Cleaner fish use tactile dancing behavior as a preconflict management strategy

The most commonly asked question about cooperative interactions is how they are maintained when cheating is theoretically more profitable [1]. In cleaning interactions, where cleaners remove parasites from apparently cooperating clients, the classical question asked is why cleaner fish can clean piscivorous client fish without being eaten, a problem Trivers [2] used to explain reciprocal altruism. Trivers [2] suggested that predators refrain from eating cleaners only when the repeated removal of parasites by a particular cleaner results in a greater benefit than eating the cleaner. Although several theoretical models have examined cheating behavior in clients [3,4], no empirical tests have been done (but see Darcy [5]). It has been observed that cleaners are susceptible to predation [6, 7]. Thus, cleaners should have evolved strategies to avoid conflict or being eaten. In primates, conflicts are often resolved with conflict or preconflict management behavior [8]. Here, I show that cleaner fish tactically stimulate clients while swimming in an oscillating dancing manner (tactile dancing) more when exposed to hungry piscivorous clients than satiated ones, regardless of the client's parasite load. Tactile dancing thus may function as a preconflict management strategy that enables cleaner fish to avoid conflict with potentially dangerous clients.

Factors affecting the success of translocations of the black-faced impala in Namibia

This study analysed 21 translocations of the vulnerable black-faced impala (Aepyceros melampus petersi) to 20 Namibian game farms that occurred between 1970 and 2001, seeking characteristics of the translocated populations and the release sites that significantly correlated with the success of the translocations. Characteristics considered were: initial population size; presence of cheetah and leopard; area; habitat type; occurrence within the historical range of the subspecies and occurrence of trophy hunting. Success of translocations was described by whether the population had a positive growth rate. The success rate of translocations of black-faced impala (62%) was higher than shown in other studies of vertebrate translocations. Initial population size was paramount to the success of translocations. Releases of larger populations were more likely to lead to positive population growth rates than were releases of small populations. The presence of cheetah also influenced the success of translocated populations. In the presence of cheetah, small populations translocated to game farms were significantly less likely to be viable than larger populations. Recommendations for the management of this vulnerable antelope include introducing large initial populations, ideally more than 15 animals, rather than attempting to eliminate cheetah following translocations of impala. (C) 2003 Elsevier Ltd. All rights reserved.

A simple practical method for bulk and rapid extraction of free-living nematodes from marine and estuarine sediments

A simple, rapid method is described for the extraction of large numbers of free-living nematodes from estuarine sediments. This method does not physically or chemically alter or damage the nematodes, but instead relies on their downward movement through a filtering layer of double ply tissue paper and into aerated water-filled trays. Seven trials each with 10 trays kept at 25degreesC for an initial period of 24 h yielded 3985 live nematodes l(-1) (+/-511.5 standard deviation) of estuarine sediment, free of sediment and with minimal debris. Time effects were statistically significantly different, with the same 10 trays yielding another 1259 nematodes l(-1) (+/-413.4) when kept for a second period of 24 h at the same temperature. Temperature effects were also significant, and 7 trials each with 10 trays kept for 24 h at 20-21degreesC, produced a lower yield of 2160 nematodes l(-1) (+/-532.7) of sediment. The method is expected to be of use in nematode extractions from both estuarine and marine sediments.

Levels and probable origin of predatory scarring on humpback whales (Megaptera novaeangliae) in east Australian waters

To investigate the incidence of non-lethal predation in Southern Hemisphere whales, more than 3400 fluke-identification photographs from resight histories of 1436 east Australian humpback whales were examined for evidence of predatory markings. Photographs were obtained from 1984 to 1996 at various locations along the east coast of Australia, from northern Queensland to southern New South Wales. Photographs were classified in terms of the level and type of scarring. The possible predator and whether the markings appeared fresh were also noted. In all, 17% of identified east Australian humpbacks possessed some form of predatory scarring, 57% of which was minor and 43% major. Almost all predatory scarring was consistent with that inflicted by killer whales. Only three whales demonstrated an increase in the level of predatory scarring after their first sightings. Two incidents of fresh scarring were recorded, and one fatal killer whale attack on a humpback whale calf was directly observed. The overall level of predatory scarring found in this study is comparable to those found in studies for Northern Hemisphere humpback whales. The low incidence of adult whales showing their first sign of predatory scarring after their initial sighting, and the small number possessing recent scarring, support the idea that east Australian humpback whales experience most predatory attacks early in life.

