Poisonous Species Research Articles

LC-MS/MS Profiling of the Poisonous Wild Mushroom, Entoloma mastoideum, (Entolomataceae, Basidiomycota) in Sabah (Northern Borneo), Malaysia

In Malaysia, mushroom poisoning poses a significant public health concern, particularly as local communities frequently consume wild mushrooms without fully recognizing the potential dangers they present. Ingestion of wild mushrooms, which resemble edible species but contain deadly chemicals, is the main cause of poisoning risk. The genus Entoloma (Fr.) P. Kumm is dispersed worldwide, with over 1,500 species recorded. Entoloma mastoideum, a poisonous mushroom, was recorded for the first time at Kota Marudu district, Sabah, Malaysia, where ten cases of mushroom poisoning outbreaks were recorded during the rainy season of October 2019. The morphological characters of the specimens were documented and their microscopic features were analyzed using compound microscope and scanning electron microscope. A phylogenetic tree was constructed using Maximum likelihood and Bayesian analysis. Chemical profiling of the poisonous mushroom specimen was done via liquid chromatograph mass spectrometry (LC-MS/MS) to identify toxic metabolites. The phylogenetic analysis showed that the Bornean E. mastoideum is closely related to the Chinese isolates (100% BS/1.0 PP). LC-MS/MS profiling detected a total of 162 metabolites that were classified into ten general groups, where several toxic compounds were detected amongst the aromatics, essential amino acids, and fatty acid derivatives. The toxic compounds identified in the mushroom extract, including amino acid derivatives such as 3,4,5,6-tetrahydroxyynorleucine, valpromide, and betaine, have been reported to cause neurotoxicity, cardiotoxicity, liver damage, and gastrointestinal harm. The presence of these toxic compounds underscores the need for caution when consuming wild mushrooms. Further research on poisonous Entoloma species is vital for developing accurate identification methods and understanding their toxic potential. This knowledge is essential for enhancing public awareness, preventing mushroom poisoning incidents and safeguarding public health.

Morphological characters and molecular data reveal ten new forest macrofungi species from Hebei Province, North China

ABSTRACT China has a complex and diverse forest ecological environment, which breeds abundant forest macrofungi, including some edible, medicinal, and poisonous species. During the investigations of macrofungi in the Saihanba National Nature Reserve, North China, we collected abundant specimens of Agaricales and Polyporales within the Agaricomycetes. Based on the morphological characters and molecular evidence of DNA sequences including the internal transcribed spacer (ITS) regions, the large subunit of nuclear ribosomal RNA gene (nLSU), the small subunit of mitochondrial rRNA gene (mtSSU), the small subunit of nuclear ribosomal RNA gene (nuSSU), the largest subunit of RNA polymerase II (RPB1), the second largest subunit of RNA polymerase II gene (RPB2), the β-tubulin gene (TUB), and the translation elongation factor 1-α gene (TEF1), this study identifies ten species of Agaricales and Polyporales new to science, viz. Cyanosporus subpopuli, Gelatinofungus betulina, Lycoperdon pseudoperlatum, Macrocystidia hebeiensis, Mycena subbrunnea, M. subpura, M. variispora, M. violocea-ardesiaca, Picipes griseus, and Pleuroflammula hebeiensis. Detailed morphological descriptions, fruiting bodies, and microscopic structure diagrams of these ten novel species are provided.

Trade-off and chaotic dynamics in a two-prey one-predator model with refuge, environmental noise and seasonal effects

