Narrow Diet Research Articles

A sensitive period for learning about food

It is proposed here that there is a sensitive period in the first two to three years of life during which humans acquire a basic knowledge of what foods are safe to eat. In support of this, it is shown that willingness to eat a wide variety of foods is greatest between the ages of one and two years, and then declines to low levels by age four. These data also show that children who are introduced to solids unusually late have a narrower diet breadth throughout childhood, perhaps because the duration of the sensitive period has been shortened. By reducing the costs associated with learning, a sensitive period for food learning should be adaptive for any omnivore (including early humans) that remains in the same environment throughout its life.

Trophic interrelations in a beach seine fishery from the northwestern coast of the Yucatan peninsula, Mexico

The main trophic interrelations were analysed in 12 species which represent 93% of the total catch from a beach seine fishery developed in Celestún, Yucatán. The diet was determined based on monthly samples over 4 yr. Five different trophic guilds were found on the basis of feeding preferences: microcrustacean and polychaete feeders, piscivores, omnivores and herbivores. For microcrustacean feeders Orthopristis chrysoptera, Eucinostomus gula, E. argenteus and Opisthonema oglinum the diet is narrow with a large overlap between. For polychaete feeders, Arius felis, A. melanopus and Haemulon plumieri diet is broad with the higher overlap between the catfishes. Among piscivores, Bardiella chrysura and Harengula jaguana have a high overlap between them, but a lower one with other species from the community. Among omnivores Lagodon rhomboides has the broadest diet and is considered to be a generalist while Acanthostraceon quadricornis is a specialist having a very narrow diet and a lower value of overlap with the other species. Finally, Archosargus rhomboidalis is a herbivore with the narrowest niche breadth and lowest overlap. In addition to a description of diets and trophic inter‐relations, the results emphasize the importance to the beach seine fishery of the benthic food resources.

Feeding ecology of the Iberian cyprinid Barbus bocagei Steindachner, 1865 in a lowland river

Patterns of food resource utilization by Barbus bocagei in a lowland river in the central part of the Iberian Peninsula are presented and discussed. Focal points include feeding activity, diet composition and seasonal and ontogenetic diet shifts. Striking features of overall feeding pattern of barbel are its continuous feeding activity, bottom habits, high consumption of detritus and dipteran larvae and narrow diet breadth. Seasonal changes in food resource availability elicited changes in food utilization patterns, revealing a trend to more generalist feeding during spring. Barbel increase consumption of plant material and large prey during ontogeny, but overlap in prey resource utilization between size classes is high. The versatility of barbel foraging behaviour may be an important feature in its exploitation of Iberian lotic systems.

Prey abundance vs diet breadth in a spider test system

‘Decisions’ made as to what prey types to include in the diet were analysed for two populations of the spider,Agelenopsis aperta existing under markedly different prey availability and predation levels. Potential prey types were ranked as to their relative profitabilities with respect to energy gain per handling effort and predation risk. Members of the population experiencing limited prey availability but low risk of predation to visually hunting predators exhibited a significantly higher capture attempt rate towards all prey encountered than the population for which prey were abundant but for which predation was a significant problem. Neither spider population preferentially attacked prey that exhibited higher profitability rankings. An experiment was completed that indicates thatA. aperta can discriminate between more and less profitable prey. Suggestions are made as to why the population experiencing abundant food did not exhibit a narrower diet when compared to the population existing under limited food.

Prey-Size Relationships and Feeding Tactics of Primitive Stream-Dwelling Darters

Prey-size use and feeding tactics varied among three cooccurring darter species in the primitive subgenus Hadropterus (genus Percina). These darters span a wide range of body sizes, yet they all utilize the same lotic prey-size spectrum. An optimal-diet index (ODI) showed that small darters had more optimal diets than large darters. However, decelerating ODI curves showed that ontogenetic shifts occurred from number-maximizing to prey-size selective feeding tactics. Interspecific differences in feeding tactics, as characterized by differences in prey size, diet breadth, and numbers of prey, also were reflected by differences in slopes of ODI power curves. Percina nigrofasciata showed a relatively prey-size selective tactic; P. sciera showed a relatively number-maximizing tactic. In darters, prey-size selection corresponded with a broad diet and number maximizing corresponded with a narrow diet. When P. nigrofasciata were compared among four Black Creek sites, relatively optimal diets were found at two sites where large macroinvertebrates also were relatively abundant, as predicted from optimal foraging theory. However, only small differences in ODI values existed between two sites showing the greatest disparity in macroinvertebrate abundance. Prey size was an important diet characteristic related to the feeding tactics of particulate-feeding darters.

