Short‐term prey field lability constrains individual specialisation in resource selection and foraging site fidelity in a marine predator

Spatio‐temporally stable prey distributions coupled with individual foraging site fidelity are predicted to favour individual resource specialisation. Conversely, predators coping with dynamic prey distributions should diversify their individual diet and/or shift foraging areas to increase net intake. We studied individual specialisation in Scopoli's shearwaters (Calonectris diomedea) from the highly dynamic Western Mediterranean, using daily prey distributions together with resource selection, site fidelity and trophic‐level analyses. As hypothesised, we found dietary diversification, low foraging site fidelity and almost no individual specialisation in resource selection. Crucially, shearwaters switched daily foraging tactics, selecting areas with contrasting prey of varying trophic levels. Overall, information use and plastic resource selection of individuals with reduced short‐term foraging site fidelity allow predators to overcome prey field lability. Our study is an essential step towards a better understanding of individual responses to enhanced environmental stochasticity driven by global changes, and of pathways favouring population persistence.     

Individual differences in foraging site fidelity are not related to time-activity budgets in Herring Gulls

Many populations consist of individuals that differ consistently in their foraging behaviour through resource or foraging site selection. Foraging site fidelity has been reported in several seabird species as a common phenomenon. It is considered especially beneficial in spatially and/or temporally predictable environments in which fidelity is thought to increase energy intake, thereby affecting time-energy budgets. However, the consequences for activity and energy budget have not been adequately tested. In this paper, we studied the consequences of fine-scale foraging site fidelity in adult Herring Gulls Larus argentatus in a highly predictable foraging environment with distinct foraging patches. We measured their time-activity budgets using GPS tracking and tri-axial acceleration measurements, which also made it possible to estimate energy expenditure. Individual variation in foraging site fidelity was high, some individuals spending most of their time on a single foraging patch and others spending the same amount of time in up to 21 patches. While time and activity budgets differed between individuals, we found no clear relationship with foraging site fidelity. We did find a relationship between the size of the birds and the level of site fidelity; faithful birds tend to have a larger body size. Although differences in foraging time and habitat use between individuals could play a role in the results of the current study, short-term consequences of variation in foraging site fidelity within a population remain elusive, even when focusing on individuals with a similar foraging specialization (Blue Mussels Mytilus edulis). Studying individuals over multiple years and under varying environmental conditions may provide better insight into the consequences and plasticity of foraging site fidelity.     

Exploring New Areas: How Important is Long-Term Spatial Memory for Mangabey (<Emphasis Type="BoldItalic">Lophocebus albigena johnstonii</Emphasis>) Foraging Efficiency?

Studies of primate foraging efficiency during the exploration of new areas can provide important insights into the adaptive value of long-term spatial memory. After 6 yr of observation of a group of gray-cheeked mangabeys (Lophocebus albigena johnstonii) in Kibale National Park, Uganda, we observed exploration of a new area, followed 7 mo later by a group split. We recorded their ranging and foraging behavior for 22 mo after the first exploration. Controlling for weather variables, we found that mangabeys moved longer daily travel distances, explored more area per day, and had larger group spreads in the new area compared to the old area in both parent and daughter groups. The increase in search swath in the new area likely enabled the monkeys to counteract their lack of knowledge of food locations in the new area, as the efficiency in finding fruit in general did not differ between the old and new areas. We did, however, find a lower efficiency in finding fruit from preferred fig trees whose edibility could not be assessed by visual cues in the new area. Fig finding efficiency remained lower, even when we controlled for potential differences in fig density. In addition, mangabeys traveled and foraged less often on the ground in the new compared to the old area. However, when the monkeys became more familiar with the new area, terrestrial behavior increased. Our results are consistent with the hypothesis that when monkeys move into an area in which they have no experience, an absence of knowledge acquired via long-term spatial memory decreases their foraging efficiency.     

