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PubMed2006

Opposable spines facilitate fine and gross object manipulation in fire ants.

Ants inhabit diverse terrestrial biomes from the Sahara Desert to the Arctic tundra. One factor contributing to the ants' successful colonization of diverse geographical regions is their ability to manipulate objects when excavating nests, capturing, transporting and rendering prey or grooming, feeding and transporting helpless brood. This paper is the first to report the form and function of opposable spines on the foretarsi of queens and workers used during fine motor and gross motor object manipulation in the fire ant, Solenopsis invicta. In conjunction with their mandibles, queens and workers used their foretarsi to grasp and rotate eggs, push or pull thread-like objects out of their way or push excavated soil pellets behind them for disposal by other workers. Opposable spines were found on the foretarsi of workers from seven of eight other ant species suggesting that they might be a common feature in the Formicidae.

Animals↗
PubMed2005

Experimental manipulation of predation risk and food quality: effect on grazing behaviour in a central-place foraging herbivore.

The relative importance of predation risk and food quality on spatial grazing pressure and activity patterns was tested in a central-place foraging herbivore: the European rabbit. Rabbits grazed less with increasing distance from their burrows into adjacent grassland, thereby creating a gradient of increasing vegetation height and plant biomass and decreasing plant nutrient concentration. When nitrogen concentration was experimentally increased by 150% through fertilizing and mowing, rabbits visited these plots four times more frequently than the untreated control plots. Addition of predator scent (mink pellets) did not result in different patch use by rabbits. The combined addition of fertilizer and mink pellets had the same effect as addition of fertilizer alone. However, the mink pellets changed the temporal activity pattern of rabbits as measured with infrared detectors. Rabbits were predominantly nocturnal but shifted their activities to the day when mink pellets were added, resulting in equal activities during night and day. We conclude that rabbits are sensitive to perceived predation risk, but that this does not influence their spatial grazing pressure. A selection for the highest food quality on the other hand can explain the observed natural rabbit grazing gradient. Food quality was highest close to the burrows, therefore rabbits selecting for high quality food should forage most intensely close to the burrows and only move further away for higher quality items or when the vegetation close to their burrows is depleted. Through intensive grazing close to the burrows rabbits facilitated for themselves either through stimulating fresh protein rich re-growth or the return of nutrients through faeces or both. This is in contrast with central-place foraging theory where intense feeding close to the burrow is assumed to lead to reduced food resources.

Animals↗
PubMed1992

Hormonal and neurochemical correlates of various forms of animal "aggression".

The majority of studies attempting to evaluate the roles of hormones and neurochemicals in "aggression" concern laboratory rodents, notably rats and mice, with fewer investigations on infrahuman primates. Studies suggest that situations used to assess aggression (e.g., social conflict tests, parental attack, predatory behavior, use of unavoidable electroshock) actually tap a diverse range of motivations whose functions include offense, defense and predation. It is also apparent that ethoexperimental techniques, i.e., those applying ethological methodologies and concepts to laboratory situations, have advantages in assessing the direct and indirect consequences of chemical treatments. In this review, the impacts of hormonal manipulation (by surgery and/or application) and varying neurotransmitters (studied in terms of regional changes and as consequences of drug treatments) on a variety of forms of behavior are assessed. Different tests do show varying responses to common treatments, confirming the heterogeneity of the available paradigms. A brief discussion is provided of which tests are likely to prove most relevant to clinical studies.

Aggression↗
PubMed2005

[Maternal inheritance in a subsocial spider: web for collective prey capturing of the young].

Construction of a safe refuge is the first step toward the evolution of social organization in spiders. In the case of the subsocial spider Amaurobius Jerox (Araneae, Amaurobiidae), the young remain in the natal nest after consuming their mother's body (matriphagy). The benefit that the young could obtain from the maternal web was investigated in their collective prey capture. The results demonstrated the adaptive value of the maternal web. The prey capturing activity was more effective when the young were allowed to stay on the maternal web than when they used the web constructed by themselves. Maternal web may also provide a better transmission of information on prey state and clutch mates' activities, because more spiderlings were recruited to contact and hold the prey in a shorter period of time than when they were on a spiderling-constructed web. The young's inheritance of the maternal nest is probably one of the crucial ways in which the mother influences the post-maternal social period of the young.

Animals↗
PubMed2006

Sporulating bacteria prefers predation to cannibalism in mixed cultures.

