Habitat utilisation, feeding tactics and age related feeding efficiency in the Caspian Gull Larus cachinnans

The feeding behaviour of the Caspian Gull Larus cachinnans was analysed in southern Poland in 2001. During the pre-breeding period, most birds foraged on a refuse dump and some foraged in a river valley. During incubation, similar numbers of birds foraged on fishponds, gravel pits and the refuse dump. During the chick-rearing period, fishponds were the most important foraging grounds. The foraging success of three main foraging tactics was analysed: digging on refuse, fishing and kleptoparasitism. We found that digging success was higher in juveniles than in immature or adult birds. However, older birds moved and ate more items per unit of time than juveniles, which indicates that older birds improved their energy gain simply by a higher speed of searching. The opposite was found for fishing success. As juvenile birds made fewer attempts than immature or adult birds, fishing success was higher in adults. Adults and immature birds interrupted more attacks than juveniles, which indicates that older birds were better able to assess the probability of fish catching than juveniles. Kleptoparasitism was observed almost exclusively on the refuse dump during the pre-breeding period. Young birds kleptoparasitised more frequently than adults, but they had a lower rate of success. However, the lower success in young birds was due to victim choice, rather than differences in flight skills. Young birds kleptoparasitised Black-headed Gulls Larus ridibundus and Jackdaws Corvus monedula more frequently than adults, but none of the attacks towards these species was successful. Generally, Caspian Gulls kleptoparasitised conspecifics more often than expected from species frequency. Only attacks towards conspecifics yielded any success.     

Food-Entrained Feeding and Locomotor Circadian Rhythms in Rats Under Different Lighting Conditions

It has been suggested that two endogenous timekeeping systems, a light-entrainable pacemaker (LEP) and a food-entrainable pacemaker (FEP), control circadian rhythms. To understand the function and interaction between these two mechanisms better, we studied two behavioral circadian rhythmicities, feeding and locomotor activity, in rats exposed to two conflicting zeitgebers, food restriction and light-dark cycles. For this, the food approaches and wheel-running activity of rats kept under light-dark (LD) 12:12, constant darkness (DD), or constant light (LL) conditions and subjected to different scheduled feeding patterns were continuously recorded. To facilitate comparison of the results obtained under the different lighting conditions, the period of the feeding cycles was set in all three cases about Ih less than the light-entrained or free-running circadian rhythms. The results showed that, depending on the lighting conditions, some components of the feeding and wheel-running circadian rhythms could be entrained by food pulses, while others retained their free-running or light-entrained state. Under LD, food pulses had little influence on the light-entrained feeding and loco-motor rhythms. Under DD, relative coordination between free-running and food-associated rhythms may appear. In both cases, the feeding activity associated with the food pulses could be divided into a prominent phase-dependent peak of activity within the period of food availability and another afterward. Wheel-running activity mainly followed the food pulses. Under LL conditions, the food-entrained activity consisted mainly of feeding and wheel-running anticipatory activity. The results provide new evidence that lighting conditions influence the establishment and persistence of food-entrained circadian rhythms in rats. The existence of two coupled pacemakers, LEP and FEP, or a multioscillatory LEP may both explain our experimental results.     

Food-Entrained Feeding and Locomotor Circadian Rhythms in Rats Under Different Lighting Conditions

It has been suggested that two endogenous timekeeping systems, a light-entrainable pacemaker (LEP) and a food-entrainable pacemaker (FEP), control circadian rhythms. To understand the function and interaction between these two mechanisms better, we studied two behavioral circadian rhythmicities, feeding and locomotor activity, in rats exposed to two conflicting zeitgebers, food restriction and light-dark cycles. For this, the food approaches and wheel-running activity of rats kept under light-dark (LD) 12:12, constant darkness (DD), or constant light (LL) conditions and subjected to different scheduled feeding patterns were continuously recorded. To facilitate comparison of the results obtained under the different lighting conditions, the period of the feeding cycles was set in all three cases about Ih less than the light-entrained or free-running circadian rhythms. The results showed that, depending on the lighting conditions, some components of the feeding and wheel-running circadian rhythms could be entrained by food pulses, while others retained their free-running or light-entrained state. Under LD, food pulses had little influence on the light-entrained feeding and loco-motor rhythms. Under DD, relative coordination between free-running and food-associated rhythms may appear. In both cases, the feeding activity associated with the food pulses could be divided into a prominent phase-dependent peak of activity within the period of food availability and another afterward. Wheel-running activity mainly followed the food pulses. Under LL conditions, the food-entrained activity consisted mainly of feeding and wheel-running anticipatory activity. The results provide new evidence that lighting conditions influence the establishment and persistence of food-entrained circadian rhythms in rats. The existence of two coupled pacemakers, LEP and FEP, or a multioscillatory LEP may both explain our experimental results.     

