Ambush Sites Research Articles

Spatial ecology and microhabitat selection of the nocturnal pitviper Viridovipera stejnegeri (Squamata: Viperidae) in relation to prey.

Habitat is fundamental for facilitating various life activities in animals, for instance, snakes procure essential energy for survival and reproduction by selecting ambush microhabitats. While there has been extensive research on the selection of microhabitat for feeding in terrestrial and aquatic snakes, little is known about arboreal snakes. In the present study, we analyzed the ambush microhabitat preferences of Viridovipera stejnegeri, a widely distributed Asian pitviper in China, conducted association analysis between snake microhabitat and prey microhabitat and abundance to determine the ro5le of microhabitat selection in feeding. Employing random forest analysis and habitat selection functions, we further constructed a predictive framework for assessing the probability of ambush site selection by V. stejnegeri. Our results revealed that V. stejnegeri exhibited a distinct microhabitat preference for ambush prey. Among the 13 environmental factors assessed, V. stejnegeri showed pronounced preferences towards 12 of these factors, including climatic factors, geographical factors, and vegetation factors. Furthermore, although the preferences of V. stejnegeri overlapped substantially with those of its prey across multiple habitat factors, food abundance shows no significant association with various habitat factors of V. stejnegeri, and does not have significant predictive effect on habitat selection of V. stejnegeri. Therefore, we infer that V. stejnegeri does not preferentially select microhabitats with the highest food abundance, which does not support the hypothesis that "snakes select habitats based on the spatial distribution of prey abundance." By analyzing the characteristics of vegetation, geography, and climate, we conclude that V. stejnegeri tends to choose microhabitats with better ambush conditions to increase attack success rate, thereby achieving the optimal feeding success rate at the microhabitat scale, which is in line with the predictions of optimal foraging theory. This study provides new insights into the predation ecology and habitat selection of snakes.

Hunting behavior and feeding ecology of Mojave rattlesnakes (Crotalus scutulatus), prairie rattlesnakes (Crotalus viridis), and their hybrids in southwestern New Mexico.

Predators must contend with numerous challenges to successfully find and subjugate prey. Complex traits related to hunting are partially controlled by a large number of co-evolved genes, which may be disrupted in hybrids. Accordingly, research on the feeding ecology of animals in hybrid zones has shown that hybrids sometimes exhibit transgressive or novel behaviors, yet for many taxa, empirical studies of predation and diet across hybrid zones are lacking. We undertook the first such field study for a hybrid zone between two snake species, the Mojave rattlesnake (Crotalus scutulatus) and the prairie rattlesnake (Crotalus viridis). Specifically, we leveraged established field methods to quantify the hunting behaviors of animals, their prey communities, and the diet of individuals across the hybrid zone in southwestern New Mexico, USA. We found that, even though hybrids had significantly lower body condition indices than snakes from either parental group, hybrids were generally similar to non-hybrids in hunting behavior, prey encounter rates, and predatory attack and success. We also found that, compared to C. scutulatus, C. viridis was significantly more active while hunting at night and abandoned ambush sites earlier in the morning, and hybrids tended to be more viridis-like in this respect. Prey availability was similar across the study sites, including within the hybrid zone, with kangaroo rats (Dipodomys spp.) as the most common small mammal, both in habitat surveys and the frequency of encounters with hunting rattlesnakes. Analysis of prey remains in stomachs and feces also showed broad similarity in diets, with all snakes preying primarily on small mammals and secondarily on lizards. Taken together, our results suggest that the significantly lower body condition of hybrids does not appear to be driven by differences in their hunting behavior or diet and may instead relate to metabolic efficiency or other physiological traits we have not yet identified.

A study of individual differences in spatial use of captive sidewinder rattlesnakes Crotalus cerastes

Many species of vipers are known to use ambush sites repeatedly, a phenomenon presumably informed by chemical cues from prey. Experimentally, we limited chemical cue availability and recorded site selection in five captive-born sidewinders Crotalus cerastes during their first active season. Snakes showed individual differences among the study subjects in spatial movement across the season and repeatedly reused specific sites in their enclosures, suggesting spatial memory and individual differences in choices of resting sites. Individual variability in spatial- and object-use and associated memories suggests attention to such should be considered in developing husbandry routines for these captive individuals.

