The foraging behavior of the central mudminnow and yellow perch: the influence of foraging site,intraspecific and interspecific competition

Summary The central mudminnow (Umbra limi) and yellow perch (Perca flavescens) are two species of fishes that commonly co-occur in small bog lakes in the Great Lakes region of North America. Both species are dietary generalists with a high degree of dietary overlap, and perch populations have been shown to have a strong negative effect on mudminnow populations. I compared the foraging rates of the two species in a series of laboratory experiments in which four foraging sites were simulated (open bottom substrate, water column, submerged aquatic macrophytes, and water surface). Fish were observed as they foraged singly, in monospecific pairs, and in mixed species pairs to evaluate the effects of intra- and interspecific competition on foraging success and the potential for resource partitioning based on foraging site. Single species trials showed that each species had similar foraging rates at each of the four sites. Across all sites combined, interspecific competition had a greater negative effect on the foraging success of mudminnows than did intraspecific competition. Conversely, intraspecific competition had a greater negative effect on the foraging success of perch than did interspecific competition. In mixed species trials perch took more food items from each of the four foraging sites than did mudminnows and caused shifts in site-use patterns of mudminnows. Differences in the foraging success of the two species reflected the superior ability of perch to discover the presence of food and to search rapidly for additional items, but were unrelated to handling times. These differences were linked to the species' foraging modes. The competitive superiority of perch, demonstrated in these experiments, could contribute to the negative impact of perch on mudminnow populations under natural conditions.     

Growth-related changes in predation behavior in incipient colonies of the ponerine antEctatomma tuberculatum (Olivier)

Summary We traced the development in the laboratory of 18 young colonies of the arboricolous ponerine antEctatomma tuberculatum. Colony foundation is of the partially-claustral type. During the early stages, when the colony is entirely dependent on the queen's behavior, the growth of the colony in terms of number of workers produced over time was relatively predictable. Afterwards, divergence in colony growth in function of the time increases as fast as the number of workers influences the efficiency of colony provisioning.Comparative analysis indicated clear changes in the predation behavior of foundresses and workers as colonies developed. For any stage of colony growth, all individuals provisioned the nest with dead prey or sugar-rich substances in the same way. However, prey hunting involves two different strategies. Foundresses and nanitic workers (originating from colonies with 9–15 workers) foraged actively, catching prey as the result of random encounters. Post-nanitic foragers (originating from colonies with 20–30 workers) and those from nature colonies developed an ambush strategy. Workers in these colonies gained experience at catching and handling prey during a period when they acted as nest guards, and so tended to be more efficient hunters than poorly experienced foundresses or nanitic foragers. The change in strategy was also positively correlated with an increase in the size of workers as the colony matured. A stable maximum in workers size is apparently reached only after the appearance of efficiently hunting foragers, presumably in numbers sufficient to provide adequate quantity and quality of larval food. Such a correlation between worker size and colony growth, assumed general for all ants, has not been demonstrated for Ponerinae before this work.     

Action spectrum of foraging behavior of the Japanese yellow swallowtail butterfly, Papilio xuthus

This paper describes the action spectrum of foraging behavior of a butterfly, Papilio xuthus. We first established an experimental protocol to evaluate learning and discrimination of monochromatic light by the butterflies. We trained butterflies to feed on sucrose solution at the window illuminated with certain monochromatic light produced through a monochromator. After confirming that they learned the monochromatic light, after 10 days of training, we tested the butterflies one by one. We presented training wavelengths for each individual at different intensities, and recorded whether they perform foraging behavior under freely-flying as well as tethered conditions. Freely-flying butterflies responded to light by visiting the window and searching for nectar around it, whereas tethered butterflies responded by extending their proboscides towards the window. The light intensity required to elicit 50% response for each tested monochromatic light was plotted. The resulting action spectrum for the visit was rather flat with the maximum sensitivity a 420 nm, whereas the spectrum for the proboscis extension had prominent peaks at 380, 500 and 600 nm. The difference in action spectra indicates that the visit and the proboscis extension are controlled by two independent mechanisms at least in part.     

A relationship of diet to prey abundance and the foraging behavior of Trematomus bernacchii

Little information is available regarding fish diets in Antarctica and how they relate to prey availability. The primary objective of this work was to describe the diet of Trematomus bernacchii. The second objective was to compare prey taken with prey present in the benthos along a spatial gradient of prey abundance using Ivlev's Index of Electivity. All samples were collected from 4 different sites on the east side of McMurdo Sound, Antarctica. Fish were captured by divers at the same depth at each site and their stomachs were flushed for dietary analysis. The diet of T. bernacchii varied among sites, and prey selectivity varied inversely with prey abundance. Many of the prey taken by T. bernacchii were sedentary species suggesting that T. bernacchii is a hunt and peck predator.     