In nature, poisonous prey species have developed toxins as an attack against predators. However, predator’s decisions to consume aposematic toxic prey are not solely determined by their toxicity. Predators often weigh the costs of ingesting toxins against the benefits of obtaining nutrients, with body size acting as a significant cue. In terms of avoiding predation, prey commonly respond by seeking refuge, a behavior that fluctuates considerably due to seasonality and environmental variability. In this study, we integrate these factors into the dynamics of two prey and one predator model. We explore the cost of fear to illustrate the trade-off dynamics of prey, and we adjust the predator’s death rate by integrating a function that serves predator loss resulting from encounters with toxic prey. Our model demonstrates bistability as a consequence of hysteresis effect and undergoes various bifurcations, including saddle–node, Hopf, Bautin, and cusp bifurcations. We observe that increasing prey refuge and reducing the level of fear contribute to system stabilization, yet chaotic behavior persists with respect to both parameters. While seasonality can introduce stability and periodicity, it may also give rise to complex and unpredictable dynamics. We comprehend that the system might undergo transitions through multiple periodic cycles as a result of changes in the degree of seasonality, yet it eventually settles into a periodic solution. Furthermore, our analysis using the stochastic model reveals that low noise levels maintain species densities close to deterministic equilibrium, whereas high noise levels result in broader dispersion or even extinction of species. The information presented in this article may help readers understand the biological knowledge gained by investigating interactions between predators and prey.

Computational analysis of hydrogen bonds network dynamics in the water layers surrounding Aβ(1-42) and Aβ(1-40) peptide dimers

The amyloid-β peptide (Aβ) dimer is involved in the development of Alzheimer’s disease through forming amyloid plaques. Aβ(1-40) and Aβ(1-42) are the most common and poisonous species causing Alzheimer’s disease. They form homogeneous dimers containing two similar peptides and heterogeneous dimers containing different ones. The low molecular weight, fast dynamics, and varying compositions of these dimers make it difficult to study them by conventional experimental methods. Hence, we clarify the effect of the diversity of the Aβ dimers on the structure of the water molecules around the peptides by the molecular dynamics (MD) simulation method in this study. MD simulations of the Aβ(1-40) and Aβ(1-42) monomers are also performed for the comparison. The calculations are repeated in the presence of dimethyl sulfoxide (DMSO). The water molecules positioned at distances of 0.5, 0.75, 1, 1.25, and 1.5 nm from the protein were chosen to investigate the distribution and dynamics of hydrogen bonds in the layers surrounding the peptide. The results show that the heterogeneity of the dimer system increases the percentage of hydrogen (H) atoms not involved in any water-water hydrogen bonds around the peptides in the different layers. While it decreases the percentage of H atoms involved in one and two water-water hydrogen bonds. The DMSO presence reduces the percentage of H atoms involved in two hydrogen bonds in the systems containing a mixture of water and DMSO. The average interaction energy of the dimers demonstrates the enhanced interactions of the two peptides in water in comparison with that in the mixture of water and DMSO. The behavior of the water molecules around the heterogeneous dimer is very similar to that around the Aβ(1-42) homogeneous dimer.

Lepiota castanea mushroom growing in Turkiye does not contain phallotoxins and amatoxins

The number of poisoning cases caused by the Lepiota genus is globally increasing. This genus has more poisonous species than the Amanita genus, and many Lepiota species can cause severe toxicity and death if ingested. As recognized in the literature, L. castanea is a toxic species containing amatoxin. Although crude analytical methods have shown that L. castanea contains amatoxins, more recent and sensitive analyses suggest otherwise. Toxin concentrations can vary even among the same fungal species due to geographical and climatic differences. Therefore, this confusion can be resolved by analyzing L. castanea toxins from different geographical regions. This study aimed to demonstrate the toxin levels of L. castanea collected from forests in different regions of Turkiye (Istanbul and Kocaeli) using sensitive methods. The collected mushrooms were analyzed for alpha amanitin, beta amanitin, gamma amanitin, amanin, phallacidin, and phalloidin levels using RP-HPLC-UV and LC-ESI-MS/MS methods. L. castanea mushroom was found to be free of amatoxin and phallotoxin. Our study revealed for the first time that L. castanea mushrooms from different geographical regions of Turkiye do not contain amatoxin and phallotoxin. Supporting these findings with new studies from different parts of the world would be appropriate.

Main Poisonous and Allergenic Plant Species in Sicilian Gardens and Parks: Applications and Recommendations for Use.

