Rapid morphological change in an insular population of feral sheep

Artificially selected qualities can reduce fitness in a wild setting, thus feral domesticates should experience strong selective forces. Domestic sheep Ovis aries have frequently become feral on islands, which differ substantially from mainland environments. We examined changes in body mass and wool traits in feral sheep inhabiting Santa Cruz Island (SCI), California for ≥90 years. To elucidate the influence of nutrition, we compared the mass of feral island sheep with that of island sheep raised in farm conditions. We found that feral sheep on SCI were smaller than purported founder breeds, and that most documented populations of insular feral sheep worldwide have converged to similar body sizes (within 6 kg). SCI rams attained greater mass in farm conditions but ewes did not, suggesting phenotypic plasticity in ram body mass. Ewes exhibited self-shedding of wool at a greater frequency than rams, and sex differences and shedding patterns were consistent with thermoregulation and the risk of fly strike disease as benefits of wool loss. Pigmentation rates did not increase, further supporting the influence of heat stress on wool traits. These changes occurred in <25 generations and may have had a genetic basis, representing a potential example of rapid evolution in insular feral sheep.     

Prevalence and transmission of pseudorabies virus in an isolated population of feral swine

Six hundred sixty-one feral swine (Sus scrofa) from Ossabaw Island, Georgia (USA) were captured, bled, and their sera tested for pseudorabies virus (PRV) antibody during a 6 yr period. Prevalence of seroconversion in females was somewhat higher than in males (10% versus 7%), but the difference was not statistically significant. Adults had a significantly higher prevalence than juveniles (29% versus 1%). An important finding in this study was that seroconversion occurred primarily in the adult feral swine.     

Community ecology of helminth parasitism in an insular passerine avifauna.

Three hundred and thirty specimens of 7 species of passerine birds from South Bass Island, Ottawa County, Ohio, were examined for helminth parasites. The total number of helminth specimens collected was 4,333. Forty-one helminth taxa were identified. Ten species of helminths were identified as having foci of infection on the island. An index of association for these 10 species is presented. The low association revealed between helminth species utilizing common species of intermediate hosts indicated that a single intermediate host specimen is likely to harbor infective stages of only one species of parasitic helminth. An index of similarity is presented to express the species importance relationships of the helminth faunas of the 7 species of birds: red-winged blackbirds (Agelaius phoeniceus), blue jays (Cyanocitta cristata), brown-headed cowbirds (Molothrus ater), common grackles (Quiscalus quiscula), house sparrows (Passer domesticus), starlings (Sturnus vulgaris), and robins (Turdus migratorius). The results reveal that competition between these avian species for invertebrate food resources helps to maximize the transmission of those helminth populations which utilize these same invertebrates as intermediate hosts. The aggregation of birds into mixed feeding flocks insures a heavy loading of the feeding grounds with agents infective for the invertebrate populations.     

Visceral helminth communities of sympatric mule and white-tailed deer from the Davis Mountains of Texas

Hybridizing populations of mule (Odocoileus hemionus) and white-tailed deer (O. virginianus) from the Davis Mountains of Texas were examined to determine similarities in species composition of their helminth communities and if abundances of helminth species in those communities varied across host species and seasonal factors. Only three cestode and three nematode species were recovered. There were very low abundances of species and little diversity in the helminth communities of both hosts. Common helminth species were shared by both deer, and the significant variance in abundances of three of the four most common helminth species appeared to result from differences in habitat preferences of the respective hosts. Our results indicated that analyses of helminth communities of deer from this geographical area do not provide a useful quantification technique for determining deer condition, degree of hybridization, or levels of intraspecific competition.     

Brucellosis in feral swine

Some 255 feral hogs were serologically tested for Brucella titers at a location in the lower coastal plain of South Carolina. Eighteen percent were reactors. The organism was cultured from lymph node tissues in one 3+ years old boar and identified as Brucella suis biotype 1. Prevalence of sero-positive animals increased with age. There were no important differences between sexes.     

Visceral field of the rat insular cortex

Structural-functional organisation of the cortical insular area relating to processes of the visceral functions control, was analysed. Representation of gastrointestinal, respiratory, and cardiovascular systems in the area, is given. Sites of respective neuronal groups and specifics of their spatial organisation within the area, were found. The data obtained suggest a scheme of the rat insular cortex's visceral field.     

