Foraging behaviour and brain morphology in recently emerged brook charr, Salvelinus fontinalis

Recently emerged brook charr (Salvelinus fontinalis) foraging in still-water pools along the sides of streams are either active, feeding on insects from the upper portion of the water column away from the stream bank, or sedentary, feeding on crustaceans emerging from the hyporheic zone near the stream bank. We tested whether the frequency of movement displayed by individual brook charr searching for prey in the field was related to the relative volume of the telencephalon, a brain region involved with movement and space use in fishes. Movement of individuals searching for prey was quantified in the field, individuals were captured and volumes of the telencephalon and of the olfactory bulbs, a brain region neighbouring the telencephalon but not implicated in space use, were measured. Individuals with larger telencephalon volumes moved more frequently on average while searching for prey in the field than did individuals with smaller telencephalon volumes. The frequency of movement was unrelated to differences in the volume of the olfactory bulbs, suggesting that the relationship between telencephalon volume and movement was not a consequence of differences in overall brain size. Demonstrating a correlation between foraging behaviour and brain morphology for brook charr exhibiting different foraging tactics suggests that diversification in brain structure and function could be important aspects of the foraging specialization believed to occur during early stages in the evolution and development of resource polymorphisms.     

Pattern-oriented modeling of bird foraging and pest control in coffee farms

We develop a model of how land use and habitat diversity affect migratory bird populations and their ability to suppress an insect pest on Jamaican coffee farms. Bird foraging—choosing which habitat patch and prey to use as prey abundance changes over space and time—is the key process driving this system. Following the “pattern-oriented” modeling strategy, we identified nine observed patterns that characterize the real system's dynamics. The model was designed so that these patterns could potentially emerge from it. The resulting model is individual-based, has fine spatial and temporal resolutions, represents very simply the supply of the pest insect and other arthropod food in six habitat types, and includes foraging habitat selection as the only adaptive behavior of birds. Although there is an extensive heritage of bird foraging theory in ecology, most of it addresses only the individual level and is too simple for our context. We used pattern-oriented modeling to develop and test foraging theory for this across-scale problem: rules for individual bird foraging that cause the model to reproduce a variety of patterns observed at the system level. Four alternative foraging theories were contrasted by how well they caused the model to reproduce the nine characteristic patterns. Four of these patterns were clearly reproduced with the “null” theory that birds select habitat randomly. A version of classical theory in which birds stay in a patch until food is depleted to some threshold caused the model to reproduce five patterns; this theory caused lower, not higher, use of habitat experiencing an outbreak of prey insects. Assuming that birds select the nearby patch providing highest intake rate caused the model to reproduce all but one pattern, whereas assuming birds select the highest-intake patch over a large radius produced an unrealistic distribution of movement distances. The pattern reproduced under none of the theories, a negative relation between bird density and distance to trees, appears to result from a process not in the model: birds return to trees at night to roost. We conclude that a foraging model for small insectivorous birds in diverse habitat should assume birds can sense higher food supply but over short, not long, distances.     

Seasonal changes in foraging strategies of nesting blackbirds (Turdus merula L.)

Summary Blackbirds are usually multiple-prey loaders and forage mainly on the ground. We analysed the foraging behaviour of ten males in an urban park in Budapest during the breeding season from 1984 to 1986. At the end of April and in May blackbirds fed their nestlings mainly on earthworms (load type I). In this period the average scarching time and route were shorter, and the territories of the pairs tended to be smaller, than in June, when males in addition brought a great variety of invertebrates per load (load type II) to the young. The average dry weight and energy content of the two load types did not differ significantly. However, the average energy delivery rate (energy content/intervisiting time) and rate of energy gain (energy content/searching time) were higher when males collected earthworms, because intervisiting and searching times were shorter. The frequency distribution of searching times for load type I suggests that the encounter with earthworms was random. For load type II birds seemed to employ a fixed-mass foraging strategy. In June, the drier conditions reduced the availability of earthworms, and blackbirds extended their foraging areas.     

