Many lifetime growth trajectories for a single mammal

Despite their importance in shaping life history tactics and population dynamics, individual growth trajectories have only been rarely explored in the wild because their analysis requires multiple measurements of individuals throughout their lifetime and some knowledge of age, a key timer of body growth. The availability of long‐term longitudinal studies of two wild boar populations subjected to contrasting environments (rich vs. poor) provided an opportunity to analyze individual growth trajectories. We quantified wild boar growth trajectories at both the population and the individual levels using standard growth models (i.e., Gompertz, logistic, and monomolecular models) that encompass the expected range of growth shapes in determinate growers. Wild boar is a rather altricial species, with a polygynous mating system and is strongly sexually dimorphic in size. According to current theories of life history evolution, we thus expect wild boar to display a sex‐specific Gompertz type growth trajectory and lower sexual size dimorphism in the poorer environment. While wild boar displayed the expected Gompertz type trajectory in the rich site at the population level, we found some evidence for potential differences in growth shapes between populations and individuals. Asymptotic body mass, growth rate and timing of maximum growth rate differed as well, which indicates a high flexibility of growth in wild boar. We also found a cohort effect on asymptotic body mass, which suggests that environmental conditions early in life shape body mass at adulthood in this species. Our findings demonstrate that body growth trajectories in wild boar are highly diverse in relation to differences of environmental context, sex and year of birth. Whether the intermediate ranking of wild boar along the precocial–altricial continuum of development at birth may explain the ability of this species to exhibit this high diversity of growth patterns remains to be investigated.     

Sex effect on habitat selection in response to hunting disturbance: the study of wild boar

Spatial variation of the ‘predation risk’ due to human activities or distribution may increase the sexual difference in habitat selection. Indeed, females with offspring are usually more risk adverse than males. Based on a long-term wild boar study, we analysed the diurnal distribution of female and male wild boar before, during and after the hunting period. Hunting, food and foliation were investigated as factors affecting patterns of forest parcel selection. As expected, dense vegetative covers were selected during resting periods, but wild boar decreased this pattern of habitat selection in response to hunting disturbance. Moreover, the habitat selection of wild boar did not fit with the variation of food availability (presence or absence of mast) and the vegetation cycle. As expected, sows responded more to the hunting disturbance than males, leading to a more pronounced sexual difference during the riskier season. The unexpected decrease of bush use may be explained either by the increased hunting effort in this habitat or by the increased movements between resting sites due to disturbance, leading to a more random habitat selection pattern. The observed difference between sexes could result from a higher response of females with offspring to hunting, leading to an increased frequentation of secondary habitats, whereas males can tolerate more risks and remain hidden in thicket plots. Our results highlight how hunting disturbance can lead game species to change their patterns of refuge habitat selection and may affect the habitat segregation between the sexes.     

Mortality rates of wild boar Sus scrofa L. in central Europe

In many parts of Europe, wild boar Sus scrofa population increase, and thus, high densities and dispersal into new areas are accompanied by economic problems. Due to many factors like insufficient hunting strategies as well as underestimation of population densities and reproduction rates, harvest rates seem to be insufficient. Thus, we calculated mortality rates of several wild boar populations from 1998 to 2009, to show the efficiency of hunting within several studies distributed over eight European states. For calculating mortality rates, the daily probability of survival of radio telemetrically observed wild boar was analysed according to Mayfield (Wilson Bull 73:255-261, 1961) and with survival analysis in R for three age classes (0, 1, ≥2 years) and both sexes. The mortality rates of wild boar per annum, especially piglets, were comparably low (about 0.5 for piglets and similar for total population). About three third of all observed animals survived at least until the next period of reproduction. Mortality rates differed between some study areas, the sexes and age classes. The sex ratio of the shot piglets equals the sex ratio of captured piglets; there seems to be no sex-biased hunting in this age class, but in an older age. Shooting was the main cause of death; only very few animals died by natural causes, e.g. diseases. The comparative analysis of all studies reflects a low mortality of wild boar in highly productive populations. Our results certified the findings of several studies that predation, natural mortality, and road mortality have only small impact on wild boar populations, whereas especially, nutrition or hunting are mainly decisive. Assuming net reproduction rates of more than 200 % according to literature data, our results indicate that harvest rates are not sufficient at our study sites. In all our studies, mortality rates and, thus, harvest rates are less than the assumed total net reproduction. Especially, the harvest rate of piglets seems to be insufficient. Thus, the population will increase further. High reproduction has to be counteracted by regulating mainly the reproductive animals. For regulating a population, combined and effective hunting methods have to be conducted to harvest at least the net reproduction. Thus, we recommend higher hunting rates of piglets (80 % of the offspring should be harvested) and of adult females. Intensified hunting of piglets by drive hunts and at an early age as well as intensified single hunt on adult females might help regulating wild boar populations.     