Growth-related changes in color and sex inHalichoeres poecilopterus

Coloration and sex change were studied in a temperate wrasseHalichoeres poecilopterus in the central part of the Seto Inland Sea, Japan. 1,270 examples, 45–179 mm SL, were collected from May to December both in 1983 and 1984. The species is a diandric, protogynous hermaphrodite, and has three color patterns: pale color type (A), brilliant color type (B) and intermediate color type (AB). A-fish were less than 142 mm SL and consisted of primary males (42.6%), females (55.4%), secondary males (0.3%) and fish with transitional gonads (1.7%). A-females changed their color to B, through AB, in the size range 101–131 mm SL. A-primary males changed their color to B, through AB, in the size range 103–134 mm SL. B-fish consisted of primary males (38.6%), secondary males (54.6%) and fish with transitional gonads (6.8%). The majority of females changed their sex to male in the size range 98–131 mm SL.     

Sex differences in diet and foraging behavior in white-faced capuchins (Cebus capucinus)

I examined sex differences in diet and foraging behavior in two groups of white-faced capuchin monkeys (Cebus capucinus)in a tropical dry forest at Santa Rosa National Park, Costa Rica. I tested three hypotheses: sex differences in diet and foraging behavior are best explained by (1) sexual dimorphism, (2) the energy demands of pregnancy and lactation for females;and (3) avoidance of competition between the sexes. Sexual dimorphism offered the best explanation of sex differences in the diet and foraging behavior of C. capucinus,accurately predicting that males do more strenuous foraging activity, make less use of small foraging supports, and spend more time on or near the ground. Females spent more time foraging than males did but probably obtained a lower protein yield per unit foraging time. Females exploited more small and embedded invertebrates, while males ate more large invertebrates and vertebrate prey. Pregnant and lactating females spent more time resting and less time foraging than other females did, increasing their foraging return by focusing on foods requiring little handling. There was little evidence of competition avoidance between the sexes.     

Sexual differences in the diet of king cormorants at Macquarie Island

Sexual differences in the diet of king cormorants,Phalacrocorax albiventer, were investigated during the 1993/1994 austral summer at Macquarie Island. The major food items, identified by otoliths in regurgitations, were demersal fish; fish mass consumed could be estimated using a wet mass-otolith length relationship. Two fish species,Paranotothenia magellanica andHarpagifer georgianus, constituted 98% of the wet mass (male and female cormorants combined). Estimated individual fish mass ofParanotothenia magellanica (19.6±11.6 g) was greater than that ofH. georgianus (2.8±1.3 g). Total wet mass of food and number of fish in regurgitations did not differ statistically between the sexes of cormorants. However, males tended to feed on larger fish than did females.     

Southern rockhopper penguin Eudyptes chrysocome chrysocome foraging at Possession Island

The foraging ecology of rockhopper penguins was studied at Possession Island, southern Indian Ocean, by counting the number of birds departing from and arriving at colonies over the course of the day and by equipping three birds with time/depth loggers, one of which was recovered having recorded a total of 12 days foraging activity. Both the counts and the results from the diving behaviour showed that the birds foraged exclusively diurnally. Maximum dive depth was 66 m although most time was spent between 10 and 25 m, depths that did not accord with the published distribution of their principal prey as detected by nets and acoustics. Received: 29 March 1996/Accepted: 10 June 1996     

Dualistic reproductive behavior in the protogynous wrasseThalassoma bifasciatum and some observations on its day-night changeover

Summary 1.Thalassoma bifasciatum is a protogynous wrasse with (partial) sexual dimorphism and male dichromatism. Sex-inversion takes place without affecting the color pattern.2. Males with female-like color dress indulge in group spawning; males with the bright color pattern perform pair spawning.3. Among the brightly colored males exists a well-established hierarchy. Dominant males only have a particular spawning area in which they spawn daily at a certain time around noon. The spawning area is optically marked by conspicuous behavior of the bright male. Courtship activities towards individual partners are rather superficial.4. The female has the leading role in pair spawning. In the extremely short spawning act a female may release, simultaneously, more than 2000 eggs.5. Group spawning occurs in well-populated reef areas only. The basic pattern of group spawning has many similarities to pair spawning.6. Day-night changeover ofT. bifasciatum is closely correlated to the time of sunset and sunrise.7. The possible biological significance of the dualistic spawning behavior is discussed, and advantages as well as drawbacks of studies in the sea and in aquaria are considered.