A nocturnally-active predator is mainly a diurnal hunter

The sit-and-wait hunter, Cerastes vipera, is a presumed nocturnally-active desert snake, although it feeds mainly on the diurnally-active lizard, Acanthodactylus spp. We hypothesized that nocturnal activity of C. vipera is primarily to locate an ambush site, and that Acanthodactylus spp. is predated mainly diurnally. We used the proportion of free-ranging C. vipera that defaecated per day to estimate daily feeding rate, and prey capture per night to estimate nocturnal feeding rate. In adult snakes (n = 161), defaecation was observed in 20.5% and nocturnal feeding in 3.1% per day. The difference between the two estimates represented the diurnal feeding rate, that is, 85% of the daily feeding was diurnal. All vipers ceased movement near midnight, when approximately 50% were in ambush. They maintained their position until morning and four individuals of each sex were followed during the day. These vipers displayed caudal luring in the presence of Acanthodactylus spp., ended ambush at approximately 10:00 when air temperature reached 40 °C, and then moved into a nearby burrow. We concluded that nocturnally-active C. vipera adults are mainly diurnal hunters, but could be classified as cathemeral predators. Diurnal caudal luring and differences in ambush strategy in C. vipera are documented for the first time.

TEMPERATURE-BASED AMBUSH SITE SELECTION IN SIDEWINDER RATTLESNAKES (CROTALUS CERASTES)

Body temperature influences the activity and behavior of reptiles, with warmer body temperatures typically being associated with improved performance. Nocturnal ambush-hunting rattlesnakes would therefore benefit from selecting warmer substrate hunting sites, allowing them to stay in ambush longer as the environment cools and, presumably, to have a higher probability of striking prey successfully. Here, we tested whether free-ranging sidewinder rattlesnakes (Crotalus cerastes) might select ambush sites based on substrate temperature. We used a thermal imaging camera to measure snake body temperature and substrate temperature at ambush sites and random locations. Rattlesnake body temperature showed a strong positive correlation with substrate temperature at the ambush site, and the substrate at ambush sites was significantly warmer than randomly chosen sites. This suggests snakes might select ambush sites based on substrate temperature. Desert pit vipers appear highly attuned to environmental conditions and might integrate several criteria to select microhabitats that increase predation success.

Do pit-building predators prefer or avoid barriers? Wormlions' preference for walls depends on light conditions

Ambush site selection by sit-and-wait predators is a complex process, involving biotic and abiotic considerations, which greatly affect hunting success and costs. Wormlions are fly larvae that dig pit-traps in loose soil and hunt the arthropod prey falling into their pits. They are abundant in urban environments, found below buildings that provide cover, and many of their pits are dug adjacent to walls. We examined here under what conditions wormlions prefer to dig their pits next to walls. We analysed our dataset in two ways: frequency comparisons among the different treatment combinations and a simulation null model assuming random movement. While the frequency comparisons suggested that wormlions avoided the walls under some cases, the simulation null model suggested that a combination of shallow sand and strong light in the centre led to an attraction towards the walls, independent of the wormlions’ initial location. We suggest that wall attraction results from the certain amount of shade the walls provide. We also demonstrate that shallow sand and strong illumination are unfavourable microhabitats, either leading to more frequent movement or the digging of smaller pits. We locate our results within the broader context of sit-and-wait predators and of animals’ attraction to barriers.

Operations in subterranean systems: Terrain and weather variable

The overall objective of the research is to summarize tactical considerations, resulting from terrain and weather analysis, to support the preparation, planning and execution of subterranean operations. The study used the Grounded Theory for collection, analysis, and systematic treatment of data. The main data sources for the study consisted of purposive sampling from operations in subterranean systems and lessons learned from them. Two new sub-variables are now proposed to be included in terrain and weather variable from mission analysis model for subterranean operations: Subterranean system’s location and accesses and subterranean system features. The key to finding subterranean systems is through terrain analysis, physical ground search, operational indicators, and intelligence products. The analysis of the features of the subterranean system and its mapping is critical for developing courses of action. Forces must be trained and equipped to manoeuvre and combat at short distances and poor visibility conditions. Surface access points and command and control bunkers usually are assessed as key terrain. Obstacles placed at intersections are excellent ambush sites. Accessing sophisticated structures requires specific techniques and equipment. Inside the subterranean systems, existing angles, barriers, walls, cavities, stairwells and other objects provide cover and concealment. Water can make it impossible to build subterranean systems, place obstacles, or even use them; droughts can “create” new avenues of approach. Clouds and fog difficult the detection of subterranean systems. The terrain and weather analysis model, the characteristics, and the tactical considerations presented, all combined, support the preparation, planning, and execution of operations in subterranean systems.

