Prey Movement Research Articles

Biting releases constraints on moray eel feeding kinematics

We present an analysis of prey capture functional morphology in eels by comparing two species of moray eels, Muraena retifera and Echidna nebulosa (Family Muraenidae), to the American eel Anguilla rostrata (Family Anguillidae). The skulls of both moray species exhibited extreme reductions of several prominent components of the suction-feeding mechanism, including the hyoid bar, the sternohyoideus muscle and the pectoral girdle. Associated with these anatomical modifications, morays showed no evidence of using suction during prey capture. From 59 video sequences of morays feeding on pieces of cut squid we saw no hyoid depression and no movement of prey toward the mouth aperture during the strike, a widely used indicator of suction-induced water flow. This was in contrast to A. rostrata, which exhibited a robust hyoid, sternohyoideus muscle and pectoral girdle, and used suction to draw prey into its mouth. Average prey capture time in morays, about 500 ms, was roughly 10 times longer than in A. rostrata, and morays frequently reversed the direction of jaw and head rotation in the midst of the strike. We tested whether the absence of suction feeding reduces temporal constraints on feeding kinematics, permitting greater variance in traits that characterize timing and the extent of motion in the neurocranium, by comparing moray eel species with A. rostrata, two Centrarchids and a cichlid. Kinematic variance was roughly 5 times higher in morays than the suction-feeding species. Prey capture by suction demands a rapid, highly coordinated series of cranial movements and the loss of this mechanism appears to have permitted slower, more variable prey capture kinematics in morays. The alternative prey capture strategy in morays, biting, may be tied to their success as predators in the confined spaces of reef crevices where they hunt for cephalopods, crustaceans and fish.

The predictive start of hunting archer fish: a flexible and precise motor pattern performed with the kinematics of an escape C-start

Once their shots have successfully dislodged aerial prey, hunting archer fish monitor the initial values of their prey's ballistic motion and elicit an adapted rapid turning maneuver. This allows these fish to head straight towards the later point of catch with a speed matched to the distance to be covered. To make the catch despite severe competition the fish must quickly and yet precisely match their turn and take-off speed to the initial values of prey motion. However, the initial variables vary over broad ranges and can be determined only after prey is dislodged. Therefore, the underlying neuronal circuitry must be able to drive a maneuver that combines a high degree of precision and flexibility at top speed. To narrow down which neuronal substrate underlies the performance we characterized the kinematics of archer fish predictive starts using digital high-speed video. Strikingly, the predictive starts show all hallmarks of Mauthner-driven teleost C-type fast-starts, which have previously not been noted in feeding strikes and were not expected to provide the high angular accuracy required. The high demands on flexibility and precision of the predictive starts do not compromise their performance. On the contrary, archer fish predictive starts are among the fastest C-starts known so far among teleost fish, with peak linear speed beyond 20 body lengths s(-1), angular speed over 4500 deg. s(-1), maximum linear acceleration of up to 12 times gravitational acceleration and peak angular acceleration of more than 450 000 deg. s(-2). Moreover, they were not slower than archer fish escape C-starts, elicited in the same individuals. Rather, both escapes and predictive starts follow an identical temporal pattern and all kinematic variables of the two patterns overlap. This kinematic equivalence strongly suggests that archer fish recruit their C-start escape network of identified reticulospinal neurons, or elements of it, to drive their predictive starts. How the network drives such a rather complex behavior without compromising speed is a wide open question.

Amphibian Biology and Husbandry

Extant amphibians comprise three lineages-- salamanders (Urodela or Caudata), frogs and toads (Anura), and caecilians (Gymnophiona, Apoda, or Caecilia)--which contain more than 6,000 species. Fewer than a dozen species of amphibians are commonly maintained in laboratory colonies, and the husbandry requirements for the vast majority of amphibians are poorly known. For these species, a review of basic characteristics of amphibian biology supplemented by inferences drawn from the morphological and physiological characteristics of the species in question provides a basis for decisions about housing and feeding. Amphibians are ectotherms, and their skin is permeable to water, ions, and respiratory gases. Most species are secretive and, in many cases, nocturnal. The essential characteristics of their environment include appropriate levels of humidity, temperature, and lighting as well as retreat sites. Terrestrial and arboreal species require moist substrates, water dishes, and high relative humidity. Because temperature requirements for most species are poorly known, it is advisable to use a temperature mosaic that will allow an animal to find an appropriate temperature within its cage. Photoperiod may affect physiology and behavior (especially reproduction and hibernation), and although the importance of ultraviolet light for calcium metabolism by amphibians is not yet known, ecological observations suggest that it might be important for some species of frogs. Some amphibians are territorial, and some use olfactory cues to mark their territory and to recognize other individuals of their species. All amphibians are carnivorous as adults, and the feeding response of many species is elicited by the movement of prey. Diets should include a mixture of prey species, and it may be advisable to load prey with vitamins and minerals.

