Effects of human perturbation on the genetic make-up of an island population: the case of the Sardinian wild boar

Game species are often manipulated by human beings, whose activities can deeply affect their genetic make-up and population structure. We focused on a geographically isolated wild boar population (Sardinia, Italy), which is classified, together with the Corsican population, as a separate subspecies (Sus scrofa meridionalis). Two hundred and ten wild boars collected across Sardinia were analysed with a set of 10 microsatellites and compared with 296 reference genotypes from continental wild populations and to a sample of domestic pigs. The Sardinian population showed remarkable diversity and a high proportion of private alleles, and strongly deviated from the equilibrium. A Bayesian cluster analysis of only the Sardinian sample revealed a partition into five subpopulations. However, two different Bayesian approaches to the assignment of individuals, accounting for different possible source populations, produced consistent results and proved the admixed nature of the Sardinian population. Indeed, introgressive hybridization with boars from multiple sources (Italian peninsula, central Europe, domestic stocks) was detected, although poor evidence of crossbreeding with free-ranging domestic pigs was unexpectedly found. After excluding individuals who carried exotic genes, the population re-entered Hardy-Weinberg proportions and a clear population structure with three subpopulations emerged. Therefore, the inclusion of introgressed animals in the Bayesian analysis implied an overestimation of the number of clusters. Nonetheless, two of them were consistent between analyses and corresponded to highly pure stocks, located, respectively, in north-west and south-west Sardinia. This work shows the critical importance of including adequate reference samples when studying the genetic structure of managed wild populations.     

Sow responsiveness to human contacts and piglet vocalization during 24 h after onset of parturition

Sow responsiveness towards external disturbances and concurrent postural changes are proposed to be an important cause of early piglet crushing. The aim of the present study was to assess whether loose housed sows change their responsiveness over time within the first 24 h after birth of the first piglet upon exposure to different types of human contact and towards piglets’ scream. The responsiveness of the sows (n = 17) was scored during: (i) blood sampling of the sow during 24 h after the onset of parturition, (ii) human handling of a piglet at 0, 30 min, 1, 2, 4, 8 and 24 h after birth, (iii) screaming when a piglet was trapped underneath the sow and (iv) exposure to playback of piglets’ screams at 10 and 24 h after the onset of parturition. A sow was scored as responsive if she changed her posture in response to the stimuli. The behavioral scores were analyzed during three predefined periods: parturition (from birth of first piglet to birth of last piglet), phase 1 (from birth of last piglet to 12 h after birth of first piglet) and phase 2 (from 12 h after birth of first piglet to 24 h after birth of first piglet). The responsiveness of sows towards humans during blood sampling differed between the three periods (p < 0.01), whereas it did not differ between periods during human handling of piglets. During blood sampling, fewer sows were responsive during phase 1 (5%) compared to during parturition (11%) and the later phase 2 (17%). We did not detect any temporal changes in sow responsiveness towards natural incidences of screaming of own trapped piglet between the three periods (it remained high: 80%), whereas sows exposed to playback of piglet screams had a higher probability (p < 0.05) to react at 12 h (50%) than at 24 h (25%). In conclusion, the responsiveness of sows toward direct human contact was lower during the first 12 h postpartum. The careful handling of piglets in the home pen had a minimal effect on the probability of postural changes in sows. However, sows were highly reactive towards the screaming of own trapped piglet during the whole 24 h period pp. The relative lower responsiveness towards playbacks, decreasing from 12 to 24 h pp, cast doubt upon the piglet scream playback test as a useful approach to evaluate maternal responsiveness in sows.     

