Variation In Feeding Patterns Research Articles

Understanding the feeding strategies of growing-finishing pigs: Exploring links with pig characteristics and behaviour

A large variation in feeding patterns between pigs and over time hampers the use of data from electronic feeding stations in the continuous monitoring of growing-finishing pig welfare. Individual feeding strategies (i.e. differences between pigs that are consistent within a pig across time) likely explain part of this variation, both at the daily level - based on feeding components intake, frequency and rate – and at the diurnal level - based on feeding components circadian rhythms and night feeding. It is, however, not known exactly which feeding strategies pigs display, nor which types of pigs display which strategies. This study aimed 1) to test which (combinations of) feeding components contribute to independent feeding strategies; and 2) to see whether pigs with different feeding strategies also differ in other physical and behavioural characteristics. To identify feeding strategies, we calculated the intra-class correlation coefficient (ICC) for each day-level feeding component, which reflects the proportion of variation explained by an individual pig effect (n=98 pigs). Subsequently, high ICC day-level components were correlated to diurnal-level components known to contain feeding strategies, to assess possible overlap. Pigs with different strategies were then characterised based on physical (n=52) and behavioural (home pen and play tests, n=22–27) variables at different ages, using (generalised) linear mixed models. Four dimensions of individual feeding strategies emerged: nibbling/meal eating, fast/slow eating, day/day-night eating and consistent/inconsistent eating from day to day, sustaining after correction for pig sex or body weight. All dimensions except day/day-night eating partially overlapped at the beginning of the growing-finishing phase, but became more distinct over time. Pigs with different feeding strategies also differed in their general activity, diurnal activity and possibly dominance rank. Feeding strategies did not relate to behaviours possibly indicative of more positive or negative emotional states of pigs. Our results demonstrate that pigs showed individual differences in their feeding behaviour that are consistent across time, along continua in four distinct dimensions. These differences went beyond differences in body weight and sex, and were related to other behavioural characteristics of pigs. The presence of feeding strategies suggests that the use of pig feeding behaviour data should be corrected for individual differences between pigs.

Feeding and biological differences induce wide variation in legacy persistent organic pollutant concentrations among toothed whales and polar bear in the Arctic

Polar bear and toothed whales in the Arctic exhibit orders of magnitude differences in concentrations of legacy persistent organic pollutants (POPs), which may be attributed to comparisons made across regions and different time frames. These interspecific differences could also be influenced by variations in biological susceptibility, including differences in xenobiotic biotransformation between polar bear, from the order Carnivora, and toothed whales, from the order Artiodactyla, as well as ecological factors, such as variation in feeding patterns. Here, we analyzed samples from subsistence-harvested toothed whales and polar bear in East Greenland collected between 2012 and 2021 and quantitatively compared interspecific differences in blubber/adipose polychlorinated biphenyl (PCB) and organochlorine (OC) pesticide concentrations. We further determined fatty acid (FA) signatures as dietary tracers to evaluate how feeding patterns influence POP concentrations relative to the influence of biological differences between taxa. Killer whale exhibited the highest mean concentrations of ΣPCBs (57.0 ± 14.0 mg/kg lw), Σdichlorodiphentlytrichloroethanes (ΣDDTs; 55.7 ± 13.1 lw), and Σchlordanes (ΣCHLs; 23.1 ± 5.6 mg/kg lw), while polar bear showed the second highest concentrations for ΣPCBs (12.5 ± 1.3 mg/kg lw), but comparable or even lower levels of all OCs relative to narwhal and pilot whale. Linear models using FA patterns as explanatory variables for POP concentrations demonstrated that, for ΣPCBs, diet differences explained most of the variation. Conversely, biological differences explained more of the variation for most OCs, especially for DDT, for which polar bear showed the lowest concentrations despite feeding on similarly high trophic position prey as killer whale. This novel quantitative comparison confirms that significant differences in legacy POP concentrations occur among Arctic marine mammal predators. Furthermore, the drivers of these differences are contaminant-specific, with feeding patterns primarily influencing PCB concentrations, taxa-specific biological characteristics (e.g., in xenobiotic biotransformation capacity) affecting DDT concentrations, and both factors contributing to variation in other OCs.

