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At least 145 records · Page 8Linked to original sources
PubMed1985

Parturition influences initial pup preferences at later onset of maternal behavior in primiparous rats.

Initial maternal responsiveness as a function of varying pup stimuli was assessed in primiparous Long-Evans rats. Pups were removed during parturition and the dams tested beginning 24 hr later. These dams were most likely to respond maternally towards newborn (0-2-day-old) rat pups (100%) and 6-8-day-old hamsters, which are the size of newborn rats (83.3%). In contrast, dams were significantly less likely to respond maternally towards newborn hamsters (50%) and 8-10-day-old rats (16.7%), pups which are half as large and twice as large, respectively, as newborn rats; indeed, dams were likely to attack these pups (33.3% and 25%, respectively). The maternal response (less than or equal to 1 hr) to dead newborn rats was similar to that towards live newborn rats, except that fewer dams retrieved dead pups rapidly (less than or equal to 1 min). Cesarean-delivered dams did not display higher maternal responsiveness towards 0-2 than towards 8-10-day-old rats. Further, whereas no parturition-experienced dam displayed infanticide towards newborn rats, 21.9% of primiparous Cesarean-delivered dams did. Thus, the exogenous and/or endogenous stimuli associated with parturition enhance selective maternal responsiveness and diminish infanticide towards pups the size of newborn rats.

Aggression↗
PubMed2002

The venom optimisation hypothesis: a spider injects large venom quantities only into difficult prey types.

The spider Cupiennius salei needs 0.01-10 microl venom to kill a prey item. Since its venom glands contain only 10 microl and regeneration requires 8-16 days C. salei should use its venom very economically. By a monoclonal antibody we measured, for the first time, the amounts of venom injected by a spider into different prey types. Crickets and stick insects, as victims without special defence mechanism, received only the minimum amount of venom which is not significantly different from the LD(50). Blowflies and ground beetles received considerably more venom because they are difficult to overwhelm or even endanger the spider by their defence behaviour. These results support our venom optimisation hypothesis which supposes that spiders use their venom as economically as possible.

Animals↗
PubMed2001

Energetic and physiological correlates of prey handling and ingestion in lizards and snakes.

In this review, we summarize the energetic and physiological correlates of prey handling and ingestion in lizards and snakes. There were marked differences in the magnitude of aerobic metabolism during prey handling and ingestion between these two groups, although they show a similar pattern of variation as a function of relative prey mass. For lizards, the magnitude of aerobic metabolism during prey handling and ingestion also varied as a function of morphological specializations for a particular habitat, prey type, and behavior. For snakes, interspecific differences in aerobic metabolism during prey handling seem to be correlated with adaptations for prey capture (venom injection vs. constriction). During ingestion by snakes, differences in aerobic metabolism might be due to differences in cranial morphology, although allometric effects might be a potentially confounded effect. Anaerobic metabolism is used for prey handling and ingestion, but its relative contribution to total ATP production seems to be more pronounced in snakes than in lizards. The energetic costs of prey handling and ingestion are trivial for both groups and cannot be used to predict patterns of prey-size selection. For lizards, it seems that morphological and ecological factors set the constraints on prey handling and ingestion. For snakes, besides these two factors, the capacity of the cardio-respiratory system may also be an important factor constraining the capacity for prey handling and ingestion.

Animals↗
PubMed2002

Overview: For crying out loud--dangers and opportunities of communicating in the public domain.

Communication often extends into the public domain, inviting "eavesdropping" and other forms of exploitation by other species. Conflict is frequently the result, although interspecific communication can be mutually beneficial even when interests conflict fundamentally, such as between predator and prey. However, the most complex communication systems are likely to involve species with mutual rather than with conflicting interests. When interests do conflict, exploitation of the communication systems of others may impose high costs on signalers and select for signals that are less exploitable. Other costs of communication in the public domain arise from "mistakes" (e.g., mating with the wrong species) and select for more species-specific signal structure. The articles in this section illustrate the complexity of interspecific communication and yield important insights into the dynamic nature of communication systems.

