Prey Volume Research Articles

Diet composition of three amphisbaenian species (Amphisbaena alba, Amphisbaena pretrei, and Amphisbaena vermicularis) from Northeast Brazil

Amphisbaenians usually have a diet composed of a wide variety of small arthropods, with some species being more selective in their feeding and others considered more generalist. Using only specimens deposited in scientific collections, the diet composition of Amphisbaena alba Linnaeus, 1758, Amphisbaena pretrei Duméril and Bibron, 1839, and Amphisbaena vermicularis Wagler, 1824 from the Northeast region of Brazil was analyzed. Except for individuals of A. alba, due to the small sample size, we also investigated the possible intersexual difference in the volume, length, and number of prey in the diet of amphisbaenians and the possible relationship between prey volume and body size (snout–vent length) of individuals was analyzed. The diet of worm-lizard in general was composed of termites, cockroaches, ants, and beetle larvae, and no intersexual differences were found in the size, length, and number of consumed prey. The body size of A. pretrei and A. vermicularis showed no relationship with the volume of prey consumed. Amphisbaenians presented a characteristic diet of opportunistic generalist predators, with several food categories in the composition of their diets, indicating that the studied species feed according to the availability and abundance of prey in the environment.

Morphology and Mechanics of the Fin Whale Esophagus: The Key to Fast Processing of Large Food Volumes by Rorquals.

Lunge feeding rorqual whales feed by engulfing a volume of prey laden water that can be as large as their own body. Multiple feeding lunges occur during a single foraging dive and the time between each lunge can be as short as 30 s (Goldbogen etal. 2013). During this short inter-lunge time, water is filtered out through baleen to concentrate prey in the oral cavity, and then the prey is swallowed prior to initiating the next lunge. Prey density in the ocean varies greatly, and despite the potential of swallowing a massive volume of concentrated prey as a slurry, the esophagus of rorqual whales has been anecdotally described as unexpectedly narrow with a limited capacity to expand. How rorquals swallow large quantities of food down a narrow esophagus during a limited inter-lunge time remains unknown. Here, we show that the small diameter muscular esophagus in the fin whale is optimized to transport a slurry of food to the stomach. A thick wall of striated muscle occurs at the pharyngeal end of the esophagus which, together with the muscular wall of the pharynx, may generate a pressure head for transporting the food down the esophagus to the stomach as a continuous stream rather than separating the food into individual boluses swallowed separately. This simple model is consistent with estimates of prey density and stomach capacity. Rorquals may be the only animals that capture a volume of food too large to swallow as a single intact bolus without oral processing, so the adaptations of the esophagus are imperative for transporting these large volumes of concentrated food to the stomach during a time-limited dive involving multiple lunges.

Prey Composition of Spotted Scat, Scatophagus argus (Linnaeus, 1766) from Madong - Sei Nyirih Waters, Tanjungpinang, Riau Island, Indonesia

Food habits and feeding ecology research are a fundamental tool to understand fish roles within their ecosystems. Fish sampling was conducted from May to July 2024 in Madong – Sei Nyirih waters. 85 fish samples were analysed by prey item, occurrence frequency, and volume of prey. The spotted scat showed flexibility in their feeding ecology was based on prey composition. The gut contents showed an ontogenetic shift in diet with an increase in length, the main food of the smaller specimens (<100 mm SL) consisted of different species of algae, while larger sized (>100 mm SL) fish have the most diversified prey items in their diet, although algae were predominant.

Notes on the diet of <em>Anolis</em> lizards (Iguanidae: Dactyloinae) from Yasuní National Park in Amazonian Ecuador

We briefly describe the diet of six species of lizards of the genus Anolis in the Yasuní National Park, located in the western part of the Amazon Rainforest. A total of 241 prey items found in the stomachs of the lizards were identified. We noted that Aranea and Hymenoptera were the most frequent diet categories used by the lizard community. In terms of prey volume, Hemiptera and insect larvae were the most representative prey. The description of the diet of Anolis provided by this study can be further combined with information related to their natural history, thus shedding light on ecological mechanisms that influence adaptation.

Morphology and diet are decoupled in nearshore notothenoids from King George Island, West Antarctica.

