Preferred Feeding Sites Research Articles

Locais e período de alimentação da cigarrinha vetora de Xylella fastidiosa, Bucephalogonia xanthophis (Berg) (Hemiptera: Cicadellidae), em mudas cítricas

A cigarrinha Bucephalogonia xanthophis (Berg) (Hemiptera: Cicadellidae) é um importante vetor da bactéria Xylella fastidiosa, agente causal da clorose variegada dos citros. Este trabalho teve como objetivo identificar o local preferido de alimentação e o período de maior atividade alimentar desta cigarrinha em citros, no sentido de elucidar o comportamento alimentar relacionado à transmissão da bactéria. O local de alimentação foi estudado em ensaio de escolha, no qual 30 insetos adultos foram liberados em gaiolas de observação (n = 10) contendo uma muda de laranja-doce [Citrus sinensis (L.) Osbeck]. Após 1; 15; 21; 25; 39; 45 e 49 h da liberação, contaram-se os insetos na parte superior (ramos com brotações) e inferior (haste principal, até H"40 cm de altura) da muda. Nos ramos da parte superior, avaliou-se a preferência entre a haste, o pecíolo e o limbo foliar. Em um segundo ensaio, 20 machos e 20 fêmeas de B. xanthophis foram confinados individualmente sobre a haste de 'seedlings' de laranja-doce para determinar os períodos de alimentação, quantificando-se a excreção de 'honeydew' (medida indireta da ingestão) em períodos sucessivos de dia e noite, durante 48 h. A maioria dos indivíduos de B. xanthophis preferiu a haste dos ramos novos (62%), na parte superior da muda cítrica (91%). Nos 'seedlings', observou-se maior volume de excreção e proporção de indivíduos excretando durante a fotofase, independentemente do sexo. Portanto, em estudos de transmissão de X. fastidiosa, deve-se considerar a preferência de B. xanthophis pela haste de brotações cítricas e sua maior atividade alimentar durante a fotofase.

Preferred Feeding Sites and Prey of the Adult Gold-spotted Pond Frog, Rana plancyi chosenica

To determine the feeding sites preferred by adult gold-spotted pond frogs, Rana plancyi chosenica, and the foods that induce favorable growth of the frogs in the laboratory, we conducted two separate experiments between 27 May and 12 July 2007 in a vivarium. In the first experiment, we counted the number of crickets eaten by four gold-spotted pond frogs in a 60 min period at four different feeding sites within the experimental arenas: on the water surface, at the edge of a pond, and at two terrestrial sites. Adult gold-spotted pond frogs ate more crickets on the water surface and at the edge of the pond than the terrestrial sites. In the second experiment, we measured the growth of SVL (snout-vent length) and body mass of adult gold-spotted pond frogs fed crickets, mealworms, maggots, or earthworms in individual experimental boxes over a one month period. The SVL and body mass of the adult gold-spotted pond frogs fed crickets, mealworms, or maggots were greater than those of the frogs that were fed earthworms. These results indicate that providing crickets, mealworms, or maggots on the water or at the edge of a pond should induce favorable growth of captive-reared adult gold-spotted pond frogs.

Tomato fruit size, maturity and α-tomatine content influence the performance of larvae of potato tuber moth Phthorimaea operculella (Lepidoptera: Gelechiidae)

Various physical and chemical properties of host plants influence insect larval performance and subsequent adult fitness. Tomato plants are relatively new hosts to the potato tuber moth, Phthorimaea operculella (Zeller), with the fruit being its preferred feeding site. However, it is unclear how the biochemical and physical properties of tomato fruits relate to potato tuber moth performance. Significant amounts of alpha-tomatine were detected in maturing green and ripening fruits of cherry (cv. Ceres) and processing (cv. Serio) types of tomatoes whereas none was detected in a fresh market variety (cv. Marglobe), at comparable stages. alpha-Tomatine is negatively and significantly correlated with development rate (head capsule size) of larvae reared in the fruits of the cherry and processing type tomatoes. Generally, survival, growth and development were significantly superior for larvae reared in the ripening fruits of the fresh market cultivar. At this stage, the fruits of this cultivar are also the largest. Based on these results it is concluded that fruit alpha-tomatine content, as well as fruit size and maturity, all affect performance of P. operculella larvae in the fruits of cultivated tomatoes.