Led by the nose: Olfaction in primate feeding ecology

Olfaction, the sense of smell, was a latecomer to the systematic investigation of primate sensory ecology after long years in which it was considered to be of minor importance. 1 This view shifted with the growing understanding of its role in social behavior 2 and the accumulation of physiological studies demonstrating that the olfactory abilities of some primates are on a par with those of olfactory‐dependent mammals such as dogs and rodents. 3 , 4 Recent years have seen a proliferation of physiological, behavioral, anatomical, and genetic investigations of primate olfaction. These investigations have begun to shed light on the importance of olfaction in the process of food acquisition. However, integration of these works has been limited. It is therefore still difficult to pinpoint large‐scale evolutionary scenarios, namely the functions that the sense of smell fulfills in primates’ feeding ecology and the ecological niches that favor heavier reliance on olfaction. Here, we review available behavioral and physiological studies of primates in the field or captivity and try to elucidate how and when the sense of smell can help them acquire food.     

The feeding ecology of the pit-making ant lion larva,Myrmeleon bore: Feeding rate and species composition of prey in a habitat

The prey species composition and feeding rate of the pit-making ant lion larva,Myrmeleon bore Tjeder, which inhabits open sandy areas, were examined. Not less than 30 prey species, most of which were ants, were collected during a research period of 1.5 years. First instar larvae most often (81.1%) captured ants. Although 3rd instar larvae captured larger-sized prey than individuals of any other instar, they also captured small prey. The feeding rate of 3rd instar larvae was estimated by using the frequency of observed predation (FOP; (no. of ant lions handling a prey)/(total no. of pits observed)), the prey-handling time and the rhythm of daily foraging activity. FOP ofM. bore larvae was constant on the whole from spring to autumn. It was estimated that each captured 1.25 prey per day on average during this period. This estimate, however, was the feeding rate for days on which there was no rain. Assuming that the larvae cannot capture prey due to pit destruction when there is more than 10 mm of rainfall per day, the figure was reduced to 1.03 prey/day. The estimated feeding rate was evaluated with reference to larval foraging behavior.     

Rank and age related feeding strategy observed through field experiments in the Koshima group of Japanese macaques

The feeding process of Japanese monkeys on soy beans which were scattered over a sandy beach on Koshima islet was studied. Younger monkeys were able to pick up more beans when 8 kg of beans were divided and given two times (“two times feeding”) than when the whole amount (8 kg) of beans was given at one time (“one time feeding”). The effect of saturation of the food intake capacity in younger monkeys at the first feeding in “two times feeding” did not appear at the second feeding one hour later. The minutely intake of soy beans (feeding speed) for each age class was analyzed. The decline of feeding speed in adult females after the peak in “one time feeding” was not related to the decline in density of beans on the ground, and this decline was caused by saturation of their food intake capacity. Adult females were divided into four classes according to their dominance rank order: high, lower-high, higher-low, and low classes. The total amount of intake in “one time feeding” was far larger in the high class than in any of the other classes. The total amount of feeding in the first feeding of “two times feeding” increased in accordance with rise in the dominance rank class, and there was no relation to rank and total feeding amount in the second feeding of “two times feeding.” Differences existed in the process of feeding between the rank classes. The feeding speed of the low class was as high as that of the high class on the curve of minutely intake, while the low class stopped feeding much earlier than the high class. The lower-high class displayed a low feeding speed, and stopped feeding the latest. The order of the duration to stay and to feed in the feeding area was lower-high > high > higher-low > low, and this order did not change under the three different feeding conditions, “one time feeding,” and the first and second feedings of “two times feeding.” Adolescent females tended to stay the longest duration in the feeding area among all age classes. Both the lower-high class females and adolescent females had an unstable social status in the Koshima group, and their social status affected their feeding behaviors. The feeding behaviors were similar in attitude depending on social status, and are considered to be maintained for a fairly long time. The feeding strategy of the lower-high class, in staying a longer duration in the artificial feeding area, and departing later, may be effective under the artificial feeding conditions, but it may be a bad strategy in a natural habitat where the food is not so clumped as in artificial feeding, and where choice of other food patches is possible. The above results agree well with previous reports for the Koshima group, indicating that the rank of the lower-high class females was unstable (Mori et al., 1989), and that their reproductive success was low (Watanabe et al., 1992).     