A Minimal Model of Pursuit-Evasion in a Predator-Prey System

A conceptual minimal model demonstrating spatially heterogeneous wave regimes interpreted as pursuit-evasion in predator-prey system is constructed and investigated. The model is based on the earlier proposed hypothesis that taxis accelerations of prey and preda- tors are proportional to the density gradient of another population playing a role of taxis stimulus. Considering acceleration rather than immediate velocity allows obtaining realistic solutions even while ignoring variations of total abundances of both modelled populations. Linear analysis of the model shows that stationary homogeneous regime becomes oscillatory unstable with respect to small heterogeneous perturbations if either taxis activities or total population abundances are high enough. The ability for active directed movement of both prey and predators is the necessary condition for spatial self-organization. Numerical simula- tions illustrate analytical results. The relation between the proposed model and conventional two-component systems with cross-difiusion is discussed.

Seasonal use of Amazon floodplains by the tucuxi Sotalia fluviatilis (Gervais 1853), in the central Amazon, Brazil

The riverine tucuxi, Sotalia fluviatilis (Gervais, 1853), inhabits an aquatic environment that changes dramatically along the year. The marked annual floods impose a seasonal rhythmicity on the wildlife on these floodplains. The present study provides an insight on tucuxi seasonal use of floodplain, use of area, group size and the occurrence of calves or juveniles within Mamiraua Reserve, Brazilian Amazon. Tucuxis occur year-round in Mamiraua with a mean number of sightings per monthly survey of 3.8. The fluctuating water level in this floodplain influenced tucuxi use of area by allowing or preventing access to water bodies, and influencing its prey movements. The highest encounter rate recorded in the Reserve, for all surveys combined, was 114.3 tucuxis per km (mean = 24.8 per km) with clear tucuxi preference for deep channels with high turbulence and productivity, where prey density is high. Tucuxis were scattered throughout the channels but avoided the lake Mamiraua. Groups of one to 30 tucuxis were recorded, with 91% of groups comprising one to six dolphins (mean = 3.3). Group size showed significant differences among the five systems studied across visual surveys, between years within Mamiraua but not among months. Tucuxi calves or juveniles were recorded year-round.

Diel and tidal rhythms in diving behaviour of pelagic sharks identified by signal processing of archival tagging data

Patterns of vertical movement in pelagic predators can be highly complex, reflecting behaviours such as foraging, thermoregulatory excursions and spawning. Here we used fast Fourier analysis to identify periodicity in the vertical movements of 6 basking sharks Cetorhinus maximus from archival tagging data that totalled 595 d. We analysed quantitatively fine-scale vertical movements of basking sharks over seasonal scales (May to February) and detected predominant periodicities related to the vertical movements of the sharks' zooplankton prey. Normal and reverse diel vertical migration (DVM) represented the main periodic dive behaviour, occurring for 11 to 72% of individual track times. A tidal pattern of vertical movement, previously unreported for sharks, was also identified. A possible mechanism for this behaviour appears related to the shark exploiting tidally-induced aggregations of zooplankton prey at depth. The youngest shark tagged showed a markedly different pattern of vertical behaviour. Long-term data sets of swimming depth are becom- ing increasingly available for pelagic predators from pressure-sensitive data loggers. This study demonstrates the utility of signal processing techniques in objectively identifying both expected and unexpected periodicity in these continuous, high-resolution tracks.

Use of Prey Hotspots by an Avian Predator: Purposeful Unpredictability?

The use of space by predators in relation to their prey is a poorly understood aspect of predator-prey interactions. Classic theory suggests that predators should focus their efforts on areas of abundant prey, that is, prey hotspots, whereas game-theoretical models of predator and prey movement suggest that the distribution of predators should match that of their prey's resources. If, however, prey are spatially anchored to one location and these prey have particularly strong antipredator responses that make them difficult to capture with frequent attacks, then predators may be forced to adopt alternative movement strategies to hunt behaviorally responsive prey. We examined the movement patterns of bird-eating sharp-shinned hawks (Accipiter striatus) in an attempt to shed light on hotspot use by predators. Our results suggest that these hawks do not focus on prey hotspots such as bird feeders but instead maintain much spatial and temporal unpredictability in their movements. Hawks seldom revisited the same area, and the few frequently used areas were revisited in a manner consistent with unpredictable returns, giving prey little additional information about risk.

