Choice of feeding sites by moose during summer, the influence of forest structure and plant phenology

We observed forage and habitat selection in radio-collared moose at feeding sites in southeast Norway. Use of older forest increased from spring to autumn. Birch Betula spp. and bilberry Vaccinium myrtillus accounted for c. 75% of the diet. Occurrence of important forage plants, height of browse, and difference in phenology between plant species all appeared to play a role in moose selection of feeding sites. Shading influences moose forage by delaying plant phenology and possibly through its effect on leaf content of water and secondary compounds. On single birch trees, feeding was concentrated to the top branches at midsummer; during spring and autumn more leaves from side branches were eaten. Greater discrimination as vegetation matured was also evident from the wider variety of forage species used at midsummer. Selection of feeding sites was not related to density of important browse species. We propose that variations in light/shade conditions may play a role in moose choice of feeding sites and that moose on summer range will benefit from a heterogeneous mixture of plantations and older forest stands.     

Moose and vole browsing patterns in experimentally assembled pure and mixed forest stands

Plants growing in diverse communities are believed to exhibit associational resistance to herbivores, but this hypothesis has seldom been tested experimentally for vertebrate herbivores in forest ecosystems. We examined browsing patterns of the two principal mammalian herbivores of Finnish boreal forests, moose and voles, in young stands where tree species diversity and composition were experimentally manipulated. The stands were composed either of monocultures or different 2–5 species mixtures of Norway spruce, Scots pine, Siberian larch, silver birch, and black alder. Voles and moose showed contrasting responses to stand diversity and species composition. In accordance with the predictions of the associational resistance hypothesis, vole damage was higher in tree monocultures than in mixed stands, although stand diversity effects were statistically significant only at one of the three study areas. Voles also damaged more trees in coniferous than in deciduous stands. In contrast, moose browsing tended to increase with the number of tree species in a stand and with the presence of the preferred tree species, birch, in a mixture. The observed differences in vole and moose responses to stand diversity and species composition are likely to be due to different feeding specialisation, foraging patterns, and movement ability of these herbivores. Voles switched to trees only when the supply of a more preferred food (grasses and forbs) was depleted and restricted their feeding choice only to the most palatable tree species regardless of the number of tree species present per stand. In contrast, tree branches and foliage represented an important part of moose diet throughout the year; moose may be able to tolerate secondary plant metabolites of different tree species better than voles and may thus benefit from diet broadening when more tree species are available. Furthermore, the home range size and foraging ability of these two very differently sized herbivores may partly explain the observed differences in utilisation of different tree species. Finally, both moose and voles showed high spatial and temporal variation in their feeding; in particular, vole damage was more influenced by tree species diversity in areas and years with high vole densities. Thus, diversification of forest stands may have very different effects on mammalian browsing depending on the herbivores present, their densities, and the tree species used in reforestation.     

Moose summer and winter diets along a large scale gradient of forage availability in southern Norway

Studies on dietary functional responses in large herbivores are traditionally conducted by following individual animals. The method is very time-consuming, and hence, typically provides only a narrow array of forage species compositions. Here we use a range level approach to look at moose (Alces alces) selectivity for and utilization of forage species in relation to availability in both summer and winter. We compare 12 Norwegian ranges representing a large scale gradient in plant communities. The most important forage species in the diet were birches (Betula spp., comprising 43% of all trees browsed in summer and 27% in winter), rowan (Sorbus aucuparia, 25% of trees browsed in summer, 37% in winter), and bilberry (Vaccinum myrtillus, 42% of herbaceous epidermal fragments in summer feces). Selectivity for birches was positively related to its availability and negatively related to availability of rowan, Salix spp., and aspen (Populus tremula) together (all more selected for than birches). Multiple regression models including availability of several forage species were thus superior to single-species models in explaining the diet content of main forage plants. Selectivity for birches was also stronger in summer than in winter, while the opposite pattern was found for rowan. The finding is relevant for our evaluation of the quality of summer and winter ranges, and hence, their relative influence on population productivity. Our study underlines the need to incorporate species composition of available forage when quantifying dietary functional responses in selective herbivores such as moose. Furthermore, care should be taken when extrapolating data on moose diet across ranges or seasons.     