Regional Variation in Feeding Patterns of Sheepshead (Archosargus probatocephalus) in the Northwest Gulf of Mexico

Feeding patterns of sheepshead, Archosargus probatocephalus, in the northwest Gulf of Mexico were examined from samples collected at two locations in Texas, USA; Galveston and Port Aransas. A total of 53 sheepshead stomachs (Galveston, n = 35; Port Aransas, n = 18) had their contents analyzed along with tissue samples from the muscle and liver for a stable isotope analysis (δ13C, δ15N, and δ34S) because they provide a contrast between short-term (liver) and long-term (muscle) measurements. Multiple species of amphipods made up the majority of the prey items in sheepshead from Galveston (%IRI = 61.79), whereas barnacles were the primary diet item for sheepshead collected in Port Aransas (%IRI = 39.53). We observed diet shifts prior to and during the spawning season. MANOVA revealed significant differences in δ13C, δ15N, and δ34S stable isotope values from the muscle and liver tissue of sheepshead based on the location. In both muscle and liver samples, δ13C values were lower in Galveston than Port Aransas, but δ15N and δ34S values were higher in Galveston than Port Aransas. Niche size and overlap also differed between sheepshead from both locations and tissue types. Sheepshead collected in Galveston had a larger niche size in the muscle and liver samples ((mean ± SD) 479.3 ± 131.2, muscle; 433.3 ± 120.3, liver) than Port Aransas (178.8 ± 54.3, muscle; 270.0 ± 80.9, liver). The trophic niche of sheepshead from Galveston overlapped Port Aransas in muscle samples by 16.47% and 18.56% in liver samples. The trophic niche overlap of sheepshead from Port Aransas measured in muscle samples overlapped with sheepshead from Galveston by 18.49% and by 39.17% in liver samples. This study shows that there are subtle but significant differences between the diets of sheepshead along the Texas coast, with the majority of the differences potentially attributable to differences in the prey field along the natural salinity gradient of the Texas coast. This work provides an insight into the widely generalist grazing behavior of sheepshead, which potentially changes during the springtime spawning season.

Aedes albopictus host odor preference does not drive observed variation in feeding patterns across field populations

Laboratory and field-based studies of the invasive mosquito Aedes albopictus demonstrate its competency to transmit over twenty different pathogens linked to a broad range of vertebrate hosts. The vectorial capacity of Ae. albopictus to transmit these pathogens remains unclear, partly due to knowledge gaps regarding its feeding behavior. Blood meal analyses from field-captured specimens have shown vastly different feeding patterns, with a wide range of anthropophagy (human feeding) and host diversity. To address this knowledge gap, we asked whether differences in innate host preference may drive observed variation in Ae. albopictus feeding patterns in nature. Low generation colonies (F2–F4) were established with field-collected mosquitoes from three populations with high reported anthropophagy (Thailand, Cameroon, and Florida, USA) and three populations in the United States with low reported anthropophagy (New York, Maryland, and Virginia). The preference of these Ae. albopictus colonies for human versus non-human animal odor was assessed in a dual-port olfactometer along with control Ae. aegypti colonies already known to show divergent behavior in this assay. All Ae. albopictus colonies were less likely (p < 0.05) to choose the human-baited port than the anthropophilic Ae. aegypti control, instead behaving similarly to zoophilic Ae. aegypti. Our results suggest that variation in reported Ae. albopictus feeding patterns are not driven by differences in innate host preference, but may result from differences in host availability. This work is the first to compare Ae. albopictus and Ae. aegypti host preference directly and provides insight into differential vectorial capacity and human feeding risk.

Morphological and scanning electron microscopic study of the lingual papillae in the Javan Pipistrelle (Pipistrellus javanicus).