Antarctic notothenioid fishes show wide adaptive morphological radiation, linked to habitat preferences and food composition. However, direct comparisons of phenotypic variability and feeding habits are still lacking, particularly in stages inhabiting nearshore areas. To assess these relationships, we collected juveniles and adults of the most common benthic species inhabiting shallow waters off the South Shetland Islands within a similar size range, the plunderfish Harpagifer antarcticus, the black rockcod Notothenia coriiceps, and the marbled rockcod Notothenia rossii. Individual size ranges varied from 44.0 to 98.9 mm standard length (LS) (H. antarcticus), from 95.8 to 109.3 mm LS (N. coriiceps), and from 63.0 to 113.0 mm LS (N. rossii). Notothenioid fish showed different morphospace variability, being larger for H. antarcticus than the other Notothenia species and associated with the position of the posterior end of the operculum, along with the location and relative size of the eye. The evolutionary allometry was low, but the static allometry was much higher, especially for H. antarcticus and N. rossii. The diet was mainly carnivorous, consisting of amphipods and euphausiids. Macroalgae were scarce or totally absent in the gut contents of all species. Only H. antarcticus showed an increase in the prey number and ingested prey volume with fish size. Finally, there was a significant covariation between shape changes and LS in all species (allometric effects), however, not with prey composition, probably due to the small size range or ontogenetic stage and the relative similarity (or lack of contrast) in the benthic environment that they utilized.

Non-native earthworms increase the abundance and diet quality of a common woodland salamander in its northern range.

The online version contains supplementary material available at 10.1007/s10530-023-03168-3.

Feeding habits of Boana raniceps (Cope, 1862) in three mountains of Brazilian semiarid

Studying the trophic ecology of animals helps us understand their life history, their relationship with the environment and other species, and their role in ecosystems. In this sense, we describe the feeding habits of the hyalid frog Boana raniceps in three high-altitude mountain ranges of Northeastern Brazil, investigating intersex differences in the diet and the relationship between the size with the volume of prey consumed. Furthermore, we investigated prey-predator interactions in the Boana genus with an ecological network approach. We analyzed the stomach contents of 62 B. raniceps specimens collected in three mountains in the state of Ceará (Northeastern Brazil) and consulted data available in the literature for information on the diet of other Boana species. We identied 82 prey items distributed in eleven categories. Overall, there were no differences in the composition of B. raniceps diet among the three mountains. Although males and females shared the majority of prey items consumed, they tended to consume prey volumetrically differently, and predator size did not influence prey volume. In addition, predator-prey interactions in the genus Boana revealed low modularity, complementary specialization, and nestedness. Therefore, species of the genus Boana follow the general pattern for the diet of most Brazilian frog species (generalist and opportunistic habits), being likely influenced by the availability of prey in the habitat. Overall, the present study constitutes a complete review of the prey items consumed by the genus Boana in Brazil, describing the general pattern of anuran-prey networks in these hylids.

Trophic ecology of small to large hylids from an Amazonia-Cerrado transitional zone in Brazil

The diet of an organism is related to its intrinsic characteristics, such as morphology, physiology, and behavior, and those of the prey it consumes. For species occurring in sympatry, the knowledge of the mechanisms that favor the co-occurrence of morphologically and ecologically similar species may be important to understand the resource partition in the assemblage. In this study, we analyze the diet of small to large hylids (i.e., Scinax fuscomarginatus, Dendropsophus anataliasiasi, Boana caiapo, and B. raniceps) in an Amazonia-Cerrado transitional zone, verifying if the diet of species with different body sizes is similar and if species diet is explained by the availability of prey in the environment. We found that the dietary patterns of the studied hylids were not driven by prey availability in the environment, with species feeding preys in an opportunistic way. In addition, the diet composition was similar among species, however, the volume of consumed prey varied according to the body size, with large species feeding more prey volume than the small ones. This pattern is predicted by the optimal foraging theory, in which larger predators tend to maximize their energy intake by consuming large prey. Altogether, the segregation depending on the body size can play a key role in trophic resource partitioning, with small species feeding small prey and larger species consuming small to large prey, but preferring the larger ones when there is an option, avoiding interspecific competition.

