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At least 343 records · Page 19Linked to original sources
PubMed2001

Food caching in orb-web spiders (Araneae: Araneoidea).

Caching or storing surplus prey may reduce the risk of starvation during periods of food deprivation. While this behaviour occurs in a variety of birds and mammals, it is infrequent among invertebrates. However, golden orb-web spiders, Nephila edulis, incorporate a prey cache in their relatively permanent web, which they feed on during periods of food shortage. Heavier spiders significantly reduced weight loss if they were able to access a cache, but lost weight if the cache was removed. The presence or absence of stored prey had no effect on the weight loss of lighter spiders. Furthermore, N. edulis always attacked new prey, irrespective of the number of unprocessed prey in the web. In contrast, females of Argiope keyserlingi, who build a new web every day and do not cache prey, attacked fewer new prey items if some had already been caught. Thus, a necessary preadaptation to the evolution of prey caching in orb-web spiders may be a durable or permanent web, such as that constructed by Nephila.

Animals↗
PubMed2006

Prey food quality affects flagellate ingestion rates.

Flagellate feeding efficiency appears to depend on morphological characteristics of prey such as cell size and motility, as well as on other characteristics such as digestibility and cell surface characteristics. Bacteria of varying morphological characteristics (cell size) and mineral nutrient characteristics or food quality (as determined by the C:N:P ratio) were obtained by growing Pseudomonas fluorescens in chemostats at four dilution rates (0.03, 0.06, 0.10, and 0.13 h-1) and three temperatures (14 degrees C, 20 degrees C, and 28 degrees C). Cells of a given food quality were heat-killed and used to grow the flagellate Ochromonas danica. Ingestion and digestion rates were determined by using fluorescently labeled bacteria of the same food quality as the bacteria supporting growth. Ingestion rates were affected by both food quality and cell size. Cells of high food quality (low carbon:element ratio) were ingested at higher rates than cells of low food quality. Multiple regression analysis indicated that cell size also influenced ingestion rate but to a much lesser extent than did food quality. Digestion rates were not correlated with either food quality or cell size. Results suggest that flagellates may adjust feeding efficiency based on the quality of food items available.

Animals↗
PubMed2004

Specializations for aerial hawking in the echolocation system of Molossus molossus (Molossidae, Chiroptera).

While searching for prey, Molossus molossus broadcasts narrow-band calls of 11.42 ms organized in pairs of pulses that alternate in frequency. The first signal of the pair is at 34.5 kHz, the second at 39.6 kHz. Pairs of calls with changing frequencies were only emitted when the interpulse intervals were below 200 ms. Maximum duty cycles during search phase are close to 20%. Frequency alternation of search calls is interpreted as a mechanism for increasing duty cycle and thus the temporal continuity of scanning, as well as increasing the detection range. A neurophysiological correlate for the processing of search calls was found in the inferior colliculus. 64% of neurons respond to frequencies in the 30- to 40-kHz range and only in this frequency range were closed tuning curves found for levels below 40 dB SPL. In addition, 15% of the neurons have double-tuned frequency-threshold curves with best thresholds at 34 and 39 kHz. Differing from observations in other bats, approach calls of M. molossus are longer and of higher frequencies than search calls. Close to the roost, the call frequency is increased to 45.0-49.8 kHz and, in addition, extremely broadband signals are emitted. This demonstrates high plasticity of call design.

Acoustic Stimulation↗
PubMed2006

Spatial heterogeneity in predator activity, nest survivorship, and nest-site selection in two forest thrushes.

The ability of prey to find and use predator-free space has far-reaching consequences for their persistence and interactions with their predators. We tested whether nest survivorship of the ground-nesting veery (Catharus fuscescens) and shrub-nesting wood thrush (Hylocichla mustelina) was related to the local absence of a major nest predator, the white-footed mouse (Peromyscus leucopus). Mouse-free space was defined by trap stations that failed to trap a mouse during the avian breeding season (approximately May through July). In addition, mouse activity was quantified at individual trap stations based on the number of captures during the same period (six 2.25-ha trapping grids, each containing 121 trap stations trapped repeatedly throughout the summer between 1998 and 2002.) Annual mouse-free space was correlated with other measures of mouse activity based on trapping data. Both mouse-free space and activity metrics were significantly related to annual rates of nest predation (i.e., nest daily mortality rate) in veery but not wood thrush. Likewise, mouse-free space and mouse activity within the nest neighborhood (approximately 30x30 m2 surrounding each nest) was significantly related to nest survivorship in veery but not wood thrush. More trap stations had consistently greater (hotspots) and lesser (coldspots) mouse activity than expected by chance, and veeries were significantly more likely to nest near stations that had below the grid-average trapping success. Our study thus documented significant spatial variability in predator activity and its relationship to nest predation and nest-site selection in a ground-nesting songbird.

Animals↗
PubMed1985

The influence of reproductive state on infanticide by wild female house mice (Mus musculus).

