Carnivorous Diet Research Articles

Trophic niche separation of two non-spinose planktonic foraminifers Neogloboquadrina dutertrei and Pulleniatina obliquiloculata

Based on laboratory observations, planktonic foraminifers are omnivorous, feeding zooplankton and phytoplankton. Spinose species tend toward greater dependence on zooplankton prey than on phytoplankton prey, while non-spinose species are more adapted to herbivorous diets. However, the trophic activity of planktonic foraminifers in the natural environment and their trophic positions in the marine food web have not yet been fully understood. The trophic position (TP) of two non-spinose species, Neogloboquadrina dutertrei and Pulleniatina obliquiloculata, was determined by differences in the nitrogen isotopic composition between two amino acids (glutamic acid and phenylalanine). Results show that TP values of N. dutertrei were ~ 2.4, indicating dependence on omnivorous (mixed herbivorous and carnivorous) diets, while those of P. obliquiloculata were ~ 2.1, indicating dependence on herbivorous diets. Together with previous laboratory observations, these TP values suggest that N. dutertrei is a detritivore or scavenger, while P. obliquiloculata is generally a herbivore. This trophic niche separation likely allows these two planktonic foraminiferal species to live within a similar depth zone in the open water column and provides a clue for understanding causes of spatial and temporal changes in their relative abundances in living and sediment assemblages.

Google Trends data reveal a sharp trend: teeth and claws attract more interest than feathers, hooves or fins

SummaryIn nature conservation, the generation of public interest, attention or emotions is an important instrument for nature, biotope and species protection; in this, charismatic flagship species play an important role. In the present study, flagship-making affiliation to a taxonomic unit as well as morphological, ecological and conservation traits were identified by analysing vertebrate species from each of the five extant vertebrate classes (Mammalia, Aves, Reptilia, Amphibia and fishes). Google Trends data on the 20 most Googled species of each of the five classes were used, a representation index was derived and the body mass, diet and protection status of these species were analysed. A clear concentration of interest in mammalian species was evident with the help of the introduced representation index. Furthermore, species with a higher body mass were clearly overrepresented in the data. Overall, important patterns in the studied traits were determined: belonging to Mammalia, a large body mass and a carnivorous diet are frequently represented among these species. For conservation purposes, such popular species can be specifically selected as flagship species or ambassadors to help protect entire biomes, which will therefore benefit less charismatic species as well. Possible ways to use traits that are perceived to be flagship-making in order to further the global conservation endeavour are briefly discussed.

Population density estimates for terrestrial mammal species

AbstractAimPopulation density is a key parameter in ecology and conservation, and estimates of population density are required for a wide variety of applications in fundamental and applied ecology. Yet, in terrestrial mammals these data are available for only a minority of species, and their availability is taxonomically and geographically biased. Here, we provide the most plausible predictions of average population density, their natural variability and statistical uncertainty for 4,925 terrestrial mammal species.LocationGlobal.Time period1970–2021.Major taxa studiedTerrestrial mammals.MethodsWe fitted an additive mixed‐effect model accounting for spatial and phylogenetic autocorrelation on a dataset including 5,412 average population density estimates for 737 species. Average density was modelled as a function of body mass, diet, locomotor habits and environmental conditions. We validated the model using spatial and taxonomic block cross‐validation and used the estimated error to quantify the uncertainty around statistical predictions of population density for 4,925 mammal species.ResultsSmall body size, fossorial behaviour and herbivorous diets were associated with the highest population densities, whereas large size, aerial behaviour and carnivorous diets were related to the lowest densities. Species in non‐seasonal environments yielded higher densities than species in environments with high precipitation seasonality. Empirical estimates of population density vary by about four times on average within the same species, and statistically independent predictions for the majority of species deviate by about five times from observed values, indicating that prediction errors are similar to the natural variability in population densities.Main conclusionsOur predictions and uncertainty estimates of average population densities open up a number of applications in macroecology and conservation biogeography, including biomass estimation, setting population targets in conservation assessments and planning, and supporting Red List assessments. The methodology can be replicated easily for other taxonomic groups with a representative sample of georeferenced density estimates.