Adult male chimpanzees inherit maternal ranging patterns

Space use often correlates with reproductive success [1, 2]. Individual site fidelity is ubiquitous across a variety of taxa, including birds, mammals, insects, and reptiles [3-9]. Individuals can benefit from using the same area because doing so affords access to known resources, including food and/or breeding sites. The majority of studies on site fidelity have focused upon strictly territorial species in which individuals range in well-defined, exclusive areas (e.g., [4, 9]). By comparison, the transient groups that define fission-fusion species allow for considerable flexibility in individual space use. Although there is evidence that individual space use can influence reproductive success [2], relatively little is known about individual ranging patterns in fission-fusion species. Here, we investigate three potential correlates of male site fidelity (age, habitat quality, and maternal space use) in wild chimpanzees (Pan troglodytes). We found that when alone, each male preferentially concentrated his space use near the area where his mother ranged when he was dependent. We suggest that solitary ranging allows males to avoid direct competition with conspecifics and that foraging in familiar areas maximizes foraging efficiency. These results highlight the importance of male foraging strategies in a species in which male ranging is typically explained in terms of mating access to females.     

The influence of time of day on the foraging behavior of the honeybee, Apis mellifera

The honeybee time sense, or Zeitged?chtnis, is highly adaptive, allowing bees to synchronize their foraging behavior with the peak time of daily floral nectar rhythms. Each foraging group within the honeybee colony shows a high degree of fidelity to one species of flower. Across the day, the temporal accuracy of foraging visits to experimental feeding times varies considerably, being nearly exact for morning-trained foraging groups but becoming less so for foraging groups trained later in the day. The evidence gained in this study suggests that the diel change in accuracy exhibited by foraging groups, which persists after the removal of many potential environmental time cues, is an endogenously driven behavior pattern. Furthermore, it appears that individual bees are continuously and accurately aware of the time of day, but are programmed to forage with greater anticipation to late-day food sources. Therefore, two separate processes contributing to the honeybee time sense are implicated. The first varies with time of day and determines the amount of anticipatory activity directed toward the food source. The second process is invariant across the day and is involved with the individual forager's continuous, accurate awareness of time.     

To be or not to be faithful: flexible fidelity to foraging trails in the leaf‐cutting ant Acromyrmex lobicornis

1. Ants using trails to forage have to select between two alternative routes at bifurcations, using two, potentially conflicting, sources of information to make their decision: individual experience to return to a previous successful foraging site (i.e. fidelity) and ant traffic. In the field, we investigated which of these two types of information individuals of the leaf‐cutting ant Acromyrmex lobicornis Emery use to decide which foraging route to take. 2. We measured the proportion of foraging ants returning to each trail of bifurcations the following day, and for 4–7 consecutive days. We then experimentally increased ant traffic on one trail of the bifurcation by adding additional food sources to examine the effect of increased ant traffic on the decision that ants make. 3. Binomial tests showed that for 62% of the trails, ant fidelity was relatively more important than ant traffic in deciding which bifurcation to follow, suggesting the importance of previous experience. 4. When information conflict was generated by experimentally increasing ant traffic along the trail with less foraging activity, most ants relied on ant traffic to decide. However, in 33% of these bifurcations, ants were still faithful to their trail. Thus, there is some degree of flexibility in the decisions that A. lobicornis make to access food resources. 5. This flexible fidelity results in individual variation in the response of workers to different levels of ant traffic, and allows the colony to simultaneously exploit both established and recently discovered food patches, aiding efficient food gathering.     

Adjustments in the Time,Distance and Direction of Foraging in Dinoponera quadriceps Workers

We measured individual decisions regarding the adjustments of time, distance and direction of foraging in Dinoponera quadriceps. We observed two colonies in an area of secondary Atlantic Forest, FLONA-ICMBio, in Northeastern Brazil. The workers were individually marked. We recorded the displacement of workers, their returns to the nest with and without food, the time spent searching for food, maximum and total distance, inter-trip latency and direction of trips. The time spent searching for food, maximum distance and transport velocity did not vary with food size. The previous trip success reduced the latency between foraging trips and increased the percentage of success on the next trip. However, this previous success did not demonstrate a significant variation relative to the time spent searching on the next trip or direction of search. The workers maintained an individual directional fidelity during foraging. The adjustments of these foraging variables under individual control contributed to the efficiency at the colony level. D. quadriceps is compatible with the central place theory and risk sensitivity model of behavior.     