This study identified the most common poisonous and allergenic plants occurring in Sicilian gardens and parks. Based on a survey conducted at 100 sites, a list was drawn up that reports the main biological and toxicological characteristics and ornamental uses of these plants. A total of 137 taxa were recorded, of which 108 were poisonous and 32 were allergenic. The most represented families were the Solanaceae, Moraceae, Apocynaceae and Fabaceae. The most represented geographical contingents were the European and the Mediterranean. A large number of toxic and allergenic plants recorded in Sicilian parks and gardens cause gastrointestinal disorders, 21 of which are deadly poisonous. Based on the results, actions for the management of existing gardens and the construction of new ones are discussed. The importance of environmental education for the population starting from school age is stressed. These recommendations aim to preserve cultivated biodiversity and, at the same time, protect human and pet health.

Ecological and agricultural assessment of the state of forage lands of boreal river floodplains in the oil-producing region (case study in the floodplain of the Kolva River, Usinsky district, Komi Republic)

Floodplain forage lands of the Pechora basin (Usinsky district of the Komi Republic) are experiencing a complex anthropogenic impact associated with both agricultural activity and pollution with petroleum products coming with flood waters. An ecological and agricultural assessment of the soil-vegetation cover of the Kolva floodplain used as hayfield (right-bank part) and pasture (left-bank part) was carried out. Soil combinations of the main part of the surveyed floodplain include alluvial sod, sod-meadow and meadow soils. Morphological signs of gley formation in meadow soils are observed in the lower part of the soil profile and are expressed moderately. Soils are characterized generally by favorable agrochemical and morphological properties, with the exception of areas subjected to pasture digression. The vegetation cover of the central and near-river part of the floodplain massif of the right bank is mainly represented by legume-cereal-grass communities formed both in inter-ridge depressions and on flat ridges. On the high floodplain of the left bank, legume-cereal-grass meadows, grass-clover and tufted hairgrass meadows are common, horsetail–butterbur, clover-cereal and cereal communities are common in the near-river part of the left bank. Despite the relatively high productivity and the presence of valuable forage species of cereals and legumes, the qualitative characteristics of hay deviate from optimal ones due to the participation of low-nutritious, unattractive, weedy and poisonous species in the herbage. On the pasture, as a result of pasture digression, there is a decrease in species diversity with the dominance of tufted hairgrass and low-value species of various grasses. In the most disturbed areas, the total projective vegetation coverage is reduced to 50%. The soil cover of the studied territory of the Kolva floodplain is currently not contaminated with hydrocarbons, with the exception of a few spots of petroleum products with a total area of 6 m2. The effect of oil pollution on the vegetation cover of the Kolva floodplain is not manifested. Background values of the content of petroleum products in soils are slightly higher in the left-bank part compared to the right-bank part.

Graphitic Armor: A Natural Molecular Sieve for Robust Hydrogen Electroxidation.

Carbon coating layers have been found to improve the catalytic performance of transition metals, which is usually explained as an outcome of electronic synergistic effect. Herein we reveal that the defective graphitic carbon, with a unique interlayer gap of 0.342 nm, can be a highly selective natural molecular sieve. It allows efficient diffusion of hydrogen molecules or radicals both along the in-plane and out-of-plane direction, but sterically hinders the diffusion of molecules with larger kinetic diameter (e.g., CO and O2) along the in-plane direction. As a result, poisonous species lager than 0.342 nm are sieved out, even when their adsorption on the metal is thermodynamically strong; at the same time, the interaction between H2 and the metal is not affected. This natural molecular sieve provides a very chance for constructing robust metal catalysts for hydrogen-relevant processes, which are more tolerant to chemical or electrochemical oxidation or CO-relevant poisoning.