Variation in the intestinal microbiota at different developmental stages of Hynobius maoershanensis.

Intestinal microbiota play an important role in the life of amphibians and its composition may vary by developmental stage. In this study, 16S rRNA high‐throughput sequencing was used to profile the intestinal microbiota of Hynobius maoershanensis, which exclusively inhabit the Maoer Mountain swamp at an altitude of approximately 2,000 m. We characterized the bacterial composition, structure, and function of the microbiota of H. maoershanensis at different developmental stages. The alpha diversity was not markedly different for the Simpson, Shannon, Ace, and Sobs indices of microbes. The beta diversity revealed that there were age‐related differences in the structure of the intestinal microbes of H. maoershanensis, specifically, at the phylum level. Bacteroidetes and Proteobacteria were the dominant bacteria present in the adult stage, and the relative abundance of Bacteroidetes was significantly higher compared with that of tadpoles. Firmicutes and Proteobacteria were the dominant phylum during the tadpole stage and their relative abundance was significantly higher compared with the adult period. Functional analysis revealed that the pathways associated with organismal systems and metabolism were significantly enriched in the adults, whereas human diseases, genetic information processing, and cellular processes were more enriched in the hindlimb bud stage. Human diseases and environmental information processing were more enriched in the forelimb bud stage at KEGG pathway level 1. Possibilities for the observed discrepancies include the adaptation to eating habits and the remodeling of the intestines during development. We speculated that H. maoershanensis adults may be more suitable to a high‐fiber diet, whereas the tadpoles are associated with a carnivorous diet. Our study provides evidence of variations in the intestinal microbiota during development in amphibians, highlighting the influence of historical developments on the intestinal microbiota and an increased understanding of the importance of physiological characteristics in shaping the intestinal microbiota of amphibians. These data will help us formulate more effective protection measures for H. maoershanensis.

Functional diversity and groups of crustacean zooplankton in the southern Yellow Sea

Functional trait and functional diversity indices reflect the variations of community structure and indicate their responses to environmental stress. In this study, based on four functional traits, including body length, feeding type, trophic group, and reproductive mode, the functional diversity and functional groups of crustacean zooplankton from the southern Yellow Sea (SYS) were explored over four seasons of 2019. A total of 53 species were identified and categorized into six functional groups. Copepods with ambush-feeding and omnivore–carnivore diet (Group Ⅱ) were dominant in spring (55.6%), while omnivore–herbivore copepods (Group Ⅰ) were the most abundant group in the other three seasons (>54.7%). The comparable distributions of functional diversity indices in different seasons were most likely due to hydrological variations. The Changjiang River Diluted Water promoted the coexistence of multiple traits carried by different functional groups (high functional richness (FRic) and functional dispersion (FDis)), but the stability of ecosystem function in this water mass was vulnerable to the loss of individual species (low functional evenness (FEve)) in summer. In winter, as a result of the Yellow Sea Warm Current, warm-water taxa increased FRic and FEve, suggesting that the community could buffer environmental fluctuations more effectively. Moreover, distribution of FRic values indicates the possible range and influence intensity of the Yellow Sea Cold Water Mass.

Phenological observations on protected natural areas associated with brown bear (Ursus arctos L.) ecology