Long-term home range stability provides foraging benefits in western gorillas

Objectives

Long-term home range stability presumably emerges because familiarity with an area improves fitness through increased foraging efficiency, reduced predation risk, or reduced costs of intergroup aggression. While the use of spatial memory by primates has been widely demonstrated, few studies have examined whether long-term space use creates opportunities for interannual reuse of spatial knowledge. Here we examine the ranging behavior of western gorillas (Gorilla gorilla) to assess the degree of long-term site fidelity and the foraging consequences of reuse of space.

Methods

We measured interannual home range overlap over a 10-year period for a single group of gorillas at the Mondika Research Center, using both grid-based and kernel density estimation. By plotting the total area used over time, we identified periods of home-range stability and expansion. We compared foraging and ranging behavior in familiar versus unfamiliar areas, considering fruit trees visited, dietary diversity, and daily path length, to determine whether the lack of spatial knowledge in unfamiliar areas was associated with foraging costs.

Results

Average interannual home range overlap by the group remained high throughout the study. During periods of home range expansion, daily path lengths increased but not the number of fruit trees visited, suggesting that reduced familiarity with the area led to decreased foraging efficiency because individuals lacked prior knowledge of where to find resources.

Discussion

Western gorillas at Mondika exhibit long-term home range stability, presumably reflecting a strategy that relies on the use of spatial memory to increase foraging efficiency that is favored by their reliance on ephemeral fruit resources.

     

The Effect of Social Hierarchy on Captive Coyote (Canis latrans) Foraging Behavior

Foraging efficiency of individuals in pack forming species may be influenced by social dynamics within a pack. The effects of social hierarchy in particular may influence individual foraging behavior in canids, such as coyotes (Canis latrans). To examine the impact of social hierarchy on foraging behavior, we tested 16 captive coyotes in eight naturally established dominant–subordinate pairs, using the guesser–knower paradigm. We measured the efficiency of subordinate coyotes to relocate a food resource when alone and then allowed pairs to forage together, such that subordinates had prior knowledge of food location but dominants did not. To determine whether (1) subordinates used a direct or discursive strategy to obtain food in the presence of a dominant and (2) dominants used an exploitative or independent strategy to obtain food in the presence of a subordinate with previous knowledge, we measured their search efficiency (e.g., correct choice of area, feeder, and latency to correct feeder). Results showed subordinates learned to relocate food and increase efficiency when alone. In a social context, however, subordinate efficiency decreased. That is, subordinates approached the correct area, but searched more feeders before finding the correct one. Dominants initially used an independent search strategy but then quickly displaced the subordinate and monopolized the resource, reducing subordinate efficiency further. Despite continual displacement and reduction in efficiency, subordinates did not alter their foraging strategy over time. Our results suggest prior information can improve individual foraging advantage, but that social status strongly impacts individual foraging efficiency in social species such as coyotes.     

Phenotypic Correlates of Scrounging Behavior in Zebra Finches: Role of Foraging Efficiency and Dominance

In flocks, individuals can search for their own food using the producer tactic or exploit the discoveries of companions using the scrounger tactic. Models of the producer–scrounger game usually assume that tactic payoffs are independent of individual phenotypic traits. However, factors such as dominance status or foraging efficiency may constrain the use of tactics and lead to asymmetric tactic use among individuals. For instance, in flocks composed of foragers with unequal foraging efficiency, foragers that are less efficient at obtaining food are expected to rely on the scrounger tactic to a greater extent. I examined the role of foraging efficiency and dominance status as potential correlates of scrounging behavior in small aviary flocks of zebra finches (Taenopygia guttata). Individual foraging efficiency was documented in each flock in a treatment that prevented scrounging. In a subsequent treatment that allowed scrounging, higher levels of scrounging occurred as predicted in foragers with lower foraging efficiency. Dominance status was a poor predictor of tactic choice. Birds that arrived later on the foraging grid foraged less efficiently when scrounging was prevented and used scrounging to a greater extent when allowed, suggesting a link between boldness, foraging efficiency and the choice of foraging tactics in small flocks of zebra finches.     