Hunters serving the ecosystem: the contribution of recreational hunting to wild boar population control

The extractive nature of recreational hunting may provide a service to both the ecosystem and society, namely the control of problem species. We reviewed the annual wild boar hunting bag data from hunting sites in Asturias (Spain) from 2000/01 to 2013/14, paying particular attention to the evolution on hunting estates after ban periods. We hypothesized that the annual hunting bag after a hunting ban would be larger than that of the pre-ban period, and that this difference could provide an indication of hunters’ relative contribution to wild boar population regulation. The total hunting bag grew during the study period, from 3723 wild boar (0.39ind/km²) in the 2000/01 hunting year to 7593 in that of 2013/14 (0.79ind/km²)—a mean annual increase of 5.63%. Low hunting quotas cannot be blamed for these growing trends, since no more than 50% of the authorized animals are hunted. The growth of the mean annual pre-ban hunting bag on the estates on which hunting bans took place was 8.46%. The hunting bag grew by 40.33% immediately after the hunting ban ended—a growth rate seven times higher than that of the background hunting bag. This constitutes a proxy of the regulatory effect of hunters on wild boar population growth. Following the remarkable increase after the ban, the wild boar hunting bag attained values that were slightly lower than those of the pre-ban period, which indicates that hunters are able to reduce wild boar abundance. Hunting, therefore, provides an important service to both the ecosystem and society by contributing to regulating the growth of problem species such as the wild boar.     

Rooting for Rewilding: Quantifying Wild Boar's Sus scrofa Rooting Rate in the Scottish Highlands

Rewilding is emerging as a promising framework within restoration ecology to help restore ecosystem function through species reintroduction. To manage effectively such projects it is necessary to predict and quantify the interactions between the reintroduced species and their environment. To date, this has not been a priority in restoration ecology. Here, we quantify wild boar's rooting rate at a range of stocking densities to explore their potential to aid the restoration of the Caledonian pine forest in the Scottish Highlands by reinvigorating the disturbance regime. Eleven enclosures of c. 0.5 ha within heather moorland, dominated by Caluna vulgaris, were used, situated on the Alladale Wilderness Reserve, 50 km north‐west of Inverness. Stocking densities varied between 4 and 15 boar/ha. The accumulation of rooted area was recorded weekly over a 13‐week period. A cost analysis was performed to compare the use of wild boar with other ground preparation techniques. The median per capita rooting rate was 42.4 m²/week (interquartile range [IQR] 45.5), but rooting rate varied temporally. Median rooting rates varied between 21.6 and 75.3 m²/week (IQR 5.6) in periods that varied in suitability for rooting. Rooting rates were consistent across stocking densities. The cost of using wild boar as a ground preparation tool ranged between £184 and £1,961 per hectare depending on stocking density and rate of rooting. This experiment has direct application for managing the impact of wild boar within free range farming conditions, managed woodland regeneration schemes, rewilding projects, and in the wild.     

Identification of embryo paternity using polymorphic DNA markers to assess fertilizing capacity of spermatozoa after heterospermic insemination in boars