There are vast numbers of bats, in terms of both individuals and species, in Indonesia, although the precise species count is currently unknown. These bats demonstrate great variation in feeding patterns, with some being insectivorous, frugivorous, nectar-eating or carnivorous. One of the insectivorous bats found on Java Island, Indonesia, is the Javan pipistrelle (Pipistrellus javanicus). This paper presents a detailed morphological description of the tongue and lingual papillae of P.javanicus, using scanning electron microscopy (SEM) and light microscopy (LM). Macroscopically, the elongated tongue of P.javanicus can be divided into three sections: the apex, corpus and radix. On the dorsal part of the tongue (corpus), there is a prominence called the mediodorsal lobe, the lobe begin from the end of apex. On the radix, in the medial part, we describe the presence of a sulcus medianus. The SEM and LM observations show that the apex of the tongue bears three types of papillae: crown filiform, pronged filiform and fungiform. The corpus bears conical and fungiform papillae, whereas the radix bears vallate, large filiform, small filiform and fungiform papillae. Taken together, these results contribute to research on the tongue anatomy and feeding habits of the bat.

Inter-regional variation in feeding patterns of skipjack tuna (Katsuwonus pelamis) inferred from stomach content, stable isotope and fatty acid analyses

Foraging habits of skipjack tuna, SKJ (Katsuwonus pelamis), were investigated in three Spanish marine regions (Balearic Sea, Alboran Sea and Gulf of Cadiz) using stomach content (SCA), stable isotope (SIA), and fatty acid (FA) analyses. The three methodological approaches yielded significant differences among locations. All the studied areas appear to serve as important foraging grounds for SKJ, but the diet composition significantly varied among them. The predominant prey species in the respective locations were the North Atlantic krill, Meganyctiphanes norvegica, in the Balearic Sea, the flyingfish, Exocœtus volitans, in the Alboran Sea, and the anchovy, Engraulis encrasicolus, in the Gulf of Cadiz. Regional differences were also found in δ13C and δ15N values; furthermore, the analysis of standard ellipse areas (SEAc) based on isotopic data showed that the broadest niche corresponded to SKJ from the Gulf of Cadiz, with no significant isotopic niche overlap between areas. Consistent with the SCA and stable isotope results, the FA composition varied among areas. Docosahexaenoic acid (DHA, 22:6n-3) was the most abundant FA in the SKJ muscle, showing its highest values in samples from the Gulf of Cadiz; this FA was the most effective in segregating SKJ geographical groups. In conclusion, this study provides evidence that SKJ in eastern Atlantic and western Mediterranean waters can easily adapt their diet to local prey availability. Furthermore, stable isotope signatures and FA profiles of muscle tissue prove to be reliable trophic markers that allow separation of populations occurring in different marine areas.

Seasonal feeding patterns of Atlantic bluefin tuna (Thunnus thynnus) in the Strait of Gibraltar

The Strait of Gibraltar (SoG) houses a large diversity of marine species including large pelagic animals that use this area as permanent or temporary habitat. In particular, the SoG is home to a population of adult and sub-adult Atlantic bluefin tuna (Thunnus thynnus) that occurs there for most of the year. To gain further insight into the life history of this ABFT population, seasonal feeding patterns were investigated combining stomach content analysis (SCA) and stable isotopes analysis (SIA) of muscle and liver tissues. Our results reveal seasonal variations in feeding patterns, which are evidenced by a significant shift in the diet composition and the highest food consumption rates that take place in spring, prior to the spawning season. These changes in feeding habits are consistent with the varying energetic needs along the species’ annual biological cycle. The present observations confirm the SoG as an important foraging ground for ABFT resident populations and may have further implications for the management of the resource.

Unravelling variation in feeding, social interaction and growth patterns among pigs using an agent-based model