Diet and Habitat Use of Proceratophrys ararype (Anura: Odontophrynidae), an Endemic Frog from the Chapada do Araripe, Northeastern Brazil

Information on the use of food resources and habitat are important tools for understanding trophic niche and ecological relationships. Many factors can influence the diet and eating habits of anurans. Species of the genus Proceratophrys are important components of the leaf litter frog communities in the Neotropical forests, including P. ararype, a species with restricted distribution in northeast Brazil. Therefore, we describe aspects of habitat use and evaluate the diet of P. ararype and compare these results with information on other Proceratophrys species. We collected, dissected, and examined the gastrointestinal tracts of 40 individuals, among which 55% contained food items, with 11 prey categories identified. We also tested the relationship between prey item categories and sampling sites, differences between males and females, and the relationship between frog size and prey. The species can be characterized as generalist, and the volume of prey ingested was not related to the average size of the individuals. Additionally, the habitat most used by the anuran was leaf litter; thus, it was inferred that this frog species uses the environment horizontally. The data found and comparisons with the literature suggest that the diet composition of P. ararype is determined by the availability of arthropods in the environment. This study demonstrates the importance of understanding habitat use, highlighting opportunistic behavior, such as the pattern found for anuran amphibians, contributing to elucidate the biology of anurans with relictual distribution, especially in semi-arid regions.

Short handling times allow for active prey selection in suspension feeding copepods

AbstractThe time it takes copepods to handle prey can vary depending on the properties of the prey, but it is still largely unknown how handling times may affect copepod feeding efficiency. We compiled data on prey‐handling times derived from video observations in 10 species of calanoid and cyclopoid copepods consuming a large variety of prey. Prey‐handling times vary by five orders of magnitude, and the largest fraction of this variation is explained by relative prey size: larger prey takes longer to handle. When normalized by prey volume (volume of prey handled per unit time), however, larger prey are handled more efficiently than smaller prey. Within this overarching pattern there are distinct differences among species. Thus, large species handle a certain prey size much faster than small species. However, when further normalizing by predator size, the data for all species (except Mesocyclops spp.) collapse on a common relationship. Handling times are generally not limiting maximum consumption rates, and less so for large prey. This allows room for prey selectivity, and indeed copepods are known to be highly selective feeders. Our data predict that copepods can afford to be more selective when feeding on larger than on smaller prey and when consumption is not limited by prey encounter rate, and this is consistent with observations of copepod feeding behavior. We argue that the fast handling times allow copepods to optimize their diet through prey selectivity, and that this is one key to the evolutionary success of pelagic copepods.

Feeding Niche and Predator–Prey Size Relationship in the Whiptail Lizard Aspidoscelis lineattissima (Squamata: Teiidae) in Insular and Continental Populations of the Mexican Pacific

We explore the feeding habits of two populations of the lizard Aspidoscelis lineattissima from two localities (Cocinas = island and Xametla = mainland) under the hypothesis that in an insular environment, there is less selection of food, because it is a relatively comfortable environment to forage due to the presence of few competitors and predators. We also examine the predator–prey size relationship in this lizard species with the intention of distinguishing possible ontogenetic changes in the choice of prey sizes in the two localities. In stomach contents of the lizards from mainland, a total of 2,616 prey items were recorded, while on the island, 1,357 prey items were found. This number of prey was divided into 18 categories for the mainland and 20 for the island. In general terms, the most important prey in the diet of lizards from both localities were Isoptera, Coleoptera (adult and larvae), Araneae, Orthoptera, Hymenoptera (ants and others), Blattodea, and Diptera. Island lizards presented a greater amount of plant material in their stomach contents. The breadth of the food niche was greater on the island than on the mainland. Although statistically there were no differences regarding food overlap between localities, the highest overlap values between groups (age classes and sexes) were found on the mainland. We found a positive relationship between morphological variables of the lizards (snout–vent length, head width, and head length) with the maximum and mean values of the prey volume in both localities. This reveals an ontogenetic change that indicates that as lizards grow, they add a greater quantity of large prey to their diet and at the same time eat smaller prey. These results showed that the diet of the lizards from both localities was similar to other species of the genus. The feeding habits of a species in contrasting environments is evidence that is helpful for understanding the foraging patterns more clearly, and the possible connection with its life history characteristics, shedding more light on the hypothesis of niche amplitude and the optimal foraging theory.

Trophic ecology of Gymnodactylus geckoides Spix, 1825 (Squamata, Phyllodactylidae) from Caatinga, Northeastern Brazil

The diet of lizards is mainly composed of arthropods. It can be affected by biotic and abiotic factors, which influence the energy supply provided by the composition of the animal´s diet. The richness and abundance of many arthropod species can be influenced by environmental seasonality, especially in the Caatinga ecoregion, due to the rainfall regimes. The present study aims to describe aspects of the seasonal and morphological variation in the lizard Gymnodactylus geckoides diet and their energy content. We collected 157 individuals (63 females, 68 males, and 26 juveniles) at the Catimbau National Park, Northeastern Brazil, of which 72 were analyzed for the dry season and 59 for the rainy season. Our data indicates Isoptera to be the most common prey in G. geckoides’s diet. Energy content, prey number was higher in the dry season, whereas prey volume and glycogen content increased in the rainy season. Proteins and lipids did not show marked differences. The present study represents the first effort to understand variations in G. geckoide’s trophic ecology, indicating that this specie presents a wide variation in their diet, especially when considering seasonal factors, revealing their needs and restrictions according to prey availability and environmental conditions.