The benefits of being in a bad neighbourhood: plant community composition influences red deer foraging decisions

Diet selection by mammalian herbivores is often influenced by plant community composition, and numerous studies have focused on the relationships between herbivore foraging decisions and food/plant species abundance. However, few have examined the role of neighbour palatability in affecting foraging of a target plant by large mammalian herbivores. We used a large-scale field dataset on diet selection by red deer Cervus elaphus in Fiordland National Park, New Zealand to: (1) estimate the palatability of native forest plant species to introduced deer from observed patterns of browse damage; and (2) examine whether intraspecific variation in browsing of plants can be related to variation in the local abundance of alternative forage species. Overall, 21 of the 53 forest species in our dataset were never browsed by deer. At a community level, plants were more likely to be browsed if they were in a patch of vegetation of high forage quality, containing high abundances of highly palatable species and/or low abundances of less-palatable species. Our findings suggest that deer make foraging decisions at both a coarse-grain level, selecting vegetation patches within a landscape based on the overall patch quality, and at a fine-grain level by choosing among individual plants of different species.     

Influence of young black spruce plantations on moose winter distribution

Logging in the boreal forest may benefit moose by increasing food availability. However, the influence of tree plantations on moose behavior, especially on moose spatial ecology, is poorly understood. We assessed the impacts of black spruce plantations on moose winter distribution at a landscape scale in the Bas-Saint-Laurent region (Québec, Canada). We used winter aerial surveys to examine relationships among plantation characteristics and other habitat variables known to affect moose distribution. The total area of plantations positively influenced moose abundance, but highly aggregated plantations resulted in fewer moose. Moose abundance was also positively associated with food availability and the density of edges between stands providing cover and stands offering high food availability, but moose abundance was negatively associated with road density. Although plantation characteristics were less influential than habitat variables related to foraging and predator avoidance, we demonstrate that the area of black spruce plantations and their configuration should be considered in moose management. We conclude that an integrated management strategy is needed to find a balance between overdeveloped road networks (needed to join homogeneously distributed plantations) and agglomerated plantations in order to mitigate impacts on moose winter distribution. © 2012 The Wildlife Society.     

Responses to harvesting intensity in a clonal dwarf shrub,the bilberry (Vaccinium myrtillus L.)

The effects of herbivory were simulated on stands of bilberry (Vaccinium myrtillus L.) in a boreal Empetrum-Myrtillus type forest. Five harvesting intensities were used (0% (A), 25% (B), 50% (C), 100% (D) of the bilberry ramets or all the ramets of all species (E)). Density and biomass of the stands, and growth of the ramets were monitored for five growth seasons, from 1986 to 1990. After damage new ramets emerged rapidly from dormant buds at the base of removed ramets. Between 70 and 97% of the density relative to the control level was regained by the final harvest. However, only between 11 and 64% of the biomass relative to the control level was recovered. Clipping reduced the branch growth, both in the new ramets and in the new parts of the old, unclipped ramets. Severe treatments (D and E) decreased the growth more than did light harvesting (B and C). Survival and fecundity of the ramets were not affected. The result therefore suggested that the bilberry is not able to recover totally from severe herbivory damage between the years of peak rodent population that shows a 3–4 year cycle. Nevertheless, extreme grazing pressure is rare in boreal ecosystems as alternative food is available for herbivores, and predators also limit the herbivore population. Hence the bilberry exhibits moderate tolerance of the usual level of herbivory damage.     

Comparative Space Use and Habitat Selection of Moose Around Feeding Stations

ABSTRACT The practice of feeding cervids in winter, either as a supplement to enhance nutritional status or to divert animals away from roads, railways, or vulnerable habitats, is rising noticeably. Moose (Alces alces) densities in Scandinavia are currently at historically high levels, resulting in amplified damage to economically important young Scots pine (Pinus sylvestris) forest stands. Nevertheless, there is limited information as to how diversionary feeding affects herbivore space use and habitat selection. We followed 32 female moose marked with Global Positioning System collars to evaluate 1) if feeding stations serve as attraction points to the extent that habitat-selection patterns resemble those of central-place foragers (i.e., high usage and more uniform selection close to the attraction point), and 2) if moose using feeding sites select young pine stands less than those not using feeding sites. Moose that used diversionary forage concentrated their space use around feeding stations and selected habitats as predicted for a central-place forager with a decreasing probability of using areas away from feeding sites and a low degree of habitat selectivity close to feeding sites. However, moose that used feeding sites continued to select young pine stands to the same extent as moose that did not use feeding sites. Feeding sites were, therefore, not successful in diverting moose away from valuable natural browse, so we recommend wildlife managers establish feeding sites in sacrifice areas where moose browsing is permissible and, if possible, >1 km from young pine plantations.     

