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Body Sizes of Animal Predators and Animal Prey in Food Webs
Journal of Animal Ecology
Abstract
In c90% of the feeding links among the animal species with known sizes, a larger predator consumes a smaller prey. Larger predators eat prey with a wider range of body sizes than do smaller predators. The geometric mean predator size increases with the size of prey. The increase in geometric mean predator size is less than proportional to the increase in prey size (ie has a slope less than one on log-log coordinates). The geometric mean sizes of prey and predators increase as the habitat of webs changes from aquatic to terrestrial to coastal to marine. Within each type of habitat, mean prey sizes are always less than mean predator sizes, and prey and predator sizes are always positively correlated. Feeding relations order the metabolic types of organisms from invertebrate to vertebrate ectotherm to vertebrate endotherm. Organisms commonly eat other organisms with the same or lower metabolic type, but (with very rare exceptions) organisms do not eat other organisms with a higher metabolic type. Mean sizes of prey increase as the metabolic type of prey changes from the invertebrate to vertebrate ectotherm to vertebrate endotherm, but the same does not hold true for predators. Prey and predator sizes are positively correlated in links from invertebrate prey to invertebrate predators. In links with other combinations of prey and predator metabolic types, the correlation between prey and predator body sizes is rarely large when it is positive, and in some cases is even negative. Species sizes are roughly log-normally distributed. Body size offers a good interpretation of the ordering of animal species assumed in the cascade model, a stochastic model of food web structure. When body size is taken as the physical interpretation of the ordering assumed in the cascade model, and when the body sizes of different animal species are taken as log-normally distributed, many of the empirical findings can be explained in terms of the cascade model. -from Authors
... A simple reasoning explains that small animals can be predated by larger predators. Oppositely, the number of small predators with the capacity to attack bigger prey must necessarily be lower [118,[172][173][174][175][176][177][178][179][180]. ...
... Although predators tend to select smaller prey, smaller prey also occasionally dare to attack big predators. However" when the difference begins to increase, the prey starts to leave the range of optimal prey [178][179][180][181]. This may be the case of adult elephants weighing over 1000 kg-megaherbivores-in which the in the Zoo setting-with presumable low predatory risk (but also with minimal needs of time for foraging)-the sleeping time is 4.0-6.5 h per night. ...
Simple Summary
Many authors have stated that sleep detracts time used for foraging, defense, and anti-predatory activities. Therefore, sleep must provide some compensating advantage. Instead, we show that the sleep-related reductions in food intake and reproductive activities may be in fact benefits, both for the individual and the species. Furthermore, we show that the optimal prey are the immature, weak, sick, and senescent animals and rarely the sleeping individuals. Indeed, the reduced amounts of sleeping time observed in prey animals occurs not because of an antipredation evolutionary pressure, but mostly because of the need for time to eat and digest the high-cellulose contents of the herbivores’ diet, a set of tasks that leaves reduced time to sleep. In summary, no animal restrains their vital activities for sleeping, and this means that the need for sleep is low on the list of the vital activities. In fact, sleeping basically consists of doing nothing, and no live being can die from insomnia. Instead, what is important is maintaining efficient wakefulness, which can be achieved only after a sufficient amount of sleep.
... This result may suggest that S. semistriatus and S. planiusculus, the smallest species we studied, feed on smaller prey than M. brunneus or M. striola. Both species of Margarinotus may have a wider prey range-larger predators eat prey with a larger range of body sizes than smaller predators (Cohen et al. 1993). Differences in the body size of predators may reduce their competition for food and enable their co-occurrence. ...
Clown beetles (Histeridae) are stable components of carrion communities, but their prey range is poorly recognised. An indirect way to deduce species' diet is to study the functional morphology of their mandibles. The use of a multimodal approach in the study of Margarinotus brunneus, Margarinotus striola succicola, Saprinus semistriatus, and Saprinus planiusculus revealed a hidden morphological diversity in their mandibles. Geometric morphometric analysis showed inter-and sex-specific differences in their shape. Synchrotron X-ray microtomography revealed variability in musculature between genera and the presence of a joint-like structure at the basal margins in the Saprinus species. Scanning electron microscopy showed variation in the surface of inner margins. Traditional morphometrics revealed differences in mandibular arc according to beetle species, sex, and left and right body sides. All species retained a roughly 17° asymmetry, with the right mandible always having the higher arc. We conclude that Saprinus species are adapted for cutting and puncturing soft-bodied prey, whereas Margarinotus beetles also feed on hard-bodied prey. Future studies should consider our findings for better planning of prey-choice experiments. Emphasis should be placed on recognising whether subtle differences in mandible shape involve differences in diets. This will be critical to determine the role of species in carrion ecosystems.