Domesticated pigs, Sus scrofa, vary considerably in feeding, social interaction and growth patterns. This variation originates partly from genetic variation that affects physiological factors and partly from behavioural strategies (avoid or approach) in competitive food resource situations. Currently, it is unknown how variation in physiological factors and in behavioural strategies among animals contributes to variation in feeding, social interaction and growth patterns in animals. The aim of this study was to unravel causation of variation in these patterns among pigs. We used an agent-based model to explore the effects of physiological factors and behavioural strategies in pigs on variation in feeding, social interaction and growth patterns. Model results show that variation in feeding, social interaction and growth patterns are caused partly by chance, such as time effects and coincidence of conflicts. Furthermore, results show that seemingly contradictory empirical findings in literature can be explained by variation in pig characteristics (i.e. growth potential, positive feedback, dominance, and coping style). Growth potential mainly affected feeding and growth patterns, whereas positive feedback, dominance and coping style affected feeding patterns, social interaction patterns, as well as growth patterns. Variation in behavioural strategies among pigs can reduce aggression at group level, but also make some pigs more susceptible to social constraints inhibiting them from feeding when they want to, especially low-ranking pigs and pigs with a passive coping style. Variation in feeding patterns, such as feeding rate or meal frequency, can indicate social constraints. Feeding patterns, however, can say something different about social constraints at group versus individual level. A combination of feeding patterns, such as a decreased feed intake, an increased feeding rate, and an increased meal frequency might, therefore, be needed to measure social constraints at individual level.

Validation of a High Frequency Radio Frequency Identification (HF RFID) system for registering feeding patterns of growing-finishing pigs

Automated monitoring of the feeding patterns of growing-finishing pigs would allow detecting problems with individual pigs or groups of pigs and thus improving health, welfare and productivity of the farm. In this paper a High Frequency Radio Frequency Identification (HF RFID) system was validated for its suitability to register individual pigs’ feeding patterns at a round trough in a group-housing context. High Frequency RFID antennas were installed above the troughs of a commercially available type of round feeder to identify feeding pigs fitted with one or two passive RFID tags on their ears. A multiplexer was used to connect multiple antennas to a single reader. During 11.5h, video observations of 20 focal pigs (equipped with two tags) at an age of 16weeks were performed to validate the system. A large variation in feeding patterns of the 20 focal pigs was found. Correlation between the number of registrations per pig and the feeding duration on video was low (R2=0.53) mainly due to four pigs with specific feeding behaviour (with the four pigs excluded: R2=0.88). The RFID registrations of the 20 focal pigs – with irregular time gaps between them – were compared with instantaneous video samples using several time window sizes around the video sample. The specificity for individual pigs with one or two tags was always above 85%, but sensitivity varied for individual pigs, tags and with different time windows used. A quantitative comparison between the use of one or two tags per pig was made based on a receiver operating characteristic (ROC) curve. For two tags per pig a sensitivity of 88.58% and a specificity of 98.34% can be reached with a time window size of 9s. For one tag per pig, sensitivity is only above 85% at a time window of size 31s. Of the total number of RFID registrations 77.11% occurred during feeding visits, and 92.23% occurred during or within 10s of feeding visits on video. This system showed good potential for measuring feeding patterns of growing-finishing pigs in commercial pig houses, for research purposes, or to detect potential problems with pigs by signalling changes in the registered feeding patterns.

Ecología trófica del pez &lt;i&gt;Arothron meleagris&lt;/i&gt; (Tetraodontiformes: Tetraodontidae) en el arrecife de Los Frailes, Baja California Sur, México

Monthly samples were taken from November 2004 to October 2005 in the Los Frailes reef, BCS, Mexico. The objective was to determine the feeding habits of the pufferfish, Arothron meleagris, as well as possible variations in feeding patterns due to size and/or sex. We captured 101 specimens, with all stomachs contained food. The index of relative importance (IRI) was used to determine the main items; which were non-identified organic matter (NIOM) (30.44%), Echinometra vanbrunti (26.25 %), Porifera (12.63 %), Pocillopora spp. (11.84%), Bryozoa (5.37 %) and Porites spp. (4.83 %). Levin's index indicated a low trophic niche breadth (Bi=0.12) and allowed us to determine that A. meleagris is a specialist predator with strong preferences towards certain food types. The Morisita-Horn index showed a high trophic overlap between sexes (Clambda=0.78), seasons (hot and cold Clambda=0.95) and among sizes (small and medium Clambda=0.94; small and large Clambda=0.74; medium and large Clambda=0.83).