Predatory behavior, a property associated with ecosystems, is not commonly observed in microorganisms. However, cannibalistic tendencies have been observed in microorganisms under stress. For example, pure culture of Bacillus subtilis exhibits cannibalism under nutrient limitation. It has been proposed that a fraction of cells in the population produce Spo0A, a regulatory protein that is responsible for delaying sporulation. Cells containing spo0A would produce a killing factor by activating skf operon and an associated pump to export the factor. Cells that do not contain spo0A in the population are lysed. However in addition to the competition among the cells of B. subtilis, these cells also compete with other organisms for the limited nutrients. In this work, we report the cannibalistic behavior of B. subtilis in presence of Escherichia coli under severe nutritional limitation. We demonstrate that B. subtilis lyses cells of E. coli using an antibacterial factor under the regulation of Spo0A. Our experiments also suggest that B. subtilis prefers predation of E. coli to cannibalism in mixed cultures. B. subtilis also demonstrated predation in mixed cultures with other soil microorganisms, such as, Xanthomonas campestris, Pseudomonas aeruginosa and Acinetobactor lwoffi. This may offer B. subtilis a niche to survive in an environment with limited nutrients and under competition from other microorganisms.

Adaptation, Physiological↗
PubMed2005

Novel effects of CRF on visuomotor behavior and autonomic function in anuran amphibians.

Administration of corticotropin-releasing factor (CRF) or exposure to stressors inhibits feeding in anuran amphibians. Since most amphibians rely on visual cues for feeding, these findings have led to the hypothesis that CRF may modulate visuomotor pathways involved in prey detection and predator avoidance. The inhibitory effects of CRF on feeding and prey capture are rapid, and do not appear to require the pituitary-adrenal axis in the short term. CRF neurons are located in key visuomotor processing areas of the anuran brain. Corticotropin-releasing factor also has potent stimulatory effects on sympathetic nervous system activity, a key regulatory system involved in both prey capture and predator avoidance. In this review I will discuss the unique model that amphibian species provide for investigating CRF effects on visual perception and visuomotor processing, and will summarize the data suggesting a role for CRF in visuomotor behavior and autonomic function in amphibians.

Adrenocorticotropic Hormone↗
PubMed2003

Are corticosterone levels a good indicator of food availability and reproductive performance in a kittiwake colony?

We evaluated the use of corticosterone to gauge forage availability and predict reproductive performance in black-legged kittiwakes (Rissa tridactyla) breeding in Alaska during 1999 and 2000. We modeled the relationship between baseline levels of corticosterone and a suite of individual and temporal characteristics of the sampled birds. We also provided supplemental food to a sample of pairs and compared their corticosterone levels with that of pairs that were not fed. Corticosterone levels were a good predictor of forage availability in some situations, although inconsistencies between corticosterone levels and reproductive performance of fed and unfed kittiwakes suggested that this was not always the case. In general, higher corticosterone levels were found in birds that lacked breeding experience and in birds sampled shortly after arriving from their wintering grounds. All parameters investigated, however, explained only a small proportion of the variance in corticosterone levels. We also investigated whether corticosterone, supplemental feeding, year of the study, breeding experience, body weight, and sex of a bird were able to predict laying, hatching, and fledging success in kittiwakes. Here, breeding experience, year of the study, and body weight were the best predictors of a bird's performance. Corticosterone level and supplemental feeding were good predictors of kittiwake reproductive performance in some cases. For example, corticosterone levels of birds sampled during the arrival stage reliably predicted laying success, but were less reliable at predicting hatching and fledging success. Counts of active nests with eggs or chicks may be more reliable estimates of the actual productivity of the colony. Supplemental feeding had strong effects on kittiwake productivity when natural forage was poor, but had little effect when natural forage was plentiful.

Animal Feed↗
PubMed2003

Time-dependent effects of cycloheximide on long-term memory in the cuttlefish.

When shown prawns in a glass tube, cuttlefish promptly learn to inhibit their predatory behavior and retain this ability for a long time. The cellular and molecular mechanisms of this long-term memory (LTM) are not yet known. In this study, we analyzed the dependency of LTM on de novo brain protein synthesis. Cycloheximide (CXM), a protein synthesis inhibitor, is injected intravenously immediately, 1 h, 3 h, 4 h or 6 h after the training. Retention is tested 24 h posttraining. The injections of CXM revealed one period of memory sensitivity to pharmacological intervention. CXM administered immediately or 6 h after training has no effect on LTM. Conversely, injections given between 1 and 4 h posttraining resulted in amnesia. Taken together, findings of this study establish for the first time in Sepia officinalis that de novo protein synthesis is an essential and time-dependent event for LTM formation of this form of associative learning.

Animals↗
PubMed1986

What makes male mice paternal?

Both copulation and postcopulatory cohabitation with pregnant females reduce infanticide and enhance paternal responsiveness in male CS1 mice. The effectiveness of copulation in this process, however, depends on the number of occasions that males have previously encountered infants. Infanticidal males which have been subordinated in brief encounters with other males are less likely to commit infanticide in subsequent tests than are those which became dominant to other males. Males which copulate and cohabit with a relatively large female are less likely to be infanticidal than are those with a relatively small female. These data suggest that males are subordinated after copulation by their mates and that this subordination is a factor in the reduction of infanticide and the initiation of paternal responsiveness.

