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Comparison of different age groups of dogs in an internet survey (Study 2) with regard to: (A) percent exhibiting daily or weekly plant consumption; (B) percent observed to consume primarily grass; (C) percent regularly showing signs of illness before eating plants and (D) percent vomiting after eating plants. 

Comparison of different age groups of dogs in an internet survey (Study 2) with regard to: (A) percent exhibiting daily or weekly plant consumption; (B) percent observed to consume primarily grass; (C) percent regularly showing signs of illness before eating plants and (D) percent vomiting after eating plants. 

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Grass or plant eating is a widely recognized behaviour amongst domestic dogs. We first estimated the prevalence of plant eating by administering a written survey to owners of healthy dogs visiting the outpatient service of a veterinary medical teaching hospital for routine health maintenance procedures. Of 47 owners systematically surveyed whose do...

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... only significant predictor of frequency of plant eating was age of the dog. In the follow-up multiple comparisons, frequency of plant eating was significantly inversely related to age group (P < 0.001; Fig. 2A). In the initial analysis, sex/gonadal status, breed group and diet were not related to frequency of plant eating (P = 0.194, 0.130 and 0.067, respectively). Table 3 Study 2, percentage of owners reporting: the length of time spent with their dog per day; the total number of times they observed their dog eating plants; the frequency of ...
Context 2
... the frequency of plant eating by their dog; their dog's age; their duration of ownership; where their dog had access to plants (N = 1571 A significant predictor with regard to type of plant eaten (grass versus non-grass) was age. In multiple comparisons there was a significant increasing tendency for older dogs to primarily eat grass (P = 0.003; Fig. 2B). Interestingly, gonadally intact dogs were more likely to eat grass than neutered dogs, even after controlling for age (P = 0.005). However, among both intact and neutered females there was an increased tendency to eat non-grass plants in the oldest age group (P = 0.024). Breed group and diet were not significant in the initial ...
Context 3
... frequently showing signs of illness before eating plants was seen in only 8% of dogs overall, the initial analysis revealed an effect of age, with an increasing tendency to show illness with increasing age (P < 0.001; Fig. 2C). No effect of diet, sex/gonadal status or breed group was apparent (P = 0.796, 0.527 and 0.114, ...
Context 4
... vomiting frequently after eating plants was seen in only 22% of dogs, the initial screening analysis revealed that age, breed group and diet were significant predictors of vomiting. The multiple comparisons revealed that the older the dog the more likely it was to regularly vomit (P < 0.001; Fig. 2D). Dogs in the hound and toy breed groups were more likely to regularly vomit than dogs in the other breed groups (P = 0.0031). Additionally, dogs fed a complete, balanced diet were more likely to regularly vomit than those fed a home-made diet (P < 0.001). Sex/gonadal status was not a significant predictor (P = 0.13). This analysis ...

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... The distribution of dog fecal δ 15 N values is consistent with meals at multiple trophic levels ( Figure 4b). The widespread plant remains in dog feces may be somewhat unexpected, yet this is consistent with modern observations of dog diet (Sueda et al., 2008) and genetic evidence that domestic dogs have experienced selection for starch digestion (Axelsson et al., 2013). Animal remains present in feces F I G U R E 5 Stable isotope data from dogs and other introduced taxa (warm colors) and endemic taxa that are potential prey or competitors (cool colors). ...