Evolution and ecology of oviposition on host plants by acridoid grasshoppers

Most members of the superfamily Acridoidea (Orthoptera) oviposit in the soil, but some species oviposit directly on or in tissue of host plants. Oviposition in association with host plants has been reported for only 6% of acridoid species for which oviposition behaviour is known, hut the behaviour is systematically and geographically widespread, including members of two families and seven acridid subfamilies on three continents. This distribution suggests that host plant oviposition by grasshoppers has evolved independently at least eleven times in the world's grasshoppers fauna. A comparative approach to investigating oviposition on host plants shows that it tends to occur in species of inundated habitats and tropical forests, in species with narrow diets, and is correlated with a reduction in clutch size.

Feeding ecology of the piscivorous birds Phalacrocorax varius, P. melanoleucos and Sterna bergii in Moreton Bay, Australia: diets and dependence on trawler discards

The diets of three piscivorous bird species from Moreton Bay, Queensland, Australia, were monitored for 14 mo from April 1986 to September 1987. Regurgitated pellets from Phalacrocorax varius (pied cormorant), P. melanoleucos (little pied cormorant) and Sterna bergii (crested tern) were collected monthly and prey items were identified from otoliths, spines and whole-fish remains. Otolith weight to fish length and weight relationships were used to aid in calculation of diet composition. Sepia sp. was the commonest prey of P. varius and P. melanoleucos; Sterna bergii took few Sepia sp. In order of decreasing importance, the teleosts Sillago maculata, Apogon fasciatus and Leiognathus moretoniensis were the next most common prey in all diets. P. melanoleucos has previously been reported to eat primarily crustaceans. The size ranges of fish prey were 18 to 452 mm for P. varius; 25 to 246 mm for P. melanoleucos; and 33 to 226 mm for Serrna bergii. The three species had similarly narrow diets. There was a significant rank correlation between the diet of P. varius and the by-catch of the prawn trawlers. This, together with observations of feeding behaviour, the similarity of the diets and the benthic and benthopelagic nature of most prey species, suggests that in Moreton Bay the three bird species are primarily dependent on food from fishery discards. The population of about 350 P. varius possibly consumes 13.7% of the total fish by-catch. The relationships between the fishery and the piscivorous birds in discussed in relation to size of bird populations and its possible dependence on the fishery.

Mating System, Mate Choice and Ultrasonic Calling in a Zaprochiline Katydid (Orthoptera: Tettigoniidae)

We describe sexual communication and the mating system of an undescribed genus of zaprochiline katydid. Males produce an ultrasonic calling song described as a series of simple pulses at a carrier frequency near 50 kHz. Zaprochilines contrast with most other katydids in having a narrow diet consisting of pollen. Males in nature exhibited a resource-defence mating system by calling in choruses near flowers which were attractive to females. We determined whether females discriminated among calling males as mates. An early-season sample of male calls showed a correlation between song frequency and both body size and the size of the glands that produce a large, nutritious spermatophore which is eaten by the female. The prediction that larger males would have a mating advantage over small individuals was supported in laboratory experiments. However, examination of paired males in nature failed to reveal any evidence of such a mating advantage. Furthermore, in other laboratory experiments it was found that females preferred high frequency call models, representative of small males, over low frequency calls. It is suggested that females do not prefer calls of large males because only in the early part of the season does male song give information on the size of the male and his spermatophore glands. In addition, spermatophore nutrients may be less important to the nutrition of female zaprochiline than other katydiyds, due to the high-protein pollen diet of this species. Since higher frequencies of calls show relatively greater attenuation with distance, the high frequency calls preferred by females may be perceived as males calling closeby.

Food resource use among five flatfish species (Pleuronectiformes) in Wellington Harbour, New Zealand

Abstract Gut content analyses of 1068 samples from flatfish in Wellington Harbour were carried out to determine patterns of food resource use among five species co‐occurring there. Diets differed between species and, for some species, varied with location, season, and time of day. Two broad patterns of food resource use were recognised. Firstly, four species (Rhombosolea plebeia, R. leporina, Peltorhamphus novaezeelandiae, Pelotre‐tis flavilatus) fed on benthic infauna and epifauna while the fifth species (Amoglossus scapha) fed on benthic epifauna and pelagic organisms. Secondly, three species (R. plebeia, R. leporina, P. novaezeelandiae) had relatively diverse diets whiph closely overlapped while two species (P. flavilatus, A. scapha) had relatively narrow diets and little dietary overlap. The same species show different patterns of food resource use elsewhere in New Zealand; it is proposed that local conditions contribute to the observed patterns in Wellington Harbour.