The Chronicles of Nature (Letopis Prirody) kept in the nature reserves of the Russian Federaton aggregate a wide spectrum of systematic field records. Information of particular interest therein is the timing of ripening of berries and their yields across years, since berries are an important food for many wildlife species, including brown bear (Ursus arctos), a core species in boreal European Russia. Such trophic links are most explicit and interesting in the autumn during fattening or hyperphagia period in bears, when the animals depend on berry availability for storing up fat. We aimed to identify the ecological relationships of brown bear applying integrated analysis of field data on the carnivore diet and of records from the Chronicles of Nature of the Kivach Nature Reserves (the middle taiga) and the Pinega Nature Reserve (the northern taiga). We have determined the prevalence (%) of the certain foods in brown bear scats sampled from transects along forest roads and paths. The number and productivity of fruit-bearing rowan trees (Sorbus aucuparia) were determined along permanent transects. Bilberry (Vaccinium myrtillus) and cowberry (Vaccinium vitis-idaea) berries dominate in brown bear diet. Berry ripening dates (19-43 days) and the average yield (scores 1.3 to 5.0) vary greatly over years. Trends in ripening onset dates follow a vector towards earlier dates. In the Pinega NR, the rate of this process is faster in bilberry. The coefficient of rank correlation between the number of fruit-bearing rowans along dirt roads and rowan prevalence in scats was r=1. The same significant correlation was found between the number of fruit-bearing rowan trees and rowan berry yield. The prevalence of different foods in brown bear scats during the hyperphagia period shows the high dietary plasticity of species. A reliable strong correlation was detected in the Pinega NR between the last sighting of brown bear tracks in autumn and the onset of berry ripening in bog bilberry and rowan. The relatively stable food supply for brown bear in the middle and northern taiga of European Russia is one of the factors defining the high numbers and wide distribution of the species. Keywords: Chronicles of Nature, nature reserves, middle and northern taiga subzones, fattening foods, berry fruiting, trophic links, dietary plasticity, Ursus arctos.

Comparative transcriptomics reveal tissue level specialization towards diet in prickleback fishes

Beyond a few obvious examples (e.g., gut length, amylase activity), digestive and metabolic specializations towards diet remain elusive in fishes. Thus, we compared gut length, δ13C and δ15N signatures of the liver, and expressed genes in the intestine and liver of wild-caught individuals of four closely-related, sympatric prickleback species (family Stichaeidae) with different diets: Xiphister mucosus (herbivore), its sister taxon X. atropurpureus (omnivore), Phytichthys chirus (omnivore) and the carnivorous Anoplarchus purpurescens. We also measured the same parameters after feeding them carnivore or omnivore diets in the laboratory for 4 weeks. Growth and isotopic signatures showed assimilation of the laboratory diets, and gut length was significantly longer in X. mucosus in comparison to the other fishes, whether in the wild, or in the lab consuming the different diets. Dozens of genes relating to digestion and metabolism were observed to be under selection in the various species, but P. chirus stood out with some genes in the liver showing strong positive selection, and these genes correlating with differing isotopic incorporation of the laboratory carnivore diet in this species. Although the intestine showed variation in the expression of hundreds of genes in response to the laboratory diets, the liver exhibited species-specific gene expression patterns that changed very little (generally <40 genes changing expression, with P. chirus providing an exception). Overall, our results suggest that the intestine is plastic in function, but the liver may be where specialization manifests since this tissue shows species-specific gene expression patterns that match with natural diet.

Reconstruction of evolutionary changes in fat and toxin consumption reveals associations with gene losses in mammals: A case study for the lipase inhibitor PNLIPRP1 and the xenobiotic receptor NR1I3.

The inactivation of ancestral protein-coding genes (gene loss) can be associated with phenotypic modifications. Within placental mammals, repeated losses of PNLIPRP1 (gene inhibiting fat digestion) occurred preferentially in strictly herbivorous species, whereas repeated NR1I3 losses (gene involved in detoxification) occurred preferentially in strictly carnivorous species. It was hypothesized that lower fat contents of herbivorous diets and lower toxin contents of carnivorous diets cause relaxed selection pressure on these genes, resulting in the accumulation of mutations and ultimately to convergent gene losses. However, because herbivorous and carnivorous diets differ vastly in their composition, a fine-grained analysis is required for hypothesis testing. We generated a trait matrix recording diet and semi-quantitative estimates of fat and toxin consumption for 52 placental species. By including data from 31 fossil taxa, we reconstructed the ancestral diets in major lineages (grundplan reconstruction). We found support that PNLIPRP1 loss is primarily associated with low levels of fat intake and not simply with herbivory/carnivory. In particular, PNLIPRP1 loss also occurred in carnivorous lineages feeding on a fat-poor diet, suggesting that the loss of this gene may be beneficial for occupying ecological niches characterized by fat-poor food resources. Similarly, we demonstrated that carnivorous species are indeed less exposed to diet-related toxins, suggesting that the loss of NR1I3 and related genes (NR1I2 and UGT1A6) resulted from relaxed selection pressure. This study illustrates the need of detailed phenotype studies to obtain a deeper understanding of factors underlying gene losses and to progress in understanding genomic causes of phenotypic variation in mammals.