Agonistic Behavior↗
PubMedDate not supplied

Flock-feeding on fish schools increases individual success in gulls.

Flock-foraging and the role of white plumage in gulls and other seabirds have been the subject of much debate. At first sight it seems that competition within the flock would render flock formation against the interest of the bird who finds the fish school, as the fish must then be shared with birds joining the flock. However, it is also possible that flock formation is neutral or even beneficial to the individual members, including the bird that found the fish (the 'first finder'). Here we show that the fishing success of individual black-headed gulls, Larus ridibundus, increases with flock size up to at least eight birds. Part of the reason is that the fish school is more vulnerable when attacked by several gulls. The first gull to reach a fish school therefore benefits from being joined by others, and conspicuous white upper parts in gulls may act as a means of attracting other gulls to the flock and hence improving hunting success.

Animals↗
PubMed2001

Effect of acoustic clutter on prey detection by bats.

Bats that capture animal prey from substrates often emit characteristic echolocation calls that are short-duration, frequency-modulated (FM) and broadband. Such calls seem to be suited to locating prey in uncluttered habitats, including flying prey, but may be less effective for finding prey among cluttered backgrounds because echoes reflecting from the substrate mask the acoustic signature of prey. Perhaps these call designs serve primarily for spatial orientation. Furthermore, it has been unclear whether the acoustic image conveyed by FM echoes enables fine texture discrimination, or whether gleaning bats that forage in echo-cluttering environments must locate prey by using other cues, such as prey-generated sounds. Here we show that two species of insectivorous gleaning bats perform badly when compelled to detect silent and immobile prey in clutter, but are very efficient at capturing noisy prey items among highly cluttered backgrounds, and both dead or live prey in uncluttered habitats. These findings suggest that the short, broadband FM echolocation calls associated with gleaning bats are not adapted to detecting prey in clutter.

Acoustics↗
PubMed2002

Overt female mate competition and preference for central males in a lekking antelope.

In mammals, there exists only scant evidence of female mate choice in species mating on arenas, so-called leks. This has led to hypotheses of lek evolution that are based on benefits to females from reduced harassment by males, low predation risk, or improved availability of scarce nutrients. Here I report that female topi antelopes (Damaliscus lunatus) compete aggressively for matings with preferred males on central lek territories. Females fight at higher rates and more likely disrupt mating attempts of others in the lek center than elsewhere. Contrary to the predictions of the alternative hypotheses, food resources were insignificant, and harassment levels and estimated predation risk were higher on than off lek. These results clearly demonstrate female competition for mates in a lekking mammal in which a female chooses between males for the sole purpose of mating. The finding suggests that the forces leading to lek evolution in mammals and birds may be more similar than previously acknowledged.

Animals↗
PubMedDate not supplied

Linking cranial kinematics, buccal pressure, and suction feeding performance in largemouth bass.

The rate and magnitude of buccal expansion are thought to determine the pattern of water flow and the change in buccal pressure during suction feeding. Feeding events that generate higher flow rates should induce stronger suction pressure and allow predators to draw prey from further away. We tested these expectations by measuring the effects of prey capture kinematics on suction pressure and the effects of the latter on the distance from which prey were drawn-termed suction distance. We simultaneously, but not synchronously, recorded 500-Hz video and buccal pressure from 199 sequences of four largemouth bass, Micropterus salmoides, feeding on goldfish. From the video, we quantified several kinematic variables associated with the head and jaws of the feeding bass that were hypothesized to affect pressure. In a multiple regression, kinematic data accounted for 79.7% of the variation among strikes in minimum pressure. Faster mouth opening and hyoid depression were correlated with lower pressures, a larger area under the pressure curve, and a faster rate of pressure reduction. In contrast, buccal pressure variables explained only 16.5% of the variation in suction distance, and no single pressure variable had a significant relationship with suction distance. Thus, although expected relationships between head kinematics and buccal pressure were confirmed, suction distance was only weakly related to buccal pressure. Three explanations are considered. First, bass may not attempt to maximize the distance from which prey are drawn. Second, the response of prey items to suction-induced flow depends on prey behavior and orientation and is, therefore, subject to considerable variation. Third, previous theoretical work indicates that water velocity decays exponentially with distance from the predator's mouth, indicating that variation among strikes in flow at the mouth opening is compressed away from the mouth. These findings are consistent with other recent data and suggest that suction distance is a poor metric of suction feeding performance.