... Additionally, individuals from medium and high trophic levels of the Ariidae family presented greater consumption of microplastics than low levels. These results are in Fig. 4 Variations in the condition factor according to their microplastic intake in species of the Ariidae and Sciaenidae families from the Colombian Pacific accordance with what was found in the Liaohe estuary in China, where MP consumption was greater in individuals of higher trophic levels, such as fish, compared to mollusks, crustaceans, and worms (Wang et al. 2021), suggesting a greater presence of microplastics in individuals of higher trophic levels due to bioaccumulation and trophic transfer (Cohen et al. 1993;Jonsson et al. 2005;Bhutto et al. 2023). ...
Microplastic pollution represents a growing threat to marine ecosystems, with potentially adverse impacts on the health of aquatic organisms, including fish. The present study investigated the relationship between the ingestion of microplastics and the biological characteristics of fish in estuaries of the bays of Tumaco and Buenaventura, Colombia, during the years 2020 and 2021, focusing on the Sciaenidae and Ariidae families. A total of 1652 fish were analyzed, covering 12 species of the Ariidae family and 28 of the Sciaenidae family, to determine the trophic level (TL) of each species and quantify the amount of microplastics ingested. The results revealed a significant positive correlation between TN and microplastic ingestion in both families (Ariidae: p = 0.0254; Sciaenidae: p = 0.0028), suggesting that fish at higher trophic levels tend to accumulate a greater amount of microplastics. Additionally, it was observed that fish that had ingested microplastics had lower condition factor (CF) values, which could indicate a negative impact on their health and development. These findings highlight the bioaccumulation of microplastics throughout the food chain and their potential detrimental effects on fish health, such as alterations in their growth. Microplastics can also act as vectors for toxic pollutants, which could exacerbate their harmful effects. Although it is hypothesized that fish could ingest microplastics due to the high availability of these contaminants in the environment and their possible confusion with natural prey, such as plankton and invertebrates, the precise origin of the identified microplastics could not be determined, despite having considered potential sources such as plastic waste and human activities. This study is distinguished from previous research by its specific geographic focus on the estuaries of the Colombian Pacific coast, a relatively understudied region for microplastic pollution compared to other areas. Additionally, it focuses on fish species from the families Sciaenidae and Ariidae, which are of great commercial importance to the region, making the findings particularly relevant to food security and the local economy. Furthermore, the study provides a detailed analysis of the bioaccumulation of microplastics at different trophic levels, allowing a better understanding of how these contaminants are transferred through the food chain and affect organisms at different levels. Together, these aspects make this study unique and contribute significantly to the understanding of the impacts of microplastics at the trophic level in tropical coastal ecosystems. Together, these aspects make this study unique and contribute significantly to the understanding of the impacts of microplastics at the trophic level in tropical coastal ecosystems. The results highlight the need to further research the bioaccumulation of microplastics and their impacts at the population and ecosystem levels, in order to develop effective management and conservation strategies to protect the health of marine ecosystems.
Graphic Abstract
... Size-dependent predation is a well-established theory for aboveground animals. It states that the size of the predators has implications for the size of their prey (Cohen et al., 1993). Most of the smaller predators prefer smaller prey, because of their mouth opening size (Hambright, 1991). ...
Protists and nematodes are dominant predators of prokaryotic communities in soil. Their strong difference in size suggests different feeding strategies and preferences. Here we analyzed the relevance of size-dependent predation by distinguishing in microcosm experiments the contribution of small-sized and large-sized protists and nematodes, respectively. Sterilized soils were inoculated with soil suspensions filtrated across 250 μm, 100 μm, 60 μm, 20 μm and 5 μm pore sized membranes and a non-filtrated control. After 60 days of incubation, only the soils inoculated with the 5 μm-filtrate showed lower abundances of bacteria, archaea and fungi, and a differently composed protistan community. The nematode communities were always dominated by the small-sized bacterivore genus Acrobeloides. Correlation analyses indicated that small-sized protists were associated with a wider range of prokaryotic taxa than larger sized protists. In contrast to small-sized nematodes, large-sized showed no correlation with specific prokaryotic taxa. The comparison of effects on prokaryotes at DNA and RNA levels suggested a preference of the soil predators for actively growing rather than resting cells. Small-sized protists (only Cercozoa) and nematodes had a more pronounced influence on the gene abundances of microbial groups and N cycling genetic potentials, i.e., bacterial amoA, nirS, and nosZII genes. Therefore, we conclude that the common ecological size-dependent predation theory also applies to trophic interactions of protists and nematodes with soil prokaryotes. The distinct feeding preferences can alter the prevalence of different N-functional genes, which could thus potentially modify the dynamics of the N cycling in soil.