Differences in sperm fertilizing capacity of males often remain undetected by routine semen parameters. Heterospermic insemination with equal numbers of spermatozoa from 2 males is an accurate method for assessing differences in fertility. Use of heterospermic insemination depends on a reliable, efficient assay to identify paternity of conceptuses or offspring. In this study, polymorphic DNA markers amplified by PCR were tested to determine paternity of Day 5 to 6 embryos. The fertilizing capacity of 2 boars (A and B) with similar semen parameters was compared after homospermic (n=14 gilts) and heterospermic (n=11 gilts) insemination. Single AI's were performed under suboptimal conditions using 1 x 10(9) spermatozoa at 12 to 24 h before ovulation to prompt differences in fertilization and to stimulate sperm competition. The fertilization rate and the number of accessory spermatozoa were determined in Day 5 to 6 embryos. Using 5 different polymorphic DNA markers, paternity could be determined in 95.8% of the embryos. Boar B sired significantly (P<0.05) more offspring than Boar A after insemination with pooled semen, and this was reflected by a significantly (P<0.05) higher number of accessory spermatozoa following homospermic insemination with semen from Boar B, although fertilization rates did not differ between the 2 boars after homospermic insemination. The results suggest that the viability of spermatozoa in the female reproductive tract contributes to differences in fertility rates of males with similar in vitro sperm quality parameters. The number of accessory spermatozoa is a more sensitive measure of boar fertility than the fertilization rate. Polymorphic DNA markers are suitable for verification of parentage even at a very early stage of embryonic development.     

Sex allocation in a polygynous mammal with large litters: the wild boar

Predictions from Trivers & Willard's (1973, Science, 179, 90-92) hypothesis of sex-biased maternal investment in polygynous species do not apply well to species where mothers produce more than one offspring per reproductive attempt. First, as litter size increases, the benefits to the mother of adjusting sex ratio decrease because (1) she could benefit more by adjusting litter size and (2) sex differences in reproductive potential are negatively related to litter size. Second, testing sex-biased investment in these species requires predictions about the simultaneous adjustment of sex ratio and litter size. The wild boar, Sus scrofa, although polygynous, produces large litters. Here we present data for 58 litters from a free-ranging wild boar population in central Spain. Maternal expenditure per individual offspring, as measured by piglet weight, was higher for male than female fetuses. In more than 81% of cases the heaviest fetus in the litter was a male regardless of the quality of the mother; this might have influenced his ranking within the 'teat order' and consequently his development and survival. Mother quality (size and weight) appeared to be related to litter size but not to the sex ratio of the litter. However, it was highly related to a variable that combined the effects of litter size and sex ratio within the litter, thus supporting Williams' (1979, Proceedings of the Royal Society of London, Series B, 205, 567-580) hypothesis that mothers should adjust both litter size and offspring sex. Copyright 1999 The Association for the Study of Animal Behaviour.     

Approaches to interval mapping of QTL in a multigeneration pedigree: the example of porcine chromosome 4

Quantitative trait loci (QTLs) have been mapped in many studies of F2 populations derived from crosses between diverse lines. One approach to confirming these effects and improving the mapping resolution is genetic chromosome dissection through a backcrossing programme. Analysis by interval mapping of the data generated is likely to provide additional power and resolution compared with treating data marker by marker. However, interval mapping approaches for such a programme are not well developed, especially where the founder lines were outbred. We explore alternative approaches to analysis using, as an example, data from chromosome 4 in an intercross between wild boar and Large White pigs where QTLs have been previously identified. A least squares interval mapping procedure was used to study growth rate and carcass traits in a subsequent second backcross generation (BC2). This procedure requires the probability of inheriting a wild boar allele for each BC2 animal for locations throughout the chromosome. Two methods for obtaining these probabilities were compared: stochastic or deterministic. The two methods gave similar probabilities for inheriting wild boar alleles and, hence, gave very similar results from the QTL analysis. The deterministic approach has the advantage of being much faster to run but requires specialized software. A QTL for fatness and for growth were confirmed and, in addition, a QTL for piglet growth from weaning at 5 weeks up to 7 weeks of age and another for carcass length were detected.     

Predation of simulated red-legged partridge nests in big game estates from South Central Spain

Over the past few decades, the wild boar has been undergoing an expansion in Europe, which may have negatively affected small game populations and particularly red-legged partridges. We aim to evaluate the red-legged partridge nest predation by wild boar at high boar abundances by placing artificial nests in nine big game estates. Predation rates were compared between nests placed in fenced controlled plots with no wild boar access (but accessible to other predators) and open plots in which the wild boar gains access. The proportion of nests and eggs predated was significantly lower in wild boar exclusion areas, recording a predation rate of 50 % for the nests and 38 % for the eggs in these areas, whereas in the presence of wild boar, the predation rate was 80 % for the nests and 58 % for the eggs. Moreover, the wild boar was identified as the main nest predator in unfenced areas, accounting for 36 and 48 % of the predated nests and eggs respectively. This study sheds light on the wild boar predation on nests of the red-legged partridges.     

