tested if individual inbreeding coefficients (f′) estimated from microsatellite data were more strongly correlated with fitness traits than MLH. MLH was more strongly associated with trait variation than f′. We found HFC for horn growth but not for body mass or faecal counts of nematode eggs. The effect of MLH on horn growth was age‐specific. The slope of the correlation between MLH and yearly horn growth changed from negative to positive as males aged, in accordance with the mutation accumulation theory of the evolution of senescence. Our results suggest that the horns of ibex males are an honest signal of genetic quality.

Horn growth but not asymmetry heralds the onset of senescence in male Alpine ibex (Capra ibex)

Senescence can be defined as accelerating phenotypic deterioration with old age. For traits that grow throughout life, such as the horns of some ungulates, senescence may be expressed as a decrease in annual growth rates, or an increase in asymmetry, in the years preceding death. Age-specific yearly horn-growth segments of 378 male Alpine ibex Capra ibex L. that died from natural causes were analysed in the Gran Paradiso National Park (Italian Alps). Horn annuli displayed fluctuating asymmetry. The hypothesis that asymmetry and size of the annuli of the horns could predict annual survival probability was tested. It was found that between 5 and 11 years of age, male ibex that grew shorter annuli than the average for the population had a greater probability of mortality over the following years than those with greater rates of horn growth. Horn asymmetry and mortality rates were not significantly correlated. Annulus size, reflecting the onset of senescence, seemed to be a better indicator of individual quality than annulus asymmetry.

Hormones, parasites and male mating tactics in Alpine chamois: identifying the mechanisms of life history trade-offs

Alternative mating tactics (AMTs) may show different trade-offs between current reproduction and survival; however, the proximate mechanisms underlying this pattern remain unclear. Among them, the relationship between reproductive effort and parasite resistance mediated by hormonal secretion has received increasing attention. We monitored 19 marked adult male chamois, Rupicapra rupicapra, within the Gran Paradiso National Park (Italy) between the pre- and postrut 2011, to investigate the trade-off between mating effort and parasites associated with AMTs, and the underlying physiological mechanism. Territorial males sharply increased mating effort, faecal androgen and cortisol metabolites, and parasite levels during the rut, whereas nonterritorial ones displayed a similar pattern only for androgen metabolite levels. During the rut, territorial males invested more in rutting activities, while having higher levels of hormone metabolites and greater faecal counts of parasites than nonterritorial males. Before and after the rut, differences between male types (territorial and nonterritorial males) were smaller. Our analysis suggests that a trade-off between mating effort and parasitism exists, and that the proximate mechanism underlying this pattern may be found in the secretion of androgen metabolites. The greater investment in rutting activities, which territorial males make, suggests potentially high mating benefits. However, mating benefits could be counterbalanced by greater risk of injuries, consumption of fat reserves and higher hormone levels, which might favour the suppression of immunological defence and the subsequent decrease in parasite resistance.

Can ground counts reliably monitor ibex Capra ibex populations

Abstract Although ground counts are often used to monitor ungulate populations, several studies show that counts of ungulates have low precision and often underestimate population size. We assessed the reliability of ibex Capra ibex counts as performed in French national parks, by analysing up to 23 years of annual censuses of six ibex populations for which a subset of animals were individually marked. We compared the population growth rate obtained from census data (estimated by use of four different methods) with the growth rate calculated from a demographic model including parameters estimated from capture-mark-recapture methods. The correlations between count-based estimates and growth rate obtained from demographic models were adequate to suggest that ground counts can monitor trends in population size of ibex, provided that the occasional undercounts are identified. Substantial undercounts in some years led to biologically impossible values of yearly population growth (λ>1.35) and, in the longest time series available, to marked autocorrelations in counts. Managers should replicate counts within the same year to check for underestimated counts. To reduce errors, population biologists analysing time series of ungulate counts should check the plausibility of annual growth rates estimated from two consecutive counts.

Spatial behaviour of adult male Alpine ibexCapra ibex ibex in the Gran Paradiso National Park, Italy

During a two year preliminary study, the spatial organization of a group of male Alpine ibexCapra ibex ibex Linnaeus, 1758 was examined in the Gran Paradiso National Park, Western Italian Alps, Italy. From December 1995 to January 1998 we measured annual, seasonal home range and home range during the rut, plus altitudinal migration of 13 radio-collared adult Alpine ibex. The small annual home range size showed a traditional use of space, confirmed by the high overlapping values between home ranges of consecutive years: the ibex used the same places from year to year. This was also true during periods of rut. Home ranges closely overlapped in consecutive ruts, while their size changed from winter to winter. Snow cover limited the movements of the ibex; winter and spring home ranges were smaller than those in summer and autumn. Mean vertical movement patterns were similar in the two years, showing the highest values in summer and the lowest in spring. Space use was never proportional to availability for each altitudinal range.

Body weight and horn development in Alpine chamois, Rupicapra rupicapra (Bovidae, Caprinae).

SUMMARY With the aim of describing the trend in somatic development, especially the attainment of asymptotic body mass of Alpine chamois, Rupicapra rupicapra rupicapra, we recorded measurements (eviscerated body weight, length and height of horns) of 548 chamois harvested in 6 different valleys of the Piedmont region (Western Italian Alps), from 1984 to 1996. In male Alpine chamois, asymptotic mass was reached at 4.5 - 5.5 years of age, and after 4.5 years of age, the horns did not grow significantly between one year and the next. Females reached maximum body weight at about 3.5 years of age. Male chamois showed rapid early somatic development with consequent early development of sexual dimorphism. The mean body weights of males and females differed significantly from 3.5 years of age onwards, while horn size differed at as early as 1.5 years of age. Highest degree of sexual dimorphism in body weight (31.3 %) was found at 7.5 years of age. Male chamois reach asymptotic body mass in correspondence with first reproduction, while females mature before achieving asymptotic growth.

Don't spit in the soup: faecal avoidance in foraging wild Alpine ibex, Capra ibex

Faeces are a major vehicle for transmission of parasites among ungulate hosts. Avoiding feeding in proximity to faeces has been shown to be an antiparasitic strategy in experimental settings with domestic and semidomestic ungulates. However, few studies have tested the faecal avoidance hypothesis in wild herbivores. We tested the faecal avoidance hypothesis in a wild population of Alpine ibex by comparing the quantity of faeces in grazed and avoided areas. We counted faecal pellets within a plot around a grazing individual and a plot around a spot actively avoided by the same individual. As predicted, grazed plots had lower densities of faecal pellets than avoided plots. Fresh faeces were avoided more often than medium-aged and old faeces. We found consistent differences in the level of faecal avoidance among individuals, but this was not related to the level of gastrointestinal parasite infection or to the age of the host. Our results suggest that wild Alpine ibex actively avoid foraging near faeces but the antiparasitic value of this behaviour is not evident.