A comparative analysis of food-niche relationships and trophic guild structure in two assemblages of vertebrate predators differing in species richness: causes, correlations, and consequences.

We conducted a comparative analysis of foodniche relationships and trophic guild structure in two assemblages of vertebrate predators (including hawks, owls, snakes, and carnivores) living in similar habitats of Chile and Spain, which differed in species richness (11 and 25 predator species, respectively), to explore how the structure of predator assemblages reflects an increase (or decrease) in the number of coexisting species. Our results indicate that the Spanish assemblage appears enriched by the symmetrical "addition" of species with disparately large and small values of body weight, diet breadth, and mean prey size, around the same median value found in Chile. Or, alternatively, the Chilean assemblage appears impoverished by the symmetrical "loss" of peripheral species - those at both tails of the frequency distribution of the above trophic estimators. Spanish predators overlap less extensively among themselves, and with smaller variance, than Chilean predators. Consequently, the higher predator richness in Spain is not ascribable to their narrower diet breadths or more extensive diet overlaps as predicted by some theoretical models. Instead, it is associated with a more spread-out use of the available resources. Trophic guilds can be recognized in the two countries, but in Spain guilds are less tightly packed. Some taxomically unrelated species are close diet analogues between Spain and Chile, whereas some closely related species cannot be matched well between countries. Circumstantial evidence suggests that the presence of some trophic guilds and of some specialist predators in either country is based on the high abundance attained by some particular prey types.

People

In Europe and southwest Asia, ungulates are generally very well represented in anthropogenically-accumulated assemblages dating to the Middle and early Late Pleistocene. In contrast, taphonomic studies have shown that fast small-sized prey taxa, such as leporids, small carnivores and birds, were rarely exploited during these time periods. These faunal patterns are often interpreted as indicating that Neandertals were characterized by a narrow diet, a finding with important social and technological implications. This paper reexamines this view using faunal data from Les Canalettes layer 4, a Middle Paleolithic faunal assemblage in Mediterranean France dominated by rabbit remains. Multiple lines of evidence, including the presence of cutmarks and shaft cylinders, suggest that humans accumulated most of the rabbit specimens found in this layer. This and other comparable assemblages raise a number of issues with respect to variations in diet breadth prior to the Upper Paleolithic.

Experimental Tests of Optimal Habitat Use in Fish: The Role of Relative Habitat Profitability

Utilizing optimal foraging theory and laboratory estimates of foraging costs, we predict the choice of foods and use of habitats by fish in the field. These predictions are tested with the bluegill sunfish (Lepomis macrochirus) foraging in three habitats (open water, sediments, and vegetation) in a pond. Relations describing prey encounter rates in each habitat as a function of prey size, prey density, and fish size were derived from laboratory experiments. These relations permitted us to estimate prey encounter rates based on weekly prey samples in each habitat of the pond. We can then determined the optimal diet and profitability (net energy return) for each habitat through time. Predictions of optimal diet exhibited good qualitative correspondence to the actual diet of the fish in the open water and vegetation, although we consistently predicted a slightly narrower diet than the fish were choosing. The model correctly predicted the magnitude of the change in size selection on Daphnia pulex with fish size and with decline in prey density. Predictions of optimal diet in the sediments were considerably in error apparently due to a tendency for late—instar midges to burrow deep in the sediments, thereby becoming unavailable to the fish. In this case habitat profitabilities were computed simply on the basis of the actual observed diet. Predictions of optimal habitat use i.e., when the fish should switch habitats to maximize feeding rates, showed striking correspondence to the actual habitat use of the fish; the bluegills switched from feeding in the open water column to feeding from the sediments within a few days of our predictions. The actual habitat use pattern differs dramatically from a null model of random habitat use. We indicate how this approach may be useful in studying intra— and interspecific exploitative interactions.

Habitat Structural Complexity and the Interaction Between Bluegills and Their Prey