Age-related Toxoplasma gondii seroprevalence in Dutch wild boar inconsistent with lifelong persistence of antibodies

Toxoplasma gondii is an important zoonotic pathogen that is best known as a cause of abortion or abnormalities in the newborn after primary infection during pregnancy. Our aim was to determine the prevalence of T. gondii in wild boar to investigate the possible role of their meat in human infection and to get an indication of the environmental contamination with T. gondii. The presence of anti-T. gondii antibodies was determined by in-house ELISA in 509 wild boar shot in 2002/2003 and 464 wild boar shot in 2007. Most of the boar originated from the "Roerstreek" (n = 673) or the "Veluwe" (n = 241). A binormal mixture model was fitted to the log-transformed optical density values for wild boar up to 20 months old to estimate the optimal cut-off value (-0.685) and accompanying sensitivity (90.6%) and specificity (93.6%). The overall seroprevalence was estimated at 24.4% (95% CI: 21.1-27.7%). The prevalence did not show variation between sampling years or regions, indicating a stable and homogeneous infection pressure from the environment. The relation between age and seroprevalence was studied in two stages. Firstly, seroprevalence by age group was determined by fitting the binary mixture model to 200 animals per age category. The prevalence showed a steep increase until approximately 10 months of age but stabilized at approximately 35% thereafter. Secondly, we fitted the age-dependent seroprevalence data to several SIR-type models, with seropositives as infected (I) and seronegatives as either susceptible (S) or resistant (R). A model with a recovery rate (SIS) was superior to a model without a recovery rate (SI). This finding is not consistent with the traditional view of lifelong persistence of T. gondii infections. The high seroprevalence suggests that eating undercooked wild boar meat may pose a risk of infection with T. gondii.     

Osteochondrosis in Wild Boar–Swedish Yorkshire Crossbred Pigs (F2 Generation)

Osteochondrotic lesions occur in very high frequency in growing pigs of all commercial breeds and are claimed to be associated with high growth rate, and not to occur, or to be milder, in slow-growing pigs. The present study monitored the magnitude and distribution of osteochondrotic lesions in a crossbred pig population of wild boar and Swedish Yorkshire ancestry. In this population, having a low growth rate, the distribution and extent of osteochondrotic lesions was similar to that of purebred Swedish Yorkshire pigs, and only weak relationships between the studied growth parameters and osteochondrosis could be found.     

Disentangling Natural From Hunting Mortality in an Intensively Hunted Wild Boar Population

Abstract We assessed age-specific natural mortality (i.e., excluding hunting mortality) and hunting mortality of 1,175 male and 1,076 female wild boar (Sus scrofa) from Chǎteauvillain-Arc en Barrois (eastern France), using a 22-year dataset (1982–2004) and mark-recapture-recovery methods. Overall yearly mortality was >50% for all sex and age-classes. Low survival was mostly due to high hunting mortality; a wild boar had a >40% of chance of being harvested annually, and this risk was as high as 70% for adult males. Natural mortality rates of wild boar were similar for males and females (approx. 0.15). These rates were comparable to rates typical of male ungulates but high for female ungulates. Wild boar survival did not vary across sex and age-classes. Despite high hunting mortality, we did not detect evidence of compensatory mortality. Whereas natural mortality for males was constant over time, female mortality varied annually, independent of fluctuations in mast availability. Female wild boar survival patterns differed from those reported in other ungulates, with high and variable natural mortality. In other ungulates, natural mortality is typically low and stable across a wide range of environmental conditions. These differences may partly reflect high litter sizes for wild boar, which carries high energetic costs. High hunting mortality may induce a high investment of females in reproduction early in life, at the detriment to survival. Despite high hunting mortality, the study population increased. Effective population control of wild boar should target a high harvest rate of piglets and reproductive females.     