Can an herbivore affect where a top predator kills its prey by modifying woody vegetation structure?

In large mammal communities, little is known about modification of interspecific interactions through habitat structure changes. We assessed the effects of African elephants (Loxodonta africana) on features of woody habitat structure that can affect predator-prey interactions. We then explored how this can influence where African lions (Panthera leo) kill their prey. Indeed, lions are stalk-and-ambush predators and habitat structure and concealment opportunities are assumed to influence their hunting success. During 2years, in Hwange National Park, Zimbabwe, kill sites (n = 167) of GPS-collared lions were characterized (visibility distance for large mammals, distance to a potential ambush site and presence of elephant impacts). We compared characteristics of lion kill sites with characteristics of random sites (1) at a large scale (i.e. in areas intensively used by lions, n = 418) and (2) at the microhabitat scale (i.e. in the direct surrounding available habitat, < 150m, n = 167). Elephant-impacted sites had a slightly higher visibility and a longer distance to a potential ambush site than non-impacted sites, but these relationships were characterized by a high variability. At large scale, kill sites were characterized by higher levels of elephant impacts compared to random sites. At microhabitat scale, compared to the direct nearby available habitat, kill sites were characterized by a reduced distance to a potential ambush site. We suggest a conceptual framework whereby the relative importance of habitat features and prey abundance could change upon the scale considered.

Infrared-sensing snakes select ambush orientation based on thermal backgrounds

Sensory information drives the ecology and behaviour of animals, and some animals are able to detect environmental cues unavailable to us. For example, rattlesnakes use infrared (IR) radiation to detect warm prey at night when visual cues are reduced. Until recently these sensory worlds have been inaccessible to human observers; now technology can allow us to “eavesdrop” on these species and understand how sensory perception drives ecology and behaviour. We used thermography and computer simulations to examine how prey-background temperature contrast and areas of temperature transitions influence the angular orientation of free-ranging rattlesnakes once they have selected an ambush site. We tracked free-ranging sidewinder rattlesnakes Crotalus cerastes to their selected ambush sites and recorded 360° near-ground thermographic panoramas from the centre of the ambush site. A computer simulation then moved a simulated prey item across the panorama and computed a contrast index for all directions. Rattlesnakes did not face ambush directions that offered stronger contrast than average, but they demonstrated a striking tendency to face directions with strong thermal transitions. Background transitions likely create a readily detected, rapidly changing stimulus when a prey animal passes. Quantifications of sensory environments like this one can boost our comprehension of how sensory function impacts the ecology, behaviour, and evolution of animals.

Larger leeches attack from higher ground – size-dependent preferences for ambush sites in the Bornean terrestrial leech Haemadipsa picta

AbstractThe rain forests of South-East Asia represent a biodiversity hotspot of terrestrial leeches, but we have only fragmentary and often anecdotal information on this component of tropical communities. To address the foraging tactics of terrestrial leeches, we studied the vertical distribution ofHaemadipsa pictaon foliage in a Bornean tropical rain forest. We investigated the links between leech body length and the above-ground height of their ambush positions under natural conditions and in a choice experiment performed under semi-natural conditions. We studied 167 leeches, which varied considerably with respect to body length (4–29 mm). On average, the leeches ambushed at lower heights under natural conditions than under experimental conditions (47.7 cm vs. 67.5 cm), though the heights of ambush positions overlapped considerably. Leeches that chose higher ambush positions under natural conditions consistently chose higher ambush positions in the experiment (Pearson r = 0.29). Under both natural and experimental conditions, leech body length was positively correlated with the height of ambush positions (Pearson r = 0.48); on average, a 1-mm increase in body length corresponded to a 2–3 cm higher ambush position. Our findings suggest thatH. pictaindividuals actively choose hunting locations according to their above-ground height, shifting their ambush sites over ontogeny to higher foliage. We hypothesize that growing leeches might target different prey following ontogenetic shifts in the foraging optima, ultimately decreasing intraspecific competition.