Spatio-temporal ranging behaviour and its relevance to foraging strategies in wide-ranging wolverines

Conservation of carnivores in an increasingly changing environment is greatly helped by understanding the decision-making processes underlying habitat patch choice. Foraging theory may give us insight into spatio-temporal search patterns and consequent foraging decisions that carnivores make in heterogeneous and fluctuating environments. Constraints placed on central-place foragers in particular are likely to influence both foraging decisions and related spatio-temporal movement patterns. We used discrete choice models to investigate the spatio-temporal ranging behaviour of GPS collared female wolverines (Gulo gulo) with dependent cubs in south-central Norway. Activity patterns, home range use and selection for elevation were analyzed in relation to spatial and temporal covariates (daily and seasonal) and related to different foraging behaviours. In spring, wolverines showed restricted movement patterns around rendezvous sites at high elevations by day, whereas during the night animals were active at lower elevations. Over the summer, this daily pattern in intensity of use diminished and their overall selectiveness for elevation decreased as cubs grow more mobile and independent. At the onset of autumn, wolverines showed intensive use of the profitable forest-alpine tundra ecotone. We argue that reproducing wolverines deployed a foraging strategy attuned to altering their movement patterns throughout the summer to address a continuous, but diminishing, trade-off between providing both food and shelter for their offspring. Incorporating spatially and temporally explicit activity patterns and home range use in discrete choice resource selection models thus enhances the understanding of the motives behind wolverine resource utilization in space and time. Such knowledge may provide guidance to managers designing regional-scale zoning, in order to facilitate carnivore recovery and to minimize conflicts with human activities.     

Optimal movement strategies for social foragers in unpredictable environments

Spatial movement models often base movement decision rules on traditional optimal foraging theories, including ideal free distribution (IFD) theory, more recently generalized as density-dependent habitat selection (DDHS) theory, and the marginal value theorem (MVT). Thus optimal patch departure times are predicted on the basis of the density-dependent resource level in the patch. Recently, alternatives to density as a habitat selection criterion, such as individual knowledge of the resource distribution, conspecific attraction, and site fidelity, have been recognized as important influences on movement behavior in environments with an uncertain resource distribution. For foraging processes incorporating these influences, it is not clear whether simple optimal foraging theories provide a reasonable approximation to animal behavior or whether they may be misleading. This study compares patch departure strategies predicted by DDHS theory and the MVT with evolutionarily optimal patch departure strategies for a wide range of foraging scenarios. The level of accuracy with which individuals can navigate toward local food sources is varied, and individual tendency for conspecific attraction or repulsion is optimized over a continuous spectrum. We find that DDHS theory and the MVT accurately predict the evolutionarily optimal patch departure strategy for foragers with high navigational accuracy for a wide range of resource distributions. As navigational accuracy is reduced, the patch departure strategy cannot be accurately predicted by these theories for environments with a heterogeneous resource distribution. In these situations, social forces improve foraging success and have a strong influence on optimal patch departure strategies, causing individuals to stay longer in patches than the optimal foraging theories predict.     

Learning during competitive positioning in the nest: do nestlings use ideal free ‘foraging’ tactics?

Begging behaviour of nestling birds may involve more than a simple, honest source of information for parents to use in provisioning. Many aspects of begging behaviour relate instead to sibling competition for food items within the nest, and we might expect evidence of adaptive learning and behavioural adjustment in response to experience of the competitive environment. In this study, we consider begging in different locations within the nest as analogous to foraging in different patches, varying in food availability. Using hand-feeding trials, we created zones of differing profitability within an artificial nest by adjusting either the prey size or number of items delivered, and allowed only indirect competition between pairs of southern grey shrike (Lanius meridionalis) nestlings. Nestlings demonstrated the ability to detect differences in zone profitability and position themselves accordingly. By the end of both the prey size and delivery rate trials nestlings had increased the amount of time spent in the high quality zone. Such movement in response to differences in load quality, as well as frequency, demonstrates the ability of nestlings to learn about their environment and to facultatively adjust their begging in order to maximise energetic rewards.     

Integrated modelling of foraging behaviour, energy budget and memory properties

A predator's foraging performance is related to its ability to acquire sufficient information on environmental profitability. This process can be affected by the patchy distribution and clustering of food resources and by the food intake process dynamics.We simulated body mass growth and behaviour in a forager acting in a patchy environment with patchy distribution of both prey abundance and body mass by an individual-based model. In our model, food intake was a discrete and stochastic process and leaving decision was based on the estimate of net energy gain and searching time during their foraging activities. The study aimed to investigate the effects of learning processes and food resource exploitation on body mass and survival of foragers under different scenarios of intra-patch resource distribution.The simulation output showed that different sources of resource variability between patches affected foraging efficiency differently. When prey abundance varied across patches, the predator stayed longer in poorest patches to obtain the information needed and its performance was affected by the cost of sampling and the resulting assessment of the environment proved unreliable. On the other hand, when prey body mass, but not abundance, varied among the patches the predator was quickly able to assess local profitability. Both body mass and survival of the predator were greatly affected by learning processes and patterns of food resource distribution.     

