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PubMed1978

Behavior and phylogeny: constriction in ancient and modern snakes.

Comparative analyses of behavior have an underappreciated potential for revealing the role of ethoecological factors in the origins of higher taxa. Twenty-seven species (13 genera) in the advanced family Colubridae exhibited 19 patterns of coil application; one or two patterns were usually consistent within a genus. Forty-eight species (26 genera) in the primitive families Acrochordidae, Aniliidae, Boidae, and Xenopeltidae usually used a single pattern, despite differences in age, size, shape, habitat, and diet. This implies the shared retention of an action pattern used by their common ancestor no later than the early Paleocene. Constriction must have been used as a prey-killing tactic very early in the history of snakes and might have been a behavioral "key innovation" in the evolution of their unusual jaw mechanism.

Animals↗
PubMed1998

Prey selection in the leopard frog: choosing in biased and unbiased situations.

When given the option between a ground-level prey presented in front and another prey presented 90 degrees to the side, leopard frogs have a front preference. When given a choice between prey objects presented at the left and right sides, some individual leopard frogs have a side preference. Repeated prey object presentations at one side predispose leopard frogs to respond to the opposite side when presented with prey objects at both sides. The phenomenon is preserved through a half minute delay between single prey presentations (biasing) and two prey presentations (testing) but not through a three-minute delay between biasing and testing. Ten biasing presentations on a side are sufficient to induce opposite side preference, while three biasing presentations are insufficient. Attempts to permanently modify preferences by completely exhausting responsiveness to a single side were unsuccessful. A neural model for the effect of biasing on behavior is shown.

Animals↗
PubMedDate not supplied

Chimpanzees use tools to harvest social insects at Fongoli, Senegal.

Use of flexible probes to fish for macrotermitine termites and manufactured wands to dip for doriline ants is reported for a new site of chimpanzee field study. The flexible probes of vegetation used in termite fishing and ant dipping by the chimpanzees of Fongoli, in southeastern Senegal, are similar to those used at Assirik (Senegal) and Gombe (Tanzania). Based on the principle that form reflects function, we predict that ant dipping when seen will prove to be the two-handed technique.

Animals↗
PubMed2005

Functional morphology of feeding in the scale-eating specialist Catoprion mento.

The wimple piranha, Catoprion mento, has a narrow-range natural diet with fish scales comprising an important proportion of its total food intake. Scales are eaten throughout most of ontogeny and adults feed almost exclusively on this food source. Catoprion exhibits a novel prey capture behavior when removing scales for ingestion. Scale feeding strikes involve a high-speed, open-mouth, ramming attack where the prey is bitten to remove scales and the force of the collision knocks scales free. Unique kinematic parameters of scale-feeding strikes include a mean gape angle of nearly 120 degrees and a ;plateau' stage of prolonged maximum displacement for cranial elevation and opercular expansion. When feeding on live fish or loose scales, Catoprion performs a typical ram/suction attack that is modulated according to the elusiveness of the prey. Captures of elusive fish elicit faster strikes with greater displacement of cranial elements than do attacks on loose scales sinking in the water column. Despite its specialized diet and suite of anatomical characters, functional versatility in feeding behavior has not been reduced in Catoprion, as predicted by many analogous studies in functional morphology. On the contrary, the behavioral repertoire of Catoprion has been broadened by the addition of a novel behavior for scale feeding.

Adaptation, Physiological↗
PubMed2000

The mechanics of prey prehension in chameleons.

Iguanian lizards generally use their tongue to capture prey. Because lingual prehension is based on surface phenomena (wet adhesion, interlocking), the maximal prey size that can be captured is small. However, published records show that prey items eaten by chameleons include small vertebrates such as lizards and birds, indicating that these lizards are using a different prey prehension mechanism. Using high-speed video recordings, cineradiography, electromyography, nerve transection and stimulation experiments, we investigated the function of the tongue during prey capture. The results of these experiments indicate that chameleons have modified the primitive iguanian system by including a suction component in their prehension mechanism. Suction is generated by the activity of two modified intrinsic tongue muscles that pull the tongue pad inwards. Moreover, we demonstrate that the mechanism described here is a prerequisite for successful feeding.

Animals↗
PubMed2000

Sub-ice foraging behavior of emperor penguins.

