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At least 325 records · Page 18Linked to original sources
PubMed2005

Heat-balling wasps by honeybees.

Defensiveness of honeybee colonies of Apis cerana and Apis mellifera (actively balling the wasps but reduction of foraging) against predatory wasps, Vespa velutina, and false wasps was assessed. There were significantly more worker bees in balls of the former than latter. Core temperatures in a ball around a live wasp of A. cerana were significantly higher than those of A. mellifera, and also significantly more when exposed to false wasps. Core temperatures of bee balls exposed to false wasps were significantly lower than those exposed to V. velutina for both A. cerana and for A. mellifera. The lethal thermal limits for V. velutina, A. cerana and A. mellifera were significantly different, so that both species of honeybees have a thermal safety factor in heat-killing such wasp predators. During wasps attacks at the hives measured at 3, 6 and 12 min, the numbers of Apis cerana cerana and Apis cerana indica bees continuing to forage were significantly reduced with increased wasp attack time. Tropical lowland A. c. indica reduced foraging rates significantly more than the highland A. c. cerana bees; but, there was no significant effect on foraging by A. mellifera. The latency to recovery of honeybee foraging was significantly greater the longer the duration of wasp attacks. The results show remarkable thermal fine-tuning in a co-evolving predator-prey relationship.

Animals↗
PubMed2007

Feeding, fins and braking maneuvers: locomotion during prey capture in centrarchid fishes.

Locomotion is an integral aspect of the prey capture strategy of almost every predatory animal. For fishes that employ suction to draw prey into their mouths, locomotor movements are vital for the correct positioning of the mouth relative to the prey item. Despite this, little is known regarding the relationships between locomotor movements and prey capture. To gain insights into how fishes move during prey capture and the mechanisms underlying deceleration during prey capture, I measured the fin and body movements of largemouth bass, Micropterus salmoides, and bluegill sunfish, Lepomis macrochirus. Using a high-speed video camera (500 frames s(-1)), I captured locomotor and feeding movements in lateral and ventral (via a mirror) view. Largemouth bass swam considerably faster than bluegill during the approach to the prey item, and both species decelerated substantially following prey capture. The mean magnitude of deceleration was significantly higher in largemouth bass (-1089 cm s(-2)) than bluegill (-235 cm s(-2)), and the timing of maximum deceleration was much later for largemouth bass (30.3 ms after maximum gape) than bluegill (6.7 ms after maximum gape). Both species employed their pectoral, anal and caudal fins in order to decelerate during prey capture. However, largemouth bass protracted their pectoral fins more and faster, likely contributing to the greater magnitude of deceleration in the species. The primary mechanism for increased deceleration was an increase in approach speed. The drag forces experienced by the fins and body are proportional to the velocity of the flow squared. Thus, the braking forces exerted by fins, without any change in kinematics, will increase exponentially with small increases in swimming speed, perhaps allowing these fishes to achieve higher braking forces at higher swimming speeds without altering body or fin kinematics. This result can likely be extended to other maneuvers such as turning.

Animals↗
PubMed2000

Vertebrate predation by sympatric tamarins, Saguinus mystax and Saguinus fuscicollis.

Vertebrate predation was examined in sympatric moustached tamarins (Saguinus mystax) and saddle-back tamarins (Saguinus fuscicollis) in the Amazon rainforest of northeastern Peru. Both species prey on frogs and lizards, and very rarely on nestling birds. As a result of divergent foraging strategies, S. mystax primarily exploited frogs at higher strata of the forest, while S. fuscicollis predominantly preyed on reptiles in the lower strata and on the ground. This difference may strengthen the niche differentiation between these two tamarin species that exists with regard to other prey.

Animals↗
PubMed2005

Chimpanzee (Pan troglodytes troglodytes) tool use in the Ngotto Forest, Central African Republic.

Over a 7-month period, stick tools constructed by chimpanzees were collected and measured at the Ngotto Forest site in Central African Republic. The chimpanzees were found to use tools to dip for ants and to probe for honey. The basic descriptions of these tools and the contexts in which they were found are presented. The lengths of two of the tool types were compared with the use of a t-test for independent groups. It was found that the lengths of the tools differed significantly depending upon their function. The location and habitat type of each tool site were plotted on a map. The tool types were distributed throughout the southern part of the study area, and with one exception all tool sites were found in the same type of habitat. Two tool sites with two other types of tools (honey hammer/club and ant club) were found. The tool types at Ngotto are compared with those found at other chimpanzee field sites, and the implications for diversity in chimpanzee material culture are discussed.

Animals↗
PubMed2007

Golden lion tamarin sleeping-site use and pre-retirement behavior during intense predation.