Aggression↗
PubMed1997

Maternal presence and rearing condition affect responses to a live predator in kangaroo rats (Dipodomys heermanni arenae).

Experiment 1 compared the responses of wild-caught adult and captive-born adult and juvenile kangaroo rats (Dipodomys heermanni arenae) to a live snake. Wild-caught adult rats were less active and monitored the snake more than during a control condition; captive-born juvenile rats did not behave differently during snake and control tests. Snake-naive adult rats behaved more like the wild-caught adult rats, but not on all measures. In Experiment 2, pups were tested at 25 and 50 days of age in 4 conditions: no-snake control, alone with the snake, with a sibling and the snake, and with the mother and the snake. Pups did not behave differently during control and snake tests, but during tests with the mother, pups faced the snake less and followed the mother. Younger pups were more often near the mother than a sibling and followed the mother more when the snake was present. Development of defensive behavior may depend on both predator experience and maternal influence.

Age Factors↗
PubMed2003

Strategy planning in cats (Felis catus) in a progressive elimination task.

Domestic cats (Felis cans) were administered a progressive elimination task in which they had to visit and deplete 3 baited sites. Cats were brought back to the starting point after each visit to any site whether the visit represented a correct or an incorrect choice. The results revealed that cats organized search as a function of the least distance principle whether they had to assess starting point to target distances (Experiment 1, n = 12) or adjacent bowl distances (Experiment 2, n = 12). The results also revealed that the starting point to target distance factor was the most influential in determining the initial choice (Experiment 3, n = 6) and in producing errors. Errors were also linked to the antero-posterior bodily axis of the cat. Results are discussed in terms of the predatory behavior of the cat.

Animals↗
PubMed2006

Evolution: a catfish that can strike its prey on land.

An important step towards understanding the evolution of terrestriality in vertebrates is to identify how the aquatic ancestors of tetrapods were able to access ground-based prey. We have discovered that the 'eel catfish' Channallabes apus, an inhabitant of the muddy swamps of tropical Africa, has a remarkable ability to forage and capture prey on land. The animal's capacity to bend its head down towards the ground while feeding seems to be an essential feature that may have enabled fish to make the transition from an aquatic to a terrestrial mode.

Africa↗
PubMed2003

Escalation of a coevolutionary arms race through host rejection of brood parasitic young.

Cuckoo nestlings that evict all other young from the nest soon after hatching impose a high reproductive cost on their hosts. In defence, hosts have coevolved strategies to prevent brood parasitism. Puzzlingly, they do not extend beyond the egg stage. Thus, hosts adept at recognizing foreign eggs remain vulnerable to exploitation by cuckoo nestlings. Here we show that the breach of host egg defences by cuckoos creates a new stage in the coevolutionary cycle. We found that defences used during the egg-laying period by host superb fairy-wrens (Malurus cyaneus) are easily evaded by the Horsfield's bronze-cuckoo (Chrysococcyx basalis), a specialist fairy-wren brood parasite. However, although hosts never deserted their own broods, they later abandoned 40% of nests containing a lone Horsfield's bronze-cuckoo nestling, and 100% of nests with a lone shining bronze-cuckoo nestling (Chrysococcyx lucidus), an occasional fairy-wren brood parasite. Our experiments demonstrate that host discrimination against evictor-cuckoo nestlings is possible, and suggest that it has selected for the evolution of nestling mimicry in bronze-cuckoos.

Adaptation, Biological↗
PubMed2003

Residual susceptibility of the red imported fire ant (Hymenoptera: Formicidae) to four agricultural insecticides.

The red imported fire ant, Solenopsis invicta Buren, is an abundant predator in cropping systems throughout its range. It has been documented to be an important predator of numerous crop pests, as well as being an agricultural pest itself. Information on the impact of insecticides on natural enemies such as fire ants is necessary for the integration of biological and chemical control tactics in an effective pest management program. Therefore, a residual vial bioassay was developed to determine the concentration-mortality responses of S. invicta workers to four commonly used insecticides: acephate, chlorpyrifos, methomyl and lambda-cyhalothrin. Fire ant workers showed a mortality response to serial dilutions to all four chemicals. Methomyl (LC50 0.04 microg/vial, fiducial limits 0.03-0.06) was the most toxic, followed by chlorpyrifos (LC50 0.11 microg/vial, fiducial limits 0.07-0.17) and acephate (LC50 0.76 microg/vial, fiducial limits 0.50-1.04). Of the chemicals assayed, it took a much higher concentration of lambda-cyhalothrin (LC50 2.30 microg/vial, fiducial limits 1.57-3.59) to kill 50% of the workers compared with the other three chemicals. The results of this study demonstrate the wide range in responses of fire ants to four insecticides that are labeled and commonly used on numerous agricultural crops throughout the United States. These results further suggest the possibility of using a discriminating dose of lambda-cyhalothrin to control the target pest species while conserving fire ants in the agricultural systems in which their predatory behavior is beneficial to the integrated pest management program.