Individual foraging site fidelity in lactating New Zealand fur seals: Continental shelf vs. oceanic habitats

Wide‐ranging marine central place foragers often exhibit foraging site fidelity to oceanographic features over differing spatial scales (i.e., localized coastal upwellings and oceanic fronts). Few studies have tested how the degree of site fidelity to foraging areas varies in relation to the type of ocean features used. In order to determine how foraging site fidelity varied between continental shelf and oceanic foraging habitats, 31 lactating New Zealand fur seals (Arctocephalus australis forsteri 1 ) were satellite tracked over consecutive foraging trips (14–108 d). Thirty‐seven foraging trips were recorded from 11 females that foraged on the continental shelf, in a region associated with a coastal upwelling, while 65 foraging trips were recorded from 20 females that foraged in oceanic waters. There were no significant differences in the mean bearings (to maximum distance) of individual's consecutive foraging trips, suggesting individual fidelity to foraging areas. However, overlap in area and time spent in area varied considerably between continental shelf and oceanic foragers. Females that foraged on the continental shelf had significantly greater overlap in consecutive foraging trips when compared to females that foraged in oceanic waters (overlap in 5 × 5 km grid cells visited on consecutive trips 55.9%± 20.4% and 13.4%± 7.6%, respectively). Females that foraged on the continental shelf also spent significantly more time within the same grid cell than females that foraged in oceanic waters (maximum time spent in 5 × 5 km grid cells: 14%± 5% and 4%± 2%, respectively). This comparatively high foraging site fidelity may reflect the concentration of productivity associated with a coastal upwelling system, the Bonney Upwelling. Lower foraging site fidelity recorded by seals that foraged in oceanic waters implies a lower density/larger scale habitat, where prey are more dispersed or less predictable at fine scales, when compared to the continental shelf region.     

Daily foraging schedule of field colonies of the eastern tent caterpillar Malacosoma americanum

Summary The daily foraging patterns of seven colonies of the eastern tent caterpillar, Malacosoma americanum, were monitored photoelectronically during the last three larval stadia to provide the first detailed record of the foraging behavior of a gregarious caterpillar under field conditions. Colonies were active an average of 49.3% of each day. Three bouts of foraging, centered about 0600 h, 1500 h and 2000 h (EST), occurred daily during the fourth and fifth stadia. Although ambient temperatures were less favorable for foraging and food processing than at other times of the day, the caterpillars were most active at dusk and dawn, and spent comparatively little time away from the tent during the daylight hours. In the last (sixth) stadium, the caterpillars foraged only under the cover of darkness. A lack of relationship between the rate at which the caterpillars processed food and the spacing of their feeding bouts, indicates that this species follows a schedule of feeding and growth shaped by factors other than those directly related to feeding efficiency and ambient temperature. Colony foraging patterns may reduce caterpillar mortality by minimizing contact between larvae and day-active predators and parasitiods.     

Small home ranges and high site fidelity in red knots (Calidris c. canutus) wintering on the Banc d’Arguin, Mauritania

Using automated and manual radio-telemetry and resightings of individual colour-ringed birds, we assessed the daily use of space of red knots Calidris canutus canutus at a tropical wintering area along the Sahara coast, the Banc d’Arguin in Mauritania. Confirming earlier suggestions, we found that birds were very faithful to their roosts and that the daily foraging range was small; in the course of several winter months birds used an area of only 2–16 km² of intertidal area. We found no differences between their movements in daylight and at night. Additionally, individuals seem to return to exactly the same locations in subsequent winters. This pattern is very different from red knots wintering in the temperate Wadden Sea. Here, they readily change roost sites and easily cover areas of about 800 km² in the course of weeks but, just as in Mauritania, no differences between day and night are apparent. In northern Patagonia and north-western Australia, red knots have range sizes closer to those on the Banc d’Arguin, but here they do show differences in space use between day and night. Ecological explanations for these contrasting patterns require further comparative data based on in-depth studies on the predictability of the food base and the presence of diurnal and nocturnal predators.     