... Predator assemblages are often size-structured, with larger predators preferentially targeting larger prey and smaller predators being restricted to smaller prey (Cohen et al. 1993;Singer et al. 2017). This size structuring not only facilitates prey partitioning but also promotes sizedependent intraguild predation (e.g., Sinclair et al. 2003). ...
Insectivorous predators play a crucial role in suppressing herbivore populations and mitigating herbivory in terrestrial ecosystems. However, the outcomes of ‘insectivore—herbivore—plant’ interactions are context dependent. This study examines the effects of vertebrate insectivores (birds and bats) and carnivorous arthropods (spiders) on herbivorous insects (caterpillars and sap suckers) and their host plant, Machilus thunbergii (Lauraceae), in a subtropical evergreen forest. We employed a factorial field experiment with four treatments: control (no exclusion), bird/bat exclusion, spider removal, and bird/bat exclusion plus spider removal. Forty trees (10 per treatment) were surveyed for herbivore abundance, degree of herbivory, and herbivore community composition. The results indicate that the predator treatments had no effects on sap suckers or sap-sucking damage. However, compared to the control, the leaf-chewing damage was higher in the bird/bat exclusion plus spider removal treatment, accompanied by shifts in leaf-chewer community composition and a trend toward increased leaf-chewer abundance. Spider abundance was lower in the control than in the bird/bat exclusion treatment, suggesting intraguild predation of spiders by birds and bats. Nevertheless, the leaf-chewing damage remained similar between these treatments, indicating that intraguild predation did not weaken the trophic cascade. This study is one of the few experiments that manipulate both vertebrate insectivores and carnivorous arthropods, and provides rare evidence that these two predator groups can perform complementary roles in suppressing herbivory. Our findings suggest that the strength of trophic interactions in the ‘insectivore—leaf chewer—plant’ system of this subtropical evergreen forest are likely to be relatively stable.
... Stable isotope analysis offers a more integrated picture (Jackson et al. 2011;Newsome et al. 2007) but, can be uncertain for generalist or omnivorous consumers (Davis et al. 2012). Additionally, analysing morphological parts, such as mouth width (Cohen et al. 1993;Wilson 1975) and intestine FIGURE 2 | The sampling sites in the Middle Luhoho used in Kisekelwa et al. (2021). Striped area represents the Kahuzi-Biega National Park; and▐: Tchinganda Falls at Bulambika. ...
Mouth morphology plays a crucial role in determining the trophic ecology of fish and sometimes underpins important lineage diversification. Freshwater teleost fish species belonging to the genus Labeobarbus, commonly found in Africa, exhibit intra‐ and interspecific variation and differences in the lower jaw occurring within and between species, respectively. Different phenotypes include a curved U‐shape (‘rubberlips’), a straight lower jaw (‘chiselmouth’) and an intermediate morphology known as the smiling phenotype. In some cases, smiling originates from hybridisation between chiselmouth and rubberlips. However, the trophic relationships of different mouth morphologies in the Labeobarbus taxa are still not well understood, particularly in the Congo Basin. Understanding the trophic ecology of Labeobarbus can enhance understanding of adaptive processes in morphologically diverse lineages. This study aims to investigate how differences in mouth morphology among multiple Labeobarbus species in the Luhoho River (Upper Congo Basin) link with different trophic niche uses. We combined information from gut morphometry, gut contents and stable isotope analyses on 202 fish specimens representing six species across four tributaries of the Middle Luhoho. All approaches consistently revealed trophic niche partitioning between chiselmouth and rubberlip species, respectively, more herbivorous/detritivorous and more insectivorous on the omnivory spectrum. In addition, trophic differences were also found between species within each mouth phenotype. Interestingly, the trophic niche of the smiling phenotype differed strongly from those of other phenotypes at all sites except for L. paucisquamatus, for which the trophic niches overlapped in Tchinganda. The pattern of trophic niche of Labeobarbus suggests subtle strategies to partition feeding resources when they occur across a narrow hydrographic scale.