Feeding by Flea Beetles (Coleoptera: Chrysomelidae; Phyllotreta spp.) Is Decreased on Canola (Brassica napus) Seedlings With Increased Trichome Density

Laboratory and field studies were undertaken to determine the effects of increased numbers of trichomes on seedling stems, petioles, and first true leaves of Brassica napus L., canola, on the feeding and behavior of the crucifer flea beetle Phyllotreta cruciferae (Goeze) (Coleoptera: Chrysomelidae). Seedlings of 'Westar' canola with genes inserted from Arabidopsis thaliana L. for increased trichome production, called Hairyl, were tested against Westar seedlings in no-choice and choice laboratory tests, and against parental plants and other cultivars grown from seed with and without insecticide in field trials at Saskatoon and Lethbridge, Canada. Analyses ofprefeeding and feeding behavior in no-choice tests of first true leaves found that flea beetles interacted with their host while off Hairyl leaves more so than beetles presented with leaves of Westar. Beetles required twice as much time to reach satiation when feeding on leaves with increased pubescence than on Westar leaves. In laboratory choice tests, flea beetles fed more on cotyledons and second true leaves of Westar than on comparable tissues of the transgenic line. In field trials, variations in feeding patterns were seen over time on cotyledons of the line with elevated trichomes. However, all four young true leaves of Hairyl seedlings were fed upon less than were the parental lines. Feeding on Hairyl plants frequently occurred at levels equal to or less than on cultivars grown from insecticide-treated seed. This study highlights the first host plant resistance trait developed in canola, dense pubescence, with a strong potential to deter feeding by crucifer flea beetles.

Seasonal, diel and ontogenetic variation in feeding patterns of small yellow croaker in the central Yellow Sea

Stomach contents of 1603 small yellow croaker Pseudosciaena polyactis, sampled from seasonal bottom trawl surveys in the central Yellow Sea between March 2001 and January 2002, were examined. The results showed that small yellow croaker was a carnivorous predator and &gt;30 prey species were identified from stomach contents analysis. Crustaceans (mainly euphausiids and decapods) were the most important prey, occurring in 93·1% of the stomachs containing food, and accounting for 77·6% of the total food by mass. Feeding activity was highest in autumn and lowest in spring and winter. Decapods were more important in summer, whereas euphausiids were more important during other seasons. Ontogenetic differences were found in the diet composition and feeding activity within the range of size (standard length, LS) studied. The importance of fishes and decapods increased with LS, whereas euphausiids, copepods and amphipods decreased in importance with LS. Dietary breadth increased markedly for adults. A positive relationship was found between LS and prey size. In each season the maximum diel feeding activity occurred at 0800 and 2400 hours, indicating that there was crepuscular and nocturnal feeding by small yellow croaker.

Relationship between maternal obesity and infant feeding-interactions

BackgroundThere are no data regarding the relationship between maternal adiposity and interaction and feeding of infants and possible contribution to childhood obesity. In this study we determined the relationship between maternal body weight and composition and infant feeding patterns and maternal-infant interaction during 24-hour metabolic rate measurements in the Enhanced Metabolic Testing Activity Chamber (EMTAC).MethodsThe amount of time four obese (BMI = 33.5 ± 5.3 kg/m2) and three normal weight (BMI = 23.1 ± 0.6 kg/m2) biological mothers, spent feeding and interacting with their infants, along with what they ingested, was recorded during 24-hour metabolic rate measurements in the EMTAC. The seven infants were 4.9 ± 0.7 months, 69 ± 3 cm, 7.5 ± 0.8 kg, 26 ± 3 % fat and 29 ± 25 percentile for weight for length. Energy and macronutrient intake (kcal/kg) were assessed. Maternal body composition was determined by air displacement plethysmorgraphy and that of the infants by skin-fold thicknesses. Pearson correlations and independent t-tests were utilized for statistical analysis (p < 0.05).ResultsInfants born to obese biological mothers consumed more energy (87.6 ± 18.9 vs. 68.1 ± 17.3) and energy as carbohydrate (25 ± 6 vs.16 ± 3; p < 0.05) than their normal weight counterparts. Most of the increased intake was due to complementary feedings. Twenty-four hour infant energy intake increased with both greater maternal body weight (r = 0.73;p < 0.06) and percent body fat. Furthermore, obese biological mothers spent less total time interacting (570 ± 13 vs. 381 ± 30 minutes) and feeding (298 ± 32 vs.176 ± 22 minutes) (p < 0.05) their infants than their normal weight counterparts. Twenty-four hour interaction time negatively correlated with both maternal body weight (r = -0.98; p < 0.01) and percent body fat (r = -0.92; p < 0.01). Moreover, infants of obese mothers slept more (783 ± 38 vs. 682 ± 32 minutes; p < 0.05) than their normal weight counterparts. However, there were no differences in total 24-hour energy expenditure, resting and sleeping metabolic rates (kcal/kg) for infants born to obese and normal weight biological mothers.ConclusionGreater maternal body weight and percent body fat were associated with greater infant energy intakes. These infants were fed less frequently and consumed more carbohydrates in a shorter period of time as compared to infants from normal weight biological mothers. These variations in feeding patterns may predispose certain infants to obesity.