Early-Season Host Plant Fruit Impacts on Reproductive Parameters of the Oriental Fruit Moth (Lepidoptera: Tortricidae)

Oriental fruit moth, Grapholita molesta (Busck) (Lepidoptera: Tortricidae), a cosmopolitan pest of tree fruits, has been a significant pest in the United States since its introduction in the early 20th Century. Grapholita molesta historically has been a major pest of stone fruit. However, since the mid to late 1990s, outbreaks in commercial apple orchards in the eastern United States have become common place. This study examined the effects of larval host (e.g., apple vs. peach) on G. molesta reproduction, as a means to better understand the increased importance of G. molesta as an apple pest in the midAtlantic region. In laboratory investigations, G. molesta adults reared on apple fruit had approximately 2-fold higher fecundity than those reared on peach (F = 10.98; df = 3,101; P < 0.001). In two separate studies, when larvae were reared under either crowded or noncrowded feeding conditions, female adult longevity and oviposition period were significantly greater among moths reared as larvae on apple than those reared on peach (2001: P = 0.019 and 0.009, respectively; 2002: P = 0.031 and 0.001, respectively). Female pupal weight was significantly higher in individuals reared on apple than those reared on peach, in both studies (2001 and 2002: P < 0.001). Similar host-influenced impacts on G. molesta reproductive phenomena could affect population dynamics of G. molesta, especially late in the season when apple fruit are a preferred feeding site.

Stage‐dependent feeding behavior by western tarnished plant bugs influences flower bud abscission in cotton

AbstractUnexplained variability in the relationship between the number of herbivores in a field and the amount of crop damage can arise if there is a large amount of variation among herbivore individuals in the amount of feeding damage each generates. In California, populations of the western tarnished plant bug, Lygus hesperus Knight (Heteroptera: Miridae), produce highly variable levels of damage to cotton plants (Gossypium hirsutum L.) (Malvaceae), even when found at low densities. Because L. hesperus populations are also highly variable in their overall stage structure, we hypothesize that differences in crop damage might result from varying impact by each L. hesperus stage on cotton flower buds (termed squares). Laboratory measurements of L. hesperus mouth‐parts and distance to anther sacs, a preferred feeding site, revealed that 1st−3rd instar L. hesperus nymphs will not be able to feed on anther sacs of larger squares (over 8 mm in length) but will be able to feed on squares that are most sensitive to L. hesperus damage (<7 mm). Because even the 1st instars can feed on the most sensitive ‘pinhead’ squares, size constraints do not rule out damaging effects from the youngest L. hesperus. Laboratory observations revealed that later developmental stages, and adults, spend more time feeding on cotton squares relative to 2nd and 3rd instars. In addition, a field experiment revealed no effect of 2nd instars on square retention (relative to control cages) but did reveal a significant decrease in square retention generated by adult L. hesperus (4th instar L. hesperus resulted in an intermediate level of square retention). In a final study we sampled L. hesperus stage structure and density across 38 cotton fields. Multiple regression revealed that the densities of 1st−3rd instars of L. hesperus are not correlated with anther sac damage or square retention. However, in 2 years 4th and 5th instars were positively correlated with anther sac damage and negatively correlated with square retention. In the a third year, adult L. hesperus showed correlations in the same direction, across fields and across sites within fields. Overall, these results suggest that the adults and the largest nymphs of L. hesperus (4th and 5th instars) are particularly damaging to cotton squares, with the 1st−3rd instars of L. hesperus causing little damage to plants.

Ant navigation en route to the goal: signature routes facilitate way-finding of Gigantiops destructor

We investigated in laboratory conditions how foragers of the tropical ant Gigantiops destructor develop individually distinctive landmark routes. Way-finding along a familiar route involved the recognition of at least two locations, nest and feeding site, and the representation of spatial relations between these places. Familiar visual landmarks were important both at the beginning and at the end of the foraging journey. A motor routine guided the ants at the start of their foraging path towards the first landmarks, which they learnt to pass consistently on the same side, before taking the next direction. At the last stage of the route, landmark recognition allowed them to pinpoint their preferred feeding site without using distant cues or odometric information. By contrast, ants en route to the goal were not systematically guided by a stereotyped sequence of snapshots recalled at each corresponding stage of the route. Each ant slalomed in an idiosyncratic distinctive way around different midway landmarks from a foraging excursion to the next, which induced a variability of the path shapes in their intermediate parts. By reducing the number of landmark recognition-triggered responses, this economical visuomotor strategy may be helpful in the Amazonian forest where many prominent landmarks are alike.