Potential interactions between humans and non-breeding shorebirds on a subtropical intertidal flat

The primary aim of this study was to investigate whether bait harvesting, with all its inherent effects, occurring in the intertidal zone of a subtropical estuary, had an impact on a migratory shorebird, the eastern curlew Numenius madagascariensis. In a large-scale manipulative study (units of experiment were 1 ha plots), callianassid shrimp Trypaea australiensis populations were harvested simulating the technique (manual pumping) and the levels of harvesting intensity per unit area (347 shrimp per hectare per harvesting event) exhibited by bait-collectors in SE Australia and South Africa. It was found that at present levels of harvesting intensity per unit area (approximately 1% of standing stock removed per harvesting event) there is no threat to the stocks of Trypaea exploited by the curlews in Moreton Bay, Australia. However, the results show that the curlews themselves apply a considerable predation pressure on Trypaea. Based on the birds' foraging rates and densities, it was estimated that they would consume up to 100% of the initial Trypaea stock over the course of a non-breeding season (October to March). However, the stable seasonal trend in the density of the size-cohort of Trypaea preyed upon by the curlews indicates that the existing rates of predation are easily counterbalanced, e.g. through continuous density-dependent recruitment of these crustaceans. We suggest that this mechanism will provide for a stable foraging environment for both the shorebirds and bait collectors.

The functional roles of passive electroreception in non-electric fishes

Passive electroreception is a complex and specialised sense found in a large range of aquatic vertebrates primarily designed for the detection of weak bioelectric fields. Particular attention has traditionally focused on cartilaginous fishes, but a range of teleost and non-teleost fishes from a diversity of habitats have also been examined. As more species are investigated, it has become apparent that the role of electroreception in fishes is not restricted to locating prey, but is utilised in other complex behaviours. This paper presents the various functional roles of passive electroreception in non-electric fishes, by reviewing much of the recent research on the detection of prey in the context of differences in species' habitat (shallow water, deep-sea, freshwater and saltwater). A special case study on the distribution and neural groupings of ampullary organs in the omnihaline bull shark, Carcharhinus leucas, is also presented and reveals that prey-capture, rather than navigation, may be an important determinant of pore distribution. The discrimination between potential predators and conspecifics and the role of bioelectric stimuli in social behaviour is discussed, as is the ability to migrate over short or long distances in order to locate environmentally favourable conditions. The various theories proposed regarding the importance and mediation of geomagnetic orientation by either an electroreceptive and/or a magnetite-based sensory system receives particular attention. The importance of electroreception to many species is emphasised by highlighting what still remains to be investigated, especially with respect to the physical, biochemical and neural properties of the ampullary organs and the signals that give rise to the large range of observed behaviours.

Influence of Observer Presence on Pacific Damsel Bug Behavior: Who is Watching Whom?

When direct observations are used to study animal behavior the presence of the observer may alter the animal and hence influence the data being collected, yet few studies have quantified this effect. We conducted direct observation studies in the glasshouse to assess the relative influence of observer presence on the behavior of Pacific damsel bugs, Nabis kinbergii, a potentially important predator of crop pests. Comparisons of predator activity, predator distribution, prey (Helicoverpa armigera) mortality and prey distribution between frequently observed and minimally observed treatments, during diurnal and nocturnal observation sessions showed that the frequency of observer presence had no apparent impact on Pacific damsel bug behavior. This is the first documented test of the impact of observer presence in an insect system. To place our results in context, we reviewed 15 papers on the influence of observer presence in a range of animals. We established that just over half of these papers found evidence for an effect. Nevertheless, direct observations should be useful in further studies of Pacific damsel bug behavior, and researchers using direct observations to study the behavior of other animals should be cognizant of observer effects during design and interpretation of their study.