Metabarcoding of feces and intestinal contents to determine carnivorous diets in red-crowned cranes in eastern Hokkaido, Japan.

The red-crowned crane Grus japonensis in Hokkaido, Japan forms a closed population as a residence that is independent of the mainland population. Based on observations of a limited number of individuals as well as cranes in captivity, red-crowned cranes are omnivores and eat fish, worms, insects and plants in their own territories except in winter, when they are fed with dent corn that is supplied in eastern Hokkaido. DNA metabarcoding based on high throughput sequencing was carried out using universal primer sets for cytochrome oxidase subunit I gene. Feces from 27 chicks collected in June and July in the period from 2016 to 2018 and intestinal contents from 33 adult and subadult cranes that were found dead almost throughout year in 2006–2013 in the field in eastern Hokkaido were used. Although compositions varied considerably in the cranes, both insects and fish were found in adults and subadults to the same extents, while insects were predominant in chicks. Both insects and fish were detected in all seasons for adults and subadults. Horse flies, scarab beetles and weevils accounted for the most of the insects regardless of the life stage. Dace, stickleback, flatfish and sculpin were the major fish species in adults, while chicks ate almost only stickleback. The results provide the first comprehensive data on carnivorous diets in wild red-crowned cranes in eastern Hokkaido as basis for conservation of red-crowned cranes, for which the life style and area continue to change.

Comparative analysis of the digestive system’s anatomical parts in two zoophagous bird species: White Stork (Ciconia ciconia) and Common Buzzard (Buteo buteo)

Aristotle in his anatomical observations is marking the beginning of functional anatomy followed by Georges Cuvier that formulate the low of the correlation of parts. According with this we can expect that the digestive system structures tend to be similar between species that consume approximately the same type of food. In this study we chose to evaluate macroscopic the digestive system of two different zoophytophagous species, with similar body size but different life behavior and feeding strategies: White Stork (Ciconia ciconia) and Common Buzzard (Buteo buteo). Data were collected after the dissection of 10 carcass (5 White Stork and 5 Common Buzzard). The digestive tract and its structures were measured and weighed. In common buzzard the beak is strong and short adapted for the laceration of the prey. In white stork the beak is long, strong, straight adapted to capture prey like a harpoon. In both species, the esophagus is located on the right side of the neck, the length is different, proportional to the neck. In common buzzard the crop is present and absent in white storks. The cuticle or koilin layer is highlighted in white stork compared to common buzzard. In common buzzard, the small intestine is reduced in size, without marked transition between the duodenum and the ileum. The white storks have a long small intestine with many loops, with no transition between the segments. In both species, the cecum is reduced in size and has a vestigial appearance; the colon is reduced in size, and extends from the level of the ileo-colic junction to the cloaca. The digestive system is adapted to a strictly carnivorous diet and the differences identified between the anatomical structures of the digestive tract of the two species are correlated with the differences of their feeding behavior.

Foraging ecology of the amphibious mudskipper Periophthalmus chrysospilos (Gobiiformes: Gobiidae).