Animals↗
PubMed2003

Reciprocal selection causes a coevolutionary arms race between crossbills and lodgepole pine.

Few studies have shown both reciprocal selection and reciprocal adaptations for a coevolving system in the wild. The goal of our study was to determine whether the patterns of selection on Rocky Mountain lodgepole pine (Pinus contorta spp. latifolia) and red crossbills (Loxia curvirostra complex) were concordant with earlier published evidence of reciprocal adaptations in lodgepole pine and crossbills on isolated mountain ranges in the absence of red squirrels (Tamiasciurus hudsonicus). We found that selection (directional) by crossbills on lodgepole pine where Tamiasciurus are absent was divergent from the selection (directional) exerted by Tamiasciurus on lodgepole pine. This resulted in divergent selection between areas with and without Tamiasciurus that was congruent with the geographic patterns of cone variation. In the South Hills, Idaho, where Tamiasciurus are absent and red crossbills are thought to be coevolving with lodgepole pine, crossbills experienced stabilizing selection on bill size, with cone structure as the agent of selection. These results show that crossbills and lodgepole pine exhibit reciprocal adaptations in response to reciprocal selection, and they provide insight into the traits mediating and responding to selection in a coevolutionary arms race.

Adaptation, Physiological↗
PubMed1996

Chemoreceptive control of feeding processes in hydra.

Cnidarians are the simplest metazoans to exhibit satiety after feeding. When hydra are fed to repletion, they close their mouths and cease to capture prey. As feeding stops, contractions of the tentacles and body column increase. Our earlier experiments showed that a gel chromatographic fraction of prey substances inhibits prey capture. We now present evidence that the same fraction reduces the duration of mouth opening induced by reduced glutathione (GSH) and inhibits the binding of GSH to its putative receptor. The fraction also induces column contractions which are similar to those normally seen in sated animals. Prey substances, of unfractionated homogenate, also induce post-feeding tentacle contractions similar to those seen in sated animals. Gut distention does not appear to induce behavior associated with satiety. Therefore, these experiments suggest that chemoreception of prey substances induce satiety in hydra.

Animals↗
PubMed2000

Pursuit plunging by northern gannets (Sula bassana) feeding on capelin (Mallotus villosus).

Northern gannets (Sula bassana) are considered to obtain prey usually by rapid, vertical, shallow plunge dives. In order to test this contention and investigate underwater foraging behaviour, we attached two types of data-logging systems to 11 parental northern gannets at Funk Island in the North-Wiest Atlantic. We documented, for the first time to the authors' knowledge, gannets performing long, flat-bottomed, U-shaped dives that involved underwater wing propulsion as well as rapid, shallow, V-shaped dives. The median and maximum dive depths and durations were 4.6 and 22.0 m and 8 and 38 s, respectively. Short, shallow dives were usually V-shaped and dives deeper than 8 m and longer than 10 s were usually U-shaped, including a period at constant depth (varying between 4 and 28s with median 8s). Diving occurred throughout the daylight period and deepest dives were performed during late morning. On the basis of motion sensors in the loggers and food collections from telemetered birds, we concluded that extended, deep dives were directed at deep schools of capelin, a small pelagic fish, and we hypothesized that V-shaped dives were aimed at larger, pelagic fishes and squids. Furthermore, these V-shaped dives allowed the birds to surprise their pelagic prey and this may be critical because the maximum swimming speeds of the prey species may exceed the maximum dive speeds of the birds.

Animals↗