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Identifying where introduced animals fit in a food web relative to each other and to endemic species is key for biodiversity conservation planning. Using a multiproxy study of dog feces from eastern Madagascar, we infer that even dogs that spend time in derived grasslands typically eat forest‐derived foods. Regardless of the time that dogs spend in cleared forest, their impacts are likely concentrated on forest‐dwelling prey. If dogs in forests mostly consume threatened endemic animals (and not other introduced animals such as rats), then the exclusion of dogs from protected forests should be a priority. Introduced predators on islands can help control invasive species yet can also contribute to the extirpation and extinction of endemic taxa. The spread of dogs on Madagascar by ~1000 years ago coincided with the introduction of livestock and spread of grazer‐adapted grasslands, and we help evaluate the extent to which modern dogs are part of novel grassland food webs. To infer dog diet, we identified food remains, where possible, and conducted stable isotope ratio analysis for n = 100 modern dog feces collected in derived grassland at varying distances from protected forest edges around Analamazoatra and Andasibe‐Mantadia National Park in eastern Madagascar. Animal remains in feces and the observed range of fecal δ15N values are consistent with dog meals at multiple trophic levels. However, the observed distribution of fecal δ13C values suggest that few dogs in the study area consumed food derived from open C4 grasslands. Existing data suggest that dogs rely primarily on C3 consumers inhabiting forest biomes (forest‐dwelling animals) for their prey, which may include endemics such as tenrecs, Malagasy rodents, and lemurs and introduced rodents such as rats. These findings indicate that dogs are not confined to the anthropogenic niche defined by grazer‐adapted grasslands, but rather use and impact animal food resources associated with protected forests. Higher resolution study of dog diet and mobility can further clarify the potential for dogs to exploit endemic prey, compete with endemic predators, and spread disease across ecotones. L'identification de la place des animaux introduits dans la chaine alimentaire les uns par rapport aux autres et aux espèces endémiques est essentielle pour la planification de la conservation de la biodiversité. En utilisant une étude multiproxy sur les excréments de chiens de l'est de Madagascar, nous en déduisons que même les chiens qui passent du temps dans les prairies dérivées mangent généralement des aliments dérivés de la forêt. Quel que soit le temps que les chiens passent dans la forêt défrichée, leurs impacts sont probablement concentrés sur les proies vivant dans la forêt. Si la majeure partie de l'alimentation des chiens dans les forêts provient d'animaux endémiques menacés (et non d'autres animaux introduits tels que les rats), l'exclusion des chiens des forêts protégées devrait être une priorité. Ny fahalalana manokana mahakasika ny anjara toerana sy fifampiakinany ireo biby samy tsy zanatany sy ireo zanatany eo amin'ny famatsiana sakafo dia tena zava‐dehibe tokoa eo amin'ny fahafahana miaro sy mametraka drafitra ho fiarovana azy ireo sy ny tontolo manodidina azy. Ny fampiasana ny atotam‐pahalalana sy hevitra mahakasika tain'alika any amin'ny ilany atsinanan'i nosy Madagasika, dia ahafahana milaza fa na dia ny alika izay monina eny aminy toerana tsy misy ala aza dia mihinana sakafo vokatra mivatana na akolana avy aminy ala. Na dia eo azy ny fotoana lanin'ny alika (mikarenjy) eny amin'ny toerana tsy misy ala. Ny trindry dia vinavinaina fa mianjerana amin'ny ireo biby fihaza miankina sy miaina ao anaty ala Raha mifototra aminy biby zanatany izay efa ho lany tamingana monina ao anaty ala mantsy ny ankamaroan'ny sakafon'alika, fa tsy amin'ireo biby tsy zanatany natsofoka teo aminy nosy toy ny voalavo, noho izany dia tena laharam‐pahamehana ary tsy azo iodivirana ny fanalana tanteraka ny alika aminy ireny ala voaharo ireny. Identifying where introduced animals fit in a food web relative to each other and to endemic species is key for biodiversity conservation planning. Using a multiproxy study of dog feces from eastern Madagascar, we infer that even dogs that spend time in derived grasslands typically eat forest‐derived foods. Regardless of the time that dogs spend in cleared forest, their impacts are likely concentrated on forest‐dwelling prey. If dogs in forests mostly consume threatened endemic animals (and not other introduced animals such as rats), then the exclusion of dogs from protected forests should be a priority.
