Prey Eaten Research Articles

Feeding in a Nocturnally active fish, Galaxias brevipinnis, in a New Zealand stream

To determine the diel feeding periodicity and diet of a lake-inlet population of Galaxias brevipinnis in New Zealand, samples of benthos, drift and fish were collected over a 24-h period in summer. Both numerically and gravimetrically, fish stomach contents revealed that feeding started some time after sunset, peaked towards midnight, and virtually ceased after sunrise. Benthic invertebrates were consumed almost exclusively, with ephemeropterans, trichopterans, and dipterans constituting 95% of the total foods eaten, a major proportion being chironomid larvae. Size of prey eaten compared with size of invertebrates in the benthos differed significantly during the night; this indicated that some size-selective feeding occurred. The benthic feeding habit of Galaxias brevipinnis appears to allow it to forage on relatively small prey during the night, a phenomenon that has been reported for other bottom-dwelling native fish species in New Zealand.

Flux hydriques et métabolisme énergétique dans un peuplement de Lacertidés des îles Kerkennah (Tunisie)

Water flux and daily energy expenditure were measured with doubly labeled water (3HH18O) in two insectivorous sympatric species of Lacertidae of Kerkennah islands (Tunisia), Eremias olivieri (mean body mass: 1.1 g) and Acanthodactylus pardalis (4.5 g) in a semiarid environment. Water turnover and field metabolic rate of Eremias olivieri (174 μL H2O g−1 d−1 and 250 J g−1 d−1) were, respectively, 2.5 and 5 times higher than those of Acanthodactylus pardalis (70 μL H2O g−1 d−1 and 52 J g−1 d−1). The water turnover of Eremias olivieri is one of the highest known among insectivorous lizards, and the daily energy expenditure of Acanthodactylus pardalis one of the lowest. The most plausible explanations are the differences in the size of the prey eaten by each species at this time of the season and in the duration of daily activity; the daily activity of Acanthodactylus pardalis is short (4.5 h d−1) although it is a sit-and-wait predator, whereas Eremias olivieri is active regularly every day for a longer period (7.5 h d−1) although it is an active forager. The high values of water turnover in Eremias olivieri suggest that food is not the only source of water for lizards in this particular insular environment.

Detrended Correspondence Analysis of Dietary Data

Abstract Niche relationships of fishes can be inferred from dietary analysis. Individual fish and their prey can be ordered along an underlying continuum that has ecological relevance, The specific arrangement is a function of the predator's behavior and the prey's spatial distribution. This distribution of prey eaten by predators conforms to the underlying assumptions of detrended correspondence analysis. This multivariate technique, designed specifically for discrete data, uncovers underlying resource gradients in the dietary data. We used it to analyse dietary information collected from banded sunfish Enneacanthus obesus and bluespotted sunfish Enneacanthus gloriosus and compared then the results with analyses by discriminant analysis, factor analysis, and principal component analysis. Detrended correspondence analysis was as effective in discriminating among species on the basis of diet as discriminant analysis, and was much better than either factor analysis or principal component analysis in produci...

The Effect of Water Depth on the Predatory Behavior of the Water Stick Insect, Ranatra-Dispar (Heteroptera, Nepidae)

The effect of water depth and prey density on the capture success (as measured by the number of prey eaten) of the aquatic, sit-and-wait predator, Ranatra dispar, was examined in the laboratory. When water depth was held constant at 5, 10, 20 or 30 cm, prey densities of 10, 15, 30 or 40 prey per container had no effect at the two shallowest depths, where very few prey were caught or eaten at any density. At 20 and 30 cm, density had a significant effect with progressively more prey being consumed as density increased. When prey density was held constant at 1, 2, 4 or 8 prey per litre, water depth significantly affected the proportion of prey eaten. At each density, predators held in 5 cm of water and, to some extent, those in 10 cm consumed significantly fewer prey than those in 20 or 30 cm. It is suggested that fewer prey are caught in shallow water because: (1) the predator cannot put itself in the position which most favours an efficient strike; (2) the absence of a significant 'vertical' component in the environment reduces the effectiveness of the sensory organs in locating prey. The lower capture success in shallow water may cause adult R. dispar to avoid shallow water, thus providing a partial refuge in which small R. dispar can avoid competing with adults for prey of similar sizes.