MODEL ODOR-ORIENTED PREDATORS AND PREY

The model of predators and prey, in which the predator judges the direction of prey's movement on the basis of the density of prey's odor will be researched in this article. The predator' s sensitivity to prey's odor is defined, so that can be simulated by Monte Carlo in L × L. It suggests the relationship between system stability and each value of Predator's sensitivity. We get three system states for different value of α (predator's sensitivity): the grass only, prey and the grass, three species in coexistence, with predators, prey and grass. But the probability of each system state is different. Their corresponding distribution will be given in this article.

Effects of temporal patterning of predation threat on movement of a stream fish: evaluating an intermediate threat hypothesis

The addition of nocturnal, Hoplias malabaricus, and diurnal, Crenicichla alta, predatory fishes downstream of barrier waterfalls increases predation threat for a killifish, Rivulus hartii, in Trinidadian streams. We hypothesized that the diel patterning of predation risk would affect prey movement rates, and tested this hypothesis by comparing movement in river sites/zones containing both the nocturnal and diurnal predator with movement in river sites/zones containing only the nocturnal taxon. We evaluated this prediction in the framework of an intermediate threat hypothesis (ITH) that holds that movement will be highest at some intermediate level of threat. We marked prey fish in study sites in two watersheds of a river, each with waterfalls that divided the river into three zones: a predator absent zone (P0), a zone with one nocturnal predator (P1), and a zone with one nocturnal and one diurnal predator (P2), and tested the ITH prediction that movement will be ordered as P0 P2. The single predator promoted longitudinal movement by Rivulus (P0 P2) as predicted by the ITH. However, movement by larger, less vulnerable Rivulus remained elevated (P1=P2 or P2>P1). A displacement experiment in each zone found that threat tended to reduce the probability of a displaced fish reaching home, but the two predator zones did not differ from one another in their effect on this probability. Hence, the prediction that predator activity over the full 24 h diel cycle would retard movement, P2<P1, was not supported with respect to homing. Because habitat and predator communities change predictably from headwater streams to larger rivers in many lotic ecosystems, we present a conceptual model for predicting fish movement behavior along this continuum. The model posits an important role for predation threat, and the size and spacing of refuge patches, suggesting that human alterations of these factors will affect the natural movement of fish in streams.

Food preferences of grey partridge chicks, Perdix perdix, in relation to size, colour and movement of insect prey

With continually changing arable farming practices, knowledge of the invertebrates in the chick diet of many farmland bird species is important, as it can help in their habitat management and conservation. Although studies have found which groups are represented in the diet, this does not necessarily mean these items are preferred. To gain some understanding of the basic principles underlying a chick's choice of food, we fed grey partridge chicks different insect taxa and coloured food pellets to determine whether preference was related to size, colour or movement of the food items. Trials were conducted against white, brown and green backgrounds. There were significant differences in the overall selection of insect taxa, with wide differences in the probability of selection between items. With no movement, choice was primarily influenced by size and colour. Colour influenced selection for similarly sized items, with a preference for green/yellow over brown/black, but size also affected choice within the most preferred colours. Red was least selected. With live insects, colour and size again had the greatest effect on choice, but movement also affected the selection of smaller items. Selection of uniformly sized coloured food pellets gave a similar colour selection choice to that obtained with insects. However, in natural habitats the preferred larger items, generally green/yellow, could be more difficult to see if immobile and cryptically coloured. They might also be located on vegetation and physically unavailable, restricting choice to the smaller, often active, but less preferred items.

Cortical Area MSTd Combines Visual Cues to Represent 3-D Self-Movement

As arboreal primates move through the jungle, they are immersed in visual motion that they must distinguish from the movement of predators and prey. We recorded dorsal medial superior temporal (MSTd) cortical neuronal responses to visual motion stimuli simulating self-movement and object motion. MSTd neurons encode the heading of simulated self-movement in three-dimensional (3-D) space. 3-D heading responses can be evoked either by the large patterns of visual motion in optic flow or by the visual object motion seen when an observer passes an earth-fixed landmark. Responses to naturalistically combined optic flow and object motion depend on their relative directions: an object moving as part of the optic flow field has little effect on neuronal responses. In contrast, an object moving separately from the optic flow field has large effects, decreasing the amplitude of the population response and shifting the population's heading estimate to match the direction of object motion as the object moves toward central vision. These effects parallel those seen in human heading perception with minimal effects of objects moving with the optic flow and substantial effects of objects violating the optic flow. We conclude that MSTd can contribute to navigation by supporting 3-D heading estimation, potentially switching from optic flow to object cues when a moving object passes in front of the observer.