Sleeping sites, their patterns of use, and cryptic pre-retirement behavior mitigate predation risk at sleeping sites and could influence prey fitness. We evaluated sleeping-site usage for 10 groups of golden lion tamarins (GLTs) from a population that recently suffered a substantial decline due to predation at sleeping sites. We recorded the average number of nights that groups spent at their different sleeping sites to determine whether patterns of sleeping-site use were influenced by predation risk, as measured by the rate of encounters with predators, or the availability of suitable sleeping sites, as measured by the size of a group's home range and amount of mature forest within their home range. In addition, we measured travel speed to sleeping sites and compared this speed with that recorded at other times of day. GLT groups spent more nights on average at each of their sleeping sites compared to other callitrichid species for which data are available. Predation risk and habitat characteristics were not significant predictors of how many times groups used each of their different sleeping sites. Groups significantly increased their travel speed just before entering the sleeping site. Rapid locomotion to secure tree cavities may help GLTs avoid crepuscular and nocturnal predators; however, we speculate that this strategy failed numerous GLTs in our study population during the previous decade because they used sleeping sites that were accessible to predators.

Animals↗
PubMed1975

Defensive distance and immobility in young precocial birds (Gallus gallus).

The manifestation and duration of the tonic immobility reaction in 3-day-old chicks (Gallus gallus) was found to vary reliably as a function of the spatial proximity between the hand of the experimenter and the immobilized chick. The results of this experiment indicate that young birds are susceptible to immobility and that the maintenance of close spatial proximity is the condition necessary for the occurrence of the reaction in young precocial birds.

Animals↗
PubMed1989

Development of antipredator responses in snakes: IV. Interspecific and intraspecific differences in habituation of defensive behavior.

Habituation of defensive attacks directed toward a threatening stimulus was investigated in neonatal garter snakes. The focus of the experiments was on differential effects of a simple experimental process in relation to species, litter, sex, and individual. In Experiment 1 newborn Thamnophis melanogaster from four liters and newborn Thamnophis butleri from three liters were given daily tests in which snakes were confronted with a nonmoving and moving human hand. Over five successive test days the T melanogaster neonates showed a decline in number of strikes directed toward the stimuli. When retested 10-13 days later the animals showed significant response recovery. Although some of the T? butleri newborns demonstrated significant habituation, there was no overall habituation of strike scores in this species. The T? melanogaster had high strike scores, more rapid habituation to moving than nonmoving stimuli, and significant liter differences in habituation rates. The T? melanogaster, but not the T? butleri neonates, showed significant habituation of flight responses over the five tests. In T? butleri, but not T? melanogaster, males were more prone to attack than were females. In both species there were large differences in both overall strike scores and habituation rates of individual newborn animals. In Experiment 2, T? melanogaster 2-months old, were tested for short-term habituation to either a moving or nonmoving stimulus for 10 successive tests on one day. Habituation of strikes was similar to both stimuli, but more animals confronted with the moving stimulus showed an initial increase in strikes, lending support to the dual-process theory of habituation. As in Experiment 1, there were large individual differences in habituation rates. The results are discussed in terms of the ecological and methodological implications for developmental studies.

Aggression↗
PubMed2004

The effects of opercular linkage disruption on prey-capture kinematics in the teleost fish Sarotherodon melanotheron.

The kinematics of prey capture in blackchin tilapia (Sarotherodon melanotheron) subjected to three experimental treatments (control, anesthetization, and opercular linkage disruption) were analyzed using high-speed video to explore the role of the opercular four-bar linkage in depressing the lower jaw in teleost fishes. A series of two-way mixed model analyses of variance (random effects=fish; fixed effects=treatment) revealed that maximum gape, lower jaw angle, gape cycle, and time to lower jaw depression differed among treatments. Tukey post-hoc comparisons revealed that the opercular linkage disruption treatment differed from the control and anesthetization treatments, suggesting that severing the opercular linkage affected the ability of fish to depress the lower jaw. We hypothesize that although the opercular four-bar linkage system may not be the only linkage mechanism involved in depressing the lower jaw, it plays a very important role in opening the mouth during feeding in teleost fishes.

Analysis of Variance↗
PubMed2006

Morphological specializations of baleen whales associated with hydrodynamic performance and ecological niche.

Feeding behavior, prey type, and habitat appear to be associated with the morphological design of body, fluke, and flippers in baleen whales. Morphometric data from whaling records and recent stranding events were compiled, and morphometric parameters describing the body length, and fluke and flipper dimensions for an "average" blue whale Balaenoptera musculus, humpback whale Megaptera novaeangliae, gray whale Eschrichtius robustus, and right whale Eubalaena glacialis were determined. Body mass, body volume, body surface area, and fluke and flipper surface areas were estimated. The resultant morphological configurations lent themselves to the following classifications based on hydrodynamic principles: fast cruiser, slow cruiser, fast maneuverer, and slow maneuverer. Blue whales have highly streamlined bodies with small, high aspect ratio flippers and flukes for fast efficient cruising in the open ocean. On the other hand, the rotund right whale has large, high aspect ratio flukes for efficient slow speed cruising that is optimal for their continuous filter feeding technique. Humpbacks have large, high aspect ratio flippers and a large, low aspect ratio tail for quick acceleration and high-speed maneuvering which would help them catch their elusive prey, while gray whales have large, low aspect ratio flippers and flukes for enhanced low-speed maneuvering in complex coastal water habitats.