Optimal foraging and fitness in Columbian ground squirrels

Summary Optimal diets were determined for each of 109 individual Columbian ground squirrels (Spermophilus columbianus) at two sites in northwestern Montana. Body mass, daily activity time, and vegetation consumption rates for individuals were measured in the field, along with the average water content of vegetation at each ground squirrel colony. I also measured stomach and caecal capacity and turnover rate of plant food through the digestive tract for individuals in the laboratory to construct regressions of digestive capacity as a function of individual body mass. Finally, I obtained literature estimates of average daily energy requirements as a function of body mass and digestible energy content of vegetation. These data were used to construct a linear programming diet model for each individual. The model for each individual was used to predict the proportion of two food types (monocots and dicots) that maximized daily energy intake, given time and digestive constraints on foraging. Individuals were classified as optimal or deviating, depending on whether their observed diet was significantly different from their predicted optimal diet. I determined the consequences of selecting an optimal diet for energy intake and fitness. As expected, daily energy intake calculated for deviators (based on their observed diet proportion) was less than that for optimal foragers. Deviating foragers do not appear to compensate for their lower calculated energy intake through other factors such as body size or physiological efficiency of processing food. Growth rate, yearly survivorship, and litter size increase with calculated energy intake, and optimal foragers have six times the reproductive success of deviators by age three. Optimal foraging behavior, therefore, appears to confer a considerable fitness advantage.     

棕果蝠对龙眼的取食行为及进食量

棕果蝠(Rousettus leschenaulti)在云南西双版纳地区是比较常见的果蝠。本文研究了棕果蝠对当地经济作物龙眼(Dimocarpus longan)的取食模式和取食时间规律,并在实验室条件下研究了其对龙眼的整夜进食量。野外观察发现:棕果蝠叼取龙眼后不在母树上停留,而是携带龙眼到其他进食地点进食。棕果蝠在19:30～5:30时有3个取食高峰期,分别是在20:30～21:00时、22:00～22:30时和1:00～1:30时之间。此外,室内笼养实验结果表明,棕果蝠对龙眼的取食个数因体重不同而有差异,个数在6～20之间,实际进食量相当于其体重的1.0～1.8倍。     

Feeding rate may affect dispersal in the orb-web spider Nephila clavata

Population parameters of the orb-web spider Nephila clavata were estimated at two sites with different spider densities (for 2 successive years at the high density site and 1 year at the low density site), and the relationship between survival rate and feeding conditions was examined. The rate of decrease of population density was almost constant over time and nearly the same at the two sites. Daily survival rate (sum of the effects of mortality and emigration) was low during August to early September and increased markedly thereafter. Daily immigration rate (number of immigrants/number of residents) was high during August to early September. Since there were strong negative correlations between survival and immigration rates, low survival rate seems to be caused by a high rate of emigration. Strong positive correlations were found between survival rate and feeding frequency (mean percent observed feeding). Analysis of covariance revealed that the parameters of the regression between survival rate and feeding frequency did not differ significantly among three occasions. These results suggest that feeding condition has a significant influence on dispersal activity of populations in this spider.     

Test of a digestion optimization model: effect of variable-reward feeding schedules on digestive performance of a migratory bird

Birds on migration often alternate between feeding and nonfeeding periods, in part because food resources may be patchily distributed and in part because birds on migration may adopt a risk-prone foraging strategy characterized by selection of variable rather than constant food rewards. Optimal digestion models predict that increases in intermeal interval like those encountered by some migratory birds should result in longer retention time of digesta and higher digestive efficiency if birds are maximizing their rate of energy intake. We tested these predictions by comparing residence time of digesta and extraction efficiency of lipid for captive yellow-rumped warblers (Dendroica coronata) feeding adlibitum and when we added intervals of time when the birds received no food. We increased the likelihood that the warblers were maximizing their rate of energy intake by increasing light levels during spring to induce hyperphagia (treatment birds (16L:8D light: dark cycle) ate 2.13 ± 0.14 g dry food day⁻¹ (n = 8) while control birds (10L:14D) ate 1.25 ± 0.03 g dry food day⁻¹ (n = 6)). Treatment birds offered food only every other 2–3 h ate 50% more during the 4-h test period than when they were always feeding adlibitum. Despite these differences in food intake, extraction efficiency of glycerol trioleate remained high and constant (93%), and mouth-to-anus total mean retention time (TMRT) did not change (overall mean: 54.8 ± 6.0 min). Residence time of lipid in the stomach increased whereas residence time of lipid in the intestine decreased when birds fed only every other 2–3 h compared to when birds always fed ad libitum. None of the results were consistent with the predictions of the optimal digestion model unless we assume that birds were minimizing their feeding time rather than maximizing their rate of energy gain. Furthermore, the ability of yellow-rumped warblers to maintain high extraction efficiency with no change in TMRT suggests some spare digestive capacity when food intake increases by as much as 50%. Received: 14 June 1997 / Accepted: 20 November 1997     