Health status of a recently discovered population of feral swine in Kansas.

Twenty feral hogs (Sus scrofa) from a newly discovered population on Fort Riley Army Base (Kansas, USA) were shot and examined from November 1993 through February 1994 to assess the health of the population. The hogs were generally healthy, although serologic evidence indicated that some individuals had been exposed to parvovirus, enterovirus, and swine influenza. We found no indications of brucellosis, pseudorabies, or porcine respiratory and reproductive syndrome. Lung worms (Metastrongylus spp.), round worms (Ascaris suum), and whipworms (Trichuris suis) were found in nine, four and two of the hogs, respectively. Seven hogs had infestations of lice (Haematopinus suis). Fence-line contacts were documented between four wild boars and domestic sows, and in three cases wild boars entered pens containing domestic sows. We recommend that hogs be examined periodically from this and other wild populations to monitor health status since new animals may enter populations through deliberate translocation, escape from shooting preserves or domestic swine producers, or dispersal from other feral populations.     

Detection of Clostridium difficile and Salmonella in feral swine population in North Carolina

We sampled 161 feral pigs in eastern North Carolina, USA, to determine the prevalence and antimicrobial resistance profile of Clostridium difficile and Salmonella. Seven (4.4%) and eight (5.0%) pigs tested positive for C. difficile and Salmonella, respectively, highlighting the importance of determining the epidemiology of these pathogens in feral pigs.     

The structure of helminth communities

The existence of both interactive and isolationist communities of helminths, each of which may be produced by any one of several processes, necessitates a pluralistic view of helminth community structure. A scheme involving three hierarchical scales of communities of helminths is proposed. Interactions between species occur in infracommunities, and should be looked for there. Interactions are often clearer in smaller groups of species, either among core species or within guilds. Infracommunities are samples of helminth communities at two larger scales: the helminth community in the host population provides core species, largely specialists, and that in the host community provides the generalists and the satellite species. The richness of each of the two large-scale communities is affected by various ecological, historical and evolutionary factors. The different concepts which have been applied to parasite communities are based on these factors.     

Genetic rescue of an insular population of large mammals

Natural populations worldwide are increasingly fragmented by habitat loss. Isolation at small population size is thought to reduce individual and population fitness via inbreeding depression. However, little is known about the time-scale over which adverse genetic effects may develop in natural populations or the number and types of traits likely to be affected. The benefits of restoring gene flow to isolates are therefore also largely unknown. In contrast, the potential costs of migration (e.g. disease spread) are readily apparent. Management for ecological connectivity has therefore been controversial and sometimes avoided. Using pedigree and life-history data collected during 25 years of study, we evaluated genetic decline and rescue in a population of bighorn sheep founded by 12 individuals in 1922 and isolated at an average size of 42 animals for 10-12 generations. Immigration was restored experimentally, beginning in 1985. We detected marked improvements in reproduction, survival and five fitness-related traits among descendants of the 15 recent migrants. Trait values were increased by 23-257% in maximally outbred individuals. This is the first demonstration, to our knowledge, of increased male and female fitness attributable to outbreeding realized in a fully competitive natural setting. Our findings suggest that genetic principles deserve broader recognition as practical management tools with near-term consequences for large-mammal conservation.     

Food preferences of an insular population of Rattus rattus

The food preferences of an insular population of Rattus rattus inhabiting colonies of the Short-tailed shearwater Puffinus tenuirostris are described from results obtained during analyses of stomach contents and droppings collected from Big Green Island, Furneaux Group, Tasmania. It was found that rats on the island maintained themselves by eating a predominantly vegetarian diet and results suggest that there was some selective feeding on monocotyledons rather than the dicotyledons present in the area. Green parts of plants were taken throughout the year and rats may select these as a water source during the summer months. Plants made up 77.2% of the 254 stomach contents analysed and of this 57.7% was green material. Insect remains were found in 24.8% of the 1400 droppings examined and made up 14.3% of the stomach contents. Few feathers of the shearwater Puffinus tenuirostris were found in the stomachs or droppings and preliminary behavioural experiments suggested that the rat does not actively predate the bird though it may remove unattended eggs and eat dead chicks.     