Impact of moose population density on the production and composition of litter in boreal forests

Recent studies of ungulates have revealed that selective foraging seems to be an important mechanism by which they can affect the structure and species composition of the plant community, and thus quantity (dry mass) and quality (chemical composition) of litter available for decomposers. Such changes in litter production may be especially important in N-limited systems like boreal forests. We chose moose ( Alces alces ) as study species to investigate this mechanism. Moose browse mainly in the tree and shrub layers year round, and because of their wide distribution and often high population densities, they can have a significant effect on litter production of trees and shrubs in Swedish boreal forests. The effects of herbivores may also vary along productivity gradients. We therefore simulated browsing and urine and fecal deposition corresponding to 4 different moose densities in exclosures along a pre-existing forest productivity gradient. Both litter quantity (g dry mass per m² and year) and contributions of C and N (g dry mass per m² and year) decreased with increasing level of simulated moose density. High moose densities over extended time can therefore reduce N contributions to soil and therefore eventually reduce site productivity in Swedish boreal forests. This effect of moose was mainly a result of decreased litter quantity, because contradictory to studies from North America, litter quality (C:N ratio and N contribution per mass unit of litter) was not affected by level of simulated moose density.     

Linking alternative food sources to winter habitat selection of herbivores in overbrowsed landscapes

During winter, ungulates in boreal forests must cope with high energetic costs related to locomotion in deep snow and reduced forage abundance and quality. At high density, ungulates face additional constraints, because heavy browsing reduces availability of woody browse, the main source of forage during winter. Under these severe conditions, large herbivores might forage on alternative food sources likely independent of browsing pressure, such as litterfall or windblown trees. We investigated the influence of alternative food sources on winter habitat selection, by studying female white-tailed deer (Odocoileus virginianus) living in 2 landscapes with contrasted browse abundance, recently logged and regenerated landscapes, in a population at high density and on a large island free of predators. We fitted 21 female white-tailed deer with Global Positioning System (GPS) collars and delineated winter home ranges and core areas. We measured snow conditions in different habitat categories and sampled vegetation in the core areas and in the rest of the home ranges to determine how forage abundance, protective cover, and snow conditions influenced habitat selection within the home range. In both landscapes, deer were less likely to use open habitat categories as snow accumulated on the ground. At a finer scale, deer inhabiting the regenerated landscape intensively used areas where balsam fir cover was intermediate with greater balsam fir browse density than in the rest of the home range. In the recently logged landscape, deer were more likely to be found near edges between clear-cuts and balsam fir stands and in areas where windblown balsam fir trees were present; the latter being the most influential variable. Although balsam fir browse was sparse and mainly out of reach in this landscape, deer increased the use of areas where it was present. Our results offer novel insights into the resource selection processes of northern ungulates, as we showed that access to winter forage, such as woody browse and alternative food sources, depends on climatic conditions and stochastic events, such as abundant compacted snow or windthrows. To compensate for these scarce and unpredictable food supplies, deer selected habitat categories, but mostly areas within those habitat categories, where the likelihood of finding browse, litterfall, and windblown trees was greatest. © 2011 The Wildlife Society.     

Effects of proximity to riparian zones on avian species richness and abundance in montane aspen woodlands

Riparian zones often provide more food or nesting resources than surrounding ecosystems and thus support more species or a greater abundance of birds. However, the extent to which the positive effects of riparian zones extend into adjoining habitats has rarely been investigated. We examined bird species richness and abundance in aspen (Populus tremuloides) woodlands of the upper East River Valley in Colorado, a region with extensive stands of aspen located upslope from riparian zones dominated by willows (Salix spp.). Our objective was to determine how species richness and abundance in aspen stands located closer to riparian zones compared to that of aspen stands farther away. To control for elevation effects, we conducted point counts for birds and examined the effects of riparian proximity on avian species richness and abundance in three elevation belts (low, 2840–2875 m; middle, 2940–2960 m; and high, 3040–3060 m). We determined riparian proximity by measuring distances from each census site to the nearest body of water and to the nearest patch of willow. Proximity to major willow patches (≥6500 m²) had a stronger influence on species richness and abundance than did proximity to water or smaller patches of willows. Total species richness and abundance significantly increased with proximity to major willow patches at low elevation sites only. This relationship was driven by a greater prevalence of riparian‐nesting species at lower elevation sites, where aspens were generally closer to riparian zones. The positive effects of willows diminished with abrupt changes in elevation. Our results highlight the importance of protecting willows around riparian zones in valley bottoms where habitat destruction caused by human land use is most prominent.     