Animals↗
PubMed2002

Brighter yellow blue tits make better parents.

Whether or not bird ornaments are a signal for direct (e.g. good parents) or indirect (e.g. good genes) benefits to prospective partners in sexual selection is controversial. Carotene coloration in Parus species is directly related to the ingestion of caterpillars, so that a brightly carotene-coloured tit may be signalling its ability to find caterpillars, a main high-quality food source for good fledgling development, and hence its parental abilities. If carotene-based plumage coloration is related to the good-parent hypothesis, we predict that yellow plumage brightness of tit fathers should be positively correlated to their investment in offspring provisioning. Here, we use cross-fostering experiments in blue tits (Parus caeruleus) to show that chick development (as measured by tarsus length) is related to yellowness of the foster father, but not to that of the genetic parents. Using these data, we were able to measure, for the first time to our knowledge, the separate contribution of genetic and environmental factors (i.e. parental plumage coloration) to chick development, and hence parental investment. Our data, which relate carotenoid coloration to models of good parents, and data from other authors, which relate ultraviolet coloration to good-genes models, stress that different kinds of coloration within an individual may provide different units of information to prospective females.

Animals↗
PubMed2002

Parental care of a cowbird host: caught between the costs of egg-removal and nest predation.

Avian brood parasites reduce host fitness through the addition of parasitic eggs and the removal of host eggs. Both parasitic egg-addition and host egg-removal may be important sources of selection on host behaviour, creating fitness trade-offs with selection imposed by nest predation. However, the relative costs hosts suffer from egg-addition and host egg-removal and the responses to these costs are largely unstudied. Through experimental manipulations and observations, we demonstrate that increased nest attentiveness by female yellow warblers (Dendroica petechia) reduces the cost of brood parasitism by reducing egg-removal by brown-headed cowbirds (Molothrus ater). However, female attentiveness does not reduce the addition of parasitic eggs. Experimentally parasitized females respond to the threat of egg-removal by increasing nest attentiveness. Increased attentiveness, however, reduces time for females to gather food and requires males to visit the nest more often to feed incubating females. This increased activity in turn increases the risk of nest predation. Thus, brood parasitism (specifically egg-removal) and nest predation produce conflicting selection on incubation strategies, as parasitized hosts are caught between the costs of egg-removal by brood parasites, and the costs of increased nest predation if the female spends more time on the nest to reduce egg-removal.

Animals↗
PubMed2002

Oystercatchers use colour preference to achieve longer-term optimality.

The optimal diet model entails that foragers look beyond the individual prey encounter, to at least the level of intake rate across a bout of foraging, but optimization over a longer time remains controversial. In this paper, we show how oystercatchers increase their intake over the longer term using mussel colour as a cue. Wintering oystercatchers Haematopus ostralegus feed extensively on mussels Mytilus edulis in the estuaries of southern Britain. They show a marked preference for brown-shelled mussels over the commoner black-shelled morph, and we show that this enables them to maximize their rate of energy gain over a longer period than a single foraging bout. The brown and black mussels did not differ in ventral thickness and energy content, which are the main criteria for mussel selection and most important for short-term optimization. The brown mussels contained significantly less moisture, so by selecting them, oystercatchers could pack more mussel flesh into their limited oesophageal storage capacity. This enables them to increase their overall consumption during a feeding bout and increases their long-run energy gain rate, to an extent that is large enough to be significant for survival, especially during the short exposure of the mussel beds in winter.

Animals↗
PubMed2004

Predation risk is an ecological constraint for helper dispersal in a cooperatively breeding cichlid.

Environmental conditions are thought to be responsible for the extent and benefits of cooperative breeding in many animal societies, but experimental tests are scarce. We manipulated predator pressure in the cooperatively breeding cichlid Neolamprologus pulcher in Lake Tanganyika, where predators have been suggested to influence helper and breeder survival, helper dispersal and group reproductive success. We varied the type and intensity of predation by releasing medium, large, or no predators inside large underwater cages enclosing two or three group territories. Helper and breeder survival, helper dispersal and group reproductive success decreased from the control, to the medium- and large-predator treatments. These effects were modified by helper body size and the number of adults protecting the group from predators, supporting the 'group augmentation hypothesis'. Predators forced helpers to stay closer to, and spend more time inside, protective shelters. The results demonstrate the importance of predators for group living in this species, and support the 'ecological constraints hypothesis' of cooperative breeding, in the sense that subordinates stay at home rather than leave and breed independently under the risk of predation.

Animals↗