Monitoring chicken flock behaviour provides early warning of infection by human pathogen Campylobacter

Campylobacter is the commonest bacterial cause of gastrointestinal infection in humans, and chicken meat is the major source of infection throughout the world. Strict and expensive on-farm biosecurity measures have been largely unsuccessful in controlling infection and are hampered by the time needed to analyse faecal samples, with the result that Campylobacter status is often known only after a flock has been processed. Our data demonstrate an alternative approach that monitors the behaviour of live chickens with cameras and analyses the ‘optical flow’ patterns made by flock movements. Campylobacter-free chicken flocks have higher mean and lower kurtosis of optical flow than those testing positive for Campylobacter by microbiological methods. We show that by monitoring behaviour in this way, flocks likely to become positive can be identified within the first 7–10 days of life, much earlier than conventional on-farm microbiological methods. This early warning has the potential to lead to a more targeted approach to Campylobacter control and also provides new insights into possible sources of infection that could transform the control of this globally important food-borne pathogen.     

The effect of environmental factors on the nesting and courtship behaviour ofTilapia zillii in Lake Kinneret (Israel)

Tilapia zillii is a polyphilic, guarding nest spawner which is widespread in west and north Africa and in the Middle East. A study of the nesting and courtship behaviour of this species in Lake Kinneret (Sea of Galilee), revealed that nesting and brood care differ according to the exposure of the nesting site to wave action and the nature of the substrate. The nests are simple and parental care is abbreviated in exposed, sandy sites whereas elaborate nests with brood chambers are excavated in sheltered areas with clayey substrates, and parental care is extensive. The implications of these findings to studies on cichlid breeding and the conservation ofT. zillii in Lake Kinneret are discussed.     

The effect of sterilizing diseases on host abundance and distribution along environmental gradients

This study analyses the effect of host-specific pathogens on range restriction of their hosts across environmental gradients at population margins. Sterilizing diseases can limit host range by causing large reductions in population size in what would otherwise be the central area of a species range. Diseases showing frequency-dependent transmission can also pull back a population from its disease-free margin. A wide range of disease prevalence versus abundance patterns emerge which often differ from the classical expectation of increasing prevalence with increasing abundance. Surprisingly, very few empirical studies have investigated the dynamics of disease across environmental gradients or at range limits.     

The effect of environmental heterogeneity on clonal behaviour of Prunella vulgaris L.

Melinis minutiflora Beauv. (Poaceae) is an African grass that is invading mid-elevation Trachypogon savannas in Venezuela. The objective of this study was to investigate the influence of soil fertility, competition and soil disturbance in facilitating Melinis' invasion and growth in these savanna sites. We manipulated soil fertility by adding nitrogen (+N), phosphorus and potassium (+PK), or nitrogen, phosphorus, and potassium (+NPK). We simultaneously manipulated the competitive environment by clipping background vegetation. In a separate experiment, we mechanically disrupted the soil to simulate disturbance. We hypothesized that germination and growth were bottlenecks to early establishment in undisturbed savanna, but that disturbance would alleviate those bottlenecks. We measured Melinis seed germination and subsequent establishment by adding seeds to all plots. We examined Melinis growth by measuring biomass of Melinis seedling transplants, 11 months after they were placed into treatment plots. Germination and establishment of Melinis from seed was extremely low. Of the 80,000 seeds applied in the experiment, only 28 plants survived the first growing season. Mortality of Melinis seedling transplants was lowest in PK fertilized plots, but in the absence of PK mortality increased with N additions and clipping. By contrast, fertilization of the savanna with NPK greatly increased Melinis seedling biomass and this effect was greatly enhanced when competition was reduced (e.g. clipping). Melinis transplant growth responded strongly to soil disturbance- a response not fully explained by removal of competitors (clipping) or changes in soil nutrients and moisture. We suspect that disruption of the soil structure allowed for greater root proliferation and subsequent plant growth. We believe that native savanna is relatively resistant to Melinis invasion, since Melinis seedlings persisted in intact savanna but exhibited little or no growth during the first year. The significant enhancement of Melinis seedling growth with clipping and nutrient additions suggests that low soil nutrients and the presence of native savanna species are important factors in the ability of native savanna to resist Melinis establishment. However, the potential for Melinis growth increases enormously with soil disturbance.     