Structural complexity of the habitat often reduces predatory efficiency by reducing prey capture rates. Prey density is often positively correlated with habitat structure because it pro- vides food and substrate to the prey as well as a relative refuge from predators. Dense structure inhibits foraging, allowing abundant, highly profitable prey to coexist with predators. Sparse structure allows efficient foraging and generally contains few highly profitable prey. This suggests that feeding rates of predators may be maximized at intermediate structure. If this is true, we might also expect predator growth rates to be higher in intermediate structure habitats. Since diet breadth is thought to be related to rates of encounter with profitable prey, we also expect diets of predators to be narrower at intermediate structure than in either sparsely or densely structured habitats. Bluegill sunfish (Lepomis macrochirus) restricted to experimental ponds varying in vegetation density grew better and consumed more prey at intermediate macrophyte density than fish held at either low or high macrophyte densities. Fish at low macrophyte density had narrower diets than expected due to high initial prey availability relative to prey available at intermediate and high macro- phyte density. Fish at high macrophyte density ate fewer, but larger, prey and thus had a narrower diet than expected. Fish predation reduced total prey biomass as well as mean prey size and altered the prey community structure by removing large active invertebrate predators and herbivores with subsequent release of smaller invertebrate predators and herbivores. These changes in prey com- munity structure were also mediated by habitat structure. Habitat structure-food density interactions may be added to temperature and presence of predators as variables that influence the use of resources by fishes.

Coexistence in a Kelp Forest: Size, Population Dynamics, and Resource Partitioning in a Guild of Spider Crabs (Brachyura, Majidae)

The population dynamics and resource partitioning of five species of spider crabs (Loxorhynchus crispatus, Pugettia producta, Mimulus foliatus, Pugettia richii, and Scyra acutifrons) were measured in a kelp forest on the central California coasts. The distribution of the five species showed zones of peak abundances along a transect from the intertidal zone through the kelp forest to a deep reef. P. richii was the most abundant species with peak densities of 6 crabs/m2 at the middle and inner edge of the kelp forest. M. foliatus was second most abundant with a peak of 3.5 crabs/m2 at the middle and outer edge of the kelp forest. S. acutifrons had peak densities of about 3 crabs/m2 at the outer edge of the kelp forest. P. producta had a peak of 2 crabs/m2 in the intertidal zone. L. crispatus was present in low densities of about 0.5 crabs/m2 from the middle of the kelp forest to the deep reef. The greatest combined density of spider crabs (11 crabs/m2) occurred at the middle of the kelp forest. Densities of all five species in the main study area in the middle of the kelp forest showed a synchronous cycle with a maximum in late summer and fall and a decline in winter to a low in spring. The cycle appeared to be caused by a combination of density—independent mortality from winter swells and storm activity and by slower development and growth rates during the upwelling period of colder water temperatures. Brooding frequencies of all the species remained high year—round. Size structures of the populations did not change during bimonthly sampling, indicating continuous recruitment. Size—frequency analysis of crab populations along the transect indicated that juveniles of Pugettia producta recruit into the intertidal and shallow Phyllospadix zones and migrate out into the kelp forest as they grow, but the other species did not have zones of recruitment separate from adult distribution. The diversity of predators which take spider crabs as a major portion of their diets indicated that the general level of predation pressure is high and may limit the overall population levels of the crabs. Predation by sea otters probably limits the density of P. producta, and the other four species are probably limited by fish predation. The crabs exhibit different color morphs, color change, and decorating behavior, which are adaptive for concealment from predators. Size at maturity of the five species spanned an order of magnitude in carapace width from small Scyra acutifrons (1 cm) to large Loxorhynchus crispatus (10 cm). Mean body size of mature females and mean body size of the entire population of all pairs of species except Mimulus foliatus/Pugettia richii had ratios larger than Hutchinson's (1959) predicted value of 1.28. Body size may reflect limitations of the crabs' utilization of crevice refuges in the microhabitat. Partitioning of the microhabitat resource was measured by substrate utilization. Mimulus foliatus had the largest microhabitat niche breadth and was found on most types of substrates, with an important refuge in kelp holdfasts. Pugettia richii was found primarily on the alga Cystoseira osmundacea and in coralline algal mats. Scyra acutifrons occurred in the interstices of algal/invertebrate turf, and Loxorhynchus crispatus was found on top of the turf. Pugettia producta occurred upon the kelp plants and had the narrowest microhabitat niche breadth. Analysis of stomach contents showed partitioning of food resources. Pugettia producta was a strict specialist grazing on giant kelp, Macrocystis pyrifera. Mimulus foliatus and Pugettia richii also had narrow diets of mostly drift M. pyrifera. Scyra acutifrons had major food categories of detritus, sponge, and pieces of M. pyrifera trapped in the algal—invertebrate turf. Loxorhynchus crispatus was a dietary generalist foraging on a broad range of invertebrates and giant kelp. Niche separation in the guild is multidimensional, and similar utilization of one resource is generally complemented by dissimilar utilization of another resource. Graphical analysis of niche separation for the three dimensions of microhabitat, food, and body size showed that Pugettia producta is an overall specialist and Loxorhynchus crispatus is a generalist. Scyra acutifrons also has a distinct niche within the algal invertebrate turf, but Mimulus foliatus and Pugettia richii exhibit extensive overlap in all of the parameters measured. However, the degree to which a species is a specialist vs. a generalist for a resource did not relate to the amount of niche overlap with the rest of the guild. Microhabitat resources appear to be the most important for niche separation and may also be explained as adaptations for minimizing predation.