Celebrating the canine II: the hunt in Medieval Ireland, with special reference to the evidence of Classical Irish poetry

This paper investigates the nature of the hunt in Medieval Ireland. It confirms from the evidence of Fianaigecht material backed up by contemporary Classical Irish poetry that the hunt was in the nature of a drive and ambush rather than a chase; that two types of hound were used in the hunt, the gadhair to drive the quarry from its covert and the coin to hem it in by securing the corridor to the ambush site, where the latter were slipped on the quarry; that this practice was common in Scotland as well as in continental Europe at the time; and that the deployment of the hunt was an important part of the training of a young nobleman in Ireland. Crossover material reflecting parallels between hound and hero celebration is also investigated.

To forage, mate, or thermoregulate: Influence of resource manipulation on male rattlesnake behavior.

Male animals should preferentially allocate their time to performing activities that promote enhancing reproductive opportunity, but the need to acquire resources for growth and survival may compete with those behaviors in the short term. Thus, behaviors which require differing movement patterns such as ambushing prey and actively searching for mates can be mutually exclusive. Consequently, males that succeed at foraging could invest greater time and energy into mate searching. We radio‐tracked sixteen male massasauga rattlesnakes (Sistrurus catenatus) and supplemented the diets of half the snakes with mice across an active season. We tested the predictions that reduced foraging needs would allow fed snakes to move (i.e., mate search) more, but that they would consequently be stationary to thermoregulate less, than unfed controls. Contrary to our first prediction, we found no evidence that fed snakes altered their mate searching behavior compared to controls. However, we found controls maintained higher body temperatures than fed snakes during the breeding season, perhaps because fed snakes spent less time in exposed ambush sites. Fed snakes had higher body condition scores than controls when the breeding season ended. Our results suggest the potential costs incurred by devoting time to stationary foraging may be outweighed by the drive to increase mating opportunities. Such instances may be especially valuable for massasaugas and other temperate reptiles that can remain inactive for upwards of half their lives or longer in some cases, and for female rattlesnakes that generally exhibit biennial or more protracted reproductive cycles.

Correlated evolution between coloration and ambush site in predators with visual prey lures.

The evolution of a visual signal will be affected by signaler and receiver behavior, and by the physical properties of the environment where the signal is displayed. Crab spiders are typical sit-and-wait predators found in diverse ambush sites, such as tree bark, foliage, and flowers. Some of the flower-dweller species present a UV+ -white visual lure that makes them conspicuous and attractive to their prey. We hypothesized that UV+ -white coloration was associated with the evolution of a flower-dwelling habit. In addition, following up on results from a previous study we tested whether the UV+ -white coloration evolved predominantly in flower-dwelling species occurring in Australia. We measured the reflectance of 1149 specimens from 66 species collected in Australia and Europe, reconstructed a crab spider phylogeny, and applied phylogenetic comparative methods to test our hypotheses. We found that the flower-dwelling habit evolved independently multiple times, and that this trait was correlated with the evolution of the UV+ -white coloration. However, outside Australia non-flower-dwelling crab spiders also express a UV+ -white coloration. Therefore, UV+ -white reflectance is probably a recurring adaptation of some flower dwellers for attracting pollinators, although it may have other functions in non-flower dwellers, such as camouflage.

Observations on the chemosensory responses of the midget faded rattlesnake (Crotalus oreganus concolor): discrimination of envenomated prey in a type II venom species

Rattlesnakes use prey chemical cues for ambush site selection and for relocating envenomated (E) prey following a predatory strike. The ability to discriminate between E and non-envenomated (NE) prey cues has been widely studied in rattlesnake species that produce type I venoms, which show high levels of snake venom metalloproteinase (SVMP) activity and low lethal toxicity [lethal dose which kills 50% of test animals (LD50) >1.0 µg/g]. However, E vs. NE prey discrimination studies have not been conducted on rattlesnake species that produce a type II venom that consists of low SVMP activity and high lethal toxicity (LD50 <1.0 µg/g). In the current study, long-term captive Crotalus oreganus concolor, which produce a type II venom, were tested for their ability to discriminate between chemical cues of natural (Sceloporus undulatus and Peromyscus maniculatus) and non-natural (Hemidactylus frenatus and Mus musculus) prey cues, as well as for their ability to discriminate between E and NE mouse carcasses, when prey envenomation occurred by a conspecific. Snakes showed significant levels of tongue flicking towards the chemical extracts of P. maniculatus and M. musculus, suggesting that C. oreganus concolor exhibit both innate and experience-based plasticity in response to prey chemical cues. In addition, C. oreganus concolor were able to discriminate between E and NE prey sources, when envenomation occurred by a conspecific, indicating that a type II venomous species can also discriminate between E and NE chemical cues.