... Yet, researchers' interpretations of the presence of plant tissues in scat samples or stomach contents are varied, possibly owing to the difficulties associated with observing this plant-eating behavior and because the amount of plant content present in these samples is often small. Some researchers believe that the presence of plant content is caused by unintentional intake (Avenant & Nel, 2002;De Villa Meza et al., 2002;Krofel et al., 2011), while others argue that there might be some advantages of plant eating (Hoppe-Dominik, 1988;Sueda et al., 2008;Tatara & Doi, 1994;Xiong et al., 2016). Indeed, observational studies indicate that felids eat plants voluntarily (Montalvo et al., 2020;Yoshimura et al., 2020) both in the captivity and in the wild, which indicates that this behavior is relatively common and natural among felids. ...
... Many animals are known to use plants to counter parasites or diseases (Hart & Hart, 2018;Huffman, 2003;Huffman & Canon, 2000). Sueda et al. (2008) reported in a questionnaire survey of owners of dogs under one year of age that these dogs ate plants more frequently, and the authors suggested that plant consumption may be a way for individuals with low immunity to fight parasites and pathogens. ...
... However, fruit was detected more frequently in domesticated cats than in feral cats living on a Croatian island (Lanszki et al., 2016), suggesting that the detection of fruit content might be associated with proximity to human activity [e.g., food provisioning or scavenging garbage (Yamane et al., 1994)]. Additionally, there were several studies showing the presence of nonfruit-bearing plants, which may have other benefits, such as parasite control (Hart, 2008;Hart & Hart, 2018;Sueda et al., 2008). ...
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Plant‐eating behavior is one of the greatest mysteries in obligate carnivores. Despite unsuitable morphological and physiological traits for plant consumption, the presence of plants in scat or stomach contents has been reported in various carnivorous species. However, researchers’ interpretations of this subject are varied, and knowledge about it is scarce, without any multispecies studies. This study assessed the extent of variation in the frequency of plant occurrence in scat and stomach contents, as well as its relationship with various factors in 24 felid species using data from 213 published articles. Since the frequency of plant occurrence has not always been reported, we created two‐part models and estimated parameters in a Bayesian framework. We found a significant negative relationship between the frequency of plant occurrence and body mass. This may be because plant‐eating behavior reduces the energy loss caused by parasites and increases the efficiency of energy intake, which has a greater importance in smaller animals that have relatively high metabolic rates. This exploratory study highlights the importance of considering plant consumption in dietary studies on carnivorous species to understand the adaptive significance of this behavior and the relationship between obligate carnivores and plants. Plant‐eating behavior is one of the greatest mysteries in obligate carnivores. This study assessed the extent of variation in the frequency of plant occurrence in scat and stomach contents, as well as its relationship with various factors in 24 extant felid species using data from 213 published articles. We found a significant negative relationship between the frequency of plant occurrence and body mass.
... In current times, many caregivers frequently see their domestic cats and dogs eating grass and other non-digestible plants and may wonder about the reason for this behavior. The behavior has been studied in dogs, where it was found that 68 percent ate plants on a daily or weekly basis [3]. Nine percent were reported to appear ill frequently before eating plants and 22 percent to vomit frequently afterwards. ...
... The questions were developed and edited by the authors (BLH, APT) after giving preliminary copies to clients of the veterinary hospital. Similar web-based surveys have been used in a variety of data-based behavioral and medical investigations, such as for evaluation of asthma treatments [5], practice patterns in treatment of urinary incontinence [6], and plant eating in dogs [3]. Studies have shown that the quality of the data from web-based surveys is comparable to traditional survey methods [7]. ...
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Plant eating by domestic cats is of interest to veterinarians and cat owners, especially with the current trend to keep cats totally indoors. Feline grass gardens are commonly provided to such cats as a reflection of cat owners believing in the need or desire of cats for eating plants. Two surveys with 1000 to 2000 returns from cat owners were launched over 10 years to test different hypotheses regarding plant eating. These hypotheses are that plant eating: (1) is a response to the cat feeling ill; (2) induces vomiting; (3) is a means of expelling hair balls from consumed hair. Additionally, a perspective acquired from observations of wild felids is that plant eating reflects an innate predisposition acquired from the ancestral cat. In this study, very few cats showed signs of illness before eating plants. However, 27 to 37 percent of cats, respectively in the two surveys, frequently vomited after eating plants, indicating that gastrointestinal disturbance may be related to vomiting in some cats. Young cats consumed plants more frequently than older cats and appeared ill and vomited less frequently in association with plant eating. Short-haired cats ate plants as frequently as long-haired cats, arguing against the hairball expelling hypothesis. Some guidelines for cat owners with indoor cats are provided.