Social cohesion and foraging decrease with group size in fallow deer (Dama dama)

We studied the impact of group size on foraging behaviour and level of movement synchronisation among female herdmates of a fallow deer population in Central Italy. Both proportion of foraging events and movement synchronisation decreased with increasing group size. The proportion of foraging events was higher for animals on the edge of the group than for deer in the centre of the group; hence, there appears to be a trade-off between protection against predators and foraging interference, both of which decrease from the centre to the periphery of the group. This is the first time this type of behaviour has been recorded for wild ungulates. As expected, we also found that the movement of peripheral animals was less synchronised than that of central animals. Consequently, peripheral animals may lose contact with their herdmates and split off the group. We conclude that social inequalities may lead to conflicting requirements among group members and instability of large groups. Movement synchronisation (as a function of group size) appears to interact with habitat openness to produce variations of group size (which appear to be adaptive for individuals) as an emergent property of these aggregations.     

Honeybees use a Lévy flight search strategy and odour-mediated anemotaxis to relocate food sources

The availability of food resources changes over time and space, and foraging animals are constantly faced with choices about how to respond when a resource becomes depleted. We hypothesise that flying insects like bees discover new food sources using an optimal Lévy flight searching strategy and odour-mediated anemotaxis, as well as visual cues. To study these searching patterns, foraging honeybees were trained to a scented feeder which was then removed. Two new unrewarding feeders, or ‘targets’, were then positioned up- and downwind of the original location of the training feeder. The subsequent flight patterns of the bees were recorded over several hundred metres using harmonic radar. We show that the flight patterns constitute an optimal Lévy flight searching strategy for the location of the training feeder, a strategy that is also optimal for the location of alternative food sources when patchily distributed. Scented targets that were positioned upwind of the original training feeder were investigated most with the numbers of investigations declining with increasing distance from the original feeder. Scented targets in downwind locations were rarely investigated and unscented targets were largely ignored, despite having the same visual appearance as the rewarding training feeder.     

The strategy of fly-and-forage migration,illustrated for the osprey (<Emphasis Type="Italic">Pandion haliaetus</Emphasis>)

Migrating birds often alternate between flight steps, when distance is covered and energy consumed, and stopover periods, when energy reserves are restored. An alternative strategy is fly-and-forage migration, useful mainly for birds that hunt or locate their prey in flight, and thus, enables birds to combine foraging with covering migration distance. The favourability of this strategy in comparison with the traditional stopover strategy depends on costs of reduced effective travel speed and benefits of offsetting energy consumption during migration flights. Evaluating these cost-benefit effects, we predict that fly-and-forage migration is favourable under many conditions (increasing total migration speed), both as a pure strategy and in combination with stopover behaviour. We used the osprey (Pandion haliaetus) as test case for investigating the importance of this strategy during spring and autumn migration at a lake in southern Sweden. The majority, 78%, of passing ospreys behaved according to the fly-and-forage migration strategy by deviating from their migratory track to visit or forage at the lake, while 12% migrated past the lake without response, and 10% made stopovers at the lake. Foraging success of passing ospreys was almost as good as for birds on stopover. Timing of foraging demonstrated that the birds adopted a genuine fly-and-forage strategy rather than intensified foraging before and after the daily travelling period. We predict that fly-and-forage migration is widely used and important among many species besides the osprey, and the exploration of its occurrence and consequences will be a challenging task in the field of optimal migration.     

Individually different foraging methods in the desert ant Cataglyphis bicolor (Hymenoptera,Formicidae)