The food composition and feeding ecology of fishes living in the intertidal zone play an essential role in understanding the energetic connectivity between terrestrial and aquatic systems. Periophthalmus chrysospilos is an amphibious fish species occurring in the intertidal zone, but data on its diet and foraging ecology is still poorly known. This study on Ps. chrysospilos was carried out from April 2020 to March 2021 at four sites within the Mekong Delta estuary to define the influence of spatio-temporal factors on the diet of this species. The diet composition and relative gut lengths (RGLs) of Ps. chrysospilos were analysed in relation to four parameters—sex, size, site, and season. A total of 1,031 individuals were collected, and their digestive tract lengths were used to calculate the RGL. The digestive tracts of only 546 individuals were with food items (approximately 1:1 of empty vs full digestive tract) and were subsequently used for further analyses. The ranges in total length and weight in both adult and juvenile individuals were 3.4–10.6 cm and 0.38–14.13 g, respectively. The RGL values varied with season, fish size and site, but was always lower than 1, indicating a predominantly carnivorous diet. The variability of food items found within the digestive tracts demonstrated its adaptability in pursuing prey items within the limits of the littoral zone, and its importance as a conduit of terrestrial-marine connectivity. This species is characterised as an opportunistic mesopredator feeding primarily on Acetes spp., Uca spp., Dolichoderus sp., and rarely on Polychaeta and Actinopterygii. Other items found within the digestive tract are Mollusca, and detritus. The diet composition of Ps. chrysospilos did not vary with season and size, but changed with sex and site parameters. Uca spp. contributed to the sexual variation in dietary component, whereas Mollusca, Uca spp., Dolichoderus sp. and detritus, were drivers for spatial variation in the dietary component. The research provides fundamental information on diet composition and feeding strategy, as well as contributes towards knowledge on foraging ecology and resource use by intertidal animal communities.

Feeding Ecology of the Large Carnivore Guild in Madikwe Game Reserve, South Africa

Southern Africa has a diverse large carnivore guild. When this large carnivore guild is confined to fenced protected areas, the degree of intraguild competition may increase. Dietary overlap is a notable point of competition and can have considerable effects on lower trophic levels. We considered the prey preferences, dietary overlap, and dietary niche breadth of the large carnivore guild in Madikwe Game Reserve through direct observations and scat analysis, over one year of sampling. These data were analysed using the Jacobs' index for prey preference, the Pianka's index for dietary overlap and Levin's index for dietary niche breadth. Leopards (Panthera pardus), cheetahs (Acinonyx jubatus) and African wild dogs (Lycaon pictus) had a high degree of dietary overlap and were specialized in their diet selection. Lions (Panthera leo), brown (Parahyaena brunnea) and spotted hyaenas (Crocuta crocuta) also showed a high degree of dietary overlap and had broad diets. Our results show similarities to those of open systems, suggesting that large carnivore diet selection may not be negatively affected when they are confined by fences. We recommend further investigations into the variables which may affect site-specific carnivore diet selection.

Influence of phylogeny on the estimation of diet from dental morphology in the Carnivora

AbstractBecause teeth are the most easily preserved part of the vertebrate skeleton and are particularly morphologically variable in mammals, studies of fossil mammals rely heavily on dental morphology. Dental morphology is used both for systematics and phylogeny as well as for inferences about paleoecology, diet in particular. We analyze the influence of evolutionary history on our ability to reconstruct diet from dental morphology in the mammalian order Carnivora, and we find that much of our understanding of diet in carnivorans is dependent on the phylogenetic constraints on diet in this clade. Substantial error in estimating diet from dental morphology is present regardless of the morphological data used to make the inference, although more extensive morphological datasets are more accurate in predicting diet than more limited character sets. Unfortunately, including phylogeny in making dietary inferences actually decreases the accuracy of these predictions, showing that dietary predictions from morphology are substantially dependent on the evolutionary constraints on carnivore diet and tooth shape. The “evolutionary ratchet” that drives lineages of carnivorans to evolve greater degrees of hypercarnivory through time actually plays a role in allowing dietary inference from tooth shape, but consequently requires caution in interpreting dietary inference from the teeth fossil carnivores. These difficulties are another reminder of the differences in evolutionary tempo and mode between morphology and ecology.