Increased prevalence of Brucella suis and pseudorabies virus antibodies in adults of an isolated feral swine population in coastal South Carolina

Two hundred twenty seven adult (> 8 mo) feral swine (Sus scrofa) trapped from April through July 1999 at three locations on a coastal South Carolina (USA) peninsula with restricted ingress and egress were tested for Brucella suis and pseudorabies virus (PRV) antibodies. Approximately 44% of the animals tested positive for B. suis antibodies and 61% tested positive for antibodies to PRV. Previous surveys (1976 and 1992) of feral swine at the same location with similar methods indicated lower seroprevalences (28% and 18% for B. suis and 0% and 19% for PRV). We also found 39% of feral swine seropositive (n = 179) for Trichinella spiralis and 49% seropositive (n = 181) for Toxoplasma gondii. Results of repeated sampling demonstrated that seroprevalence to pathogens can increase with time in an isolated, unhunted population of feral swine suggesting an increased risk to local domestic livestock and potentially to human health.     

Persistence of pseudorabies virus in feral swine populations

Serologic surveys for evidence of exposure to pseudorabies virus (PRV) in feral swine were conducted from November 2001 to April 2002 at 10 sites in the southeastern United States, where evidence of previous PRV exposure had been documented during 1979-89. Sera were tested in the field on the day of collection by latex agglutination. Maximum sample size per site was to be 30 animals, but sampling was discontinued before reaching this number when positive results were obtained. Positive results were obtained at all of the study sites, demonstrating long-term persistence of PRV in feral swine populations. Overall, 38 of 100 (38%) animals were positive for antibodies. Consistent results from latex agglutination tests conducted in the field and laboratory demonstrated that this test was useful as a rapid and reliable diagnostic tool when used in the field.     

Influenza exposure in United States feral swine populations

Swine play an important role in the disease ecology of influenza. Having cellular receptors in common with birds and humans, swine provide opportunities for mixed infections and potential for genetic reassortment between avian, human, and porcine influenza. Feral swine populations are rapidly expanding in both numbers and range and are increasingly coming into contact with waterfowl, humans, and agricultural operations. In this study, over 875 feral swine were sampled from six states across the United States for serologic evidence of exposure to influenza. In Oklahoma, Florida, and Missouri, USA, no seropositive feral swine were detected. Seropositive swine were detected in California, Mississippi, and Texas, USA. Antibody prevalences in these states were 1% in Mississippi, 5% in California, and 14.4% in Texas. All seropositive swine were exposed to H3N2 subtype, the predominant subtype currently circulating in domestic swine. The only exceptions were in San Saba County, Texas, where of the 15 seropositive samples, four were positive for H1N1 and seven for both H1N1 and H3N2. In Texas, there was large geographical and temporal variation in antibody prevalence and no obvious connection to domestic swine operations. No evidence of exposure to avian influenza in feral swine was uncovered. From these results it is apparent that influenza in feral swine poses a risk primarily to swine production operations. However, because feral swine share habitat with waterfowl, prey on and scavenge dead and dying birds, are highly mobile, and are increasingly coming into contact with humans, the potential for these animals to become infected with avian or human influenza in addition to swine influenza is a distinct possibility.     

Ixodid ticks associated with feral swine in Texas

Ixodid ticks were collected from feral swine in eight Texas ecoregions from 2008–2011. Sixty‐two percent of 806 feral swine were infested with one or more of the following species: Amblyomma americanum, A. cajennense, A. maculatum, Dermacentor albipictus, D. halli, D. variabilis, and Ixodes scapularis. Juvenile and adult feral swine of both sexes were found to serve as host to ixodid ticks. Longitudinal surveys of feral swine at four geographic locations show persistent year‐round tick infestations of all gender‐age classes for tick species common to their respective geographic locations and ecoregions. Amblyomma americanum, A. cajennense, A. maculatum and D. variabilis were collected from 66% of feral swine harvested through an abatement program in seven ecoregions from March to October in 2009. These results indicate westward geographic expansion of D. variabilis. Summary results show feral swine are competent hosts for ixodid species responsible for the transmission of pathogens and diminished well‐being in livestock, wildlife, and humans.     