Summary Observations and field experiments on the foraging behaviour of individual workers of Cataglyphis bicolor in a Southern Tunisian shrub desert are reported. The workers search singly for their food (mostly animal carcasses) and are singleprey loaders. The individuals differ to a great extent in their persistence to re-search the place of a find on a previous foraging excursion. The differences range continuously from thoroughly researching a place to just walking by. If, in an experiment, the same reward is offered farther from the nest, each ant persists more in re-searching the place than if food is offered close to the nest. In a further experiment, some individuals persisted less in searching near the former finding site if they had collected a fly than after collecting a piece of cheese. There is, however, evidence that individuals do not differ in their food preference. Persistent individuals, which re-search the place of a former find, are faster than non-persistent ones in retrieving food that is experimentally arranged in an aggregated manner. The experiment failed to demonstrate the (reverse) superiority of non-persistent individuals foraging on homogeneously distributed food. The observations of unmanipulated foraging excursions in the field suggest such an advantage for non-persistent foragers under natural conditions where food in general occurs widely dispersed. The colony as a whole retrieves more food within the same time from an experimental lay-out that is homogeneous than from an aggregated one. The behavioural differences between individuals could be caused by a training bias of the short-lived foragers, leading to a different assessment of the profitability of a searching method which implies returning to a formerly rewarding place. Thus, each worker uses the most promising behaviour according to its individual experience. Alternatively, the individually different searching methods could mainly contribute to the welfare of the colony as a whole rather than leading to a maximal short-term efficiency of each individual. In particular, the colony, disposing of only a few highly persistent foragers, could quickly exploit occasional short-lived, but unpredictible, clumps of food within its foraging range.     

Information transfer and gain in flocks: the effects of quality and quantity of social information at different neighbour distances

We assessed experimentally how the quality and quantity of social information affected foraging decisions of starlings (Sturnus vulgaris) at different neighbour distances, and how individuals gained social information as a function of head position. Our experimental set up comprised three bottomless enclosures, each housing one individual placed on a line at different distances. The birds in the extreme enclosures were labelled senders and the one in the centre receiver. We manipulated the foraging opportunities of senders (enhanced, natural, no-foraging), and recorded the behaviour of the receiver. In the first experiment, receivers responded to the condition of senders. Their searching rate and food intake increased when senders foraged in enhanced conditions, and decreased in no-foraging conditions, in relation to natural conditions. Scanning was oriented more in the direction of conspecifics when senders behaviour departed from normal. In the second experiment, responses were dose dependent: receivers increased their searching rate and orientated their gaze more towards conspecifics with the number of senders foraging in enhanced food conditions. In no-foraging conditions, receivers decreased their searching and intake rates with the number of senders, but no variation was found in scanning towards conspecifics. Differences in foraging and scanning behaviour between enhanced and no-foraging conditions were much lower when neighbours were separated farther. Overall, information transfer within starling flocks affects individual foraging and scanning behaviour, with receivers monitoring and copying senders behaviour mainly when neighbours are close. Information transfer may be related to predation information (responding to the vigilance of conspecifics) and foraging information (responding to the feeding success of conspecifics). Both sources of information, balanced by neighbour distance, may simultaneously affect the behaviour of individuals in natural conditions.Communicated by H. Kokko     

Cryptic prey colouration increases search time in brown trout (<Emphasis Type="Italic">Salmo trutta</Emphasis>): effects of learning and body size

Little is known about how cryptic colouration influences prey search in near-surface aquatic habitats, although such knowledge is critical for understanding the adaptive value of colour crypsis as well as the perceptive constraints influencing foraging behaviour in these environments. This study had two main aims: (1) to investigate how background colour matching by prey affects foraging efficiency by brown trout parr and (2) to investigate how foraging ability on cryptic and conspicuous prey is affected by fish size at age (reflecting dominance). We addressed these questions by training wild brown trout parr to forage individually on live brown-coloured maggots on a cryptic (brown) or conspicuous (green) background. A separate experiment confirmed the absence of trout preference for brown or green substrate. The results show that prey background colour matching increases search time in brown trout. Search time generally decreased by learning, but conspicuous prey remained an easier prey to find throughout the six training trials. Thus, perceptive constraints appear to limit search efficiency for cryptic prey, suggesting that cryptic colouration can confer survival benefits to prey in natural environments. Smaller fish generally found conspicuous prey faster than larger individuals, whereas search time for cryptic prey was not influenced by body size. This suggests that smaller individuals compensate for inferior competitive ability by increasing foraging activity rather than improving cognitive ability. The technique of varying cognitive demands in behavioural tasks could be used more in future studies aimed at distinguishing motivational effects from cognitive explanations for variation in behavioural performance.     

Costs and benefits of pocket gopher foraging: linking behavior and physiology

Animals can attain fitness benefits by maintaining a positive net energy balance, including costs of movement during resource acquisition and the profits from foraging. Subterranean rodent burrowing provides an excellent system in which to examine the effects of movement costs on foraging behavior because it is energetically expensive to excavate burrows. We used an individual-based modeling approach to study pocket gopher foraging and its relationship to digging cost, food abundance, and food distribution. We used a unique combination of an individual-based foraging-behavior model and an energetic model to assess survival, body mass dynamics, and burrow configurations. Our model revealed that even the extreme cost of digging is not as costly as it appears when compared to metabolic costs. Concentrating digging in the area where food was found, or area-restricted search (ARS), was the most energetically efficient digging strategy compared to a random strategy. Field data show that natural burrow configurations were more closely approximated by the animals we modeled using ARS compared to random diggers. By using behavior and simple physiological principles in our model, we were able to observe realistic body mass dynamics and recreate natural movement patterns.     