Adaptation, Biological↗
PubMed2006

Odontocete suction feeding: Experimental analysis of water flow and head shape.

The role of cranial morphology in the generation of intraoral and oropharyngeal suction pressures in odontocetes was investigated by manipulating the jaw and hyolingual apparatus of submerged heads of three species presenting varied shapes. Hyoid and gular muscles were manually employed to depress and retract the tongue. Pressures were recorded at three locations in the oral cavity, as gape and site, speed, and force of pull were varied. A biomechanical model was also developed to evaluate pressure data. The species with the shortest, bluntest head and smallest mouth opening generated greater negative pressures. Suction generation diminished sharply as gape increased. Greatest negative pressures attained were around -45 mmHg (-6,000 Pa), a magnitude deemed suitable for capture of small live prey. Odontocetes utilizing this bidirectional flow system should profit by evolution of a rounder mouth opening through progressive shortening and widening of the rostrum and jaws, a trend evident in cranial measurements from fossil and recent odontocetes. Blunt heads correlate with anatomical, ecological, and behavioral traits associated with suction feeding. Small-gape suction (with minimally opened jaws) could be used by odontocetes of all head and oral shapes to draw prey sufficiently close to the mouth for suction ingestion or grasping via dentition. Principal limitations of the experimental and mathematical simulations include assumption of a stationary odontocete with static (open or closed) jaws and potential scaling issues with differently sized heads and gapes.

Animals↗
PubMed2002

Sight of a predator can stimulate a corticosterone response in the great tit (Parus major).

The corticosterone response to the sight of a natural predator was investigated in free-living and captive great tits (Parus major). Free-living great tits responded to the sight of a stuffed, slowly moving Tengmalm's owl, a major predator of great tits, with warning calls and a change in behaviour around a feeder. Great tits returned to the feeder within a few minutes and began to approach the owl, and there was no increase in plasma corticosterone levels in birds sampled 30-50 min after they first saw the owl. Captive great tits in an aviary were exposed for 30 min to a stuffed Tengmalm's owl, to a stuffed brambling, and to a cardboard box. All three stimulus objects were slowly rotated during the exposure period. Great tits exposed to the owl changed their behaviour immediately, and spent most of the time when the owl was visible flying around the aviary and hanging from the roof, with very few visits to a feeder. Great tits exposed to the brambling and to the moving box also changed their behaviour and made fewer visits to the feeder. The great tits responded to the sight of the owl with a marked increase in plasma corticosterone levels, whereas there was no change in corticosterone levels (mean levels < 11 ng/ml) in birds exposed to the brambling or to the moving box. Mean corticosterone levels were high (37.1 +/- 4.9 ng/ml) 0.5 h after exposure to the owl, remained high (38.9 +/- 6.0 ng/ml) 1 h after exposure, and had returned to basal (5.3 plus minus 1.3 ng/ml) 3 h after exposure to the owl. This is the first demonstration for any bird of a complete corticosterone response to a predator. The sight of a predator initiated a corticosterone response in great tits that could not move more than 3 m away, whereas free-living great tits that could choose how far to fly away from the predator either did not initiate a corticosterone response, or had a small corticosterone response in which corticosterone levels were not significantly different from basal 30-50 min later. The results indicate that the initiation of a corticosterone response in birds depends on whether or not a bird perceives that a stimulus is a threat. Furthermore, they illustrate the importance of not making generalised conclusions based on laboratory experiments.

Animals↗
PubMed1982

Models of the influence of predation on aspect diversity in prey populations.

By considering a model incorporating behavioral changes by predators and prey evolution, we demonstrate how under certain conditions apostatic predation influences the maintenance of diversity within prey populations, and among different prey species. Further, we estimate the intrinsic "diversity" wavelength of the system when apostasy combines with other factors to lead to nonuniform distributions of prey along aspect gradients.

Animals↗
PubMed1982

A predator prey model with age structure.

A general predator-prey model is considered in which the predator population is assumed to have an age structure which significantly affects it fecundity. The model equations are derived from the general McKendrick equations for age structured populations. The existence, stability and de-stabilization of equilibria are studied as they depend on the prey's natural carrying capacity and the maturation period m of the predator. The main result of the paper is that for a broad class of maturation functions positive equilibria are either unstable for small m or are destabilized as m decreases to zero. This is in contrast to the usual rule of thumb that increasing (not decreasing) delays in growth rate responses cause instabilities.

Aging↗
PubMed1986

The role of vibrissae in behavior: a status review.

Vibrissae or tactile hairs are an important part of the tactile sensory apparatus of many mammals. A wide range of suggested functions found in the literature include food acquisition, prey attack, aggression and attack behavior, facial expression in intraspecies communications, dispersion of pheromones, maintaining head position in swimming, and a wide range of environmental monitoring (e.g., current detection in water, wind direction on land). There is little work done specifically on domestic animals or their feral relatives. Work on the tactile senses in general and vibrissae in particular is an open field of study. A set of general questions for study of vibrissa function in domestic animals is presented.

Aggression↗