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Dualistisches Fortpflanzungsverhalten bei dem protogynen LippfischThalassoma bifasciatum und einige Beobachtungen über dessen Tag-Nacht-Wechsel

Kurzfassung Der protogyne Blaukopf-LippfischThalassoma bifasciatum laicht in den Korallenriffen des westlichen Atlantiks auf zwei verschiedene Weisen. Das typische Blaukopf-Männchen mit seinem besonderen Farbkleid laicht paarweise, während die Männchen mit Schlichtfärbung (ihre Färbung gleicht der der Weibchen) Gruppenlaichen betreiben. Beobachtungen an markierten Individuen im Korallenriff zeigten, daß Sekundärmännchen, die durch Geschlechtsumwandlung aus Weibchen entstehen, ebenso erfolgreich laichen wie Primärmännchen mit dem Blaukopf-Prachtkleid. Beide Laichweisen ähneln sich darin, daß die laichenden Fische schnell zur Oberfläche des Wassers hinschwimmen, die Körper der Tiere sich für Bruchteile einer Sekunde berühren, dabei die Geschlechtsprodukte entlassen werden und die Partner sich danach schnell voneinander trennen und nach unten fortschwimmen. Ungefähr 1000–2000 Eier werden bei einem einzigen Laichakt abgegeben. Innerhalb kurzer Zeit können viele Paar- und Gruppenlaichakte stattfinden. Laichaktive Prachtmännchen verhalten sich während der täglichen Laichzeit in den Mittagsstunden territorial. Sie können über Wochen hinweg ihre dominante Stellung in der Population behaupten.T. bifasciatum ist das ganze Jahr hindurch fortpflanzungsfähig. Zur Nachtzeit suchtT. bifasciatum Versteckplätze im Riff auf, welche Territorialcharakter haben. Der Übergang zur Ruhephase ist mit der Zeit des Sonnenuntergangs, der Wiederbeginn der Tagesaktivität mit dem Sonnenaufgang eng korreliert.

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Supported by the Deutsche Forschungsgemeinschaft.     

The diet of the King Penguin Aptenodytes patagonicus at Macquarie Island

The diet of King Penguins Aptenodytes patagonicus at Macquarie Island was studied between November 1984 and November 1985 based on stomach flushed samples (obtaining 93% of the total stomach content) from ten birds each month. The mean stomach content mass of the 118 samples was 923 0 g. Percentage by number, percentage by weight and dietary coefficient analysis all showed the main prey of the penguins to be myctophid lantern fish of the species Electrona carlsbergi and Krefftichthys anderssoni. Juvenile fish of both species were eaten from December to July, and adults in August and September. Cephalopods were relatively unimportant in contrast to previous indications. The amount of food brought ashore and the composition of the diet varied over the year, with K. anderssoni the dominant food in all but the winter months when E. carlsbergi replaced it as the principal food item.     

Sex differences in giraffe foraging behavior at two spatial scales

We test predictions about differences in the foraging behaviors of male and female giraffes (Giraffa camelopardalis tippelskirchi Matchie) that derive from a hypothesis linking sexual size dimorphism to foraging behavior. This body-size hypothesis predicts that males will exhibit specific behaviors that increase their dry-matter intake rate relative to females. Foraging behavior was examined at two hierarchical levels corresponding to two spatial and temporal scales, within patches and within habitats. Patches are defined as individual trees or shrubs and habitats are defined as collections of patches within plant communities. Males were predicted to increase dry-matter intake rate within patches by taking larger bites, cropping bites more quickly, chewing less, and chewing faster. Within habitats, males were expected to increase intake rate by increasing the proportion of foraging time devoted to food ingestion as opposed to inter-patch travel time and vigilance. The predictions were tested in a free-ranging population of giraffes in Mikumi National Park, Tanzania. Males spent less total time foraging than females but allocated a greater proportion of their foraging time to forage ingestion as opposed to travel between patches. There was no sex difference in rumination time but males spent more time in activities other than foraging and rumination, such as walking. Within patches, males took larger bites than females, but females cropped bites more quickly and chewed faster. Males had longer per-bite handling times than females but had shorter handling times per gram of intake. Within habitats, males had longer average patch residence times but there was no significant sex difference in inter-patch travel times. There was no overall difference between sexes in vigilance while foraging, although there were significant sex by habitat and sex by season interactions. Although not all the predictions were confirmed, overall the results agree qualitatively with the body-size hypothesis. Sex-related differences in foraging behavior led to greater estimated intake rates for males at the within-patch and within-habitat scales. Received: 20 November 1995 / Accepted: 5 November 1996     