Lévy flight patterns are predicted to be an emergent property of a bumblebees’ foraging strategy

Bumblebees forage uninterrupted for long periods of time because they are not distracted by sex or territorial defense and have few predators. This has led to a long running debate about whether bumblebees forage optimally. This debate has been enriched by the possibility that bumblebees foraging within clover patches have flight patterns that can be approximated by Lévy flights. Such flight patterns optimise the success of random searches. Bumblebees foraging within a flower patch tend to approach the nearest flower but then often depart without landing or probing it if it has been visited previously; unvisited flowers are not rejected in this manner. Here, this foraging behaviour has been replicated in numerical simulations. Lévy flight patterns are found to be an inconsequential emergent property of a bumblebees’ foraging behaviour. Lévy flights are predicted to emerge when bees reject at least 99% of previously visited flowers. A foraging bumblebee can certainly empty a clover flower head of nectar in one visit, but lower rates of rejection are observed for many other flowers. These findings suggest that Lévy flight patterns in foraging bumblebees are rare and specific to a few flower species and that if they exist, then they are not part of an innate, evolved optimal searching strategy.     

The role of thermoregulation in lizard biology: Predatory efficiency in a temperate diurnal basker

Summary Decreasing levels of simulated solar radiation have the following effects in the diurnal basking lizard Lacerta vivipara: (i) increase in time spent basking with a consequent decrease in time available for foraging (ii) decrease in speed of movement whilst foraging (iii) decrease in total foraging distance, and hence contact with potential prey (iv) decrease in searching efficiency in an experimental arena. Complete absence of simulated solar radiation accentuates these effects, and reduces the proportion of faster-moving prey in the diet. Time taken to swallow prey (handling time) increases exponentially with decreasing body temperature. It is concluded from these results that maintaining relatively high activity temperatures (30–36°C) is adaptive for the species because the loss of potential foraging time caused by lengthy periods of basking is offset by the following advantages: increased contact with and capture of prey, increased efficiency of prey handling, and availability of a wider range of prey types.     

GPS tracking a marine predator: the effects of precision,resolution and sampling rate on foraging tracks of African Penguins

We used a prototype GPS logger to track the movements of breeding African Penguins (Spheniscus demersus). The loggers also recorded temperature and water depth, which allowed us to reconstruct foraging tracks in three dimensions, although GPS signals are interrupted when the birds dive. Here we report the loggers performance in the field and assess the effects of GPS error, resolution and sampling rate on estimates of foraging track length and speed. There is a trade-off between sampling rate and battery lifespan. We tested loggers at sampling intervals of 1 s, 10 s, 1 min, 2 min and 10 min. Sampling less frequently increases the chance of tracking an entire foraging trip, but it slows uplink times, slightly decreases the accuracy of positional fixes, and significantly reduces the ability to measure fine-scale aspects of foraging behaviour. Compared with radio or satellite tracking, GPS loggers offer unprecedented detail about animal movements. The results of our analysis suggest that techniques that sample relatively infrequently, such as satellite tracking, underestimate actual track lengths by up to 50%. However, caution is needed when interpreting fine-scale sampling for relatively slow-moving organisms. Re-sampling 1-s tracks suggests that c. 35% of apparent movements at this scale are due to measurement error and, more importantly, the limited spatial resolution of GPS (1.85×1.54 m at the study area). We recommend that researchers use a 1-s sampling rate for fine-scale studies, but resample at less frequent intervals to remove spurious noise for slow-moving animals. At current levels of resolution, animals should move at least 4 m per sampling interval. We provide empirical correction factors to compare inferred track length sampled at different rates, but caution that these are idiosyncratic and strongly dependent on the animals behaviour. Overall, GPS loggers offer a significant advance for studies of fine-scale animal movement patterns.Communicated by O. Kinne, Oldendorf/Luhe     