Graphitic Armor: A Natural Molecular Sieve for Robust Hydrogen Electroxidation

AbstractCarbon coating layers have been found to improve the catalytic performance of transition metals, which is usually explained as an outcome of electronic synergistic effect. Herein we reveal that the defective graphitic carbon, with a unique interlayer gap of 0.342 nm, can be a highly selective natural molecular sieve. It allows efficient diffusion of hydrogen molecules or radicals both along the in‐plane and out‐of‐plane direction, but sterically hinders the diffusion of molecules with larger kinetic diameter (e.g., CO and O2) along the in‐plane direction. As a result, poisonous species lager than 0.342 nm are sieved out, even when their adsorption on the metal is thermodynamically strong; at the same time, the interaction between H2 and the metal is not affected. This natural molecular sieve provides a very chance for constructing robust metal catalysts for hydrogen‐relevant processes, which are more tolerant to chemical or electrochemical oxidation or CO‐relevant poisoning.

An appraisal of traditional knowledge of plant poisoning of livestock and its validation through acute toxicity assay in rats.

Background: Kashmir Himalaya hosts the most diverse and rich flora in the world, which serves as grazing land for millions of small ruminants in the area. While most plant species are beneficial, some can be poisonous, causing economic losses and animal health issues for livestock. Consequently, this study is the first comprehensive report on the traditional phyto-toxicological knowledge in District Muzaffarabad and the assessment of its authenticity through experimental studies in rats. Methods: The data regarding traditional knowledge was gathered from 70 key respondents through semi-structured interviews, which was quantitatively analyzed and authenticated through plant extract testing on Wistar female rats and comparison with published resources. Results: A total of 46 poisonous plant species belonging to 23 families and 38 genera were reported to be poisonous in the study area. Results revealed that leaves were the most toxic plant parts (24 species, 52.1%), followed by the whole plant (18 species, 39.1%), stem (17 species, 36.9%), and seeds (10 species, 21.7%). At the organ level, liver as most susceptible affected by 13 species (28.2%), followed by the gastrointestinal tract (15 species, 32.6%), nervous system (13 species, 8.2%), dermis (8 species, 17.3%), renal (7 species, 15.2%), respiratory (4 species, 8.7%), cardiovascular system (3 species, 6.5%), and reproductive system (2 species, 4.3%). The poisonous plant species with high Relative frequency citation (RFC) and fidelity level (FL) were Nerium oleander (RFC, 0.6; FL, 100), Lantana camara (RFC, 0.6; FL, 100), and Ricinus communis (RFC, 0.6; FL, 100). Experimental assessment of acute toxicity assay in rats revealed that Nerium oleander was the most toxic plant with LD50 of (4,000mg/kg), trailed by Ricinus communis (4,200mg/kg), L. camara (4,500mg/kg), and Datura stramonium (4,700mg/kg); however, other plants showed moderate to mild toxicity. The major clinical observations were anorexia, piloerection, dyspnea, salivation, tachypnea, constipation, diarrhea, tremor, itchiness, and dullness. Conclusion: This study showed that numerous poisonous plants pose a significant risk to the livestock industry within Himalayan territory, leading to substantial economic losses. Consequently, it is of utmost importance to conduct further comprehensive studies on the phytotoxicity of plants.

Review: Harvesting therapeutically important bioactive compounds from possible poisonous Clitocybe species

Review: Harvesting therapeutically important bioactive compounds from possible poisonous Clitocybe species

Ethnobotanical knowledge of Isaan Laos tribe in Khong Chai District, Kalasin Province, Thailand with particular focus on medicinal uses