Temporal pattern of resource use and variation in diets of individual grasshoppers (Orthoptera: Acrididae)

Patterns of resource fidelity, switching, and variation in individual diet were examined in the polyphagous grasshopper Taeniopoda equesforaging in experimental cages over an 11-day period. Ten novel dicots were provided in the cages, but grasshoppers fed primarily on kale (Brassica oleraceavar. acephala),lobelia (Lobelia erinus),pansy (Viola x wittrockiana),and dry bermuda grass (Cynodon dactylon).Grasshoppers showed significant fidelity to a single plant within a meal but tended to eat less of the same plant in the next meal and, in the case of pansy, on the next day. Grasshoppers switched nonrandomly, suggesting that compensatory feeding on complementary resources may have occurred. There was no evidence that behavioral interactions among individuals increased switching rate or lowered fidelity. Overall patterns of resource use varied significantly among grasshoppers during the study, despite frequent switching among resources and a significant tendency to aggregate while feeding. All individuals were polyphagous but differed in relative consumption of available plants. The results suggest that individual grasshoppers express different feeding patterns that are consistent over time and that variation in diet among individual observed in the field may be more than simple sampling error.     

Return Customers: Foraging Site Fidelity and the Effect of Environmental Variability in Wide-Ranging Antarctic Fur Seals

Strategies employed by wide-ranging foraging animals involve consideration of habitat quality and predictability and should maximise net energy gain. Fidelity to foraging sites is common in areas of high resource availability or where predictable changes in resource availability occur. However, if resource availability is heterogeneous or unpredictable, as it often is in marine environments, then habitat familiarity may also present ecological benefits to individuals. We examined the winter foraging distribution of female Antarctic fur seals, Arctocephalus gazelle, over four years to assess the degree of foraging site fidelity at two scales; within and between years. On average, between-year fidelity was strong, with most individuals utilising more than half of their annual foraging home range over multiple years. However, fidelity was a bimodal strategy among individuals, with five out of eight animals recording between-year overlap values of greater than 50%, while three animals recorded values of less than 5%. High long-term variance in sea surface temperature, a potential proxy for elevated long-term productivity and prey availability, typified areas of overlap. Within-year foraging site fidelity was weak, indicating that successive trips over the winter target different geographic areas. We suggest that over a season, changes in prey availability are predictable enough for individuals to shift foraging area in response, with limited associated energetic costs. Conversely, over multiple years, the availability of prey resources is less spatially and temporally predictable, increasing the potential costs of shifting foraging area and favouring long-term site fidelity. In a dynamic and patchy environment, multi-year foraging site fidelity may confer a long-term energetic advantage to the individual. Such behaviours that operate at the individual level have evolutionary and ecological implications and are potential drivers of niche specialization and modifiers of intra-specific competition.     

Spatial Ecology of the Endangered Milne-Edwards’ Sifaka (Propithecus edwardsi): Do Logging and Season Affect Home Range and Daily Ranging Patterns?

Primates often live in human-altered habitats; Malagasy lemurs are no exception. It is important to understand if habitat alteration affects primates’ space use patterns across multiple spatial and temporal scales, as this drives population density. We quantified the daily, seasonal, and annual space-use of seven groups of Milne-Edwards’ sifaka (Propithecus edwardsi) living in unlogged and logged rain forest in Ranomafana National Park, Madagascar between December 2002 and November 2003. Concurrent data showed that sifakas consumed higher quality foods in the unlogged than in logged forests; thus we explored how space use patterns were related to energy use strategies. Sifaka groups in the logged rain forest traveled 7–13% less per day than groups in the unlogged rain forest, despite their larger home ranges (median: 46.12 and 23.52 ha, in the logged and unlogged forests, respectively). Sifakas may thus use an energy-minimizing strategy at the scale of the individual day but an energy-maximizing strategy at the annual home range scale. Sifakas exhibited fidelity to the home range across seasons, but their core area of use shifted considerably with season. We found no difference in population density between sites. However, given the interannual variability in sifaka foods, a multiyear study is needed to assess if energy strategies observed in this study are consistent across longer time periods. Our findings suggest that lemurs may persist in logged habitats by altering spatial use patterns; future work should attempt to quantify the threshold level of forest regeneration from logging that will allow lemurs to persist at similar densities as in unlogged forest.     