Effect of gastrointestinal motility and feeding tube site on aspiration risk in critically ill patients: a review

Objective The purpose of this literature review is to examine the effect of the interaction between gastrointestinal motility and feeding site on the aspiration risk in critically ill, tube-fed patients. Methods and results A single answer to the question of the preferred feeding site is not likely to be found because the degree of aspiration risk varies significantly according to individual variations in gastrointestinal motility and multiple pre-existing and treatment-related risk factors. However, regardless of the feeding site, it is ultimately regurgitated gastric contents that are aspirated into the lungs. For this reason, the clinical assessment of greatest interest is the evaluation of gastric emptying, usually monitored clinically by measuring gastric residual volumes. Conclusion Current recommendations for monitoring residual volumes and preventing aspiration are provided.

Specificity of attachment sites of larval water mites (Hydrachnidia, Acari) on their insect hosts (Chironomidae, Diptera) – evidence from some stream-living species

This study concerns the parasite-host associations of water mite larvae and their chironomid hosts in a small stream on the North German Plain. The different feeding sites on the host were tested as to whether they represented a strategy of the parasites regarding host partitioning. The attachment sites of nine ectoparasitic water mite species were observed in detail: Aturus fontinalis, Atractides nodipalpis, Feltria rouxi, Hygrobates nigromaculatus, Protzia eximia, Sperchonopsis verrucosa, Sperchon clupeifer, S. setiger and Lebertia inaequalis. Aturus fontinalis, A. nodipalpis, F. rouxi and H. nigromaculatus distinctly preferred sites on the abdomen of the host, whereas the other species preferred feeding sites on the thorax. The four species that preferentially attached to the abdomen of the host showed a distinct specificity for selected segmental and/or intersegmental regions. All species differed in their sites along the length of the abdomen. The order of attachment on the abdominal segments was, from anterior to posterior: H. nigromaculatus, F. rouxi, A. fontinalis and A. nodipalpis. The sites were analysed with regard to segmental and intersegmental attachment, the proportion of dorsal and ventral sites and the differences between attachment to different host species. Larvae attached to their hosts as single individuals showed only slight differences from the sites of mites on hosts that carried many mite larvae. The finding that less than 10% of the chironomids were parasitized by more than one water mite species suggested that, at least in the zoocoenosis of the studied collecting site, the interspecific competition for attachment sites was not strong. However, the specificity of attachment sites clearly had the potential of diminishing competition between water mite species by host partitioning. Intra- and interspecific competition for preferred sites and preparasitic constraints are discussed.

Utilization of landsat tm and digital elevation data for the delineation of avalanche slopes in yoho national park (canada)

There is an ongoing need for a long-term Grizzly Bear Management Plan in Yoho National Park as a result of human-bear conflicts and periodic human mortality. Avalanche slopes offer preferred feeding sites to the grizzly bear population, and hence a more detailed knowledge of their location and extent is needed as a management tool. Landsat Thematic Mapper (TM) satellite image bands, a normalized difference vegetation index (NDVI), and the principal component associated with "greenness" (derived from the TM image data), along with digital elevation model variables provided the best classification with an avalanche slope accuracy of 82%. The classified data were imported into a geographic information system (GIS) and the area of the avalanche slopes determined to be 66 km/sup 2/ or approximately 5% of the total park area. The resulting GIS database is being used by the park for management purposes.

The Value of Immaculate Mates: Relationships between Plumage Quality and Breeding Success in Shelducks

AbstractImmaculateness, a novel measure of bird plumage quality, defined as the regularity of the borders of a coloured patch of feathers, and the uniformity of the colour within the patch, tends to decline as a result of feather wear and damage. If it declines more quickly amongst birds in poor condition, it has the potential to act as an honest signal of individual quality and therefore be subject to social and sexual selection. We scored plumage immaculateness in shelducks Tadorna tadorna, based on the absence of white feathers in the red‐brown chest band and the evenness of the band's border. We monitored body condition and plumage quality in birds at feeding sites in the Severn Estuary (UK) during the early breeding season when females were forming eggs, and later in the season when chicks arrived. Drakes had more immaculate chest bands than ducks. At preferred feeding sites, drakes were more immaculate, and birds of both sexes were in better body condition. Birds with more immaculate plumage tended to mate assortatively at preferred sites and were more likely to produce a brood that survived the journey to the feeding areas. Immaculateness could therefore be an honest signal of parental quality. Although our evidence is only correlational, we suggest that plumage immaculateness indicates the ability to establish and maintain control over the best breeding sites and feeding territories in the face of competition with other shelducks.