... Plant eating, especially grass eating, is commonly appeared in all domestic cats and dogs, and to vomit when they feel ill themselves (to recover the gastric problems or gastrointestinal parasites) or because of dietary deficiencies or as general behavior, they eat plants. In this condition, it is appeared in not only dogs kept in house and in but also wolves and other wild dog species (Sueda et al., 2008). Tendencies of cats to eat plants are less than those of dogs (Sueda et al., 2008). ...
... In this condition, it is appeared in not only dogs kept in house and in but also wolves and other wild dog species (Sueda et al., 2008). Tendencies of cats to eat plants are less than those of dogs (Sueda et al., 2008). In a study made by Sueda et al. (2008), it has been reported that 79% of well-kept healthy dogs eat grass, eating plant in domestic dogs is a behaviour commonly seen, and also that dogs are appeared normal before eating plant and 87% of dogs do not vomit after eating plant. ...
... Tendencies of cats to eat plants are less than those of dogs (Sueda et al., 2008). In a study made by Sueda et al. (2008), it has been reported that 79% of well-kept healthy dogs eat grass, eating plant in domestic dogs is a behaviour commonly seen, and also that dogs are appeared normal before eating plant and 87% of dogs do not vomit after eating plant. ...
... The frequency was not consistent with that of plant-eating, thus we conclude that snow leopards did not eat plants to promote vomit hairballs through stimulation of the throat or stomach. According to an internet survey targeting the owners of plant-eating dogs, only 22% of the dogs frequently vomit after eating plant materials, thus they concluded that plant-eating is not related to vomiting [39]. In this study, hairs were evacuated in scats, regardless of the presence or absence of plants in the enclosures. ...
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Although most felids have an exclusive carnivore diet, the presence of plant matter in scat has been reported among various species. This indicates that there may be an adaptive significance to the conservation of plant-eating behavior in felid evolution. Some studies have hypothesized that felids consume plants for self-medication or as a source of nutrition. In addition, it is thought that plant intake helps them to excrete hairballs, however, no scientific work has confirmed these effects. Thus, the objective of this study is to investigate the relationship between plant intake and hair evacuation in felid species. We selected snow leopards (Panthera uncia) as the study species because they have longer and denser hair than other felids. The behavior of 11 captive snow leopards was observed and scat samples from eight of them and two other captive individuals were analyzed. Snow leopards evacuate hair possibly by vomiting and excreting in scats. The frequency of plant-eating and vomiting and the amount of hair and plant in scat were evaluated. We found that the frequency of vomiting was much lower than the frequency of plant-eating. In addition, there was no significant relationship between the amount of plant matter contained in scats and the amount of hair in scats. Contrary to the common assumption, our results indicate that plant intake has little effect on hair evacuation in felid species.
... Fenn (1790) wrote that dogs eat grass to vomit, but for cats Fenn stated only that they eat grass as medicine. Recent studies show that when domestic cats or dogs consume grasses or other vegetation, they usually do not vomit nor appear to the owners to be nauseous (Sueda et al. 2007;Hart 2008;Bjone et al. 2009;McKenzie et al. 2010;Hart et al. 2019). Dudley (1892: 87) also noticed that dogs frequently ate grass without vomiting, but rather suggested that grass ingestion prevented vomiting. ...
... Detailed quantitative data collected in controlled conditions found that vomiting is quite rare following grass ingestion in domestic dogs (Bjone et al. 2007(Bjone et al. , 2009, while more subjective reports from surveys to pet owners give a sense that vomiting is more frequent (Sueda et al. 2007;Hart & Hart 2013;Hart et al. 2019). From direct observations of 2,108 total feeding events on grass by 36 dogs (Canis familiaris), only 11 times (0.5%) did a vomiting event follow (Bjone et al. 2007(Bjone et al. , 2009. ...
