Effects of early horn growth on reproduction and hunting mortality in female chamois.

1. Environmental conditions during early development can affect the growth patterns of vertebrates, influencing future survival and reproduction. In long-lived mammals, females that experience poor environmental conditions early in life may delay primiparity. In female bovids, annual horn growth increments may provide a record of age-specific reproduction and body growth. Horn length, however, may also be a criterion used by hunters in selecting animals to harvest, possibly leading to artificial selection. 2. We studied three populations of chamois (Rupicapra rupicapra) in the western Alps to explore the relationships between female horn length and early growth, age of primiparity and age-specific reproduction. We also compared the risk of harvest to reproductive status and horn length. 3. Early horn growth was positively correlated with body mass in pre-reproductive females and with reproduction in very young and senescent adults. Females with strong early horn growth attained primiparity at an earlier age than those with weak early growth. Horn length did not affect hunter selection, but we found a strong hunter preference for nonlactating females. 4. Our research highlights the persistent effects of early development on reproductive performance in mammals. Moderate sport harvests are unlikely to affect the evolution of phenotypic traits and reproductive strategies in female chamois. A policy of penalizing hunters that harvest lactating females, however, may increase the harvest of 2-year-old females, which have high reproductive potential.

Analysing the isotopic life history of the alpine ungulates Capra ibex and Rupicapra rupicapra rupicapra through their horns.

The horn of ungulate grazers offers a valuable isotopic record of their diet and environment. However, there have been no reports of the spatio-temporal variation of the isotopic composition of horns. We investigated patterns of carbon (delta(13)C) and nitrogen (delta(15)N) isotopic composition along and perpendicular to the horn axis in Capra ibex and Rupicapra rupicapra rupicapra to assess the effects of animal age, within-year (seasonal) and inter-annual variation, natural contamination and sampling position on horn isotope composition. Horns of male C. ibex (n = 23) and R. r. rupicapra (n = 1) were sampled longitudinally on the front (only R. r. rupicapra) and back side and on the surface and sub-surface. The sides of the R. r. rupicapra horn did not differ in delta(13)C. In both species, the horn surface had a 0.15 per thousand lower delta(13)C and a higher carbon-to-nitrogen (C/N) ratio than the sub-surface. Washing the horn with water and organic solvents removed material that caused these differences. With age, the delta(15)N of C. ibex horns increased (+0.1 per thousand year(-1)), C/N ratio increased, and (13)C discrimination relative to atmospheric CO(2) ((13)Delta) increased slightly (+0.03 per thousand year(-1)). Geostatistical analysis of one C. ibex horn revealed systematic patterns of inter-annual and seasonal (13)C changes, but (15)N changed only seasonally. The work demonstrates that isotopic signals in horns are influenced by natural contamination (delta(13)C), age effects ((13)Delta and delta(15)N), and seasonal (delta(13)C and delta(15)N) and inter-annual variation (delta(13)C). The methods presented allow us to distinguish between these effects and thus allow the use of horns as isotopic archives of the ecology of these species and their habitat.