Temporal stability of insular avian malarial parasite communities

Avian malaria is caused by a diverse community of genetically differentiated parasites of the genera Plasmodium and Haemoproteus. Rapid seasonal and annual antigenic allele turnover resulting from selection by host immune systems, as observed in some parasite populations infecting humans, may extend analogously to dynamic species compositions within communities of avian malarial parasites. To address this issue, we examined the stability of avian malarial parasite lineages across multiple time-scales within two insular host communities. Parasite communities in Puerto Rico and St Lucia included 20 and 14 genetically distinct parasite lineages, respectively. Lineage composition of the parasite community in Puerto Rico did not vary seasonally or over a 1 year interval. However, over intervals approaching a decade, the avian communities of both islands experienced an apparent loss or gain of one malarial parasite lineage, indicating the potential for relatively frequent lineage turnover. Patterns of temporal variation of parasite lineages in this study suggest periodic colonization and extinction events driven by a combination of host-specific immune responses, competition between lineages and drift. However, the occasional and ecologically dynamic lineage turnover exhibited by insular avian parasite communities is not as rapid as antigenic allele turnover within populations of human malaria.     

Venereal transmission of pseudorabies viruses indigenous to feral swine

Between 1995 and 1998, we designed a series of studies in which we attempted to determine the main routes of transmission involved in the natural infection of pseudorabies virus (PRV) indigenous to free-ranging feral swine (Sus scrofa). Naturally infected feral sows transmitted the infection to uninfected feral boars, with which they had been commingled for a 6-wk period. Pseudorabies virus was isolated from boar preputial swabs, but not from nasal swabs. Three of the same PRV-infected feral sows did not transmit the infection to domestic boars during a 16 wk commingling period, despite the fact that they became pregnant. Feral boars, naturally infected with PRV transmitted the virus to domestic gilts while penned together during 6 wk. Pseudorabies virus was isolated from vaginal swabs, but not from nasal swabs of gilts, after 2 and 3 wk of commingling. When the same infected boars were commingled with either feral or domestic boars for 13 wk, PRV transmission did not occur. None of the exposed boars developed neutralizing antibodies or yielded virus from their preputial or nasal swabs. Our results indicate that PRV indigenous to feral swine is preferentially transmitted to feral or domestic swine of the opposite sex by the venereal route. This mode of transmission differs from that seen in the natural transmission of PRV prevalent in domestic swine, where contaminated secretions, excretions and aerosols are responsible for the spread of the virus. Based on these results, we feel that as long as feral swine do not come into direct contact with domestic swine, PRV-infected feral swine probably pose only a limited risk to the success of the National Pseudorabies Eradication Program. The fact that PRV is usually transmitted from feral to domestic swine at the time of mating would indicate that the isolation of domestic herds by the use of a "double fence," should be adequate protection against reinfection with PRV.     

Spatial and seasonal variation in abundance within an insular grey parrot population

Populations of Psittacidae are endangered by habitat loss and the international pet market. The grey parrot (Psittacus erithacus) is among the most traded species, yet little is known about densities and their variability in time and space. The population of grey parrots on the island of Príncipe (Gulf of Guinea) was estimated with distance sampling, in both pre‐ and postbreeding seasons. Abundance was related to a range of habitat features using generalized additive models. Densities averaged 48 ± 3 (SE) individuals km^?2 in the prebreeding and 59 ± 4 in the postbreeding season, both extremely high compared to elsewhere in Africa and to other parrot species. Despite a population of 6000–8000 individuals over only 139 km², parrots were patchily distributed, being unrecorded in ~25% of surveyed areas. Abundance varied seasonally, with densities being significantly higher in secondary compared to primary forest in the post‐ but not in the prebreeding season. Abundance was most tied to the presence of nest‐tree species prior to breeding and to feeding‐tree species and lightly sloping ground after breeding. These results highlight the need to preserve a matrix of habitat types to provide resources for parrots across seasons and ensure that surveys recognize seasonality in habitat use as a potential bias.