Prédation de mollusques dulçaquicoles par les larves malacophages de Tetanocera ferruginea Fallen, 1820 (Diptera, Sciomyzidae)

The range of prey of Tetanocera ferruginea larvae has been established from the freshwater snails living in one of its biotopes. Three predator–prey systems were examined, using the most common prey species of the larvae: Planorbis contortus, Lymnaea palustris, and Physa acuta. Analysis in terms of numbers and biomass of ingested prey has revealed the influence of morphology, ethology, and size of prey in these systems. By employing an appropriate dimensional connection with the prey, the data show that T. ferruginea larvae consume, on average, 45 Planorbis, 28 Lymnaea, or 30 Physa. As the Planorbis biomass is less than that of the two other species, the larvae partly compensate by eating more of them and so reduce the differences between the biomass of each prey eaten. When mollusks of similar biomass are used, the observed differences in terms of number of prey and biomass are not significant. In all cases, because of the amount and diversity of mollusks killed during its larvae cycle, T. ferruginea appears to be a most effective predator.

A female‐dominated feeding hierarchy in juvenilesepia officinal isin the laboratory

Ten juvenile Sepia officinalis were observed during feeding, as two five‐member groups, to look for possible dominance relationships during feeding. Three measures of feeding, number of shrimp prey eaten, priority to take prey and access priority over another individual, were measured. After ten days the ten animals were grouped differently and the study was repeated. Priority of access and priority to eat were significantly related, r = 0.67 and 0.78. However, of the other four correlations, only one was significant with this group size, suggesting a weak relationship between ability to gain access to food and actual intake. When animals’ overall rankings given the two different groupings were correlated, the relationship was very high (r = 0.96). Female Sepia tended to dominate males and larger females tended to dominate smaller ones (r = 0.58). Thus juvenile Sepia have the capacity to form dominance relationships within a feeding situation.

Effect of prey availability on foraging and production efficiencies of larvalMetasyrphus corollae [Dipt.: Syrphidae

We determined the effects of number of prey and the area over which they were distributed on the number of prey eaten and the production efficiency ofMetasyrphus corollae (F.) (formelySyrphus corollae F.) larvae. We hypothesized that, for a given number of prey offered per day, increased plant size would reduce foraging efficiency and production efficiency. Also, increased prey number was expected to increase production efficiency. Individual larvae were offered 10, 20, 40 or 60 pea aphids each day on plants with 7.5, 35 or 73 cm2 surface area. When more aphids were offered, larvae ofM. corollae killed more of them but left larger aphid carcasses. Foraging efficiency (percentage of available aphids eaten) declined as aphid abundance and plant size increased. Foraging costs were not decreased by increasing prey density and therefore production efficiency was not increased.

Foraging decisions of American robins: somatic and reproductive tradeoffs

We examined the behavior of a central place forager, the American robin (Turdus migratorius), with emphasis on the self-feeding component of foraging bouts. Among individuals the mean percentage of all prey captured that was consumed by adults varied from 10% to 60% (x ; 31%). Size of prey appeared important in determing whether the prey was eaten; adults generally consumed small prey and fed larger prey items to their young. In addition, females consumed more prey per bout than males, although rates of prey consumption were similar between sexes. For those robins in which a correlation was demonstrated between bout duration and amount of prey captured, amount of prey eaten by adults influenced bout length more strongly than size of the load. Attempts to model the robins' foraging process indicated that prey size, quantity of prey in the bill, and time away from the nest were important in determining when to terminate a bout. The rate at which robins foraged in their territory increased with age of the nestlings. In addition, mated pairs partitioned territories roughly in half, presumably as a mechanism for increasing foraging efficiency in a fairly homogeneous environment. Foraging activity declined as distance from the nest increased, but not in the manner predicted by optimality models.