The role of food plant and pathogen-induced behaviour in the persistence of a nucleopolyhedrovirus

Insect baculoviruses can survive between epidemics as infectious particles external to the host. Many pathogens persist in reservoirs, i.e., microhabitats where survival is enhanced, for example due to protection from the degrading effects of UV irradiation. However, the probability of infecting new susceptible hosts is usually reduced. Persistence of pathogens and their movement in and out of reservoirs is an important, albeit little understood, aspect of insect pathogen ecology. This study investigated interactions between the behaviour of infected insect hosts, virus distribution and plant species on the persistence of the winter moth (Operophtera brumata) nucleopolyhedrovirus. Habitat influenced the persistence of infectious baculovirus in the field: virus on Sitka spruce (Picea sitchensis) and oak (Quercus robur) in forested areas retained more infectivity than virus on heather (Calluna vulgaris) in an unshaded habitat. Plant species per se did not directly affect the persistence of virus on the foliage of potted seedlings. Virally infected insects had altered behaviour and moved down plants relative to control insects, whereas in other systems larvae show height-seeking behaviour. Consequently, the majority of virus particles were distributed on plant stems. In two experiments (one using winter moth NPV and one Mamestra brassicae NPV) virus persisted better on plant stems relative to foliage. Neonate larvae were shown to be able to acquire infections from tree stems contaminated with a low level of virus. These data suggest that plant stems may be important reservoirs for between-year persistence of this pathogen. The observed virus-induced changes in host behaviour in winter moth could enhance the viral persistence by increasing the deposition of occlusion bodies in these reservoirs.     

Three-dimensional computer simulations of feeding behaviour in red and giant pandas relate skull biomechanics with dietary niche partitioning

The red (Ailurus fulgens) and giant (Ailuropoda melanoleuca) pandas are mammalian carnivores convergently adapted to a bamboo feeding diet. However, whereas Ailurus forages almost entirely on younger leaves, fruits and tender trunks, Ailuropoda relies more on trunks and stems. Such difference in foraging mode is considered a strategy for resource partitioning where they are sympatric. Here, we use finite-element analysis to test for mechanical differences and similarities in skull performance between Ailurus and Ailuropoda related to diet. Feeding simulations suggest that the two panda species have similar ranges of mechanical efficiency and strain energy profiles across the dentition, reflecting their durophagous diet. However, the stress distributions and peaks in the skulls of Ailurus and Ailuropoda are remarkably different for biting at all tooth locations. Although the skull of Ailuropoda is capable of resisting higher stresses than the skull of Ailurus, the latter is able to distribute stresses more evenly throughout the skull. These differences in skull biomechanics reflect their distinct bamboo feeding preferences. Ailurus uses repetitive chewing in an extended mastication to feed on soft leaves, and Ailuropoda exhibits shorter and more discrete periods of chomp-and-swallow feeding to break down hard bamboo trunks.     

Resource influence on the form of fur rubbing behaviour in white-faced capuchins

Self-medicative behaviours have been largely documented in vertebrates and, in particular, the use of plants for pharmacological purposes has been mainly reported in primates. White-faced capuchins are known to rub specifically chosen plants and other substances on their fur. To better understand the mechanisms underlying this phenomenon and investigate the influence of different plant resources on the form of fur rubbing activity, we conducted experiments using different randomly selected plant items: oranges and onions. We found that (1) capuchins showed different degrees of interest in the materials used to fur rub; (2) the mean group dynamics differ drastically according to the resource supplied; and (3) individuals present strong differences in their social behaviour, i.e. they spent more or less time fur rubbing in spatial proximity of conspecifics according to the material used for fur rubbing. We propose hypotheses on possible proximal causes for these differences and highlight that some precautions have to be taken in behavioural studies including only one resource type.