Co-feeding studies of ticks infected with Anaplasma marginale.

Ticks often cluster at preferred feeding sites on hosts, and the co-feeding of ticks at the same site has been shown to increase feeding success and the transmission of some pathogens. While the major route of infection of ticks with pathogens is via the bloodmeal during feeding on a parasitemic host, non-systemic transmission of viruses and spirochetes has been shown to occur from infected to uninfected ticks at common feeding sites on uninfected hosts. In this research, two separate studies were done using the tick-borne rickettsial pathogen of cattle, Anaplasma marginale. In one study we tested whether A. marginale could be transmitted non-systemically from infected to uninfected Dermacentor variabilis males while co-feeding on rabbits. Infection of ticks was determined by allowing them to transmission feed on susceptible cattle and by DNA probe and microscopy studies on salivary glands. In the second study, we tested whether the co-feeding of male and female ticks on parasitemic cattle would increase the acquisition and development of A. marginale in males. A. marginale infections in salivary glands were determined by quantitative PCR after the ticks were allowed to transmission feed on susceptible cattle. Non-systemic transmission of A. marginale did not occur from infected and uninfected ticks that fed at the same site on rabbits and, therefore, does not appear to be a means of A. marginale transmission. A. marginale infections in male ticks were not increased while co-feeding with females. Thus, co-feeding of adult Dermacentor spp. does not appear to influence the dynamics of A. marginale transmission.

Allometric analysis of the induced flavonols on the leaf surface of wild tobacco ( Nicotiana attenuata)

Trichomes excrete secondary metabolites that may alter the chemical composition of the leaf surface, reducing damage caused by herbivores, pathogens and abiotic stresses. We examined the surface exudates produced by Nicotiana attenuata Torr. Ex Wats., a plant known to contain and secrete a number of secondary metabolites that are toxic or a deterrent to herbivorous insects. Extractions specific to the leaf surface, the trichomes, and the laminar components demonstrated the localization of particular compounds. Diterpene glycosides occurred exclusively in leaf mesophyll, whereas nicotine was found in both the trichomes and mesophyll. Neither rutin nor nicotine was found on the leaf surface. Quercetin and 7 methylated derivatives were found in the glandular trichomes and appeared to be excreted onto the leaf surface. We examined the elicitation of these flavonols on the leaf surface with a surface-area allometric analysis, which measures changes in metabolites independent of the effects of leaf expansion. The flavonols responded differently to wounding, methyl jasmonate (MeJA), herbivore attack and UV-C radiation, and the response patterns corresponded to their compound-specific allometries. Finding greater amounts of quercetin on younger leaves and reduced amounts after herbivore feeding and MeJA treatment, we hypothesized that quercetin may function as an attractant, helping the insects locate a preferred feeding site. Consistent with this hypothesis, mirids ( Tupiocoris notatus) were found more often on mature leaves sprayed with quercetin at a concentration typical of young leaves than on unsupplemented mature leaves. The composition of metabolites on the leaf surface of N. attenuata changes throughout leaf development and in response to herbivore attack or environmental stress, and these changes are mediated in part by responses of the glandular trichomes.

Winter habitat selection by two sympatric forest grouse in western Switzerland: implications for conservation

Two endangered tetraonids, the capercaillie ( Tetrao urogallus) and the hazel grouse ( Bonasa bonasia rupestris), are sympatric throughout part of their distribution range in central Europe. Precise information on their specific habitat requirements is needed if the coexistence of both species in exploited forests is to be maintained. We quantified winter habitat selection for both species in the upper part (1100–1600 m) of the Jura mountains (Switzerland). No preference for altitude or exposure could be detected. Capercaillie preferred open forests (including grazed forests) with a sparse canopy dominated by spruce ( Picea abies) and fir ( Abies alba), and avoided dense undercanopy and understorey, especially when dominated by spruce and beech ( Fagus sylvatica). By contrast, hazel grouse preferred feeding sites with a dense understorey of rowan ( Sorbus aucuparia), willow ( Salix sp.), beech and spruce. These preferences can be related to the feeding habits and predator avoidance behaviour of both species. Coexistence thus requires a mosaic distribution of habitat types, with a matrix of open forests (30% canopy cover) where fir is favoured, and understorey kept sparse (20%). Group-cuts of mature trees should allow regeneration patches, where a dense understorey (50% cover) should provide suitable habitats for hazel grouse.