Abstract. Niamngon P, Saensouk S, Saensouk P, Junsongduang A. 2023. Ethnobotanical knowledge of Isaan Laos tribe in Khong Chai District, Kalasin Province, Thailand with particular focus on medicinal uses. Biodiversitas 24: 6793-6824. Isaan Laos ethnic group in Khong Chai District, Kalasin Province, Thailand hold a unique ethnobotanical knowledge on plant utilization, yet such knowledge and wisdom are facing gradual erosion due to modernization. Therefore, this study aimed to investigate comprehensively the ethnobotanical knowledge on the uses of plants among the Isaan Laos ethnic group residing in Khong Chai District. Data was gathered between July 2022 and July 2023 via vegetation survey, semi-structured interviews and focus group discussions with 23 villagers residing in village adjacent to the forested area to collect data on plant local names and its utilization. The data was then analyzed for Cultural Important Index (CI), Informant Agreement Ratio (IAR), and Fidelity Level (%FL). In total, Isaan Laos ethnic group in Khong Chai District utilize 291 plant species belonging to 229 genera and 88 families for various purposes. These plants are further categorized into 12 groups based on their traditional uses, including 168 species used for food and spices, 109 species for medicinal purposes, 74 species for ornamental purposes, 40 species for construction materials, 35 species for beliefs and rituals, 27 species for fuels, 20 poisonous species, 17 species for beverages, 5 species for dyeing, 4 species for cosmetics and perfumery, 3 species for industrial crops and 2 species for apparel. Oryza sativa is the most often utilized plant, with a CI value of 4.74, followed by Senna siamea (3.39) and Pandanus amaryllifolius (3.30). The body ache with the highest Index of IAR=0.94 is associated with Curcuma longa, which has the highest values of Fidelity Level (%FL). The most common use of Curcuma longa is to treat flatulence and expelling wind, as well as skin illness. Additionally, Curcuma longa has the highest CI value of 9.83. This study recorded ethnobotanical data in detail as fundamental knowledge for the conservation of plants to be utilized by future generations.

Zootoxins and Domestic Animals: A European View.

Zootoxins are produced by venomous and poisonous species and are an important cause of poisoning in companion animals and livestock in Europe. Little information about the incidence of zootoxin poisoning is available in Europe, with only a few case reports and review papers being published. This review presents the most important zootoxins produced by European venomous and poisonous animal species responsible for poisoning episodes in companion animals and livestock. The main zootoxin-producing animal species, components of the toxins/venoms and their clinical effects are presented. The most common zootoxicoses involve terrestrial zootoxins excreted by the common toad, the fire salamander, the pine processionary caterpillar, and vipers. The lack of a centralized reporting/poison control system in Europe makes the evaluation of the epidemiology of zootoxin-induced poisonings extremely difficult. Even if there are many anecdotal reports in the veterinary community about the exposure of domestic animals to terrestrial and marine zootoxins, the number of published papers regarding these toxicoses is low. Climate change and its consequences regarding species distribution and human-mediated transportation are responsible for the emerging nature of some intoxications in which zootoxins are involved. Although new venomous or poisonous animal species have emerged in regions where they were previously unreported, zootoxins produced by native species remain the main concern in Europe. The diversity of poisonous and venomous animal species and the emerging nature of certain poisonings warrant the continuous update to such knowledge by veterinary professionals and animal owners. This review offers an overview about zootoxin-related poisonings in domestic animals in Europe and also provides important information from a health perspective.

An Ethnobotanical Survey of Poisonous Medicinal Plants in the Shouf Biosphere Reserve, Lebanon

Local communities of the Shouf Biosphere Reserve (SBR) have a long history of traditional use of medicinal plants. However, such use has sometimes been accompanied by toxicity symptoms. Therefore, this study aimed to document the ethnobotanical knowledge about the toxicity of medicinal plant species used by local people. Ethnobotanical information was collected during 2019-2021 using semi- structured questionnaires and personal interviews involving 133 local informants (68 women and 65 men with an average age of 58 years). The Frequency of Citation (FC) index was calculated from the data collected during the interviews, which allowed the generation of a list of poisonous plant species used to treat different diseases. The toxicity of highly cited species was discussed according to phytochemical profiles reported in the literature. The findings resulted in a list of 31 plant species from 22 botanical families, with Asteraceae, Euphorbiaceae, and Solanaceae being the most dominant. The most toxic plant species were Ecballium elaterium (L.) A.Rich (FC 11%), Sambucus ebulus L., Ricinus communis L., and Arum palaestinum Boiss. (each of FC 10%). Herbs were the most dominant life form of the cited species. The most toxic parts were the leaves (22% of citations), followed by whole plants and seeds (each 17%), and fruits (11%). Oral ingestion and skin contact were the main routes of toxicity. According to the published literature, toxicity can be primarily attributed to biochemical compounds, such as cucurbitacins, proteaceous glycoprotein, ricin, tropane alkaloids, atropine, cyanogenic glycosides, and pyrrolizidine alkaloids, among other compounds. This work highlights the importance of the traditional knowledge of poisonous plants used in folk medicine and the need for phytochemical and toxicological research. The development of regulatory measures on the use and trade of medicinal plants as well as raising awareness of practitioners and public are also deemed necessary.