Emperor penguins (Aptenodytes forsteri) were equipped with a remote underwater video camera, the Crittercam, to evaluate sub-ice foraging behavior while the birds dived from an isolated dive hole. Three birds dived and foraged successfully for 1 h periods after being trained to wear and to dive with a harness for camera attachment. Video and depth profile recordings revealed that emperor penguins travel at shallow depths (<50 m), ascend to the undersurface of the ice to feed on fish, and descend back to depth to return to the exit hole. Although the mean durations of dives of individual birds with the Crittercam were 21-35 % shorter than the diving durations of these same birds without the camera, the dive profiles in both situations were similar, thus demonstrating a similar foraging strategy in birds diving without the camera. Despite shorter diving durations with the camera, the penguins were still successful at prey capture in 80 % of 91 dives greater than 1 min in duration. Prey included the sub-ice fish Pagothenia borchgrevinki. Hunting ascents (from depth to within 5 m of the surface) occurred in 85 % of dives, ranged from zero to three per dive, and were associated with successful prey capture in 77 % of 128 ascents. Occasionally, several fish were captured during a single ascent. These observations and this application of video technology create a model for further physiological and behavioral studies of foraging, and also emphasize the potential importance of shallow dives as sources of food intake for emperor penguins during foraging trips to sea.

Animals↗
PubMed2001

The acoustic advantage of hunting at low heights above water: behavioural experiments on the European 'trawling' bats Myotis capaccinii, M. dasycneme and M. daubentonii.

We have demonstrated in behavioural experiments that success in capturing prey from surfaces in 'trawling Myotis' (Leuconoë-type) depends on the acoustic properties of the surface on which the prey is presented. Two types of surface structure were ensonified with artificial bat signals to probe their acoustic characteristics. We have shown that perception of prey by echolocation is easier if the prey is presented on a smooth surface (such as calm water) than if it is presented on a structured surface (such as vegetation or the ground). This is because the smooth surface reflects a much lower level of clutter echoes than the structured one if ensonified at an angle typical for bats foraging low over water. The ensonification experiments revealed that the sound pressure level of the echo was even higher for mealworms on a smooth surface than for mealworms suspended in air. This might be because waves travelling via the surface also contribute to the echo (e.g. reflection from the surface to the mealworm, back to the surface and then to the receiver). From the behavioural experiments, we conclude that 'trawling Myotis' take isolated objects on smooth (water) surfaces for prey. Those objects reflect isolated, stationary acoustic glints back to the echolocating bats. Conversely, 'trawling Myotis' will not recognise prey if prey echoes are embedded in numerous clutter echoes. We have demonstrated marked similarities between the three European 'trawling Myotis' species M. dasycneme, M. daubentonii and M. capaccinii in echolocation behaviour, search image, foraging strategy and prey perception. We propose that a combination of prey abundance and acoustic advantages could have led to repeated and convergent evolution of 'trawling' bats in different parts of the world.

Acoustics↗
PubMed2001

Prey detection in selective plankton feeding by the paddlefish: is the electric sense sufficient?

The long rostrum of the paddlefish Polyodon spathula supports an extensive array of ampullary electroreceptors and has been proposed to function as an antenna for detecting planktonic prey. Evidence in support of this hypothesis is presented in experiments that preclude the use of other sensory mechanisms for plankton detection. Paddlefish swimming in a recirculating observation chamber are shown to feed normally in the dark when prey-related chemical and hydrodynamic sensory cues are masked or attenuated. Specifically, we demonstrate that the spatial distribution of plankton captured by paddlefish is little changed when the plankton are individually encapsulated in agarose, when a high background concentration of plankton extract is added to the chamber, when the nares are plugged and under turbulent water flow conditions. Paddlefish also discriminate between encapsulated plankton and 'empty' agarose particles of the same size. Although capture distributions differed somewhat under certain conditions, the general pattern and effectiveness of prey capture were not disrupted by these procedures. These results support the conclusion that paddlefish, as zooplanktivores, rely on their passive electric sense for prey detection.

Animals↗
PubMed2002

The effect of stimulus features on the visual orienting behaviour of the salamander Plethodon jordani.