Food supplementation affects the foraging ecology of a low-energy, ambush-foraging snake

The effect of food availability on the spatial ecology of animals varies within and across study systems because a multitude of factors can affect the spatial activity of organisms. Low-energy specialists, such as ambush-foraging snakes, feed infrequently and can endure long periods without food. Because they have low-energy requirements, one possible tactic for feeding may be to simply ambush for longer periods when prey availability is low, thereby decreasing the potential costs associated with locating new ambush sites. We used radiotelemetry, supplemental feeding, and remote video cameras on free-ranging male puff adders (Bitis arietans) in South Africa to test the hypothesis that food intake affects the foraging ecology of extreme low-energy, ambush foragers and to quantify their natural feeding rates. Supplementally fed puff adders improved their body condition, spent less time foraging, and decreased distance traveled compared to control snakes. However, movement frequency and home range size did not differ between the two groups. These findings indicate that control snakes traveled farther within similar-sized home ranges compared to fed snakes and did so at no survival cost. Further, naturally foraging puff adders successfully caught a prey of small size once every 10 days on average. Hence, despite their “sit-and-wait” foraging strategy and their low-energy intake/requirements, underfed puff adders travel widely to presumably find appropriate ambush sites that maximize prey capture. Our research provides the first strong evidence that the spatial activity of a terrestrial vertebrate species with extremely low energetic demands is significantly affected by food intake. Because animals travel their home range partly to forage, their space use can be affected by the amount of food available in nature. We show that, despite a low-energy lifestyle, the movement level of an ambush-foraging snake that feed infrequently is linked to the amount of food they eat. Underfed snakes traveled greater distances in search of prey, within similar-sized home ranges, compared to well-fed snakes, and they did so at no survival cost. Hence, our research adds to our understanding of the effect of food on the spatial ecology of animals, by providing conclusive evidence that the spatial response of an organism with extremely low-energy demands can be affected by food.

The Foraging Behavior of Free-ranging Rattlesnakes (Crotalus oreganus) in California Ground Squirrel (Otospermophilus beecheyi) Colonies

Abstract Foraging is a key aspect of a species’ ecology and decisions made while foraging affect fitness in many ways. Although much research has focused on snake foraging, only a handful of detailed studies have been conducted on free-ranging individuals, all on Crotalus horridus. We used fixed videography to collect data on free-ranging Northern Pacific Rattlesnake (Crotalus oreganus) behavior to qualitatively test predictions regarding interspecific differences in rattlesnake foraging behavior. We analyzed foraging behaviors based on encounter rates with prey and strike rates on prey, distances moved between consecutive ambush sites, residency time at each site, and poststrike behaviors. Snakes encountered approximately 4 prey/d, with California Ground Squirrels (Otospermophilus beecheyi) being encountered at much higher rates than other prey types. Crotalus oreganus typically did not remain at hunting sites for long durations compared with other species, and generally exhibited short distance movement...

Activity cycles and foraging behaviors of free-ranging sidewinder rattlesnakes (Crotalus cerastes): the ontogeny of hunting in a precocial vertebrate

Predators often employ a complex series of behaviors to overcome antipredator defenses and effectively capture prey. Although hunting behaviors can improve with age and experience, many precocial species are necessarily effective predators from birth. Additionally, many predators experience innate ontogenetic shifts in predatory strategies as they grow, allowing them to adapt to prey more appropriate for their increased size and energetic needs. Understanding how the relative roles of innate age-specific adaptation and learning have evolved requires information on how predation behavior develops in situ, in free-ranging predators. However, most of the research on the ontogeny of predation behavior is based on laboratory studies of captive animals, largely due to the difficulty of following newborn individuals in nature. Here, we take advantage of the unique tracks left by juveniles of a precocial viperid, the sidewinder rattlesnake (Crotalus cerastes), which we used to follow free-ranging snakes in the field. We recorded details of their ambush hunting behavior, and compared the behaviors of these juveniles to adult snakes that we monitored in the field via radio telemetry. Although juvenile and adult behaviors were similar in most respects, we did find that adults chose more effective ambush sites, which may be due to their increased experience. We also found that juveniles (but typically not adults) perform periodic tail undulations while in ambush, and that juveniles displayed slightly different activity cycles. Both of these latter differences are likely the result of age-specific adaptations for juveniles’ greater reliance on lizards versus small mammals as prey. We also compared the general predatory behavior of sidewinders to that of other species in the genus Crotalus. These findings will provide important baseline field information for more detailed empirical research on the ontogeny of predation behavior in precocial vertebrates.