The invasion and impacts of the African sharptooth catfish (Clariidae: Clarias gariepinus) in the Malay Peninsula

Abstract The African sharptooth catfish, Clarias gariepinus, is a globally invasive species with known severe impacts, including native species declines through ecological (e.g., competition, predation) and genetic interactions (e.g., hybridisation, introgression). The species was introduced to the Malay Peninsula in the late 1980s, and has since become widely established. In this study, we used structural equation models (SEMs) (habitat analyses) and stable isotope analyses (dietary analyses) to elucidate the determinants of C. gariepinus invasion success in streams of the Malay Peninsula and investigate potential impacts on native counterparts. Our SEMs indicate that C. gariepinus invasions were mediated by greater anthropogenic influences as well as environmental conditions associated with open streams (large channels, higher temperatures and lower canopy cover). Additionally, on the one hand, we find that invasions by C. gariepinus have led to substantial negative impacts on the native Asian walking catfish, Clarias batrachus, with the latter being displaced, or in some areas extirpated, from its characteristic open‐stream habitats. On the other hand, C. gariepinus invasions did not appear to impact the native forest specialist, Clarias leiacanthus. Stable isotope analyses showed that all three Clarias species were opportunistic, generalist feeders. There was substantial overlap in the diets of C. gariepinus and C. batrachus. However, C. leiacanthus generally assimilated comparatively greater volumes of aquatic macroinvertebrate prey, therefore reducing dietary overlap with introduced C. gariepinus. Our findings indicate that propagule pressure and exaptations probably have played a major role in facilitating C. gariepinus invasions in the Malay Peninsula. Furthermore, our results suggest that habitat competition may have acted synergistically with trophic competition to drive C. gariepinus impacts on native species, although this was mitigated by differentiation in ecological preferences. Our results help shed light on the general characteristics of invasive species, the mechanisms facilitating their proliferation, and the potential outcomes of biological invasions. These highlight the urgent need to manage the introduction, spread and impacts of invasive C. gariepinus in the Malay Peninsula and elsewhere in its invaded range.

Seasonal Variation in Terrestrial Invertebrate Subsidies to Tropical Streams and Implications for the Feeding Ecology of Hart’s Rivulus (Anablepsoides hartii)

Terrestrial invertebrates are important subsidies to fish diets, though their seasonal dynamics and importance to tropical stream consumers are particularly understudied. In this year-round study of terrestrial invertebrate input to two Trinidadian headwater streams with different forest canopy densities, we sought to (a) measure the mass and composition of terrestrial inputs with fall-in traps to evaluate the influences of seasonality, canopy cover, and rainfall intensity, and; (b) compare terrestrial and benthic prey importance to Anablepsoides hartii (Hart’s Rivulus), the dominant invertivorous fish in these streams, by concurrently measuring benthic and drifting invertebrate standing stocks and the volume and composition of invertebrates in Rivulus guts throughout the year. The biomass of terrestrial invertebrate fall-in was 53% higher in the wet versus dry season; in particular, ant input was 320% higher. Ant biomass fall-in also increased with the density of canopy cover among sampling locations within both streams. Greater precipitation correlated with increased ant inputs to the more open-canopied stream and increased inputs of winged insects in the more closed canopy stream. Concurrently, the biomass of benthic invertebrates was reduced by more than half in the wet season in both streams. We detected no differences in the total volume of terrestrial prey in Rivulus diets between seasons, though ants were a greater proportion of their diet in the wet season. In contrast, benthic prey were nearly absent from Rivulus diets in the wet season in both streams. We conclude that terrestrial invertebrates are a substantial year-round prey subsidy for invertivores in tropical stream ecosystems like those we studied, which may contrast to most temperate streams where such terrestrial inputs are significantly reduced in the cold season. Interestingly, the strongest seasonal pattern in these tropical streams was observed in benthic invertebrate biomass which was greatly reduced and almost absent from Rivulus diets during the wet season. This pattern is essentially the inverse of the pattern observed in many temperate streams and highlights the need for additional studies in tropical ecosystems to better understand how spatial and temporal variation in terrestrial subsidies and benthic prey populations combine to influence consumer diets and the structure of tropical stream food webs.