Seasonal change in foraging areas and dive depths of breeding king penguins at Heard Island

The seasonal variation in the foraging behaviour of king penguins (Aptenodytes patagonicus) was studied at Heard Island (53°05′S, 73°30′E) during 1992/1993. On seven occasions throughout the breeding cycle, time-depth-light recorders were deployed on breeding adults to record the dive activities and foraging. Foraging locations changed with season: in autumn and spring 1992, adults foraged between 48–52°S and 74–78°E, about 370 km NNE of Heard Island close to the Polar Front. Two penguins tracked in winter travelled 2220 km east of Heard Island (95°E) along the northern ice limit, and 1220 km south of Heard Island to approximately 65°S, respectively. In spring (October), the penguins again foraged further north than during winter. The foraging area utilised in October overlapped the area where the penguins foraged in March/April. The penguins' diving behaviour also varied seasonally: the modal depth of deep dives (>50 m) increased from about 100 m in February to 220 m in October. Mean dive depths increased from 70 ± 52 m in March 1992 to 160 ± 68 m in August 1992. Penguins dived deep (>50 m) only during daylight hours (16 h in February, 9 h in July). Mean dive durations ranged from 2.9 ± 1.1 min in March 1992 to 5.1 ± 1.2 min in August 1992. Associated with changes in foraging location and dive behaviour was a change in diet composition: during summer the penguins ingested mainly myctophid fish (>90%) while in winter the most important diet item was squid. Accepted: 19 October 1998     

Growth-related changes of non-histone chromatin proteins from Kirkman-Robbins hepatoma

1. Non-histone chromatin protein fractions NHCP1 and NHCP2 eluted from hydroxyapatite with 50 and 100 mM phosphate buffer (pH 6.8) from nuclei of Kirkman-Robbins hepatoma from 4th, 7th and 9th day of growth were analysed by one- and two-dimensional gel electrophoresis as well as Western blot technique in the presence of antibodies elicited against NHCP1, NHCP2 and dehistonized chromatin of hamster hepatoma and liver. 2. The presence of electrophoretically and immunologically specific components among NHCP1 and NHCP2 fractions during Kirkman-Robbins hepatoma growth was stated.     

Fish foraging behavior at different stability levels of food distribution

The foraging behavior of four fish species—bream, Abramis brama (L.); roach, Rutilus rutilus (L.); crucian carp, Carassius auratus (L.); and a tropical catfish, Corydoras paleatus (Jenins)—differing in their degrees of morphological specialization for benthic foraging has been studied. In the modeling of a stable environment, fish encountered a constant pattern of food location, while under unstable conditions, food location varied between subsequent trials. In contrast to an unstable environment, after long exposures to constant conditions, there was an increase in motor activity not associated with foraging and the feeding rate fell. This drop in feeding rate resulted in decreased growth rates in the studied fish.     

The diet of the Wandering Albatross Diomedea exulans at Subantarctic Marion Island

Summary The diet of the Wandering Albatross at Subantarctic Marion Island was studied by inducing recently fed chicks to regurgitate and by stomach flushing adults about to feed chicks. Liquid comprised 70.2% of stomach content mass recovered from chicks. Solid material comprised cephalopods (58.6% by mass), fish (36.5%) and crustacean, cetacean and seabird material as minor items. Twenty-three taxa of cephalopods were identified, the onychcteuthid squid Kondakovia longimana being the most important. Estimated average mass of squid was 694 g with a maximum of over 8 kg. Diet of the Wandering Albatross at Marion Island was broadly similar to that at other studied localities. The high proportion of cephalopods known to float after death in the diet, and the deep-water habits of the few fish identified, suggest that scavenging plays an important role in foraging behaviour.     

Climatic determinants of diet and foraging behaviour in baboons

Baboons (Papio spp.) are characterised by a large degree of variation in foraging behaviour and dietary composition. Previous analyses have suggested that much of this can be traced to differences in ecological conditions between sites. The proximate mechanism underlying these relationships is assumed to be mediated via the impact of climatic conditions on food availability, and ultimately the impact that this has on dietary composition. This paper examines these relationships more explicitly. Data from 15 baboon populations were used to assess the relationship between foraging variables and dietary composition. Only feeding time showed significant relationships with dietary composition, with percentage of time spent feeding decreasing with proportion of fruit in the diet, and increasing with the proportion of subterranean items. No relationships were found between diet composition and moving time or day journey length, although significant relationships were found between these variables and group size. The proportions of feeding time spent feeding on fruit, subterranean items and leaves were functions of the ecological conditions experienced by that population, although no relationships were found for the percentage of feeding time devoted to flowers or animal material. The relationships between the proportion feeding time spent on fruits, leaves and subterranean items and ecological variables could be best explained through understanding the way in which bush and tree level vegetation respond to the climatic environment and the impact this has on fruit availability. In this respect, temperature and seasonality are the key climatic parameters. This provides good support for the idea that the proximate mechanism underlying the relationship between foraging time and ecological variables is mediated via the impact of the climatic environment on vegetation structure and food availability. Similar factors have been proposed to explain much of the geographic variation in species diversity, suggesting that these relationships have far wider relevance and may account for much of the observed geographical variation in mammalian behaviour.     