Experience overrides colour in lizard contests

We examined the role of conspicuous coloration in male-male contests for two species of Australian dragon lizards, Ctenophortis decresii and C. vadnappa, in which conspicuous coloration has a demonstrated predation cost. We conducted contests in which the overall conspicuousness of male coloration was manipulated using paints that matched the spectral reflectance of the lizards, as well as natural (control) contests. There was little evidence for an influence of colour on contest outcome or aggression levels for either species when all experiments were considered. However, we found a significant effect of trial order and experience on contest outcome and aggression levels (the same pair of males was used for both types of contest), despite a 2-3 week interval between contests. When we examined only the first trial between unfamiliar males, we found that male C. vadnappa that had been painted to appear more conspicuous consistently won. Comparison with the natural trials suggests that the aspect of colour manipulation that was responsible for this result was the 'hue' of the throat: males with yellower throats consistently beat males with bluer throats in both natural and painted trials. The difference in coloration of flank markings also predicted the difference in aggression scores between contestants in the natural trials. These results suggest that although colour is important in opponent assessment and in determining contest outcome in C vadnappa, previous agonistic experience can override the effects of colour and have a long-lasting influence on aggressive behaviour.

Factors affecting the vigilance and flight behaviour of impalas

This study investigated the influences of various natural and anthropogenic factors on the vigilance and flight behaviour of impalas in the Save Valley Conservancy, Zimbabwe, using multivariate statistical techniques. The factor that most significantly affected the proportions of time that individuals spent being vigilant and their rates of vigilance was the position of a focal animal in the group; impalas on the periphery of a group were more vigilant than central impalas. Both measures of vigilance were also negatively related to group size. Males spent more total time being vigilant but females raised their heads more often. Impalas spent more time being vigilant in the late afternoon than in the early morning, when greater than ten metres from cover, and when predators had been nearby within the previous six hours. Impalas spent more time vigilant at the property where more impalas were hunted, possibly reflecting the differences in the intensity of hunting by humans on the two properties. Flight distances at the approach of humans were significantly greater at one property than the other, and were also greater for small groups. Further research into the effects of hunting by humans on animals' antipredator behaviours would provide valuable insights for wildlife managers.

Eradicating feral cats to protect Galapagos Land Iguanas: methods and strategies

A three-year programme to eradicate Feral Cats Felis catus from the island of Baltra in the Galapagos archipelago achieved good results by Initially poisoning with sodium monofluoroacetate (compound 1080) then trapping or shooting the remaining cats. The poisoning campaign removed 90% of the cats, its success being attributable to pre-baiting with unpolsoned baits to accustom cats to eating baits and placing enough baits to ensure that all cats encountered several baits within their home range. This, together with the use of metaclopromide (Pileran) as an anti-emetic, overcame a problem associated with poor retention of 1080 in thawed fish baits that limited the dose available to 1 mg 1080lbait, a quality Insufficient to kill large cats. Removal of the remaining cats was delayed by a weather-Induced irruption of Black Rats Rattus rattus and House Mice Mus musculus that enabled recruitment of kittens in 2002, but made cats more susceptible to trapping and shooting in 2003 when rodent populations collapsed. Since July 2003 no sign of a cat has been detected on Baltra despite extensive searching and monitoring throughout 2004. As cat abundance has decreased there have been more locally-bred Juvenile iguanas (Conolophus subcristatus) seen during annual censuses. However, such recruitment may reflect the increasing maturity and higher fecundity of iguanas repatriated from 1991 onwards rather than being a direct result of reduced cat predation alone. More time is necessary to determine the benefits of reduced cat predation on the Iguana population.

Sampling tissue for DNA analysis of trees: Trunk cambium as an alternative to canopy leaves

The number of studies of tropical tree species that use molecular tools is increasing, most of which collect leaf tissue for genomic DNA extraction. In tropical trees the canopy is not only frequently inaccessible, but also, once reached, the leaf tissue is often heavily defended against herbivory by high concentrations of anti-predation compounds, which may inhibit downstream applications, particularly PCR. Cambium tissue, accessed directly from the tree trunk at ground level, offers a readily accessible resource that is less hampered by the presence of defensive chemicals than leaf tissue. Here we describe a simple method for obtaining tissue from the cambial zone for DNA extraction and test the applicability of the method in a range of tropical tree species. The method was used successfully to extract DNA from 11 species in nine families. A subset of the DNA extracts was tested in more detail and proved to be highly suitable for AFLP analysis.