Female siskins choose mates by the size of the yellow wing stripe

Commonly, female birds use the brightly coloured patches on males to choose the best-quality mates. Coloured wing patches, however, have received little attention or have been previously related to social behaviour (as a signal to recruit conspecific individuals at feeding patches) or foraging (to flush prey) contexts, rather than to sexual selection. Here we provide evidence that in siskins (Carduelis spinus), wing patches function in mate choice. Mate-choice experiments showed that females were attracted by the size of the yellow wing stripe of the male, but not by the size of its black bib, body size, general plumage brightness or age. Experiments on birds with manipulated yellow wing stripes showed that females were sensitive to the size of this colour patch, irrespective of other male qualities. The preference of female siskins for males with larger wing patches when searching for a mate may be explained by the relationship of this trait to foraging ability, which would ensure females good parental investment from the chosen male.Communicated by W.A. Searcy     

All clear? Meerkats attend to contextual information in close calls to coordinate vigilance

Socio-demographic factors, such as group size and their effect on predation vulnerability, have, in addition to intrinsic factors, dominated as explanations when attempting to understand animal vigilance behaviour. It is generally assumed that animals evaluate these external factors visually; however, many socially foraging species adopt a foraging technique that directly compromises the visual system. In these instances, such species may instead rely more on the acoustical medium to assess their relative risk and guide their subsequent anti-predator behaviour. We addressed this question in the socially foraging meerkat (Suricata suricatta). Meerkats forage with their head down, but at the same time frequently produce close calls (‘Foraging’ close calls). Close calls are also produced just after an individual has briefly scanned the surrounding environment for predators (‘Guarding’ close calls). Here, we firstly show that these Guarding and Foraging close call variants are in fact acoustically distinct and secondly subjects are less vigilant (in terms of frequency and time) when exposed to Guarding close call playbacks than when they hear Foraging close calls. We argue that this is the first evidence for socially foraging animals using the information encoded within calls, the main adaptive function of which is unrelated to immediate predator encounters, to coordinate their vigilance behaviour. In addition, these results provide new insights into the potential cognitive mechanisms underlying anti-predator behaviour and suggest meerkats may be capable of signalling to group members the ‘absence’ of predatory threat. If we are to fully understand the complexities underlying the coordination of animal anti-predator behaviour, we encourage future studies to take these additional auditory and cognitive dimensions into account.     

Modeling high-frequency position data of large herbivores with a phase-state model

Understanding the rules and factors that drive the foraging behavior of large herbivores is important to describe their interaction with the landscape at various spatial scales. Some unresolved questions refer to landscape-behavioral interactions that result in oriented or random search in seasonally changing landscapes. Remotely sensed position data indicate that herbivores select local patches of heterogeneous landscapes depending on a complex host of dynamically varying animal and environmental conditions. Since foraging paths consist in successions of relatively short steps, increasing the frequency at which position information is acquired would contribute to entangle the mechanisms resulting in herbivores’ foraging paths. We addressed the question whether herbivores would obtain information at a patch scale that would modify their distribution at a landscape scale based on directed movement or navigation ability. We considered a set of 100,000 high-frequency (1 min intervals) position data of several free-ranging sheep (Ovis aries) at a seasonal-varying range (Patagonian Monte, Argentina) and observed their movements at landscape and at single vegetation patch scales. At a landscape scale, we inspected the spatial co-variation of seasonally varying forage offer and ewes’ movement speeds. At a patch scale, we developed a phase-state (P-S) model of movement cycles based on the occurrence of behavioral phases along foraging paths, and fitted it to the observed daily time series of ewes’ movement speeds. Ewes were preferentially distributed in areas with high forage offer during periods of low forage availability and the reverse occurred during the season of high forage availability. Parameters of the model of activity cycles amenable to control by ewes (duration of speed phases, time elapsed between speed cycles) did not covariate with forage offer, but varied significantly among ewes. The shape (kurtosis) parameter of the model of movement cycles, one which is unlikely under ewes’ control, co-varied significantly with spatial forage offer but did not differ among ewes. We conclude that ewes allocated foraging time along a series of similar movement efforts irrespective of forage availability at small patches. Average forage scarcity at multi-patch level increases the ratio of searching to feeding time. This results in apparent selective time allocation to richer forage areas but does not imply evidence for oriented movement at a landscape scale. We advance a behavioral-based definition of forage patches and discuss its implications in developing foraging theory and models. The P-S model applied to high-frequency position data of large herbivores substantially improves the interpretation of the factors controlling their time allocation in space with respect to previous models of herbivore spatial behavior by discriminating among behavioral-based and environmentally induced components of their movements.