The diet of the subantarctic fur seal Arctocephalus tropicalis at Marion Island

Scats of subantarctic fur seals Arctocephalus tropicalis at Marion Island were collected from 1996 to 2,000, to examine temporal variability in the diet, factors affecting the variability and how the diet differed from that of the Antarctic fur seal A. gazella in the same period. For A. tropicalis, 19 prey species, of which 18 were fish and one a cephalopod, were identified in 213 scats. Fish were the main prey, occurring in 98.1 % of scats, whereas the cephalopod was present in only 1.4 % of scats. Amongst fish species, Myctophidae were most abundant, with Gymnoscopelus piabilis, G. fraseri and Electrona carlsbergi being the commonest prey items. Other fish families present in the diet in small numbers were Channichthyidae, Paralepididae, Nototheniidae, Microstomatidae and Notosudidae. Fish eaten ranged in size from Protomyctophum bolini and Krefftichthys anderssoni of standard length (SL) 25 mm to a single Dissostichus eleginoides of SL 249 mm. Differences in the diet existed between summer and winter. However, prey type accounted for most variability in the diet. In previous studies based on scats, a dominance of fish in the diet of A. tropicalis was also found at Possession Island (Iles Crozet), Amsterdam Island and Macquarie Island, but the dominant prey species differed between the various localities, also suggesting that prey availability is a major determinant of diet. At Marion Island, from 1996 to 2000 the diet of A. gazella comprised similar prey to that of A. tropicalis, but the proportional contribution of prey types differed in instances.     

Growth-related changes in the mechanical properties of collagen fascicles from rabbit patellar tendons

Growth-related changes in the mechanical properties of collagen fascicles (approximately 300 microm in diameter) were studied using patellar tendons obtained from skeletally immature 1 and 2 months old and matured 6 months old rabbits. Tensile properties were determined using a specially designed micro-tensile tester. In each age group, there were no significant differences in the properties among cross-sectional locations in the tendon. Tangent modulus and tensile strength significantly increased with age; the rates of their increases between 1 and 2 months were higher than those between 2 and 6 months. The tangent modulus and tensile strength were positively correlated with the body weight of animals. However, growth-related changes in the mechanical properties were different between collagen fascicles and bulk patellar tendons, which may be attributable to such non-collagenous components as ground substances and also to mechanical interactions between collagen fascicles.     

Optimal foraging and intraspecific diet differences in the lizard Cnemidophorus sexlineatus

Summary Previous studies have shown that adult and juvenile six-lined racerunners, Cnemidophorus sexlineatus, consume different sizes and taxa of arthropod prey. the purpose of this study was to determine if these differences could be explained in terms of energy cost and benefit parameters as related by the optimal diet model. Handling times and encounter rates with each of five categories of prey were determined by direct observation of lizard foraging behavior in the field. Energetic cost of search and energy content of prey were estimated from data in the literature. Mean values of all these parameters were used in the classic optimal diet model to determine which prey types yield the greatest rate of net energy gain for adult and juvenile racerunners. Grasshopper-like insects were the most valuable prey for adults, whereas plant and ground arthropods were the most valuable prey for juveniles. These findings correspond to the age-class specific diet differences.Each age-class adopts foraging tactics that increase the chance of finding the most valuable prey. Adult racerunners move hastily over a large area to find the relatively rare, but large and mobile grasshopper prey. Juveniles move much more slowly, and carefully investigate twigs and leaves to find smaller, cryptic plant and ground arthropods. However these foraging tactics do not preclude the taking of less valuable prey items, should they be encountered. This is because it is energetically better on average to eat the prey item rather than skipping it to search for better prey, except for the case of juvenile racerunners eating grasshoppers. That juvenile racerunners will attempt to capture and consume even very large grasshoppers is contrary to the expectations derived from the optimal diet model. This behavior may be the result of the foraging rule of thumb racerunners use to find their prey.