... The trophodynamic theory indicates that community-level abundance or biomass decrease log-linearly with body size (Rice and Gislason, 1996), despite variable relative abundances or biomass of a single species (Cohen et al., 1993;Emmerson and Raffaelli, 2004). Based on this principle, several studies have used fish community's sizes to assess ecosystem conditions and functioning through fitting linear regressions with log-transformed abundance and size class datasets (e.g. ...
Finding easily accessible indicators to assess the biodiversity conservation is crucial in regions where long-term monitoring data is deficient. This is particularly true for tropical freshwater ecosystems, which house most of the known fish biodiversity and faces multiple natural and anthropogenic threats. Fish sizes serve as a key ecological indicator of ecosystem productivity and responses to environmental changes. Using length measurements of 354,465 fish produced by multiple projects and researchers, we investigated the spatial patterns and main drivers of fish productivity and mortality across 11 widely distributed basins in the Brazilian Amazon. Specifically, we examined if fish mortality and ecosystem productivity vary among environments, water types, Amazon sampling regions, and landscape metrics. Our findings show that fish size structure vary between water types and sampling regions, with Northern regions of the Amazon Basin exhibiting larger fish sizes and lower mortality than Southern region. Human population demography and forest cover also influenced fish productivity and size-160X/© 2025 Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). structure, affecting complexity and diversity of ecosystem trophic chains. We provide evidence that maintaining at least 75% forest cover is critical for supporting fish fauna size structure, highlighting the importance of considering terrestrial-freshwater links in conservation programs aiming to enhance sustainable fishing.
... Taller individuals are more likely to win dyadic confrontations and display interpersonal dominance (Stulp et al., 2015), shorter men express intrasexual jealousy more intensely than taller men (Brewer & Riley, 2009;Buunk et al., 2008), shorter men may be more antagonistic (Kozłowska et al., 2023), and taller men are less sensitive to cues of dominance in other men compared to their shorter compatriots (Watkins et al., 2010). This association is not limited to humans; in many nonhuman species, height and size play critical roles in dominance and survival (Cohen et al., 1993;Preisser & Orrock, 2012) and play a role in reproductive fitness (Haley et al., 1994). ...
Height is a fundamental variable in intersexual selection and intrasexual competition. Taller men are rated as more desirable and formidable as romantic partners and rivals, respectively, than shorter ones. In this study (NMTurk = 302; 63% male), we focused on the latter and examined individual differences in (a) intrasexual competition, (b) self-reported height in centimeters, and (c) perceptions of one’s height. We found that (a) shorter people, men in particular, scored higher on intrasexual envy, jealousy, and competitiveness; (b) those who had a shorter ideal height, men in particular, scored higher on intrasexual envy and jealousy; (c) both sexes with a greater desire to be taller were more intrasexually competitive regardless of the aspect of intrasexual competitiveness; and (d) those who were shorter or reported shorter ideal heights and desired to be taller scored higher on intrasexual jealousy and competitiveness. We replicated effects about body image and intrasexual competition and link, for the first time that we are aware of, individual differences in height and attitudes therein with individual differences in intrasexual competitiveness.
... Ensuite, l'existence ou l'absence de certaines interactions dépend des traits morphologiques, phénologiques ou comportementaux des deux espèces considérées pour ces interactions potentielles. Un exemple est celui de la taille des individus : la plupart des prédateurs sélectionnent des proies plus petites, créant un rapport de force qui permet la réalisation d'une interaction trophique (Cohen et al., 1993;Brose et al., 2006). La variabilité inter-et intraspécifique des traits dans l'espace implique ainsi différentes probabilités d'interaction entre deux mêmes espèces dans des réseaux trophiques distants. ...
Understanding the ecological drivers and limitations of adaptive convergence is a fundamental challenge. Here, we explore how adaptive convergence of planktivorous fishes has been influenced by multiple ecological factors, evolutionary history, and chance. Using ecomorphological data for over 1600 marine species, we integrate pattern-based metrics of convergence with evolutionary model fitting to test whether phenotypic similarities among specialist planktivores exceed expectations under null models and whether ecology, evolutionary history, or their combined effects best explain trait evolution. We find that planktivores are significantly more similar in phenotype than expected. Traits with functional relevance for prey detection and capture, such as eye diameter and lower jaw length, are strongly convergent, while general body size and shape are constrained by deep divisions between clades where the effects of evolutionary history are most pronounced. Since not all traits undergo strong selection toward a convergent ecomorph, their evolutionary trajectories have not entirely overcome ancestral differences in the multivariate trait space, resulting in a specific form of convergence termed conservatism. We show how adaptive responses to feeding ecology intertwine with other ecological pressures (i.e., light environment) and historical contingency to shape fish phenotype evolution over deep time, offering key insights into the generality of phenotypic evolution.