Linking Moose Population and Plant Growth Models with a Moose Energetics Model

Selective foraging by large mammals can change ecosystem properties such as plant species composition, nutrient cycling rates, and soil fertility. These changes, in turn, alter the availability of forage and could affect the relative efficiencies of foraging strategies used by these animals. We used a simulation model to predict how alternate foraging strategies affected the net annual energy balance of moose (Alces alces), moose density, and distribution of browse across the landscape. The model simulates the spatial distribution of vegetation in an 8-ha landscape of 1-m² cells with seasonal changes in the energetic needs of free-ranging moose and plant phenology. The energetics model was integrated with a moose population model and a plant-growth model for long-term simulations. Changes in bite density in each feeding station are predicted with height and biomass logistic curves modified by a quadratic response to browsing. We tested foraging strategies using random, fractional, and marginal value theorem (MVT) algorithms on landscapes with a range of bite densities and differing spatial distributions. Small-scale disturbances (that is, tree-fall gaps) were required to maintain browse supply and prevent moose population extinction under all foraging strategies. Populations using a fractional stopping rule survived the 100-year simulations because moose browsed across much of the landscape and did not overbrowse patches with high bite density. Populations using random and MVT stopping rules became extinct in about 25 and about 50 years, respectively. Moose using a random stopping rule were in negative energy balance because travel time was high and the net energy intake rate was low on an annual basis. Moose using the MVT stopping rule were initially in positive energy balance, but as the high-density browse patches were overbrowsed and low-density unbrowsed patches grew out of reach, bite density decreased, and energy balance became negative in subsequent years. Thus, the foraging strategy used by individual moose resulted in creation of landscapes that strongly affected browse density, browse distribution, moose population density, and moose survival. Received 30 April 1997; accepted 5 August 1997.     

Foraging by moose on two species of birch when these occur in different proportions

The two tree-like birch species Betula pendula and B. pubescens are of medium preference to moose during winter in northern Sweden. Because these birches are abundant in many biotopes, they form a major part of the moose diet. The two birches are very similar in appearance and often occur in mixed stands. Twenty-one birch stands where B. pendula formed from 2 to 97% of the birches were investigated to determine how the relative composition of the stands affected browsing of the two species by moose. In stands composed of 60% or less of B. pendula , there was a preference for this species when regarding 1.5–3.0 m high birches, which carry the largest amount of available browse per tree. At higher proportions B. pendula was still preferred, but use was closer to availability. However, in all stands there were significantly more moose bites per tree of B. pendula than of B. pubescens . In four birch stands browsing on 1.0–1.5 m high birches was also investigated. For this height class there was still a preference for B. pendula , but the difference between the two species was less pronounced than for the 1.5–3.0 m height class.     

Colonisation of ephemeral forest habitats by specialised species: beetles and bugs associated with recently dead aspen wood

The most appropriate strategy for preserving fragmented populations depends on a species’ ability to colonise distant habitat patches. Insects associated with early decay stages of dead wood are expected to have a high capacity to colonise new habitat patches. To study the dispersal ranges of beetles (Coleoptera) and flat bugs (Hemiptera: Aradidae) dependent on recently dead aspen (Populus tremula) wood in Finland, we set out 58 piles of recently cut aspen logs at various distances up to 1.6 km from forests that contained a high density of old aspen trees. We captured insects by trunk window-traps, and counted beetles’ exit holes. Habitat connectivity was measured in terms of the amount of suitable aspen-wood in the surrounding environment, with the closest dead wood items up-weighted by a negative-exponential function. The log-piles attracted many saproxylic insects including four red-listed aspen-specialist species. The exposure of log-piles to the sun, and high levels of habitat connectivity increased the species richness of aspen-specialists, whereas bark peeling by moose decreased richness. The spatial scale at which species richness had its strongest response to habitat was 93 m. Among individual species there was a wide variability in spatial scale of response. This study supports the view that conservation efforts in boreal forests should be concentrated on sites where colonisation by target species is most likely. Restoration of habitat by re-locating logs may be useful at localities with a rich and specialised fauna but which have too low rate of formation of dead wood by natural processes.     