Effect of Competition Between Two Freshwater Fishes on Prey Consumption and Abundance

The effect of inter- and intraspecific competition on the type and quantity of food consumed by fish, and on the abundance of macroinvertebrate prey, was examined by manipulating densities of yellow perch (Perca flavescens) and pumpkinseed (Lepomis gibbosus) stocked into littoral zone enclosures at levels approximating 0.5, 1.0, and 2.0 times the measured total fish biomass on the littoral zone. In intraspecific competition experiments, neither species showed a change in the type of prey eaten (principally macroinvertebrates). The amount of food eaten by yellow perch reared at high (26 g/m2) densities was significantly depressed relative to that of perch reared at low (6.5 g/m2) and natural (13 g/m2) densities. There were no significant differences in the amount of food eaten by pumpkinseed at the three fish densities. The gut fullness of pumpkinseed reared at high densities, however, was biased to a significant but unknown degree by the inclusion of a nonfood item, macrophyte fragments, in the estimates. No other fish consumed macrophytes. In interspecific competition experiments, the gut fullness of yellow perch and pumpkinseed reared together (combined density 13 g/m2) did not differ from that of fish reared alone at low or natural densities. The diet (principally macroinvertebrates) of the superior competitor, pumpkinseed, did not change relative to that of pumpkinseed reared alone. The inferior competitor, yellow perch, exhibited a significant change in diet. Microcrustaceans (an energetically inferior food) comprised 30–53% of the diet (by weight) of yellow perch reared with pumpkinseed compared with < 1% of the diet of perch reared alone. Total macroinvertebrate biomass and abundance were unaffected by differences in fish biomass in the enclosures.

A comparison of prey eating by spontaneous mouse killing rats and rats with lateral septal, medial accumbens, or medial hypothalamic lesions

Rats with lesions of the medial hypothalamus and spontaneous mouse killing rats were tested for mouse and rat pup killing in their living cages 1 and 3 days postoperatively. The lesioned and spontaneous killers did not differ significantly in amount of prey eaten within 10 min following a mouse kill on either Day 1 or 3 postoperatively. Both groups ate significantly more of the prey than did sham-lesioned rats that were presented with a freshly killed mouse. When 4 hr was allowed for eating following a kill, rats with lesions of the lateral septum, medial accumbens, and medial hypothalamus each ate significantly more than spontaneous mouse killing rats. The greater prey eating by the lesioned animals is probably not the result of the prey being a highly palatable food since rats with medial hypothalamic lesions but not those with medial accumbens or septal lesions showed enhanced consumption of a sweetened lab chow over a 4 hr period. The quantitative similarity in the prey eating by spontaneous and lesion-induced mouse killers in the period immediately following the kill serves to further establish a relationship between these two kinds of killing. The greater eating that occurs in lesioned animals when a longer time is allowed for eating is consistent with other observations of excesses in the killing behavior of lesioned animals relative to spontaneous killers.

Dissociation of prey killing and prey eating by naloxone in the rat

Mouse killing rats matched for killing latency and prey eating were injected (IP) with 0.5, 2.0, or 5.0 mg/kg naloxone or 0.9% saline. Naloxone did not significantly inhibit prey killing or alter prey killing latency at any dose but did reduce prey eating by 50% at the two higher doses. The dissociation of prey killing and prey eating by naloxone is consistent with other evidence that these two behaviors are separate components of predation in rats.

Growth responses of fish to changing environmental conditions in a South Carolina cooling reservoir

Significant changes in growth of bluegills,Lepomis macrochirus, largemouth bass,Micropterus salmoides, and black crappies,Pomoxis nigromaculatus, were observed in Keowee Reservoir, South Carolina, during the 10 years (1968–1977) following impoundment. During this period the reservoir filled, water temperatures were increased by heated effluent from a nuclear power plant, and threadfin shad,Dorosoma petenense, were stocked. Growth was apparently regulated by abundance and size of prey eaten by fish; elevated water temperatures had no measurable effect.