Life history and phenology of the eucalyptus psyllid, Ctenarytaina eucalypti in Ireland

SummaryDuring the early 1990s, the eucalyptus psyllid, Ctenarytaina eucalypti Maskell, was accidentally introduced into Ireland and began to threaten economically a newly developing ornamental foliage production industry based in the south west. The life cycle of the psyllid was studied at three field sites in Co. Kerry. The psyllid exhibited a complex seasonal population dynamic suggesting that two, largely overlapping population cohorts over‐winter as eggs and nymphs, respectively, in a state of reduced development or temporary dormancy. The duration of this dormancy is short. Evidence of a resumption of activity was monitored at all sites in early February with increasing adult numbers and renewed egg laying being seen before any significant rise in temperatures. This strongly suggests that retarded development, and resumption of psyllid activity in early spring, are at least partially consequences of the changing nutritional quality of the food plant, probably mediated by changing day length. As a consequence of seasonally inhibited development, individual egg and nymphal over‐wintering cohorts probably alternate in the completion of two or three generations per growing season. Analysis of psyllid numbers on shoot samples showed that greater population densities were found on shoots at the top of the food plant compared with lower‐placed shoots. Evidence was also found that the distribution of nymphal instars changed seasonally, probably in response to population density and increased competition for preferred feeding sites. Overall psyllid abundance, and the finer details of seasonal population dynamics, varied between plantations. In the absence of effective predation or parasitism by indigenous natural enemies, these differences were also likely to be due to variation in nutritional quality of the host plant and may be influenced by crop husbandry factors such as the timing and severity of crop pruning.

PARASITIC NEMATODES ASSOCIATED WITH OLIVE IN COUNTRIES BORDERING THE MEDITERRANEAN SEA

PARASITIC NEMATODES ASSOCIATED WITH OLIVE IN COUNTRIES BORDERING THE MEDITERRANEAN SEA

NeonateGalerucella calmariensis(Coleoptera: Chrysomelidae) Behavior on Purple Loosestrife (Lythrum salicaria) Contributes to Reduced Predation

Galerucella calmariensis L. has been widely released in North America to control Lythrum salicaria L., an invasive Eurasian wetland perennial. Previous studies suggest that generalist predators such as Coleomegilla maculata (DeGeer) may affect establishment and spread of G. calmariensis. The objectives of this study were to determine the preferred feeding sites of neonate G. calmariensis, to quantify neonate survivorship on L. salicaria leaves and shoot tips, to assess the relationship between larval density and residence time in shoot tips, and to determine if larval density insuences survivorship of larvae on L. salicaria in the presence/absence of predators. Neonate G. calmariensis exhibited a signiÞcant propensity to ascend L. salicaria stems and conceal themselves inside shoot tips, where 77% were located after 1 h. Neonate survival in the presence of C. maculata was higher in shoot tips (70%) than on leaves (7.1%). At low densities (one to two larvae per shoot tip), G. calmariensis fed inside shoot tips for a prolonged period of time with only 25Ð30% exiting the shoot tip by 126 h. At higher densities, larvae left shoot tips more rapidly with 50% (seven larvae per shoot tip) and 80% (16 larvae per shoot tip) exiting by 126 h. The number of larvae that fed externally on foliage, i.e., were exposed to potential predation, similarly increased with increasing larval density. In the presence of adult C. maculata, G. calmariensis survival was inversely density dependent. At low larval densities, larvae remained concealed in shoot tips longer and were protected from predation. However, at high densities, larvae left shoot tips resulting in greater mortality by predators. This study indicates that density-dependent predation of G. calmariensis may occur as sheltered feeding sites within shoot tips become a limiting resource. This would occur under high G. calmariensis density and require the concurrent presence of effective predators. Further studies are necessary to determine if these conditions occur in nature and are of sufÞcient magnitude to alter G. calmariensis establish- ment or spread as a biological control agent of L. salicaria.