Pikeperch habitat use within a canal network in spring

Thirteen pikeperch Sander lucioperca were implanted with acoustic transmitters and 10 were successfully tracked twice a week from March to early July in a drainage canal connected to a brackish lagoon located in the Rhône delta. Pikeperch was found in the main canal and in narrow tributaries, but never in the lagoon. Pikeperch avoided shallow parts of the canal and selected areas with high riparian vegetation (mainly trees). No between sexes differences occurred in habitat selection. At the basin scale, while both sexes remained in the upstream part of the canal during the spawning period, after spawning, females migrated downstream and also into the tributaries. This migration may have been induced by the movement of prey while males remained guarding the nests.

Scale dependent effects of predatory fish on stream benthos

In open predation experiments the effects of predators on prey densities can be influenced by predator consumption and by prey movements in to and out of experimental arenas. A published model predicts that the predator effects observed in such experiments are scale dependent over the scale range where there is a transition from movement control (of prey densities) to consumption control. The scale dependence follows from the assumption that per capita rate of emigration out of an experimental arena decreases with increasing arena size.To test this model the effects of a small benthic fish (Cottus gobio) on densities of stream invertebrates was investigated in instream channels of different length (0.5, 2 and 8 m). The effect of fish predation was scale dependent for four prey taxa. For three of these taxa predator effects increased with experimental scale, which is in agreement with model predictions. However, this proved to be a case of “making the right prediction for the wrong reason” as the basic assumption of scale dependent emigration rate was not upheld. By analyzing the behaviour of the model, parameterized with emigration and consumption rates observed in the experimental channels, it was found that observed scale effects occurred because prey emigration in response to the predator treatment was modified by the experimental scale. Further analysis of the parameterized model suggested that the densities of most prey taxa were controlled by prey movements and not by consumption by the sculpins.

Planning for success: Serengeti lions seek prey accessibility rather than abundance

Summary We used long‐term radio‐telemetry data to investigate how Serengeti lions (Panthera leo) distribute themselves with respect to hunting opportunities. Specifically, we investigate whether lions hunt in areas where prey are easy to capture or where prey are locally abundant. We used resource‐selection functions (logistic regressions) to measure the location of kills/carcasses with respect to five different habitats: the view‐sheds from large rocky outcrops, river confluences, woodland vegetation, erosion embankments and water sources. As expected for a sit‐and‐wait predator, resting lions spent more time in areas with good cover. On a broad‐scale, lions shifted their ranges according to the seasonal movement of prey, but at a finer scale (&lt; 100 m) lions fed in areas with high prey ‘catchability’ rather than high prey density. Plains lions selected erosion embankments, view‐sheds from rocky outcrops, and access to free water. Woodland lions tended to use erosion embankments, and woody vegetation. The results emphasize the importance of fine‐scale landscape and habitat features when assessing predator–prey theory and conservation.

TROUT PREDATORS AND DEMOGRAPHIC SOURCES AND SINKS IN A MAYFLY METAPOPULATION

Habitat patches often differ in environmental conditions, and the degree of environmental heterogeneity among patches is thought to influence population dynamics at the regional (metapopulation) scale. In a previous study, I found evidence of a source– sink dynamic in a metapopulation of the mayfly Callibaetis ferrugineus hageni occupying beaver ponds with or without brook trout predators, where adult females frequently dispersed among ponds, and frequently oviposited in ponds with trout. Here, I tested the hypothesis that trout create habitat sinks by manipulating trout densities and estimating local population growth rates (λ) of Callibaetis. In addition, Callibaetis emergence rates were estimated in the mayfly generation before the manipulation. Among ponds, λ ranged from 0.062 to 2.631, and nine Monte Carlo simulations scenarios revealed that four ponds had λ significantly below replacement (sinks) while the presence of source ponds was less conclusive. The manipulation of trout did not result in a detectable treatment effect, perhaps because of low statistical power resulting from high within-treatment variation in trout densities. However, point estimates of λ and emergence rates were negatively and exponentially related to trout density, such that nearly all ponds with more than 1 trout/100 m2 were sinks. Further, multiple regression analyses were consistent with the hypothesis that trout reduced λ and emergence rates, while other biotic and abiotic factors did not provide explanatory power. The results support the hypothesis that source–sink population dynamics may be common in freshwater habitats, and that prey metapopulation dynamics may be predicted from the distribution of predators, prey movement and habitat selection behaviors, and factors influencing the outcome of predator–prey interactions.