Coping in a human-dominated landscape: trade-off between foraging and keeping away from roads by moose (Alces alces)

Roads fragment moose habitat and cause increased mortality through moose–vehicle collisions. Previous studies have found that moose avoid areas near roads. In late winter, when moose face depleting food resources elsewhere, moose may be more prone to use areas near roads for foraging. However, this presumed trade-off between foraging and keeping away from roads has not previously been investigated. We sampled positions from global positioning system-collared moose in late winter from a high-density moose population in Southern Norway that is heavily influenced by human infrastructure. We combined data on moose positions with detailed field surveys of food abundance at sites that were, respectively, intensively used or sparsely used by moose. The probability that a site was intensively used increased with increasing abundance of high-quality browse and also with increasing distance to the nearest road. This indicates that moose trade-off foraging against keeping away from roads. We also found that spatio-temporal movements in relation to roads were influenced by variation in perceived human-derived risk; moose moved closer to smaller roads (low traffic volume) than to major roads (higher traffic volume) and closer to roads at night than at day. Males moved closer to roads than females. In conclusion, moose clearly exhibited behavioural adaptations to cope with roads and traffic in the study area. Because availability of high-quality forage substantially influenced habitat use, it may be an option to establish artificial feeding sites during winter to keep moose away from the roads.     

Impact of simulated moose densities on abundance and richness of vegetation,herbivorous and predatory arthropods along a productivity gradient

Large herbivores can affect vegetation structure and species composition as well as material and energy flows in the ecosystem through their selective feeding, defecation, urination and trampling. These changes have a large potential to indirectly affect other trophic levels, but the mechanisms are poorly known. We studied the impacts of moose Alces alces browsing along a gradient of site productivity by experimentally simulating four different moose densities. Here we show that moose can affect the richness and abundance of three trophic levels in Swedish boreal forests through complex direct and indirect impacts, but in qualitatively different ways depending on how the physical habitat or food resources of a trophic level are affected. Vegetation richness had a hump‐shaped (unimodal) response to increased moose density. Leaf litter production decreased when browsing increased, which in turn depressed the abundance of flying prey for spiders. Consequently, spider abundance and richness declined monotonically. The responses of spider richness to moose density were further conditioned by site productivity: the response was positive at productive and negative at unproductive sites. In contrast, herbivorous Hemiptera were not affected by moose, most likely because the abundance of their food plants was not affected. The highest simulated moose density had an impact on all variables responding to moose even after a few years of treatment and can be considered as overabundance. We also show that the impacts of low or moderate moose density can be positive to some of the organisms negatively affected by high density. The level of herbivore population density that leads to substantial community impacts also depends on site factors, such as productivity.     

Range Expansion of Moose in Arctic Alaska Linked to Warming and Increased Shrub Habitat

Twentieth century warming has increased vegetation productivity and shrub cover across northern tundra and treeline regions, but effects on terrestrial wildlife have not been demonstrated on a comparable scale. During this period, Alaskan moose (Alces alces gigas) extended their range from the boreal forest into tundra riparian shrub habitat; similar extensions have been observed in Canada (A. a. andersoni) and Eurasia (A. a. alces). Northern moose distribution is thought to be limited by forage availability above the snow in late winter, so the observed increase in shrub habitat could be causing the northward moose establishment, but a previous hypothesis suggested that hunting cessation triggered moose establishment. Here, we use recent changes in shrub cover and empirical relationships between shrub height and growing season temperature to estimate available moose habitat in Arctic Alaska c. 1860. We estimate that riparian shrubs were approximately 1.1 m tall c. 1860, greatly reducing the available forage above the snowpack, compared to 2 m tall in 2009. We believe that increases in riparian shrub habitat after 1860 allowed moose to colonize tundra regions of Alaska hundreds of kilometers north and west of previous distribution limits. The northern shift in the distribution of moose, like that of snowshoe hares, has been in response to the spread of their shrub habitat in the Arctic, but at the same time, herbivores have likely had pronounced impacts on the structure and function of these shrub communities. These northward range shifts are a bellwether for other boreal species and their associated predators.     