Addendum to the Fauna of Venomous Snakes of Nakhchivan (Azerbaijan)

The article is devoted to the results of the study of the taxonomic status and ecological characteristics of venomous snake’s species distributed in the territory of the Nakhchivan. Materials for research were collected in various biotopes and landscapes in the highlands during 2011-2023. Information is given on 3 types of poisonous species: Macrovipera lebetina, Montivipera raddei, Pelias eriwanensis.

Ni-doped TiO2 supported Pt single-atom catalyst for partial oxidation of ethylene glycol to high-value chemicals in alkaline media

Pt-based electrocatalysts are usually used in several catalytic reactions. However, its high cost, scarcity, and susceptibility towards poisonous intermediate species highly limit these catalysts' large-scale applications. Downsizing catalysts to single-atom scale (SAC) have fascinated extensive research interests due to their higher activity, selectivity, and stability. Herein, we prepared highly active, selective, and poisoning-tolerant PtSACs on Ni-doped TiO2 support (PtSAC-Ni0.1Ti0.9O2). Ni in the catalyst creates a suitable environment to adsorb more OH− and make Pt accessible and ready for further oxidations. Thus, it exhibits higher electrocatalytic performance towards EGO than PtSAC-TiO2 does. It is also by far better than PtNP– Ni0.1Ti0.9O2. The higher catalytic performance by PtSAC-Ni0.1Ti0.9O2 is due to the synergistic effects of Ni and Pt. The catalyst selectively produces glycolate, formate, and hydrogen. Glycolate and formate are high-value chemicals for domestic uses or as inputs for industries to produce other chemicals. The catalyst also shows excellent Faradaic efficiency (>98 %) and stability towards EGO in alkaline media. The strong metal-support interactions between the catalyst and the support retard the agglomeration of the single atoms, thereby increasing their stability.

Agaricus micromegethus, a new record for Turkish Mycobiota

The Agaricaceae is a monophyletic group of saprotrophic fungi distributed worldwide. The family exhibits considerable variations such as spore color and structure of pileus covering in morphology. Agaricus is the type genus of the family containing both edible and poisonous species, with more than 500 species worldwide. This genus includes many species that are considerably important so takes attention of scientists in the fields of medicine, biochemistry and food science. This study aims to introduce a new record, Agaricus micromegethus, for the Turkish mycobiota based on macro- and micromorphology. An illustrated description of the record is provided.

Biological Characteristics of Poisonous Species of the Ranunculus L. Genus in the Flora of Nakhchivan

Annual and perennial herbaceous plants belonging to the Ranunculus L. genus of the Ranunculaceae family were studied. It has been established that 103 out of 2000 species of the family are common in Azerbaijan and many of them are poisonous. In the taxonomic spectrum of the Nakhchivan flora, 55 species belonging to 14 genera of the Ranunculaceae family were identified. As a result of the research, toxic compounds were identified in 47 species belonging to 11 genera. Ranunculus L. is widespread in pastures and meadows and is represented by 33 species and 15 species, of which 13 are poisonous pasture plants. It is important to survey the distribution area of Ranunculus L. species, especially poisonous species, and improve the quality of pastures.