... From direct observations of 2,108 total feeding events on grass by 36 dogs (Canis familiaris), only 11 times (0.5%) did a vomiting event follow (Bjone et al. 2007(Bjone et al. , 2009. From surveys, pet owners reported that vomiting after grass consumption was relatively common in about 20-30% of domestic cats (Hart & Hart 2013;Hart et al. 2019) or dogs (Sueda et al. 2007). Possibly a greater amount of variables influences the rates reported in these surveys such as the belief that grass ingestion causes vomiting, a wider variety of breeds, confounding health issues, a wider variety of grass species encountered some of which may be more toxic, and the possibility of toxins like pesticides on grasses causing adverse reactions. ...
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Within the Carnivora order, the consumption of fibrous plant tissues (FPT), such as leaves and stems, is only known to serve the nutritional needs of eight species in the Ailuridae and Ursidae. Apart from the Ailuridae and Ursidae, the extent of FPT ingestion in the Carnivora is poorly understood. A literature search was conducted to compile studies containing evidence of FPT consumption in the Carnivora, primarily based on analyses of scats or gastrointestinal tracts. Among 352 studies, there was evidence of FPT consumption in any amount in 124 species, or 41%, of the Carnivora. Grass consumption was documented in 95 species, while ingestion of sedges, marine plants, bryophytes, conifers, and dicots was much less frequent. A few species showed evidence of consuming fungi or soil. Nine studies observed co-occurrences of intestinal parasites with grasses or sedges in the scats of the Carnivora, suggesting these abrasive or hairy plant tissues help to expel intestinal parasites. The relevance of consuming marine plants, bryophytes, conifers, dicots, fungi, or soil has also been underappreciated. Deliberate ingestion of FPT may be more widespread and important than previously realized in the Carnivora.
... As undigested material, grass volume is overrepresented relative to the remains of other items consumed. Grass consumption by wild and domestic canids is commonly documented and is considered to be a normal behavior of healthy individuals (Bjone et al., 2007); however, the reason for grass consumption remains unknown (Sueda et al., 2008;McKenzie et al., 2010). ...
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Wildlife managers needed to understand coyote (Canis latrans) ecology in order to develop management plans on the nascent Valles Caldera National Preserve in northern New Mexico. Managers concerned about low elk (Cervus elaphus) recruitment had observed an increase in sightings of coyotes and observations of coyote predation on elk calves. Our objective was to identify and quantify coyote diet, and assess the temporal variation in coyote diet on the Valles Caldera National Preserve, particularly as related to elk calf consumption. We examined coyote food habits using 1,385 scats analyzed monthly from May 2005 to November 2008. The most frequent taxa were rodents (predominantly voles from the genus Microtus, and northern pocket gophers, Thomomys talpoides), elk, insects from the orders Orthoptera (grasshoppers and crickets) and Coleoptera (beetles), mountain cottontail rabbit (Sylvilagus nuttallii), and plant material (mainly grass). We detected rodent and elk in scats during all months of the study and were each present in 54% of scats overall. We identified elk remains in 43% of spring scats, 72% of winter scats, and 56% of fall scats. During summers, we could distinguish calf from adult elk hair: 8% of summer the scats contained adult elk hair and 39% contained calf elk hair. The frequency of prey items varied significantly over most seasons and years, with notable exceptions being that elk did not vary among summers and winters, and rabbits were a consistent diet item through all seasons. The high frequency of elk in the coyote diet bears further study on the density of elk calves, the vulnerability of elk to predation, the nutritional impacts from the quality of forage available to elk, and the role of hunting and other mammalian predators in providing carcasses.
... Interestingly, many reads from the Virgaviridae family were detected in the tick viromes from dogs and are thought to result from the dogs' grassand plant-eating behaviors. Sueda et al. described that 68% of dogs eat vegetation on a daily or weekly basis[36]. To determine ...