Bombesin elicits satiety in sham feeding rats

The satiety effect of intraperitoneal injections of the synthetic tetradecapeptide bombesin (BBS) was examined in rats equipped with chronic gastric cannulas. BBS produced potent, dose-related suppressions of both sham feeding (on days when gastric cannulas were open) and feeding (on days when gastric cannulas were closed). BBS not only suppressed sham feeding, but also elicited the behavioral sequence characteristic of normal satiety. The results demonstrate the potency of BBS in eliciting behavioral satiety under conditions in which gastric, intestinal and postabsorptive mechanisms are minimally activated by ingested food. These findings are consistent with previous reports suggesting a role for BBS in satiety.     

Risk of predation and feeding rate in tropical freshwater fishes: field evidence

Summary In a previous study (A. Prejs and K. Prejs in press) we found that at the end of the dry season small fish species trapped together with piscivorous fish in small, shallow pool varied in their level of food intake. The two smallest of these species fed little, whereas larger species fed at high rate. By examining the species and size composition of the diet and gape limitations of predatory species, I found that the decreased feeding rate of small fish was in response to a high risk of predation by gape-limited predators. The reduction of feeding rate was very substantial when compared to that of the same species in predator free area.     

三角帆蚌食性及摄食率的初步研究

三角帆蚌( Hyriopsis cumingii) 属滤食性双壳贝类, 通过滤水来摄食水中的浮游生物和有机碎屑等食物, 可使水质得到相应改善。作者在水库已连续多年开展了较大规模的三角帆蚌净水试验研究工作。       

Optimal feeding strategy of the temperate herbivorous fish Aplodactylus punctatus: the effects of food availability on digestive and reproductive patterns

In this study we examined differences in feeding behevior of populations of the marine temperate herbivorous fish Aplodactylus punctatus, in three different localities off the Chilean coast, which differ qualitatively and quantitatively in food availability. We test whether food selection follows optimal foraging strategics, whether there is any modification of the fishes' digestive tracts in relation to their diets, and whether differences in diet quality affect the allocation of energy into reproduction and maintenance in these populations. Samples of this fish and of the understore algal assemblages were taken seasonally from May 1989 to February 1990. For each population we analyzed dietary composition, weight of the digestive tract and of the food content, the condition factor (K), and the gonadosomatic index (GSI). Our results showed that the diet observed in the three populations closely resembled the differences in macro-algal abundance and composition among the three localities studied. Local differences in diet quality were inversely related to the amount of food consumption and size of the digestive tract, suggesting that under differential conditions of food availability A. punctatus is able to compensate for variations in food quality through a flexibility in its digestive strategies. The nutritional status (K) of individuals, and their reproductive pattern (GSI) were directly related to diet quality. These results indicate that although A. punctatus is able to adjust its digestive processes to different algal food regimes, the digestive modifications observed in food-poor environments are not sufficient to compensate for the lack of food and allow fish to reach the nutritional status and reproductive output reached in a food-rich environment. This study represents the first natural experiment demonstrating a direct relationship among food availability, feeding patterns, digestive processes, and reproductive effort.     

Site-specific differences in the feeding ecology of the California sheephead,Semicossyphus pulcher (Labridae)

Synopsis The feeding ecology of four populations of Semicossyphus pulcher was examined with respect to such factors as site-specific prey availability, density of the sheephead population, and size of the sheephead. The diets of the sheephead were typically broad, though only a few prey categories dominated. There was considerable between-site differences in the dominant prey. The availability of potential prey (in terms of abundance) also differed between sites both in total abundance and abundance of specific prey types. The diets of the sheephead generally reflected the availability of prey where prey were abundant (i.e. San Nicolas Island) but not where prey were scarce (e.g. Cabo Thurloe). Where prey were scarce and the sheephead population biomass was large (e.g. Cabo Thurloe and Isla Guadalupe), the sheephead apparently switched to alternative, and presumably, lower priority prey (i.e., bryozoan encrusted algae). Some abundant, potential prey were avoided in areas where sheephead were typically small, suggesting an inability of the small fish to handle large prey. The interaction of the kind and abundance of prey, and the size and abundance of the sheephead is discussed in relation to the influence of sheephead predation on their prey populations and community structure.     