Diet niche relationships among North American grassland and shrubsteppe birds.

We consider the dietary relationships of the numerically dominant breeding bird species in four North American grassland/shrubsteppe habitats, sampled over 2-3 consecutive years. Overall, the diets of these species contained primarily insects: orthopterans comprised 29% of the diet biomass, coleopterans 24%, and lepidopteran larvae 23%, while seeds contributed 15% of the average diet. These diets varied substantially, however, and we evaluated several aspects of this variation. Intersexual differences in diets within a species were few, despite the occurrence of significant sexual size dimorphism in several species. For many species, however, there were substantial shifts in dietary composition between years at a given location; overall, the average between-year similarity of species' dietary composition was 70%. Different species exhibited rather different diet patterns. Horned Larks were relatively omnivorous, had broad diet composition niches, and varied considerably in diets between different locations. Meadowlarks were also broad-niched and geographically variable in their diets, but were the most highly carnivorous of the species we considered. Dietary niche breadths of Grasshopper Sparrows were intermediate, but diet composition was rather stable, both between years and between locations. Chestnut-collared Longspurs exhibited narrow diet niches, but substantial annual variation: each year this species apparently exploited a different but limited set of prey types rather heavily. Larger avian predators generally consumed a broader array of functional groups of prey, but did not differ in the taxonomic variety of their diets from small birds. Variation in diet composition between individuals within local populations was considerable; in most species, an individual contained on the average 30-40% of the prey taxa represented in entire population smaples.Patterns of dietary overlap among species were quite inconsistent from year to year at most locations, although at the shrubsteppe site overlap among all species present was consistently quite high. Relatively few cooccurring species pairs exhibited low diet overlap. The degree of diet niche overlap was unrelated to body size differences of the birds, despite as much as six-fold differences in weight among some coexisting species. Relationships of the bird species on another dimension of the trophic niche, prey size, also differed substantially between sites and years. The ranking of co-occurring species by the mean sizes of the prey they consumed generally did not parallel their rankings by body sizes, and in some cases the smallest and the largest species present ate prey of similar sizes. At the shrubsteppe site, all the breeding species exhibited quite similar frequency distributions of prey sizes in their diets.As species number and diversity increased in the breeding avifaunas, diet niche breadths generally decreased, species packing by prey size decreased, and diet composition niche overlap remained relatively unchanged. These trends are in at least partial agreement with predictions of diffuse competition theory, but the patterns were derived from broad inter-site comparisons of overall site averages, and the relationships generally did not hold within local assemblages of species. In general, our attempts to match values of dietary niche features with site characteristics failed to demonstrate close agreement with the predictions of prevailing ecological theory based upon assumptions of resource limitation and competition. Instead, our findings seem generally most consistent with the suggestion that food is not normally limiting to bird populations in these systems, and individuals and populations are exploiting the food resources in an opportunistic fashion, which leads to considerable individual, between-year, and between-location variation in diet compositions and interspecific overlaps.Our attempts to discern clear relationships that accord with theoretical expectations in these avian assemblages are thwarted by our lack of detailed information on the resource base and by the lack of clear tests that will separate alternative hypotheses of community organization and structuring. We suggest that these complications may compromise the findings of many community studies.

Specific food sensitiveness

To sum up, then, although there are more disappointments than miracles in the search for and the curing of severe manifestations of food sensitiveness, the miracles are so gratifying when they come that, each time, the clinician will resolve to spend more time looking for them. The field is still much neglected; more diets much be fitted and fewer handed out ready made. A good history will often show that the diet is probably not the cause for the patient’s discomfort. Patients much not be left too long on narrow elimination diets; such diets are for testing and not for treatment. Some cases of diarrhea and pseudo-ulcer are due to the milk that is taken by way of treatment, and not infrequently certain foods irritate or greatly depress the brain. Somnolence after meals can be due to a particular food, and canker sores in the mouth can be produced by food. Efforts to use an elimination diet are often instructive in showing the physician that he is dealing with an unreasonable, overly fussy, querulous, or psychopathic person. Food sensitiveness is not necessarily allergic or due to protein. Perhaps partly for this reason, skin tests are of little help in finding the foods that cause indigestion.