Analysis of Feeding and Drinking Patterns of Dairy Cows in Two Cow Traffic Situations in Automatic Milking Systems

With increasing possibilities for obtaining online information for individual cows, systems for individual management can be developed. Feeding and drinking patterns from automatically obtained records may be valuable input information in these systems. With the aim of evaluating appropriate mixed-distribution models for feeding and drinking events, records of 30 fresh cows from visits at feeding stations (n=83,249) and water bowls (n=67,525) were analyzed. Cows were either allowed a high-milking (HF) or a low-milking (LF) frequency by being subjected to controlled cow traffic with minimum milking intervals of 4 and 8h, respectively. Milking frequency had significant effects on feeding patterns. The major part (84 to 98%) of the random variation in feeding patterns of the cows was due to individual differences between cows. It can be concluded that cows develop consistent feeding and drinking patterns over time that are characteristic for each individual cow. Based on this consistency, patterns of feeding and drinking activities have valuable potential for purposes of monitoring and decision making in individual control management systems. Use of a Weibull distribution to describe the population of intervals between meals increased the statistical fit, predicted biologically relevant starting probabilities, and estimated meal criteria that were closer to what has been published by others.

Diurnal and seasonal variation in feeding patterns of Atlantic salmon, Salmo salar L., in sea cages

Atlantic salmon, Salmo salar L., in sea cages exhibit feeding patterns that vary both diurnally and seasonally. Hitherto, there are no data reporting feed rate and its variation through a complete annual cycle. Here we present data from Scotland showing diurnal and interseasonal variation in feeding patterns and feeding rates of Atlantic salmon fed daily to satiation from shortly after transfer to seawater until harvest about 11 months later. A major feeding peak regularly occurred soon after dawn, and feeding rates remained high for, approximately one hour. Over the remainder of the day, the fish fed at a lower but steady rate. Relative feed intake varied over the trial, being initially high in summer followed by a sharp decline in autumn, and then further declining until fish reached harvest size at the beginning of the following summer. Further investigations of the relationship between variation in circannual feeding patterns and environmental parameters should now be carried out to improve the understanding of the mechanism behind these patterns.

Seasonal Variation in Feeding Patterns and Food Niche Overlap in the Mediterranean Blennies Scartella cristata, Parablennius pilicornis and Lipophrys trigloides (Pisces: Blenniidae)

Abstract. Gut contents of a total of 180 specimens of the blennies Scartella cristata (L., 1758). Parablennius pilicornis (Cuvier, 1829) and Lipophrys trigloides (Valenciennes, 1836) caught in the course of 1990 off Playa de la Mora (Prov. Tarragona, Spain) were analysed. The quantitative composition of food differed considerably between the 3 species (mostly algae in the herbivorous S. cristara. Amphipoda in the carnivorous L. trigloides and a variety of items in omnivorous P. pilicornis). The 3 species in the course of a year overlap little in food resource use, with overlap reaching its maximum in April when juvenile Mytilus on the rock substrate are in ample supply. In S. cristata and L. trigloides, diversity of food items is similarly lowest in July and April, respectively, when these 2 species attain their optimal nutritional status. In contrast, diet diversity and food intake are inversely correlated in P. pilicornis. Evidently, resource sharing between blenniid species in the rocky shore habitat is clearly structured, but subject to seasonal dynamics. It is concluded that food niche analyses should consider seasonal plasticity in feeding patterns and refrain from premature conclusions based on short‐term studies.