Preliminary species diversity and community phylogenetics of wood-inhabiting basidiomycetous fungi in the Dabie Mountains, Central China reveal unexpected richness

Wood-inhabiting fungi have important economic values as well as playing a major ecological role in forest ecosystem cycles. The Dabie Mountains, at the junction of Henan, Hubei, and Anhui Provinces, Central China, provide an ideal climate and favorable niches for the speciation and diversification of various forms of life including fungi. We studied the species diversity and community phylogenetics of wood-inhabiting basidiomycetous fungi that revealed 175 wood-inhabiting basidiomycetous species, of which 20 represented unidentified species, based on morphological and phylogenetic analyses of 575 specimens collected from ten sampling sites. These species belonged to two classes, 11 orders, 42 families, and 106 genera of Basidiomycota, and included 12 edible species, 28 medicinal species, four poisonous species, and seven forest pathogens. Four types of fungal distribution pattern at the genus level were recognized for 65 genera, while another 41 genera could not be placed in any known distribution pattern. The five sampling sites in the eastern part of the Dabie Mountains had significantly higher species diversity and phylogenetic diversity of wood-inhabiting basidiomycetous fungi than those in the western part, and thus deserve priority in terms of conservation. The community of wood-inhabiting basidiomycetous fungi in the Dabie Mountains is generally affected by a combination of habitat filtering and competitive exclusion. This study provides a basis on which to build actions for the comprehensive recognition, utilization, and conservation of wood-inhabiting basidiomycetous fungi in the region.

PSII-17 Sheep Foraging Relative to Stock Density, Time of Day, and Sheep Type in a Poisonous Plant Context

Abstract Plains larkspur (Delphinium geyeri) is a poisonous plant species that can be highly toxic at certain growth stages on western Great Plains rangelands. Targeted sheep grazing has been proposed as a mitigation strategy to reduce larkspur abundance and poisoning risk for cattle due to their greater toxicological resilience to the diterpenoid alkaloids. We incorporated targeted-sheep grazing in a northern mixed-grass prairie with our objective to determine the influence of stocking density, time of day, and sheep type on foraging behavior. During May 2022, Dorper (< 1-year-old lambs, n = 123, BW 25 kg ± 0.4; and 3 to 6-year-old ewes, n = 14, BW 47 kg ± 1.8) and Rambouillet (3 to 6-year-old ewes, n = 13, BW 76 kg ± 2.9) sheep were used in three stocking density treatments 1) 120 AU/day (1 day in a 0.25 ha paddock), 2) 60 AU/day (2 days in a 0.5 ha paddock), and 3) 40 AU/day (1 day in a 0.75 ha paddock) that were replicated four times. Sheep were housed overnight in a common area. We observed bite counts daily for nine randomly chosen sheep (three from each category) over five-minute intervals, in the morning and afternoon. We used a generalized linear model to assess the fixed effects of sheep type (Rambouillet ewe vs. Dorper ewe; Dorper ewe vs. Dorper lamb) and stock density on bite counts. Least squared means were analyzed for stock density using Tukey test, and for breed and age using student’s T test. We observed contrasts between morning and afternoon sheep foraging and diet selection. Mechanistically, this is likely due to the introduction of sheep into a new paddock in the morning after confinement and satiation diluting differences in the afternoon. Sheep breed influenced the proportion of graminoids consumed (96.9% Rambouillet vs 99.3% Dorper, P = 0.02), but differences were not observed between Dorper ewes and lambs (P = 0.57). The proportion of forb bite counts did not differ between Dorper ewes and lambs (0.6% vs. 0.4%, respectively, P = 0.6), nor between the Dorper ewes and Rambouillet ewes, despite the latter having a 3.5-fold greater selectivity (2.1%, P = 0.08). Larkspur consumption was no different between Dorper ewes and lambs (0.04% ewes vs. 0.01% lambs, P = 0.48), nor between Dorper ewes and Rambouillet ewes (0.28%, P = 0.09). Stock density influenced forb consumption; the proportion of forb bite counts were 12 times greater in the 0.5 ha paddock (3%) compared with the 0.25 ha paddock (0.3%, P = 0.005). Despite all consuming > 95% grass in the diet, results indicate that Rambouillet sheep trended towards greater selectivity than Dorper sheep, and greater selectivity in light to moderate stock densities may increase the proportion of larkspur in sheep diets.