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In this study, we explored the viral diversity and community structures of the ticks collected from dogs and detected possible tick-borne viruses (TBVs) using metagenomic analysis. Additionally, full-length sequences and the structural, phylogenetic and molecular features of the possible TBVs were characterized using bioinformatics tools. The sequence run produced 12,254,268 reads and 6,667,259 unique reads from the tick pools. Further analysis of the viral reads revealed that 92.73% were similar to ssRNA viruses, and 90.5% of the total viral sequences belonged to Non-classified viral families. Of the 29 classified viral families, most virome sequences were homologous with vertebrate viruses from Circoviridae, plant viruses from Virgaviridae, phages from Microviridae, insect viruses from Baculoviridae, and giant viruses from Mimiviridae. In the process of assembly of reads, large contigs representing four virus families were identified, including Phenuiviridae, Chuviridae, Parvoviridae and Non-classified families. Some sequences of Non-classified family shared a highly divergent amino acid sequence identities from existing virus sequences. The importance of these newly identified virus contigs to public and veterinary health needs additional researches. Because of the lack of the acquired viral reads from these families, we only demonstrated the complete sequences of Circoviridae in detail. The complete canine circovirus (CaCV)-NC21 genome detected from police dogs was 2063 bp long with a GC content of 53.6%. Our results suggested that tick viromes collected from dogs contained diverse sequences with a broad range of animal, insect, plant, and phage viruses, which may reflect the ecological characteristics of the dogs and their ticks. Furthermore, our study revealed the existence of the partial contigs belonging to the four virus families in ticks. More researches are needed to verify their importance to public and veterinary health. As well, our detection of CaCv-NC21 demonstrated that ticks can harbor and potentially transmit canine circoviruses.
... Aristotle then continues explaining that "these carnivorous animals never eat grass except when they are sick, just as dogs bring on a vomit by eating grass and thereby purge themselves". Many studies suggest that it is a way to fight stomach distress, but other reasons include improving digestion, treating intestinal worms or fulfilling some unmet nutritional need, for example, the need for fiber [17,18] . In regard to the hibernation of bears (Ursus sp.), he observed that: ...
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The term zoopharmacognosy was first introduced in 1987 as a multidisciplinary study of the self-medication behavior of many kinds of animals. Humans and non-human animals have been observing and interacting with each other since prehistoric times and learning about nature together. Humans have probably been aware for a long time that animals used specific substances in certain ways when they were sick and that this sometimes helped them to heal. Thanks to zoopharmacognosy, we are beginning to learn more concrete aspects of this relatively new branch of science that deals with how animals treat disease with organic or inorganic substances that they find in their environment. In some cases, they even seem to use plants or other natural items as drugs in a very similar way to ourselves in order to treat the very same symptoms that we do. Although zoopharmacognosy is a young science, in this study we searched for and analyzed the relevant early data and precedents in published papers and from historical sources that endorse the remarkable antiquity of the attention and concern of humankind for it.
... In veterinary clinical practice, the traditional explanation for plant-eating in dogs and cats is that there is a dietary deficiency or that plant-eating is a way of inducing vomiting. In two broad-ranging Web-based surveys of thousands of dog and cat owners, it was found that the great majority of dogs and cats appeared normal before and after eating plants and did not vomit [72,73] (figure 4). An important finding was that animals under 1 year of age ate plants much more frequently than older ones, the explanation being that the young are more vulnerable to the cost of intestinal parasites, and hence have an evolved tendency to eat plants more frequently. ...
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Mammals live and thrive in environments presenting ongoing threats from parasites in the form of biting flies, ticks and intestinal worms and from pathogens as wound contaminants and agents of infectious disease. Several strategies have evolved that enable animals to deal with parasites and pathogens, including eliminating away from the sleeping–resting areas, use of an array of grooming techniques, use of saliva in licking, and consuming medicinal plant-based compounds. These strategies all are species-specific and reflect the particular environment that the animal inhabits. This article is part of the Theo Murphy meeting issue ‘Evolution of pathogen and parasite avoidance behaviours’.