Daily feeding rhythms in Atlantic salmon II: size‐related variation in feeding patterns of post‐smolts under constant environmental conditions

Previous studies of feeding rhythms in post‐smolt Atlantic salmon Salmo salar have produced variable results. Therefore, the present study was performed to clarify the source of these differences and to examine size‐related variation in daily feeding patterns. A small group of hatchery reared post‐smolts was kept in an indoor seawater tank under conditions of constant photoperiod and light intensity, and negligible diurnal variation in water temperature. Feeding responses were monitored by video camera throughout the day. The resultant feeding pattern for the population mirrored an earlier study, with the highest levels of feeding activity in the early morning and late evening. Differences between this and other studies may be due to variation in climate, season or life‐history stage. Daily feeding patterns were size‐dependent. The largest fish fed at a relatively constant level through the day, medium‐sized fish fed in a pattern similar to that described above for the population and small fish fed most at first and last light. These differences were due probably to the effect of competitive interactions upon fish of different sizes.

Daily feeding rhythms in Atlantic salmon II: size-related variation in feeding patterns of post-smolts under constant environmental conditions

Previous studies of feeding rhythms in post-smolt Atlantic salmon Salmo salar have produced variable results. Therefore, the present study was performed to clarify the source of these differences and to examine size-related variation in daily feeding patterns. A small group of hatchery reared post-smolts was kept in an indoor seawater tank under conditions of constant photoperiod and light intensity, and negligible diurnal variation in water temperature. Feeding responses were monitored by video camera throughout the day. The resultant feeding pattern for the population mirrored an earlier study, with the highest levels of feeding activity in the early morning and late evening. Differences between this and other studies may be due to variation in climate, season or life-history stage. Daily feeding patterns were size-dependent. The largest fish fed at a relatively constant level through the day, medium-sized fish fed in a pattern similar to that described above for the population and small fish fed most at first and last light. These differences were due probably to the effect of competitive interactions upon fish of different sizes.

Orangutan activity budgets: Monthly variations and the effects of body size, parturition, and sociality

The activity budgets of individual orangutans were investigated at the Kutai Reserve, Indonesia. Activity profiles within and between individuals were compared to examine monthly variations in feeding patterns, potential energetic constraints imposed by large body size and parturition, and the costs of sociality. Animals showed monthly changes in travelling, feeding, and resting patterns. Monthly increases in travelling and feeding were associated with marked reductions in the time spent resting. Inter-individual variations in activity budgets did not exist among animals of the same age-sex class. Activity patterns differed, however, as a function of age and sex. Adult females and subadult males travelled and fed significantly longer than an adult male. Parturition had predictable effects on activity; one female reduced her feeding and travelling immediately following parturition. Adult male orangutan sociality appears to be limited by travel costs. Associations with females forced a male orangutan to travel significantly more compared with periods in which he was solitary. The male did not lose an appreciable amount of time feeding when accompanying a female.

Patterns in feeding: a behavioural analysis using Locusta migratoria nymphs

ABSTRACT. Feeding patterns of Locusta migratoria L. nymphs, kept under LD 12:12 at 30°C with ample food, were analysed over the first 6 days of the fifth instar. A number of differences were found between the light and dark phases. (1) More was eaten during the light than the dark, with the differences becoming progressively larger over the 6 days. (2) During light phases most insects showed an increasing tendency to feed with time since the last meal, while in the dark the probability of starting to feed remained constant. (3) There was little variation in feeding patterns within the light phase, but marked changes occurred within the dark phase, feeding declining to a low level in the last 4h. The amount eaten during a meal was regulated similarly in the light and dark, with time rather than amount eaten being of paramount importance in terminating a meal. The time when feeding started was somewhat influenced by the size of the preceding meal, but once feeding began meal size was largely independent of the preceding meal. The importance of food quality in determining the pattern of feeding is discussed.