Behavioral Characteristics and Self-Reported Health Status among 2029 Adults Consuming a "Carnivore Diet".

ABSTRACTBackgroundThe “carnivore diet,” based on animal foods and excluding most or all plant foods, has attracted recent popular attention. However, little is known about the health effects and tolerability of this diet, and concerns for nutrient deficiencies and cardiovascular disease risk have been raised.ObjectivesWe obtained descriptive data on the nutritional practices and health status of a large group of carnivore diet consumers.MethodsA social media survey was conducted 30 March–24 June, 2020 among adults self-identifying as consuming a carnivore diet for ≥6 mo. Survey questions interrogated motivation, dietary intake patterns, symptoms suggestive of nutritional deficiencies or other adverse effects, satisfaction, prior and current health conditions, anthropometrics, and laboratory data.ResultsA total of 2029 respondents (median age: 44 y, 67% male) reported consuming a carnivore diet for 14 mo (IQR: 9–20 mo), motivated primarily by health reasons (93%). Red meat consumption was reported as daily or more often by 85%. Under 10% reported consuming vegetables, fruits, or grains more often than monthly, and 37% denied vitamin supplement use. Prevalence of adverse symptoms was low (<1% to 5.5%). Symptoms included gastrointestinal (3.1%–5.5%), muscular (0.3%–4.0%), and dermatologic (0.1%–1.9%). Participants reported high levels of satisfaction and improvements in overall health (95%), well-being (66%–91%), various medical conditions (48%–98%), and median [IQR] BMI (in kg/m2) (from 27.2 [23.5–31.9] to 24.3 [22.1–27.0]). Among a subset reporting current lipids, LDL-cholesterol was markedly elevated (172 mg/dL), whereas HDL-cholesterol (68 mg/dL) and triglycerides (68 mg/dL) were optimal. Participants with diabetes reported benefits including reductions in median [IQR] BMI (4.3 [1.4–7.2]), glycated hemoglobin (0.4% [0%–1.7%]), and diabetes medication use (84%–100%).ConclusionsContrary to common expectations, adults consuming a carnivore diet experienced few adverse effects and instead reported health benefits and high satisfaction. Cardiovascular disease risk factors were variably affected. The generalizability of these findings and the long-term effects of this dietary pattern require further study.

Diet alters how opaleyes cope with heat

When the water gets hot, cold-blooded (ectothermic) animals have three choices: move on somewhere else, wait a few generations for their descendants to come to terms with the new situation, or modify their own physiology quickly to cope in the warm conditions, a process known as acclimation. As option one isn't always viable and option two is more long term, most ectotherms must do their best to get on with life; but those changes usually comes at a price. ‘To undergo a successful acclimation response, ectotherms require energy and nutritional building blocks obtained from their diet’, says Emily Hardison from the University of California, Santa Barbara (UCSB), USA. So how much of an impact does an ectothermic fish's diet have on its ability to weather warm water? Knowing that some ectotherms naturally change their diet as the temperature rises, Hardison and PI Erika Eliason, also at UCSB, wondered whether a switch from a carnivorous diet to a brine shrimp and seaweed diet for omnivorous opaleyes (Girella nigricans) – which supplement their carnivorous diet with algae in warmer water – might affect their ability to cope in hotter conditions.Collecting young opaleyes from the Santa Barbara Harbor, USA, in spring 2019, Hardison provided the animals with a new home in the lab where she kept half of the fish in comfortable 12°C water, while the remaining had a warmer existence at 20°C. Then, she divided the cool fish into two additional groups, one fed a diet of brine shrimp with seaweed and the other fed brine shrimp alone, and repeated the process with the warm water fish. After keeping the four groups of fish in their respective situations for 3 weeks, Hardison and Eliason, with Krista Kraskura, Jacey Van Wert and Tina Nguyen (all from UCSB), then tested the fish's fitness and physiology to find out how well their carnivorous and omnivorous diets had helped them to prepare for life in warm water.Not surprisingly, the hearts of the warm water fish coped better with high temperatures than the hearts of fish from the cooler conditions, but the fish didn't seem to benefit from the more varied diet. The carnivores were just as fit as the omnivores and they were both able to sprint at the same high speeds when chased around the tank. If anything, the hearts of the fish from hot water that had supplemented their diet with seaweed didn't fare as well as the hearts of the fish that only feasted on brine shrimp. In addition, the resting metabolic rate of the algae-supplemented fish was higher, probably because their digestive systems had to work harder to digest the more diverse diet. But, even though the change in diet didn't seem to benefit any of the physiological qualities that Hardison and colleagues had monitored, that doesn't mean that other aspects of the animals’ physiology – such as their gut flora and swimming ability – do not benefit from an alteration in diet as the temperature rises. And, the ability to switch diet as it gets hotter may allow more adaptable animals to survive situations that would be more risky for less versatile diners, if, for example, the food supply suddenly changed thanks to a predator moving in or a particular prey species dying off.One thing is sure, the diet an ectothermic animal consumes definitely impacts their physiology – with specific physical traits reacting to temperature changes in subtly different ways depending on the diet – making diet a key component that physiologists must take into account when investigating how individual ectothermic species react and adapt to our increasingly changing climate.