The majority of female mice (Mus musculus) from laboratory stocks are spontaneously parental. In contrast, the majority of adult wild female house mice exhibit infanticide (the killing of preweanling young), but the frequency with which infanticide is observed varies as a function of age and reproductive state. Prepubertal females were less likely to exhibit infanticide (39%) than were adult virgin females (61%). The frequency of infanticide increased during pregnancy, with over 90% of females exhibiting infanticide just before parturition. But, after parturition, previously infanticidal females cared for their own litters. When lactating female mice were tested after two days of separation from their own nursing young for their behavior toward a novel newborn pup on either the tenth or twenty-fifth day after parturition, the proportion of the females that exhibited infanticide was not significantly different from that of adult virgin females (about 60%). After only two hours of separation from their own nursing young on the tenth day after parturition, however, all females continued to exhibit parental behavior toward a novel pup.

Aggression↗
PubMed1986

Mesial prefrontal cortical lesions and timidity in rats. III. Behavior in a semi-natural environment.

Behavior of adult male rats with and without lesions in mesial prefrontal cortex (MFC) was studied in a large (72 m2) semi-natural environment (SNE) equipped with numerous wooden nest boxes. The experiment was conducted in 2 partial replicates, one in summer, one in mid-winter. Subjects were introduced to this environment 11 days after surgery, in groups. In the first replication, control and lesioned rats were subjected to mild food deprivation, beginning two weeks after introduction into the SNE. In the second replication, rats were first restricted to separate areas of the SNE, then later allowed full run of the environment. This procedure was then repeated. Summarizing the findings of both replicates, MFC rats were more likely to be found inside nest boxes than controls, changed nest boxes less often, and were less likely to obtain or hoard food from the daily feeding sessions, or to hoard and use nesting material. MFC rats were lower in social rank than controls, and lost less weight during the initial two weeks in replicate one, perhaps due to their relative inactivity. These differences waned over time when MFC rats were competing only within their group, but not when the brain damaged rats were forced to compete with intact controls. It is concluded that the timidity previously described in studies of MFC rats in a laboratory setting (Holson, Holson and Walker) has ethological validity, in that it is also evident in an SNE. The implications of these findings for an understanding of the evolution and function of prefrontal cortex are briefly discussed.

Animals↗
PubMed1985

The effect of long time delays in predator-prey systems.

Past studies have indicated that a time delay longer than the natural period of a system will generally cause instability; however here it is shown that including long maturational time delays in a general predator-prey model need not have this effect. In each of the three cases studied (a predator delay, a prey delay, and both), local stability can persevere despite the presence of arbitrarily long time delays. This perseverence depends upon an interaction between delayed and undelayed features of the model. Delayed processes always act to destabilize the model. For example, prey self-regulation, usually a source of stability, becomes destabilizing if subject to a long delay. However, the effect of such a delay is offset by undelayed regulatory processes, such as a stabilizing functional response. In addition, the adverse effects of delayed predator recruitment can be reduced by the nonreproductive component of the numerical response, a feature not usually involved in determining stability. Finally, it is shown that long time delays are not necessarily more disruptive than short delays; it cannot be assumed that lengthening a time delay progressively reduces stability.

Aging↗
PubMed1996

Exploration and predation models of anxiety: evidence from laboratory and wild species.

The current article addresses several issues within the context of issues within the context of modeling human anxiety disorders in the laboratory. First, evidence is presented to support the suggestion that behavior in exploration models of anxiety may be motivated by apprehension relating to intraspecific encounters rather than interspecific, predator/prey interactions, which has consequences for the interpretation of findings generated using these tests. Second, data are reviewed concerning the use of stimuli indicating the presence of a predator in the context of anxiety modeling, and it is suggested that tests involving the reactions of animals following exposure to such stimuli may be more closely related to pathologic anxiety mechanisms than tests employing observations during contact with these stimuli. Third, comparative studies, using wild-caught rodents, are outlined that show that, although there are similarities in the defensive strategies adopted by these animals in response to the call of an owl, there are also important differences. Finally, the suggestion is made that the distance-dependent-defense-hierarchy may be of important heuristic value in the interpretation of these data and that, perhaps more significantly, it may also provide a mechanism that allows animal defensive strategies and human anxiety disorders to be placed within the same conceptual framework.

Animals↗
PubMed1981

Toward a neuroethology of mammalian vision: ecology and anatomy of rodent visuomotor behavior.

The great diversity of the niches inhabited by rodents, and the variety of the visual demands of these niches, present an excellent prospect for a comprehensive neuroethological analysis of rodent visuomotor behavior. To this end, rodent taxonomy is reviewed, with special attention to the multiple independent invasions of arboreal, terrestrial, fossorial and aquatic niches by distantly related rodent species. Current work on rat, gerbil and hamster is reviewed with emphasis on visual contributions to naturalistic behaviors such as exploration, foraging, predator detection and conspecific recognition.

Animals↗
PubMed1993

Persistence of a four species food chain with full omnivory.

We consider here a food chain composed of four species with full omnivory with Lotka-Volterra dynamics. Conditions for uniform persistence and weak persistence of the food chain are derived. It is also shown that the system exhibits a heteroclinic cycle.

Animals↗