Cougar Food Habits in Southern Utah

Diets of cougars (Felis concolor) were studied from December 1978 to August 1981, on a 4,500km2 study area near Escalante, Utah. Prey eaten by cougars was estimated from analysis of 112 animals consumed as prey and from 239 cougar scats. Composition of diet was corrected based on feeding trials using captive cougars. Mule deer (Odocoileus hemionus) were found to be the major prey item, 81% of biomass consumed. Lagomorphs, large rodents, and smaller predators were also important components of the diet. Cattle comprised less than 1% of the diet, although they were abundant on the cougars' summer range. Age structure of deer killed by cougars indicated that older (>7 years) deer were killed more often than expected (P < 0.005). J. WILDL. MANAGE. 48(1):147-155 Cougar dietary habits have been studied in Utah (Connolly 1949, Robinette et al. 1959), Idaho (Hornocker 1970), Arizona (Shaw 1977, 1982), Oregon (Toweill and Meslow 1977), British Columbia (Spalding and Lesowski 1971), and the West in general (Young and Goldman 1946). Food habits were generally similar, the diet consisting predominantly of wild and domestic ruminants, with lesser amounts of rodents, rabbits, and other predators. Results of the more intensive studies in Utah, Idaho, and Arizona differed, however, in the relative proportions of mule deer, elk (Cervus elaphus), and cattle in the diet. During years of peak snowshoe hare (Lepus americanus) abundance in British Columbia, 27% of the cougars' diet was composed of hares, indicating that cougars take advantage of numerically abundant prey. Because inferences are frequently drawn from food-habits studies of predators to predict their influence on the dynamics of prey populations, it is important tha results from such studies accurately describe the diet. Floyd et al. (1978) determined that the number of field-collectible scats produced by gray wolves (Canis lupus) was inversely related to prey size. Selective feeding on flesh alone resulted in loose, liquid scats that would seldom be found in the field. Consumption of smaller prey, on the other hand, would generally include more indigestible material and would result in more persistent scats. In addition, Johnson and Aldred (1982) and Weaver and Hoffman (1979) have documented differential digestibility of smaller mammals and the problems of enumerating small mammals in scats. The method employed to collect foodhabits data may further reduce general applicability. Dietary samples from cougars killed by sport hunters or damagecontrol personnel may be biased toward specific groups of cougars or may be restricted to specific seasons of the year (Young and Goldman 1946, Robinette et al. 1959, Spalding and Lesowski 1971, Toweill and Meslow 1977). Only Robinette et al. (1959) and Shaw (1982) reported summer food habits. Several authors have indicated that vulnerability of mule deer to cougar predation is influSFunding was provided by Utah Div. of Wildl. Resour. (UDWR), and the study was conducted under auspices of the Utah Coop. Wildl. Res. Unit, UDWR, Utah State Univ., U.S. Fish and Wildl. Serv., and Wildl. Manage. Inst. cooperating. 2 Present address: Idaho Department of Fish and Game, P.O. Box 21, Soda Springs, ID 83276. J. Wildl. Manage. 48(1):1984 147 This content downloaded from 157.55.39.175 on Thu, 11 Aug 2016 06:18:10 UTC All use subject to http://about.jstor.org/terms 148 COUGAR FOOD HABITS * Ackerman et al. enced by sex of the deer and season of the year (Robinette et al. 1959, Hornocker 1970, Shaw 1977) and by age of the deer (Hornocker 1970, Spalding and Lesowski 1971). This paper reports on an intensive effort to determine the year-round diet of cougars and relative vulnerability of the various age-classes of mule deer to cougar predation between December 1978 and August 1981. We are grateful to A. J. Button for his indispensable help as our houndsman and chief technician. T. Rettberg, our pilot, flew many long days for us. W. Button helped in capture operations and provided a site for our winter camp. The Button and Coleman families, M. Reid, F. Van Dyke, K. A. Johnson, D. Shepardson, K. Parr, M. H. Hemker, B. A. Blakesley, R. E. Gruenig, L. Cox, and R. D. Peters assisted with the field work. F. H. Coles, J. G. Guyman, N. V. Hancock, F. C. Jensen, and T. Gardiner of the UDWR provided important support and advice. F. Coles, J. A. Gessaman, and F. F. Knowlton gave valuable criticism of the manuscript. Cooperation was provided by the U.S. For. Serv. and Bur. of Land Manage. The Ecol. Cent. at Utah State Univ. provided assistance during the analysis stage.