Mean free-path length theory of predator–prey interactions: Application to juvenile salmon migration

Ecological theory traditionally describes predator–prey interactions in terms of a law of mass action in which the prey mortality rate depends on the density of predators and prey. This simplifying assumption makes population-based models more tractable but ignores potentially important behaviors that characterize predator–prey dynamics. Here, we expand traditional predator–prey models by incorporating directed and random movements of both predators and prey. The model is based on theory originally developed to predict collision rates of molecules. The temporal and spatial dimensions of predators–prey encounters are determined by defining movement rules and the predator's field of vision. These biologically meaningful parameters can accommodate a broad range of behaviors within an analytically tractable framework suitable for population-based models. We apply the model to prey (juvenile salmon) migrating through a field of predators (piscivores) and find that traditional predator–prey models were not adequate to describe observations. Model parameters estimated from the survival of juvenile chinook salmon migrating through the Snake River in the northwestern United States are similar to estimates derived from independent approaches and data. For this system, we conclude that survival depends more on travel distance than travel time or migration velocity.

Temporal changes in feeding habits and daily rations of Hoplostethus mediterraneus in the bathyal Ionian Sea (eastern Mediterranean)

Data on the diet, feeding habits and daily rations of Hoplostethus mediterraneus Cuvier, 1829 in the bathyal eastern Ionian Sea (Mediterranean Sea) are presented. A total of 430 specimens collected by bottom trawls at depths ranging from 473 to 603 m during four 24-h day–night sampling cycles covering the four annual seasons was examined. H. mediterraneus diet consisted of pelagic and vagile epibenthic prey, mainly crustaceans, and was dominated by benthopelagic natantian decapods (83.35% IRI, index of relative importance). Seasonal changes in diet were apparent and related to seasonal fluctuations in suprabenthic and zooplanktonic prey in the environment. Diel patterns in stomach fullness and trends in diel feeding cycles are discussed in relation to the vertical migratory movements of available prey (i.e. suprabenthos and zooplankton). Daily-ration estimates were determined by evacuation-rate models and ranged from 0.143% to 0.397% WW/WW. Overall, daily-ration estimates were within the range of the daily consumption of other deep-sea fish. Deduced from diet contents, we found a constant gross energy intake (305–316 kcal g–1) during all seasons. As a possible response to the reproductive peak of mature females observed in summer, H. mediterraneus increases its food consumption, which, in turn, is coupled with an increase in food availability.

Visible Verbs Become Spoken

Many movements that humans see naturally suggest something other than themselves. This is a legacy from the remotest time. Among animals, movements of prey and predator give each an indication of what may happen next and a basis for choosing their own actions. As species evolved, the movements that could be made and the meanings that could be suggested in those movements became increasingly sophisticated. Among the higher primates, grooming, aggressive and submissive displays, begging, and other movements regulate complex social interactions. Humans also interpret movements; they inform us of what others do, what happens to things, and how a movement maker feels—all this is instinctive. It has been understood for a long time that movements, gestures, among them, have semantic interpretations. The argument of these chapters, however, is that syntactic interpretation has also evolved and is also eminently natural. Humans not only make, see, and interpret movement but also discern patterns in it: "Something dropped," "That one leapt," "She took it." Movements, when they become the primary symbols of a sign language, have a syntactic structure that can represent these patterns and many others that grow out of them. Sounds can alarm, warn, beckon, threaten, and so on; but unaided by convention they cannot represent nounlike or verblike concepts. Powerless to make even this fundamental grammatical distinction, [End Page 152] sounds have no natural, direct way to show concepts linked in the relationship called predication or syntax. Only convention can link sounds to word meanings and sentence meanings. Click for larger view Figure 1 The direction of movement of a sign can be crucial to understanding the meaning of the sign. Primary sign languages are more natural than spoken languages because a visible sign often carries a visual clue to what it signifies. For example, the meaning of "I give" reverses the meaning of "I was given." Gestured, the two meanings are clearly opposite: the former sign moves outward from the signer; "I was given" moves toward the signer (see fig. 1). But when meanings like these are spoken in English, one must know the language to understand the crucial difference between them. To a speaker or reader of English, the auxiliary was signals the difference. Using was reverses the direction of the giving, but neither the vocal sounds that compose was nor the word itself refer to the direction of transitivity. In a sign language, however, what is given goes from the giver to the receiver; no rule is needed until language becomes spoken. Humans possess an innate, clear understanding, gained early in life, that movement (of anything) toward self differs from movement away from self. Infants acquire this understanding when activity around them and their own hands and eyes and brain circuitry bring [End Page 153] it into their ken. Later, of course, well beyond the period of infancy, they learn that a speaker's use of active or passive voice signals this basic reversal of direction, which was clear to them previously. Speakers of languages have had to come up with various devices to indicate the difference between giving and being given and the whole active/passive distinction. Signers simply make opposed movements to signal the reversal of direction. This relationship of language sign to meaning is not derived from abstract rules. We first understood the active/passive meaning difference by seeing, moving, feeling—by physical experience cognized. Observing the direction of physical actions is so simple and obvious that one may wonder why spoken languages need complex active—passive rules; but the explanation is obvious: sounds that voices make can no more directly indicate the difference between give and receive than that between to and from. As the previous chapter revealed, alternate sign languages used by hearing people may differ from primary sign languages used by those who are deaf, but whether the difference is deep-seated or only one of degree has yet to he determined. If an alternate sign language fully represents a spoken language, it is just as correct to...