黑龙江凤凰山国家级自然保护区野猪冬季容纳量及最适种群密度

近年黑龙江省凤凰山国家级自然保护区野猪数量不断增长,人猪冲突加剧,保护区资源保护管理工作面临较大管理压力.为确定野猪种群的实际数量,同时评估该保护区的野猪的容纳量水平,以便为保护区管理局针对野猪的管理提供相关指导意见.2009-2010年冬季,在保护区采用样带调查、雪地足迹链跟踪和观察食痕的方法,并结合已有野猪生态研究确定野猪食性.野猪主要食物种类包括:木贼(Equisetum hiemale)、红松(Pinus koraiensis)果实松籽、胡桃楸(Juglans mandshurica)果实核桃、蒙古栎(Quecusmongolica)果实橡子、稠李(Padus racemosa)、榛子(Corylus heterophlla)、苔草(Carex spp.)、辽东葱木(Aralia elata).研究期间共布设长3-5km、单侧宽度50m、总长134 km的样带30条.调查中,每隔200 m布设10 m×10 m的大样方,并在每个大样方中央及四角布设1 m×1 m的小样方,共布设大样方350个,小样方1 750个.通过样方调查,统计野猪栖息生境当年可食植物枝条及其食物种类,然后计算其食物的总供给量,再结合食物营养成分,通过粗蛋白、粗纤维、粗脂肪的能量转换,按照每克粗蛋白和粗纤维的能量转换系数为16.74kJ、每克粗脂肪的能量转换系数为37.66 kJ,确定野外生境食物总能量供给.结合野猪冬季日营养需求,以能量为基础估算保护区野猪的营养容纳量.在种群密度调查过程中,通过足迹链判断个体方法为:单一清晰足迹链确定为一个体所留,30m内多条足迹穿越同一样带被认为是一个野猪群所留,调查中根据个体分开时的足迹链数确定野猪个体数,同时将粪便、卧迹、啃食痕迹作为个体判断的辅助信息.研究结果表明:凤凰山保护区内能够提供的总能量为7.375 ×107MJ,冬季平均每头野猪生存所需能量为(14 677.698±409.92) MJ,野猪营养容纳量为(1 006±28)头,种群密度为(3.79±0.11)头/km2.此外,调查中发现30余个野猪套及2头野猪被猎杀现场,反应出当地的人猪冲突较为严重.结合调查中发现的野猪套数量及野猪被猎杀概率,对野猪种群数量引入20％的死亡风险系数.最终确定凤凰山野猪种群的最适数量在(603±17)头左右,最适密度为(2.27±0.06)头/km2.通过样带法调查得出凤凰山自然保护区实际野猪种群数量为(596±155)头,密度(2.24±0.58)头/km2,已趋近营养容纳量.因此,野猪并未过量,不能采取狩猎等降低种群数量的措施,同时保护区也应对野猪种群进行持续监控,防止野猪种群过度繁殖以至成灾.     

Combined analyses of data from quantitative trait loci mapping studies. Chromosome 4 effects on porcine growth and fatness

For many species several similar QTL mapping populations have been produced and analyzed independently. Joint analysis of such data could be used to increase power to detect QTL and evaluate population differences. In this study, data were collated on almost 3000 pigs from seven different F(2) crosses between Western commercial breeds and either the European wild boar or the Chinese Meishan breed. Genotypes were available for 31 markers on chromosome 4 (on average 8.3 markers per population). Data from three traits common to all populations (birth weight, mean backfat depth at slaughter or end of test, and growth rate from birth to slaughter or end of test) were analyzed for individual populations and jointly. A QTL influencing birth weight was detected in one individual population and in the combined data, with no significant interaction of the QTL effect with population. A QTL affecting backfat that had a significantly greater effect in wild boar than in Meishan crosses was detected. Some evidence for a QTL affecting growth rate was detected in all populations, with no significant differences between populations. This study is the largest F(2) QTL analysis achieved in a livestock species and demonstrates the potential of joint analysis.     

Patterns of crop damage by wild boar (Sus scrofa)in Luxembourg over a 10-year period

In many European countries, the wild boar (Sus scrofa) is often associated with crop damage. In this study, we analyse data relating to 13,276 cases of wild boar damage to agricultural crops over a 10-year period in Luxembourg (an area of 2,586 km² in Western Europe). Results show that (1) damage is more severe in this area than in others; (2) damage to permanent grassland is far more frequent and more severe than damage to annual crops; (3) trichomatous crops such as barley are avoided; (4) damage is seasonally distributed according to type of crop; (5) damage is distributed spatially in a non-uniform manner; (6) damage intensity is significantly correlated with wild boar hunting bags, both over time and space. We suggest that wild boar management strategy should always take into account the issue of damage to agricultural crops. Our results imply that measures for preventing or reducing damage should be more targeted in time and space and that adjustments to cropping patterns should contribute towards a reduction of wild boar damage.     