Palestine Saw-scaled Vipers hunt disadvantaged avian migrants

The selection of an ambush-cum-foraging site and proper prey are indispensable for maintaining an adequate energy intake by sit-and-wait predators to optimize survival and future fitness. This is important for snakes, where an ambush site has suitable ambience. We studied the foraging strategy of the Palestine Saw-scaled Viper (Echis coloratus) at an avian migratory stopover site. Following initial observations, we hypothesized that vipers are able to discern the body mass of a perched bird and hunt accordingly. We implemented an experiment where vipers chose between four groups of migratory Blackcaps with different body mass. Prey choice by vipers of both age classes was not random and adults focused on Blackcaps with the lightest body mass. Juveniles displayed a variability of prey choice but selected mainly birds from the lightest categories. We concluded that Saw-scaled Vipers hunt prey based on thermal cues; juveniles practice on different prey groups prior to perfecting their foraging techniques i.e., hunting is a learned process; and that they prefer birds with the lowest body mass. The last because Blackcaps, when on migration, save energy by entering a state of deep torpor in which they sacrifice their vigilance capabilities.

Increases in food availability can tempt oribi antelope into taking greater risks at both large and small spatial scales

Differences in food availability and predation risk can influence how herbivores use landscapes. As a result, trade-offs between costs and benefits can influence habitat and patch selection. To determine how oribi antelope, Ourebia ourebi, weigh up costs and benefits when making habitat and patch level foraging decisions, we measured giving-up densities in artificial patches. First, we determined large-scale habitat use, and then explored how different variables explained patch use within habitats. When the availability of food within patches across the different habitats was equal, oribi preferred to feed in short and tall grasslands and avoided woodlands. Furthermore, the avoidance of woodlands extended into the surrounding grasslands, resulting in oribi feeding less intensively in grassland areas within 15 m of the woodlands. Within the safe grassland habitats, oribi preferred to feed in patches close to tall grass (i.e. escape cover), and where they could see beyond 2 m. These results suggest that oribi select habitats and patches in relation to perceived predation risk (i.e. predation costs outweigh potential food intake benefits). However, when we increased food availability within woodlands, oribi increased their large-scale risk-taking behaviour and fed in these woodlands. Furthermore, this increased risk taking extended to small-scale foraging decisions whereby an increase in food availability within woodlands caused oribi to increase their relative usage of patches that had sight lines as well as patches that were closer to potential ambush sites. Ultimately, these results highlight how changes in food availability can determine the degree to which herbivores are willing to increase their risk-taking behaviour, and how these changes can affect overall landscape use.

Ontogenetic shifts in ambush-site selection of a sit-and-wait predator, the Chacoan Horned Frog (Ceratophrys cranwelli)

Ontogenetic shifts in habitat use are widespread among vertebrates. These niche shifts are often attributed to age-specific patterns of resource use, which are correlated with changes in morphology, diet, and habitat. We examined the ontogeny of ambush-site selection in a sit-and-wait predator, the Chacoan Horned Frog (Ceratophrys cranwelli Barrio, 1980), in the Gran Chaco ecoregion of Bolivia. We quantified covariation in microhabitat and morphological variables and tested for microhabitat selection against randomly selected points. We identified an ontogenetic shift in ambush-site selection between adult and metamorph frogs. When compared with random points, metamorphs selected a subset of available habitat, whereas adult frogs did not appear to select ambush sites. Metamorphs, compared with adults, selected ambush sites farther from a pond’s edge with a greater proportion of dry mud. The metamorph of C. cranwelli may have selected ambush sites based on spatial distribution of certain size classes of prey. Alternatively, metamorphs could have selected sites to minimize asymmetric agonistic intraspecific interactions with adults. These mechanisms are not mutually exclusive and probably occur in concert. Habitat selection and ontogenetic niche shifts by these organisms provide insights to the trade-offs between foraging strategy and mortality risk.