Diet mediates thermal performance traits: implications for marine ectotherms

Thermal acclimation is a key process enabling ectotherms to cope with temperature change. To undergo a successful acclimation response, ectotherms require energy and nutritional building blocks obtained from their diet. However, diet is often overlooked as a factor that can alter acclimation responses. Using a temperate omnivorous fish, opaleye (Girella nigricans), as a model system, we tested the hypotheses that (1) diet can impact the magnitude of thermal acclimation responses and (2) traits vary in their sensitivity to both temperature acclimation and diet. We fed opaleye a simple omnivorous diet (ad libitum Artemia sp. and Ulva sp.) or a carnivorous diet (ad libitum Artemia sp.) at two ecologically relevant temperatures (12 and 20°C) and measured a suite of whole-animal (growth, sprint speed, metabolism), organ (cardiac thermal tolerance) and cellular-level traits (oxidative stress, glycolytic capacity). When opaleye were offered two diet options compared with one, they had reduced cardiovascular thermal performance and higher standard metabolic rate under conditions representative of the maximal seasonal temperature the population experiences (20°C). Further, sprint speed and absolute aerobic scope were insensitive to diet and temperature, while growth was highly sensitive to temperature but not diet, and standard metabolic rate and maximum heart rate were sensitive to both diet and temperature. Our results reveal that diet influences thermal performance in trait-specific ways, which could create diet trade-offs for generalist ectotherms living in thermally variable environments. Ectotherms that alter their diet may be able to regulate their performance at different environmental temperatures.

Effect of diet on body size and survival of omnivorous crickets

AbstractOmnivory is a feeding habit in which animals prey on organisms from two or more trophic levels. Omnivorous species play important roles in predator–prey interactions, food web dynamics, and ecosystem functions. Although cricket species have been considered omnivores, quantified investigations of their feeding habits have not been carried out. Therefore, we compared the developmental time, body size and mortality rate of the band‐legged ground cricket, Dianemobius nigrofasciatus (Matsumura) (Orthoptera: Trigonidiidae) reared on diets meant for carnivores and herbivores. Furthermore, to examine whether the crickets can balance their nutritional conditions through their food choices, we set up two additional diet treatments, which comprised diets for carnivores and herbivores provided simultaneously or by rotation. The mortality rate of the carnivore diet treatment was higher than that of the other diet treatments. This result suggests that D. nigrofasciatus is a “herbivore” that also obtains nutrients from resources other than plant materials. Although developmental time did not significantly differ among the dietary treatments, the body size of the crickets that were provided both diets simultaneously was significantly larger than that of the crickets provided with only the diets for either carnivores or herbivores. These results suggest that an appropriate amount of carnivorous feeding is advantageous for the development of the cricket, and indicates that crickets can balance nutrition on their own.