Seasonal shifts in habitat use and diet by eland confined in a small fenced reserve

Large‐scale environmental changes create challenges for conservation of wildlife, particularly in fenced, insular protected areas where many wildlife populations persist. Moreover, large mammalian herbivores inhabiting spatially and temporally heterogeneous environments face the challenge of securing highly variable forage resources. Mixed feeders like the eland (Taurotragus oryx) can switch between browse and grass, but the cues that elicit that switch are not well understood. We investigated the seasonal diet shift of eland confined to a small fenced reserve and the role of greenness to elicit that shift. Eland changed from a diet in the wet season, consisting of grasses and browse found in woodland and grassland vegetation types, to a diet in the dry season dominated by the greenest browse species still available in woodland vegetation types, as greenness of dry season forage decreased. Our results suggest that eland switch from browsing to grazing in response to phenophase of the grass sward, which could explain the varying selection of grasses versus browse observed across the species range.     

Influence of size and density of browse patches on intake rates and foraging decisions of young moose and white-tailed deer

We examined the functional response and foraging behavior of young moose (Alces alces) and white-tailed deer (Odocoileus virginianus) relative to animal size and the size and distribution of browse patches. The animals were offered one, three, or nine stems of dormant red maple (Acer rubrum) in hand-assembled patches spaced 2.33, 7, 14, or 21 m apart along a runway. Moose took larger twig diameters and bites and had greater dry matter and digestible energy intake rates than did deer, but had lower cropping rates. Moose and deer travelled at similar velocities between patches and took similar numbers of bites per stem. We found that a model of intake rate, based on the mechanics of cropping, chewing, and encountering bites, effectively described the intake rate of moose and deer feeding in heterogeneous distributions of browses. As patch size and density declined, the animals walked faster between patches, cropped larger bites, and cropped more bites per stem, and hence, dry matter intake rates remained relatively constant. As is characteristic of many hardwood browse stems, however, potential digestible energy concentration of the red maple stems declined as the size and number of bites removed (i.e., stem diameter at point of clipping) by the animals increased. Therefore, the digestible energy content of the diet declined with decreasing patch size and density. Time spent foraging within a patch increased as patch size increased and as distance between patches increased, which qualitatively supported the marginal-value theorem. However, actual patch residence times for deer and moose exceeded those predicted by the marginal-value theorem (MVT) by approximately 250%. The difference between actual and predicted residence time may have been a result of (1) an unknown or complex gain function, (2) the artificial conditions of the experiments, or (3) assumptions of MVT that do not apply to herbivores.     

The Nutritional Balancing Act of a Large Herbivore: An Experiment with Captive Moose (Alces alces L)

The nutrient balancing hypothesis proposes that, when sufficient food is available, the primary goal of animal diet selection is to obtain a nutritionally balanced diet. This hypothesis can be tested using the Geometric Framework for nutrition (GF). The GF enables researchers to study patterns of nutrient intake (e.g. macronutrients; protein, carbohydrates, fat), interactions between the different nutrients, and how an animal resolves the potential conflict between over-eating one or more nutrients and under-eating others during periods of dietary imbalance. Using the moose (Alces alces L.), a model species in the development of herbivore foraging theory, we conducted a feeding experiment guided by the GF, combining continuous observations of six captive moose with analysis of the macronutritional composition of foods. We identified the moose’s self-selected macronutrient target by allowing them to compose a diet by mixing two nutritionally complementary pellet types plus limited access to Salix browse. Such periods of free choice were intermixed with periods when they were restricted to one of the two pellet types plus Salix browse. Our observations of food intake by moose given free choice lend support to the nutrient balancing hypothesis, as the moose combined the foods in specific proportions that provided a particular ratio and amount of macronutrients. When restricted to either of two diets comprising a single pellet type, the moose i) maintained a relatively stable intake of non-protein energy while allowing protein intakes to vary with food composition, and ii) increased their intake of the food item that most closely resembled the self-selected macronutrient intake from the free choice periods, namely Salix browse. We place our results in the context of the nutritional strategy of the moose, ruminant physiology and the categorization of food quality.