Seasonal and ontogenic variation in the trophic spectrum of Anatolian water frogs, Pelophylax ridibundus group, in the Eastern Mediterranean (Amphibia: Anura)

Seasonal and ontogenic variation of food composition in Anatolian water frogs (Pelophylax ridibundus group) were analysed in the Seyhan and Ceyhan Deltas, southern Turkey. A total of 1,226 prey items were retrieved from the stomachs of 335 individuals (75 juveniles, 148 males, 112 females) in spring, summer and autumn. The frogs fed mainly upon invertebrates, especially insects (80.4%), and the prey spectrum was strongly influenced by prey availability in the environment. The most frequently consumed prey items were Hemiptera (31.6%), Coleoptera (29.0%), Hymenoptera (23.6%), and Diptera (21.5%). While adult frogs consume various invertebrate preys such as annelids, gastropods, arachnids, and insects, the diet of juveniles is mostly confined insects. No significant differences were found in the seasonal variation of prey types between sexes. Prey diversity and volume increased in spring and summer, and decreased in autumn with the decrease of the air temperature and reduced activity of the frogs.

Diet composition: A proximate mechanism explaining stream salamander declines in surface waters with elevated specific conductivity

Changes in land use, such as mountaintop removal mining with valley fills (MTR-VF), often results in headwater streams with elevated specific conductivity (SC). Stream salamanders appear to be particularly sensitive to elevated SC, as previous studies have shown occupancy and abundance decline consistently among all species and life stages as SC increases. Yet, the proximate mechanism responsible for the population declines in streams with elevated SC have eluded researchers. We sampled salamander assemblages across a continuous SC gradient (30–1966 μS/cm) in southeastern Kentucky and examined the diet of larval and adult salamanders to determine if the ratio of aquatic to terrestrial prey (autochthony), total prey volume, aquatic prey importance (Ix), and body condition are influenced by SC. Further, we asked if threshold points for each diet component were present along a gradient of SC. Larval salamanders experienced a 12–fold decline in autochthony at 153 μS/cm, a 4.2–fold decline in total prey volume at 100 μS/cm, a 2.2-fold decline in aquatic Ix at 135 μS/cm, and a rapid decline in body condition as SC increased. Adult salamanders experienced a 3–fold decline in autochthony at 382 μS/cm, no change in prey volumes, a 2-fold decline in aquatic Ix at 163 μS/cm, and a decline in body condition as SC increased. Our results indicate that SC indirectly affects stream salamander populations by changing the composition of diet, which suggests that food availability is a proximate mechanism that leads to reduced population occupancy, abundance, and persistence in streams with elevated SC.

Feeding habits of Lithobates megapoda (Anura: Ranidae), a threatened leopard frog used for human consumption, in Lake Chapala, Mexico

The Big-footed Leopard Frog (Lithobates megapoda) is a threatened and endemic species from western Mexico. This species has aquatic habits and it is distinguished by its large size, particularly by the length of its legs, reason for which it is captured for human consumption. Also, knowledge about its natural history is scarce and incomplete. In this study, we analyzed the composition of the diet of L. megapoda on the shore of Lake Chapala, the largest lake in Mexico. A total of 69 adult individuals were collected lifeless in fishing nets, during the rainy season (June-October), of which 48 had stomach contents. A total of 96 prey items were identified, which correspond to 13 prey categories. Fish constituted the most dominant prey category in the diet in terms of number, volume, frequency of occurrence, and relative importance. No significant differences were found in the consumption by prey type (aquatic or terrestrial). However, the aquatic preys had a greater relative importance and were more voluminous than the terrestrial ones. The diversity of prey categories, in terms of prey volume, indicates males may have a higher dietary diversity than females, but we not evaluated possible bias. In addition, a significant effect was found in the interaction of size (SVL) of frogs with the average of prey volume. Females (that are larger than males) consumed prey within a wide volume range and, the larger they are, more voluminous are prey. In this way it is possible that intraspecific competition for trophic resources in the environment is reduced. This study helps us understand the trophic ecology of L. megapoda, a frog species that plays an important role in the food web where it lives, as a predator feeding on aquatic and terrestrial organisms.