Partial Substitution of Meat with Insect (Alphitobius diaperinus) in a Carnivore Diet Changes the Gut Microbiome and Metabolome of Healthy Rats.

Insects are suggested as a sustainable protein source of high nutritional quality, but the effects of insect ingestion on processes in the gastrointestinal tract and gut microbiota (GM) remain to be established. We examined the effects of partial substitution of meat with insect protein (Alphitobius diaperinus) in a four-week dietary intervention in a healthy rat model (n = 30). GM composition was characterized using’ 16S rRNA gene amplicon profiling while the metabolomes of stomach, small intestine, and colon content, feces and blood were investigated by 1H-NMR spectroscopy. Metabolomics analyses revealed a larger escape of protein residues into the colon and a different microbial metabolization pattern of aromatic amino acids when partly substituting pork with insect. Both for rats fed a pork diet and rats fed a diet with partial replacement of pork with insect, the GM was dominated by Lactobacillus, Clostridium cluster XI and Akkermansia. However, Bray-Curtis dissimilarity metrics were different when insects were included in the diet. Introduction of insects in a common Western omnivore diet alters the gut microbiome diversity with consequences for endogenous metabolism. This finding highlights the importance of assessing gastrointestinal tract effects when evaluating new protein sources as meat replacements.

Evolutionary loss of inflammasomes in the Carnivora and implications for the carriage of zoonotic infections.

SummaryZoonotic pathogens, such as COVID-19, reside in animal hosts before jumping species to infect humans. The Carnivora, like mink, carry many zoonoses, yet how diversity in host immune genes across species affect pathogen carriage is poorly understood. Here, we describe a progressive evolutionary downregulation of pathogen-sensing inflammasome pathways in Carnivora. This includes the loss of nucleotide-oligomerization domain leucine-rich repeat receptors (NLRs), acquisition of a unique caspase-1/-4 effector fusion protein that processes gasdermin D pore formation without inducing rapid lytic cell death, and the formation of a caspase-8 containing inflammasome that inefficiently processes interleukin-1β. Inflammasomes regulate gut immunity, but the carnivorous diet has antimicrobial properties that could compensate for the loss of these immune pathways. We speculate that the consequences of systemic inflammasome downregulation, however, can impair host sensing of specific pathogens such that they can reside undetected in the Carnivora.

Conservation Detection Dogs Increase Efficacy for Prey Detection at Carnivore GPS Cluster Sites During Summer

ABSTRACTCombining carnivore movements with site visits to investigate predation events can inform investigators of carnivore diets, kill rates, and risk factors for prey. However, detecting remains of prey can be challenging when prey is small or when vegetation conceals prey. Conservation detection dogs (CDDs) have assisted with wildlife surveys to locate objects of conservation interest, often improving detection over human counterparts. We hypothesized that CDDs would improve efficacy for detection of prey remains at kill locations compared to human searchers. We compared the efficacy of CDD teams (1 dog, 1 human handler) and technician teams (2 humans) for locating prey remains at 729 carnivore cluster (potential predation) sites in the Upper Peninsula of Michigan, USA, during May to August of 2015. Carnivore species included gray wolves (Canis lupus), coyotes (C. latrans), bobcats (Lynx rufus), and American black bears (Ursus americanus). Overall, CDD teams identified prey remains at 2.3 times more clusters, required 42% less search time, and handlers traveled 83% less distance per detected prey remain compared to technician teams. Within carnivore species, CDD teams detected small prey remains at a greater rate than technician teams (4.0–4.3 times greater) for all carnivores except for bobcat which had similar detection rate. Detection of large prey remains (e.g., adult ungulates) was similar between CDD teams and technician teams. Our study supports CDDs ability to outperform humans when searching for objects of conservation interest which are visually cryptic but traceable by scent. Where logistics allow, we recommend use of CDDs over human searchers when it is a priority to locate remains of small prey and when vegetation is dense and may obscure even larger prey items. © 2021 The Wildlife Society.