Feeding ecology of a large social antelope in the rainforest

We studied the feeding ecology of the bongo (Tragelaphus eurycerus) in the Dzanga National Park in the rainforest of the Central African Republic to understand better the trade-off between food selectivity, ranging behaviour and social organization of a large, forest-dwelling, social antelope. Food plants and vegetation types were registered along a 311-km route travelled by bongos. Food availability was determined by identifying and counting the plants in 19 randomly chosen forest plots. Bongos showed pronounced selectivity for 26 out of 100 woody forest species. They predominantly consumed younger leaves, which suggests that high protein and low fibre content influence plant choice. In addition to leaves, bongos also ate fruits of two and flowers of one species. Furthermore, the diet was supplemented by grasses and herbs consumed on large natural licks. Such licks were regularly visited by the bongos. According to Jarman's ecological classification of antelopes, selective browsers are relatively small and live alone or in pairs to avoid competition over food. The bongo's large size and gregariousness should not allow it to survive in the rainforest as a pure selective browser. Our data suggest that the bongo relies on the opportunity to graze in bulk which it finds on the natural licks. We hypothesize that such licks either limit the distribution of bongos in other rainforest areas or allow larger group sizes than in areas without licks. Received: 8 June 1998 / Accepted: 30 November 1998     

Sucking pump activity in feeding behaviour regulation in carpenter ants

Modulation of liquid feeding-rate would allow insects to ingest more food in the same time when this was required. Ants can vary nectar intake rate by increasing sucking pump frequency according to colony requirements. We analysed electrical signals generated by sucking pump activity of ants during drinking solutions of different sucrose concentrations and under different carbohydrate-deprivation levels. Our aim was to define parameters that characterize the recordings and analyse their relationship with feeding behaviour.Signals showed that the initial and final frequencies of sucking pump activity, as well as the difference between them were higher in sugar-deprived ants. However, these parameters were not influenced by sucrose solution concentration, which affected the number of pump contractions and the volume per contraction. Unexpectedly, we found two different responses in feeding behaviour of starved and non-starved ants depending on concentration. Starved ants drank dilute solutions for the same length of time as non-starved ants but ingested higher volumes. While drinking the concentrated solutions, starved ants drank the same volume, but did so in a shorter time than the non-starved ones. Despite these differences, for each analysed concentration the total number of pump contractions remained constant independently of sugar-deprivation level. These results are discussed in the frame of feeding regulation and decision making in ant foraging behaviour.     

皮氏菊头蝠夏季的捕食行为对策

利用蝙蝠超声波探测器和CoolEditor 2 0 0 0声波分析软件研究了皮氏菊头蝠 (Rhinolophuspearsoni)的超声波信号 ,同时在野外研究了其捕食行为。研究结果显示皮氏菊头蝠是FM/CF/FM型的食虫蝙蝠。其回声定位信号的CF声波两端均附有短暂的FM信号 ,每次声波脉冲包含 2段信号 ,第 1段信号的CF频率为 (6 1 0 8±0 0 19)kHz ,持续时间为 (4 6 85± 3 72 )ms ;第 2段信号的CF频率为 (6 0 97± 0 0 3)kHz ,持续时间为 (35 12± 2 6 7)ms。在对皮氏菊头蝠的捕食行为研究中 ,通过运用生物多样性指数分析和Spearman相关性分析 ,结果表明皮氏菊头蝠在常绿阔叶落叶混交林中主要以式捕食鳞翅目 (Lepidoptera)、鞘翅目 (Coleoptera)等中型个体的昆虫 ,对食物种类及其体型具有选择性。此外 ,其形态与回声定位功能之间还表现出相关性。     

Estimating nest locations of bumblebee <Emphasis Type="Italic">Bombus ardens</Emphasis> from flower quality and distribution

The central-place forager in a social-insect colony, e.g., the bumblebee, has been expected to maximize its net rate of energy gain to increase the success of its colony. In addition to foraging behavior, the nest location is an important factor for the success of the colony. The bumblebee’s nest location would be affected by the spatial distribution of flowers and their food quality. In this study, we constructed a model to estimate bumblebee nest sites, using the net energy intake rate at available food sites for workers foraging from the nest site. We hypothesized that the probability of colony establishment at a site in coordinates (x, y) was high as the sum of the net energy intake rate I(x, y) increased. To obtain I(x, y), nectar standing crop, sugar concentration, and foraging time were measured for ten plant species in the study site covering 6.25 km². As available flowers changed seasonally, I(x, y) was calculated for three periods: the end of April, the beginning of May, and the middle of May. To verify our hypothesis, we compared the estimations in our model with the actual nest sites of Bombus ardens found in the beginning of May and June by means of tracking bumblebees. From the results, we considered that the net energy intake rate at mid-May might represent the probability of colony establishment, because it could affect colony persistence and reproductive success.