Crab Diets Differ Between Adjacent Estuaries and Habitats Within a Sheltered Marine Embayment

Portunid crabs contribute to significant commercial and recreational fisheries globally and are commonly fished in estuaries and/or marine embayments, which are amongst the most degraded of all aquatic ecosystems. Portunus armatus were collected seasonally between April and February from five locations across three systems in temperate south-western Australia. The dietary composition of crabs was quantified and compared between two estuaries (Peel-Harvey and Swan-Canning) and a sheltered marine embayment (Cockburn Sound) containing three distinct habitats: shallow seagrass, shallow sand and deep sand. Overall, crabs ingested large volumes of bivalves (both live organisms and dead shell), polychaetes, crustaceans (e.g., amphipods, small decapods), and smaller volumes of teleosts, echinoderms and plant material (seagrass, algae). Analysis of Similarities showed that dietary composition varied significantly among the five locations (two estuaries and three habitats within Cockburn Sound) and seasons, with greater location than seasonal differences in the two estuaries. Diets were most distinct in the Cockburn Sound seagrass due to greater volumes of decapods and teleosts and smaller volumes of bivalve shell consumed in this habitat. Crabs from both estuaries consumed greater quantities of bivalves than those from Cockburn Sound. Seasonal differences in both estuaries were greatest between summer and winter, with a more diverse range of prey and large quantities of bivalves ingested in summer, whereas small bivalves and bivalve shell in the Peel-Harvey and polychaetes and other crustaceans in the Swan-Canning, were consumed in greater quantities in winter. The summer diet in the Peel-Harvey Estuary in the current study was compared to that 20 years previous and with documented change in the benthic macroinvertebrate fauna. Currently, crabs consume smaller volumes of high-calorie prey, i.e., polychaetes, small bivalves and teleosts, and instead ingest greater proportions of calcareous material than previously. This marked shift in dietary composition parallels changes in benthic macroinvertebrates in the Peel-Harvey Estuary. Overall, prey availability appears to be the major factor influencing the spatial and temporal differences in P. armatus diets in these three coastal systems.

Trophic Relationships among Five Species of Anura in the Colombian Caribbean Tropical Dry Forest: A Spatial and Temporal Approach

Species of Bufonidae and Leptodactylidae are common in the Colombian tropical dry forest. Although some of them are associated with active foraging and consumption of termites and ants, their trophic ecology is mostly unknown. The diet of five anuran species of Bufonidae (Rhinella horribilis, R. humboldti) and the leptodactylid subfamily Leiuperinae (Engystomops pustulosus, Pleurodema brachyops, and Pseudopaludicola pusilla) was examined at six sites of the Colombian Caribbean in fragments of dry forest and different land uses. A total of 310 food items were identified. The greatest contribution was represented by Coleoptera, Hymenoptera (Formicidae), Isoptera, and Diptera. The species differed in number and volume of prey. Except for Pseudopaludicola pusilla, which behaves as a generalist predator, species had high intake of termites and ants. Engystomops pustulosus preferred termites, Pleurodema brachyops had high consumption of ants and termites, and the two bufonid species were myrmecophagous. Except for Pseudopaludicola pusilla, predator and prey size was related. Most species have overlapping diets (spatially and temporally) when analyzing food items identified at the order level. However, the richness of different prey within these orders allows the coexistence of species. The diet of these species presents similar trends in different habitats throughout their distribution area.

Effect of Stream Permanence on Predation Risk of Lotic Crayfish by Riparian Predators

Given the importance of crayfish in stream ecosystems, gaining insight into the role of stream permanence in maintaining predator–prey interactions is critical. Our objectives were to determine the influence of stream permanence and season on crayfish predation and assess the role of stream permanence and crayfish density on the presence of predators, while accounting for imperfect detection. We conducted surveys of crayfish density, mammalian scat, and environmental variables within 10 intermittent and 10 permanent streams in the Ozark Highlands. We used occupancy modeling to assess the relationship between predator presence, crayfish density, and environmental variables. Stream permanence did not play a role in determining relative frequency of occurrence or percent volume of crayfish prey in mammalian diets. However, percent volume and relative frequency of crayfish prey found in scats differed by season, with both highest in spring and summer. The relative frequency and percent volume of fish prey showed a significant interaction of season by stream permanence, which may be the first instance of this observation. Procyon lotor (Raccoon) had the highest detection probability (p = 0.39), whereas Neovison vison (American Mink; p = 0.15) and Lontra canadensis (River Otter; p = 0.03) had low detection probabilities. Further study into predator–prey interactions in the context of hydrology, particularly when related to imperiled groups like freshwater crayfishes, is needed since climate change is expected to alter hydrologic patterns.