Directional fidelity as a foraging constraint in the western harvester ant,Pogonomyrmex occidentalis

Summary Understanding the foraging behavior of an animal is critically dependent upon knowledge of the constraints on that animal. In this study, I tested whether fidelity to foraging direction acts as a behavioral constraint to foraging western harvester ants, Pogonomyrmex occidentalis. Individual P. occidentalis foragers showed strong fidelity to foraging route and direction. Directional fidelity in this population was not related to trunk trail use, food specialization, colony activity levels, or mortality risks. Directional fidelity constrained individual foraging decisions; when colonies were offered seeds of different quality in 2 directions, individuals did not switch directions to obtain the energetically more rewarding seeds. Colony-level recruitment was increased for energetically more profitable seeds, indicating that colonial responses may compensate for the constraints of directional fidelity on individual foragers.     

Field study on the foraging characteristics of a ponerine ant,Hagensia havilandi Forel

Summary A field study of the foraging strategy used by the ponerine ant,Hagensia havilandi is reported. They have permanent nests in the leaf litter of coastal forests.H. havilandi is a diurnal forager and collects a variety of live and dead arthropods. These predatory ants exhibit individual foraging with no cooperation in the search for or retrieval of food items. Three colonies were observed and showed similar temporal and spatial foraging patterns. The paths of individual ants were followed and the results showed that the foragers exhibit area fidelity, and return to the nest via a direct route on finding on prey item. Several foragers did not return to the nest at dusk but returned the following morning. Occasionally a limited amount of tandem recruitment was displayed.     

Seasonal patterns of diet and ranging in two species of tamarin monkeys: Stability versus variability

From June through December, data were collected on the diet and ranging patterns of moustached (Saguinus mystax) and saddle-back (Saguinus fuscicollis) tamarin monkeys in the Amazon Basin of northeastern Peru. During this 7-month period, insects and nonleguminous fruits accounted for 83% of tamarin feeding and foraging time. Despite marked seasonal variation in rainfall and forest productivity, patterns of habitat utilization, day range, dietary diversity, resource exploitation, and activity budget remained relatively stable throughout the year. Moustached and saddle-back tamarins appear to solve problems of food acquisition and exploit patchily distributed feeding sites using a relatively limited set of foraging patterns. In general, these primates concentrate their daily feeding efforts on several trees from a small number of target plant species. These feeding sites are uncommon, produce only a small amount of ripe fruit each day, and are characterized by a high degree of intraspecific fruiting and flowering synchrony. Trees of the same species are frequently visited in succession, and individual feeding sites are revisited several times over the course of 1–2 weeks. This type of foraging pattern occurred during both dry and wet seasons and when exploiting fruit, nectar, legume, and exudate resources. Seasonal variation in the percentage of feeding and foraging time devoted to insectivory was also limited. In this investigation, there was no consistent evidence that temporal changes in overall forest fruit production had a major impact on the feeding, foraging, or ranging behavior of either tamarin species.     

Individual foraging components of harvester ants: movement patterns and seed patch fidelity

Summary We investigated individual foraging components of the western harvester ant,Pogonomyrmex occidentalis, in the native seed background of a shrub-steppe environment. Our study identified factors affecting foraging movements and seed selection by individual ants. Some assumptions and predictions of central-place foraging theory and a correlated random walk were evaluated for individual foragers. Results showed that ant size was only weakly correlated with the seed sizes harvested; seed size was a more important constraint than a predictor of seed selection. Individual ants spent more time in localized search behavior than traveling between search areas and nests.P. occidentalis foragers encountered seeds randomly with respect to time, and handled a mean of 1.7 seeds/trip. A correlation of increased search effort with greater travel distances was consistent with central-place foraging theory but, contrary to it, search and travel effort were not associated with energetic reward.Individual ants exhibited fidelity in both search site and native seed species. Spatial analyses of foraging movements showed a highly oriented travel path while running, and an area-restricted path while searching. Searching ants moved in a manner consistent with a correlated random walk. The deterministic component of patch fidelity and the stochastic component of search may override energetic foraging decisions in individualP. occidentalis ants.