The effects of the visual features of prey-like objects on the orienting behaviour of the salamander Plethodon jordani were studied. Two stimuli (cricket dummies, rectangles), moving in opposite directions, were presented simultaneously on a computer screen. They differed in size, contrast, velocity and movement pattern of the entire body or the body appendages. Size and velocity appeared to be the dominant features; shape was of lesser importance. Contrast and movement pattern were of intermediate importance and local motion of little importance. This rank order was the same when the probability of a response to the different stimuli was estimated by means of the maximum-likelihood method. Cluster analysis revealed that in all animals stimuli could be grouped into five clusters. Among individuals, the rank order of stimuli was similar for high- and low-ranking stimuli and varied for those of intermediate rank; stimuli could be grouped into 3-5 clusters. Our findings favour the view that, in amphibians, prey recognition is guided by a number of visual features acting either alone or in combination and depending on internal motivational or attentional states and individual experience.

Animals↗
PubMed2000

Dental development and ontogenetic diet shifts of Roeboides paranensis pignalberi (osteichthyes, Characinae) in pools of the upper Rio Paraná floodplain (state of Paraná, Brazil).

Species of the characid genus Roeboides are known for their habit of tearing off and ingesting scales from other fishes. Specimens of Roeboides paranensis were taken monthly from March 1992 through February 1993 in five pools of the upper Rio Paraná floodplain and in one site in the Rio Paraná itself, with the aim of relating the dental development to ontogenetic diet shifts. Between 15-22 mm SL, fish had teeth with hypertrophied bases (mammiform) that moved to the outside of the mouth in both maxillas. During ontogeny, the diet shifted, with the smallest individuals eating more microcrustaceans and the larger ones eating more scales. Lepidophagy is non-obligatory, because the ingestion of insects and other invertebrates occurred at all sizes. Spatial variation in diet was large, however diet similarity was great for Roeboides from three floodplain pools that had similar proportions of the main diet categories.

Animals↗
PubMed2000

Diet of the colubrid snake, Thamnodynastes strigatus (Günther, 1858) from Paraná State, Brazil, with field notes on anuran predation.

Dissection of 44 specimens of the colubrid snake Thamnodynastes strigatus (Serpentes: Colubridae) provided data on food habits. Prey items include frogs (71.4% of the sample), rodents (14.3%), fishes (10.7%), and lizards (3.6%). The most of the anuran species recorded (Bufo sp., Leptodactylus sp., Physalaemus cuvieri and Scinax fuscovarius) are ground dwellers or call at the water level. Field observations provided information on the feeding behavior.

Animals↗
PubMed1989

[Aegla platensis Schmitt, 1942 (Decapoda: Anomura) a predator of immature stages of Simuliidae (Diptera: Culicomorpha)].

For the first time, preferential predation of larvae and pupae of Simuliidae by the crustacean, Aegla platensis Schmitt, 1942, was observed in the field and in the laboratory. Field observations and collections were done in the Carpintaria stream, Dois Irmãos, Country Rio Grande do Sul, Brazil. The possibility of using this freshwater crab in an integrated control of Simuliidae is discussed.

Animals↗
PubMed2006

Effect of food on immature development, consumption rate, and relative growth rate of Toxorhynchites splendens (Diptera: Culicidae), a predator of container breeding mosquitoes.

Food utilization by the larvae of Toxorhynchites splendens (Wiedemann) was studied in the laboratory by offering larvae of Aedes aegypti Linnaeus, Anopheles stephensi (Liston), and Culex quinquefasciatus (Say). Quantitative analyses of data indicated that immature development was significantly faster with increase in food availability. The regression analysis showed that the degrees of the relationship between immature duration (Id) and food availability were higher when offered early instars of prey (first and second instars) than late instars. Consumption rate (Cr) of the predator increased with increase in food availability and this relationship was highly significant when larvae of An. stephensi were offered as food. Consumption rate to food level decreased with increase in the age class of the prey. There was a significant negative correlation between Id and Cr. This aspect helps to increase population turnover of T. splendens in a shorter period when the prey is abundant. Conversely, the predator compensated the loss in daily food intake at low food level by extending Id thereby attains the minimum threshold pupal weight for adult emergence. There was an increase in the relative growth rate (RGR) of the predator when An. stephensi was offered as prey and this was related to the high protein content of the prey per body weight. There was a positive correlation between Cr and RGR. This adaptive life characteristic strategy of this predator is useful for mass-rearing for large scale field release programmes in the control of container breeding mosquitoes is discussed.

Animals↗