Optimal foraging and growth in bluegills.

Two models of foraging behaviour (optimal prey selection and random prey selection) were used to calculate the potential net energy intake of bluegill sunfish (Lepomis macrochirus) in a small Michigan lake. These predictions were then compared to the actual growth exhibited by bluegills in the lake. Predictions of net energy gain derived from optimal foraging criteria were significantly correlated with the seasonal gain in mass by the fish; both energy gain and growth were positively related to bluegill length. Predictions of net energy intake based upon non-selective foraging (i.e. prey eaten as encountered) were not significantly correlated with bluegill growth. Comparing the net energy intake of bluegills feeding optimally versus non-selectively demonstrates that optimal prey selection increases average energy gain by 4 to 10 fold. This result illustrates the strong evolutionary advantage afforded to foragers that maximize net energy intake in a natural environment. Finally, the potential usefulness of optimal foraging models to the study of species and/or size-class interactions is discussed and a heuristic example pertaining to the development of "stunted" populations in fishes is provided.

Patterns of coexistence in busyconine whelks

The general question of how the juveniles of a large species avoid significant resource overlap with adults of a smaller species was examined using two carnivorous gastropods in the subfamily Busyconinae (Melongenidae). Although Busycon contrarium (Conrad) reaches a maximum size almost three times that of sympatric Busycotypus spiratum (Lamarck) in the Turkey Point region of northwestern Florida, local B. contrarium populations were characterized by predominance of small individuals. By manipulating field densities of small (< 120 mm) B. contrarium and monitoring changes in B. spiratum densities, I have been able to show that competition was occurring on grass flats, but not on oyster bars. B. spiratum and small B. contrarium had high overlap in microhabitat usage and activity patterns, but low dietary overlap. Prey eaten by B. contrarium and B. spiratum belonged to four broad categories: 1. (1) bivalves which attempted to thwart predators by tightly closing the valves together (= passive bivalves); 2. (2) bivalves which used active escape mechanisms (= active bivalves); 3. (3) gastropods; and 4. (4) carrion. In the field B. spiratum fed largely on active bivalves and to a lesser extent on gastropods and carrion. Small B. contrarium fed almost exclusively on passive bivalves. These dietary differences were correlated with morphological and behavioral differences between the two species. B. spiratum has a large foot which allows it to crawl more rapidly and more completely envelop active prey than B. contrarium. Consequently, B. spiratum is significantly more efficient at capturing active bivalves than is B. contrarium. Preference experiments showed that B. contrarium preferred active over passive bivalves, but due to a low efficiency of capturing prey, combined with the aggressive dominance of B. spiratum in contests over food, B. contrarium was able to obtain few active bivalves in the field. B. contrarium was able to subsist on the less preferred passive bivalves due to a well-developed chipping behavior for opening these prey. On oyster bars, high predation rates by the stone crab ( Menippe mercenaria) (Say) precluded competition. B. spiratum was more vulnerable to crab predation than B. contrarium due to a thinner shell, and completely disappeared from oyster bars during the summer months when Menippe was most abundant.

Interspecific territoriality and competition for food between the reef fishes Forsterygion varium and Pseudolabrus celidotus