Temperature influences the coercive mating and swimming performance of male eastern mosquitofish

Although the functional consequences of temperature variation have been examined for a wide range of whole-animal performance traits, the implications of thermal variation for reproductive behaviour or performance are poorly known. I examined the acute effects of temperature on the mating behaviour and swimming performance of male eastern mosquitofish, Gambusia holbrooki, which rely on a coercive strategy to obtain matings and are routinely exposed to wide daily temperature fluctuations. Males showed reproductive behaviours across the entire test temperature range of 14-38 degrees C, representing one of the widest reproductively active temperature ranges for any ectotherm. Both the time spent in pursuit of females and the total number of mating attempts increased with temperature to a plateau that started at approximately 22-26 degrees C. However, males maintained a constant level of copulations at 18-34 degrees C, the temperature range they routinely experience in southeast Queensland. In contrast, maximum swimming performance and approach speeds during copulations were highly thermally dependent across this temperature range. Thus, acute temperature variation has important fitness implications for male G. holbrooki, but mating performance was significantly limited only at extreme temperatures. (c) 2005 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.

Microhabitat use by black-faced impala in the Etosha National Park, Namibia

We Studied microhabitat use by black-faced impala in different herd types during the rut in the cold dry seasons of 2001 and 2002 in the Etosha National Park, Namibia. We investigated whether black-faced impala select feeding sites consistently for their microhabitat characteristics in 2 vegetation types, Karstveld and Tamboti Woodland. We also investigated intra-population differences in microhabitat use between herds of different types. In both habitats, sites used by impala for feeding were more likely to be in the shade, within 2 m of the edges of wooded areas and grassy clearings, with high visibility at I m height, and with lower grass swords than nearby nonfeeding sites. In Karstveld, feeding sites of impala were also located closer to the nearest shrub than were nonfeeding sites. A degree of fine-scale sexual segregation in microhabitat use was demonstrated, but it was not consistent across habitats. Incorporating these trends in the microhabitat use of black-faced impala into management, decisions should maximize the success Of Small populations released at selected off-park sites.

Costs of learning: the dynamics of mixed-prey exploitation by silver perch, Bidyanus bidyanus (Mitchell, 1838)

Although generalist predators have been reported to forage less efficiently than specialists, there is little information on the extent to which learning can improve the efficiency of mixed-prey foraging. Repeated exposure of silver perch to mixed prey (pelagic Artemia and benthic Chironomus larvae) led to substantial fluctuations in reward rate over relatively long (20-day) timescales. When perch that were familiar with a single prey type were offered two prey types simultaneously, the rate at which they captured both familiar and unfamiliar prey dropped progressively over succeeding trials. This result was not predicted by simple learning paradigms, but could be explained in terms of an interaction between learning and attention. Between-trial patterns in overall intake were complex and differed between the two prey types, but were unaffected by previous prey specialization. However, patterns of prey priority (i.e. the prey type that was preferred at the start of a trial) did vary with previous prey training. All groups of fish converged on the most profitable prey type (chironomids), but this process took 15-20 trials. In contrast, fish offered a single prey type reached asymptotic intake rates within five trials and retained high capture abilities for at least 5 weeks. Learning and memory allow fish to maximize foraging efficiency on patches of a single prey type. However, when foragers are faced with mixed prey populations, cognitive constraints associated with divided attention may impair efficiency, and this impairment can be exacerbated by experience. (c) 2005 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.

Diurnal polyp expansion behavior in stony corals may enhance carbon availability for symbionts photosynthesis

Photosynthesis of zooxanthellate stony corals may be limited by inorganic carbon at high irradiances. We demonstrated that oxygen consumption of expanded corals is higher than that of contracted corals in both night-expanding and day-expanding corals. It is assumed that at the single-polyp level, the expansion of tentacles increases the surface area for solute exchange with the surrounding water, which may alleviate potential carbon limitation and excess oxygen levels in the tissue under high irradiance. We investigated this hypothesis using stable carbon isotope (613 C) analysis of coral species from the Red Sea exhibiting different morphologies. delta C-13 ratios in zooxanthellae of branched coral colonies with small polyp size that extend their tentacles during daytime (diurnal morphs) showed lower delta C-13 values in their zooxanthellae - 13.83 +/- 1.45 parts per thousand, compared to corals from the same depth with large polyps, which are usually massive and expand their tentacles only at night (nocturnal morphs). Their algae delta C-13 was significantly higher, averaging - 11.33 +/- 0.59 parts per thousand. Carbon isotope budget of the coral tissue suggests that branched corals are more autotrophic, i.e., that they depend on their symbionts for nutrition compared to massive species, which are more heterotrophic and depend on plankton predation. (c) 2005 Elsevier B.V. All rights reserved.