The sexual function of wallowing in male wild boar (Sus scrofa)

The wild boar (Sus scrofa) is a medium-sized ungulate that produces a large variety of marks. Traditionally, wallowing is an activity that has fundamentally been related to several processes such as thermoregulation, reduction in the number of ectoparasites or disinfection of wounds in the skin of males resulting from fights to reach females. In this study, I analysed another possible function of wallowing in free-ranging wild boar populations when temperatures are low and parasitic numbers are not significant. The results indicate that during the sampling time, from October to February, the number of wild boars with a mud layer on their skin was 47, out of a total of 558 wild boar analysed. Of these 47 wild boars, 44 were males and within this group, 40 individuals were adult males. The wallowed males were bigger and older than non-wallowed males hunted at the same time. In addition, I found that males wallowed mainly during autumn (90.9% of all cases). In the total number of wild boars analysed, I did not notice individuals with wounds resulting from fights other than from the hunting day. On the other hand, the analysis of the females reproductive systems indicated that the rut period took place during the last days of October and the first days of November. From these results, the coincidence of the rut period with the maximum of wallowing in adult males could be indicative of a sexual function of this activity.     

Oral immunisation of wild boar against classical swine fever: uptake studies of new baits and investigations on the stability of lyophilised C-strain vaccine

The aim of this study was to investigate the uptake of new spherical and cuboid baits by wild boar and domestic pigs and to evaluate the stability of lyophilised C-strain vaccine stored at different environmental temperatures. New baits were designed to improve the consumption of the vaccine against classical swine fever by young wild boar. Our uptake studies showed that neither wild boar nor domestic pigs at the age of 2 months picked up the baits at all. Although the animals began to pick up the baits incompletely at the age of 3 months, a complete uptake of both the new baits and the older ones was only observed from the age of 4 (domestic pigs) and 4.5 (wild boar) months on. Nevertheless, the larger spherical baits with a diameter of 3 cm were taken up more effectively than the recent vaccine baits. As expected, lyophilised vaccine showed a higher stability than liquid vaccine, especially at temperatures ≥24°C. Independently of the stabiliser (GS4 or TSM) used, there are no differences between the virus titres detected within a storage period of 7 days. As the lyophilised C-strain vaccine was more stable at higher temperatures than the liquid vaccine formulation, we recommend to use lyophilised vaccine for oral immunisation of wild boar in the future, as oral vaccination is also carried out in the summertime.     

First evidence of long-distance dispersal of adult female wild boar (Sus scrofa) with piglets

Using GPS telemetry and ear tagging, we monitored wild boar sounder (a 2-year sow, a female yearling and eight piglets) captured in northern Slovenia. Five months after the capture, the sounder left its home range and first travelled 100 km west, to the three-border area between Slovenia, Austria and Italy, and from there toward southeast. The sow and three piglets were shot 2 months after start of dispersal 60 km from the capture site and in-between travelled at least 500 km. At least one piglet continued dispersal after the death of the sow, and the yearling split from the sounder during dispersal. This is the first documented case of long-distance dispersal of adult female wild boar with piglets. Several arguments suggest that long-distance dispersal of female wild boar is more common than previously reported in the literature. For wild boar and other species with predominant male dispersal, data on occasional far-dispersing females like presented here are important for understanding biology of species (e.g. metapopulations, rate of population expansion, local sex and age structure of population) and for management including control of diseases.     

6个中国猪地方品种和3个瑞典猪DNA分子系统发育相关关系

线粒体DNA遗传多样性用于评价6个中国地方猪种和3个瑞典家猪系统发育关系。采用PCR和序列分析方法得到了来自9个品种140头猪的线粒体中控制区440bp和细胞色素b基因798bp核苷酸序列。系统发育分析结果表明：6个中国地方猪种起源于亚洲野猪。中国地方猪种和欧洲野猪的线粒体DNA核苷酸序列变异发生在413000－875000年以前,而亚洲紧猪的变异仅发生在7000－156000上以前,由于2000年以前或18世纪初中国猪种导入欧洲家猪,因此瑞典家猪既属于欧洲类也属于亚洲类。