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At least 451 records · Page 25Linked to original sources
PubMed1988

A model of the visual localization of prey by frog and toad.

In this paper we demonstrate how prey localization can be achieved rapidly and accurately by coupling prey-selection and lens-accommodation processes within a feedback loop. Information derived from prey selection supplies a setpoint for accommodation. In turn, adjustment of the lens modifies the visual input and can alter the prey selection process. The natural feedback of this goal-seeking system automatically corrects for the problem of ambiguity in binocular matching. Although it is of general interest as a depth algorithm, we tie the model to the known anatomy, physiology and behavior of frogs and toads. Instead of building a global depth-map we propose that the goal of catching a prey leads a frog or toad to select a particular region of its visual world for special scrutiny. We suggest that the first step of the prey-catching sequence is to adjust the accommodative state of the lenses and thus lock the visual apparatus on to a stimulus. We identify brain regions that could provide the neural substrates necessary to support the model's various functional stages and present experiments, with a computer simulation, that compare its functioning to animal behavior.

Animals↗
PubMed1986

Defensive alkaloid in blood of Mexican bean beetle (Epilachna varivestis).

The blood of the Mexican bean beetle (Epilachna varivestis) contains a homotropane alkaloid, euphococcinine (1). The beetles 'reflex bleed' when disturbed, thereby deploying the alkaloid, which is provenly deterrent to spiders and ants. Newly emerged adults lack the alkaloid, but the compound builds up to deterrent levels in their blood within days. Eggs and larvae of Epilachna are devoid of the compound.

Alkaloids↗
PubMed2004

The ladybird Thalassa saginata, an obligatory myrmecophile of Dolichoderus bidens ant colonies.

The larvae and pupae of the ladybird Thalassa saginata develop inside colonies of the dolichoderine ant Dolichoderus bidens. This association is the first specific and obligatory relationship recorded between ants and ladybirds. The ants provide shelter and protection to the larvae but the diet of the latter remains unclear. The integration of T. saginata larvae into the ant colonies is achieved by mimicking the cuticular patterns of the ants' brood. Moreover, the larvae secrete substances from their hairs and anal gland that are likely to enhance their attractiveness.

Animals↗
PubMed2006

Behavioural evidence of UV sensitivity in jumping spiders (Araneae: Salticidae).

Jumping spiders are known to possess ultraviolet (UV) receptors in the retinas of their large-principal eyes. The existence of UV visual cells, however, does not prove that jumping spiders can see into the UV part of spectrum (300-400 nm) or whether such an ability plays any role in salticid intra-specific interactions. In the study reported herein, we performed behavioural experiments to test whether a UV-reflecting jumping spider, Cosmophasis umbratica, is sensitive to UV wavelengths and whether UV cues are important in intra-specific communication. The absence of UV cues not only affected intra-specific behaviour by significantly reducing the frequency of agonistic displays, but also elicited unprecedented courtship displays in males towards their own mirror images and conspecific opponents. Furthermore, C. umbratica males were able to respond rapidly to changes in UV cues of conspecific mirror images by switching between agonistic and courtship displays. These findings clearly demonstrate that C. umbratica males are capable of seeing UV wavelengths and that UV cues are necessary and sufficient for this species to enable the agonistic displays. Hence, UV light may have an important role to play in intra-specific communication in jumping spiders.

Animal Communication↗
PubMed2003

New observations of ant-dipping techniques in wild chimpanzees at Bossou, Guinea.

Ant-dipping behavior is often cited as a clear example of chimpanzee culture, since different populations have apparently different dipping techniques (the one-handed method used by chimpanzees in Bossou, Guinea and Taï, Côte d'Ivoire, and the two-handed method used in Gombe, Tanzania). Here we report a new observation of ant-dipping behavior from Bossou using the two-handed method, in addition to the first detailed description of the one-handed method. Although the main dipping pattern was the one-handed method in Bossou, one adult male was observed dipping for ants using the two-handed method, while other chimpanzees employed the conventional one-handed method in the same episode. The two-handed method was also sporadically observed in a juvenile and in adolescents, who were still immature in dipping techniques and hence prone to suffer from ant attacks. Cross-population comparisons of dipping techniques suggest that there are two sub-types of the one-handed method, and the Bossou one-handed technique may be substantially different from that of Taï. In terms of overall behavioral repertoire in ant dipping, the Bossou pattern appears more similar to that of Gombe than Taï. This may be explained by the difference in target ant species.