Interactions between social and feeding motivations on the grazing behaviour of herbivores: sheep more easily split into subgroups with familiar peers

Social grouping tendencies are known to influence the grazing behaviour of domestic herbivores. Here, we investigate how the strength of social bonds in a flock influences the choice of grazing location in sheep. Eight experimental ewes of INRA 401 breed grazed in plots in which a preferred feeding site, i.e. a patch of taller grass, was located 35 m away from a socially attractive site, i.e. five sheep confined in a pen, at one end of the plot. These penned sheep were either all familiar or all unfamiliar to the experimental ewes. Each experimental ewe was tested with one or four companions, which were either familiar or unfamiliar to her. The two group sizes, two degrees of familiarity with the penned sheep and two degrees of familiarity with the companions were incorporated into a Latin square design. In a series of 20 min tests, we recorded the behaviour of the experimental ewes by focal sampling and the location of each animal in the plots by scan sampling. As in a previous experiment, ewes in a larger group were more likely to move away from the penned sheep and to graze the preferred feeding site, and were also less vigilant. There was an additive effect of the degree of familiarity: the ewes with familiar companions grazed the preferred feeding site for longer, vocalised less and were less vigilant than those with unfamiliar companions. Inter-individual distances were also reduced when ewes grazed with familiar companions. Conversely, the degree of familiarity with the penned sheep had no effect on the ewes’ behaviour. Differences in the strength of social bonds within a flock are thus likely to affect the formation of subgroups and influence the way herbivores forage in patchy grasslands.

Oviposition preference and reproductive performance of Japanese Helicoverpa armigera (Huebner) (Lepidoptera: Noctuidae).

We investigated the host selection behavior and reproductive performance of Helicoverpa armigera (Hubner) in glasshouse bioassays. Irrespective of the growth stages of the host species tested, females showed strong oviposition preference for maize and okra, followed by tomato. There was a distinct non-preference for eggplant and pepper. The preferred ovipositional site on tomato, maize, okra and pepper was on leaves, and on eggplant, flowers and fruits were more preferred. The within-plant distribution of larvae based on the number of larvae feeding per plant part was highest on flowers and fruits of tomato and on the silk, cob and tassel of maize. Leaves were the preferred feeding sites for neonates on okra. Bionomics studies indicated a significant variation in the ability of different host plants to support the life history stages of the insect. Larvae reared on maize and okra had low survival rates, and produced smaller pupae that were more likely to die, and emerged adults were less fecund compared to those reared on tomato, eggplant, pepper and artificial diet. These results suggest that for H. armigera, growth and survival of offspring appear unrelated to adult host plant choice.

Factors affecting feeding site preferences of lightbrown apple moth, epiphyas postvittana (lepidoptera: Tortricidae), on apple trees in New Zealand

The infestation of apple (Malus domestica) trees by Epiphyas postvittana (Walker) larvae was studied over 3 years. Fresh damage to leaves increased progressively during the season, although in Nelson it declined in April. Fruit damage was first detected in December and increased throughout the season. The incidence of fruit damage was most strongly correlated with the surface area of fruit. Single leaves were the preferred feeding site for larvae on terminal shoots, although when whole branches were examined, most shelters occurred between two leaves. Feeding sites on fruit predominantly involved contact with a leaf or another apple. A field experiment examined the influence of physical contact and fruit maturation on leafroller damage. E. postvittana larvae were offered a choice of feeding sites involving leaves and three types of “apple” namely untreated apples, apples treated with chlorethephon to promote ripening, and plastic balls. There was 16% more damage on treated compared with untreated fruit, but similar levels of damage to leaves touching the three types of apple. Although riper fruit were more attractive to E. postvittana larvae, their preference for physical contact had a greater influence on the selection of feeding sites. The increase in fruit damage over time was mainly due to the increasing extent of contact between leaves and other fruit as the apples enlarged.

Grazing behaviour of sheep in a situation of conflict between feeding and social motivations

We investigated how food preferences and social bonds interact to determine the choice of grazing location in sheep. Ewes of INRA 401 breed were grazed in plots in which taller areas, i.e. preferred feeding sites, were left to grow at 15 or 50 m from a socially attractive site, i.e. familiar ewes placed in a public pen at one end of the plot. Eight experimental ewes were tested either alone or in groups with one, three or six accompanying animals chosen amongst 20 other familiar ewes. We used a Latin square design, in which the eight treatments (two distances×four group sizes) were balanced in 8 measurement days. We recorded, in 20-min tests, the behaviour of the experimental ewes by focal sampling, and the location of each animal in the groups by scan sampling. Foraging location, dietary choices and vigilance behaviour of ewes were affected by both the distance between the group of public peers and the preferred feeding site, and the size of their own group. Our results suggest that a sheep will move whether alone or with a few peers to a preferred feeding site located close to the core of its social group. In a small sub-group, its frequency of vigilance behaviour increases, probably to maintain social contact with the rest of the group. Conversely, a sheep will not leave its group to reach a preferred feeding site located further away unless it is followed by several other peers.