Dursban, an organophosphorus insecticide, was applied on June 3, June 18, and July 1 to eight shallow (24 cm) experimental ponds near Bakersfield, California. Four ponds were treated at 0.028 kg/ha (=0.025 lb./acre), four were treated at 0.28 kg/ha, and four were kept as controls. Phytoplankton, zooplankton, and insect populations were sampled on 21 dates between May 20 and August 16. Insect larvae and nymphs were more reduced in numbers than were insect adults, reflecting in part the ability of the latter to emigrate and immigrate. Twenty-four-hour posttreatment samples for the second and third, but not first, treatments showed greater reductions of predaceous Notonectidae, Dytiscidae, Coenagrionidae, larval Hydrophilidae) than of @'herbivorous@' (Corixidae, Baetidae, adult Hydrophilidae) insect populations. Predaceous insect populations generally recovered to control-pond levels more slowly than herbivorous insect populations. Five weeks after the last insecticide treatment, predaceous insects averaged only 45% and 9% as abundant in low dose and high dose ponds, respectively, as they were in control ponds (P
Numbers of individuals of arthropod species were sampled by direct observation at four sites in each of three different east central Illinois soybean fields at weekly intervals from plant emergence until harvest. Soybean plant development at each field was monitored throughout the season.The number of species detected in a field was greater at the edge (site A) than in the middle (site D). Site A vs. site D differences in numbers of herbivore species were greater than for predator/parasitoid species. Habitat space development (i.e. plant growth) was correlated with the pattern of soybean field colonization by arthropods: a relatively constant number of species per habitat space existed throughout most of the season in all three fields. The mean number of species per habitat space was higher at site A than at site D for both herbivores and predators/parasitoids.A windbreak at the edge of a field concentrated certain aerially dispersed herbivores at the leeward edge early in the season. Arthropod food webs during most of the season were very complex compared to early season trophic relationships. Suggestions for further study, including investigation of the effects of planting time, row-width, and interplanting on seasonal development of the soybean arthropod community are discussed.
The fauna of Lake George is dominated by herbivores, in particular the fish Tilapia nilotica and Haplochromis nigripinnis, and the cyclopoid copepod Thermocyclops hyalinus. Digestion, and the assimilation of carbon from algae, by these herbivores were studied in detail. It was found that, contrary to previous observations reported in the literature, both fish and zooplankton were able to digest and assimilate blue-green algae. The diurnal feeding patterns of the herbivores were examined, and methods devised for assessing, in terms of carbon, the daily ingestion of algae. Hence, using biomass data, the total amount grazed by the herbivores was calculated. Estimates of carbon requirements at other trophic levels were made, as was an assessment of the required level of net production by the algae for comparison with figures for standing crop and net algal production measured by other means. Food selection by secondary and tertiary producers is discussed, and in several species age correlated changes in selectivity were examined. Both the major herbivorous species of fish adopt phytoplankton feeding after a period of carnivorous or omnivorous feeding as fry. Thermocyclops hyalinus is herbivorous all its life, but the size of particle taken changes with age. There are more species of carnivorous than herbivorous fish and these exploit a wider variety of food sources; the few species studied also show changes in food preference with age.
The Norwegian subalpine lake. Øvre Heimdalsvatn, has a surface area of 0.78 km2 and a maximum depth of 13 m. It is ice-covered for 7.5–8 months, has a marked spring spate and a mean annual renewal period of about two months. The water is poor in electrolytes. Intensive studies have been made by an interdisciplinary team of the lake's physical and chemical properties, primary production and secondary production under the auspices of IBP/PF from 1969 to 1973, Allochthonous material accounted for 1/3 of utilized plant input. The major lake predator, the brown trout, fed largely on benthic organisms and did not exploit the zooplankton biomass. On account of the long period of ice cover and the rapid rise in temperature after ice break, many organisms (both planktonic and benthic) showed synchronous development. Abiotic conditions, such as the nature of the spring spate and the temperature rise, strongly affect species and community development.