Age Factors↗
PubMed2006

Ant fishing by wild chimpanzees is not lateralised.

Right-dominant handedness is unique and universal in Homo sapiens, suggesting that it is a highly derived trait. Our nearest living relations, chimpanzees, show lateralised hand preference when using tools, but not when otherwise manipulating objects. We report the first contrary data, that is, non-lateralised tool-use, for ant fishing as done in the Mahale Mountains of Tanzania. Unlike nut cracking, termite fishing, and fruit pounding, as seen elsewhere, in which most individuals are either significantly or wholly left- or right-biassed, ant fishers are mostly ambilateral. The clue to this exception lies in arboreality; all other patterns of chimpanzee elementary technology are done on the ground. Arboreal tool use usually requires not only that one hand be used to hold the tool, but also that the other hand gives postural support. When the supporting hand is fatigued, then it must be relieved by the other. Terrestrial tool use entails no such trading off. To test the hypothesis, we compared frequency of hand changing with the incidence of major hand support, and found them to be significantly positively correlated. The evolutionary transition from arboreality to terrestriality may have been a key enabler for the origins of human laterality.

Animals↗
PubMed2006

The effects of prey patchiness, predator aggregation, and mutual interference on the functional response of Phytoseiulus persimilis feeding on Tetranychus urticae (Acari: Phytoseiidae, Tetranychidae).

The spatial distributions of two-spotted spider mites Tetranychus urticae and their natural enemy, the phytoseiid predator Phytoseiulus persimilis, were studied on six full-grown cucumber plants. Both mite species were very patchily distributed and P. persimilis tended to aggregate on leaves with abundant prey. The effects of non-homogenous distributions and degree of spatial overlap between prey and predators on the per capita predation rate were studied by means of a stage-specific predation model that averages the predation rates over all the local populations inhabiting the individual leaves. The empirical predation rates were compared with predictions assuming random predator search and/or an even distribution of prey. The analysis clearly shows that the ability of the predators to search non-randomly increases their predation rate. On the other hand, the prey may gain if it adopts a more even distribution when its density is low and a more patchy distribution when density increases. Mutual interference between searching predators reduces the predation rate, but the effect is negligible. The stage-specific functional response model was compared with two simpler models without explicit stage structure. Both unstructured models yielded predictions that were quite similar to those of the stage-structured model.

Animals↗
PubMed2006

Pheromone-induced priming of a defensive response in Western flower thrips.

The Western flower thrips Frankliniella occidentalis produces conspicuous anal droplets that function as a direct defense against various predators. These droplets also function in pheromonal communication in that they contain a mixture of decyl acetate and dodecyl acetate, which acts as an alarm. Exposure of thrips to synthetic pheromone is known to promote takeoff or refuge seeking, but the effect of the natural pheromone has not yet been studied. Here, we not only studied the response to natural pheromone, but also tested the new hypothesis that the alarm pheromone primes a defensive response in thrips. This test was carried out by measuring the reaction time to a simulated predator attack after exposure to synthetic or natural alarm pheromone (against a control with no pheromone at all). The reaction was quantified in terms of the time it takes a thrips larva to produce a droplet after attack. We found that thrips larvae produce droplets of alarm pheromone faster when cues associated with danger are present. There were no significant differences in reaction times of responses to synthetic pheromone, natural pheromone, or odors from a patch with a predator attacking a thrips larva. This implies that the synthetic pheromone mimics the natural pheromone, and that other cues emanating from the predator play a minor role. We conclude that the alarm pheromone increases the vigilance of the thrips, and this may promote its survival.

Animals↗