Retinal specialisations in the dogfish &lt;i&gt;Centroscymnus coelolepis&lt;/i&gt; from the Mediterranean deep-sea

The present work attempted to study the importance of vision in Centroscymnuscoelolepis , the most abundant shark in the Mediterranean beyond a depthof 1000 m, by using anatomical and histological data. C.coelolepis exhibited large lateral eyes with a large pupil, spherical lens and a tapetum lucidum that gave the eye a strong greenish-golden “eye shine”. In the outer retinal layer, a uniform population of rod-like photoreceptors was observed while in the vitreal retina a thick inner plexiform layer comprised up to 30% of the whole retinal thickness. The cell distribution of the ganglion cell layer formed a thin elongated visual streak in the central plane of the eye that provided a horizontal panoramic field of view. A specialised area of higher visual acuity was located caudally at 32-44o from the geometric centre of the retina and 5-10o above the horizontal plane of the eye. This position indicated that the visual axis pointed in a slightly outward-forward direction with respect to the fish body axis. A non-uniform distribution of large ganglion cells was also found in the horizontal plane of the retina that practically coincided with the distribution of the total cell population in the ganglion cell layer. This is the first time that this type of retinal specialisation has been observed in the elasmobranchs. These characteristics indicate that the retina of C.coelolepis is designed not only to increase sensitivity in the horizontal field of view, as was also observed in other sharks, but also to improve motion detection in the same plane. The visual capacities evolved by C.coelolepis make this species adapted for discriminating the horizontal gradation of light that exists in the mesopelagic environment. Similarly, the large ganglion cell distribution observed in its retina seems to be related to its predatory behaviour, since it allows this shark to perceive the movement of bioluminescent prey against a totally dark background.

Spotted hyenas (Crocuta crocuta) follow migratory prey. Seasonal expansion of a clan territory in Etosha, Namibia

AbstractThe spatial organization of one clan of spotted hyenas Crocuta crocuta in the centre of the Etosha National Park, Namibia, is described during the dry and the wet seasons. The clan comprised 11 adults and sub‐adults and occupied a territory of 160 km2 in the dry season and 320 km2 in the wet season. The dry season territory contained a low density (one animal/km2) of resident herbivores, such as gemsbok Oryx gazella, kudu Tragelaphus strepsiceros, giraffe Giraffa camelopardis, steenbok Raphicerus campestris and ostrich Struthio camelus, and a higher density of migratory species (12 animals/km2), principally springbok Antidorcas marsupialis, zebra Equus burchelli and wildebeest Connochaetes taurinus. These migratory species were the main prey of clan members. At the start of the wet season, the migratory herbivores migrated to the north‐west, resulting in a considerable decline in the density of prey in the area used by clan members during the dry season. In response to this decline in prey, clan members followed the migratory herds and shifted the focus of their activities to an area grazed by migratory herbivores during the wet season. There existed a strong spatial relationship between the hyena density and the migratory prey density in both the dry and wet season. We postulate that the considerable enlargement of the clan territory in the wet season is a response to both the migratory movements of prey and an increase in the dispersion of prey during the wet season.