Long-term behavioural studies were made of the blennioid fish Forsterygion varium and the wrasse Pseudolabrus celidotus in the Cape Rodney-Okakari Point Marine Reserve in New Zealand. Both male and female F. varium defended small 1 to 2 m2 territories from the wrasse all year round, althoughl aggressive encounters were most frequent from December to April. Only Large P. celidotus (≧180 mm standard length) were observed to dominate the blenny in interactions. Defence of nests, which were found only on the territories of males between May and October, did not explain the distribution of F. varium aggression between the sexes and seasons. An extensive overlap in the categories and size of prey eaten suggested that protection of food was a major function of F. varium territoriality. F. varium was most frequently aggressive toward P. celidotus of an intermediate size (110 to 160 mm SL) and exhibited greatest overlap in diet with wrasses in this size lange. This dnected the study toward examining the effect of F. varium on the feeding activity of P. celidotus. Within a shallow, Leterogeneous reef habitat, feeding pressure by P. celidotus (bites/are/time) was inversely related to the density of F. varium. Removal of F. varium from small 5x5 m quadrats resulted in large increases in wrasse feeding pressure, suggesting that the blenny influences the foraging of wrasses within their home ranges. When F. varium were removed from the entire home ranges of five 1+yr (110 to 130 mm SL) P. celidotus, these fish exhibited relative increases in both feeding rate and foraging time. The results suggest that P. celidotus grow through a period during which individuals compete with F. varium for food, adding support to the contention that territoriality in F. varium functions to preserve its food supply.

Mouse and weanling rat killing by spontaneous mouse killing rats, and by rats with lesions of the lateral septum or the region ventral to the anterior septum: Similarities in killing latency and prey eating

Mouse and rat pup killing by male rats with lesions of the lateral septum or of the region ventral to the anterior septum were compared with that of spontaneous mouse killing rats. Latency to kill, latency to eat, and the amount of the prey eaten were similar for all groups. The killing and eating of weanling rats and mice were also similar across groups and occurred in a novel environment as well as in the home cage. However, the tendency to kill weanling rats is significantly higher in lesioned animals that kill mice than in natural killers which kill mice. In addition, some lesioned rats but no unlesioned rats also killed and ate young (150 to 200 g) male rats. It is argued that the killing behavior of rats with lesions of the lateral septum or of the region ventral to the anterior septum represents an enhanced predatory behavior.

A laboratory study of preferential predation by the newt Notophthalmus v. viridescens

Experiments were performed to determine if the newt Notophthalmus v. viridescens preferred the amphipod Hyalella over the cladoceran Daphnia under laboratory conditions and how temperature, relative proportion of prey, and total abundance of prey affects prey preference. Experiments demonstrate that Hyalella is the preferred prey at high prey densities but that Daphnia is preferred at low prey densities. Relative density of prey does not affect the preference for Hyalella at high prey density, but reduced temperature eliminates the preference for Hyalella at these high densities. Turbid water reduces the feeding rate.The experimental results can be attributed to hunting behavior of the newt and to size and activity patterns of the prey. The results suggest that the newt is an opportunistic feeder and that prey movement affects numbers of prey eaten.

The effects of d-amphetamine on prey killing and prey eating in the rat and mouse

d-Amphetamine inhibited mouse, frog, and cricket killing in the rat and cricket killing in the laboratory mouse. Feeding on the same prey was also inhibited, but required a lower dose of the drug. While the anoxeric effects of d-amphetamine may contribute to the drug’s inhibition of prey killing, other actions of the drug also appear to be involved.

The Functional Responses of Stethorus punctum 1 to Densities of the European Red Mite 234

The functional response of the predator Stethorus punctum (LeConte) was tested at various densities of the European red mite, Panonychus ulmi (Koch). Overwintered S. punctum adult females were tested at a range of densities from 4–30 mites/cage, whereas, the 2nd and 3rd generation larvae, female and male adults were tested at a range of densities from 4–80 mites/cage. Various types of mathematical models were fit to the data, using weighted regression analysis, to estimate the relationship between the number of prey eaten and prey density. Three types of functional response curves were exhibited by the different stages and sexes of S. punctum , a linear response, a negatively accelerated curve and an S-shaped rise to a plateau. Two factors partially responsible for these 3 types may be the different environmental conditions for each test and the replenishment of prey on an hourly basis. S. punctum was found to stop feeding at dusk and to resume ca. 2 h after sunrise. The feeding of S. punctum increased as temperatures rose during the day with a maximum consumption occurring during the warm afternoon hours.