Foraging behavior and spatial use of a rock specialist: the southern vizcacha (Lagidium viscacia), and the exotic European hare (Lepus europaeus) in rocky outcrops of northwestern Patagonia, Argentina

The southern vizcacha (Lagidium viscacia) and the exotic European hare (Lepus europaeus) are two medium-sized herbivores that inhabit rocky outcrops in Patagonian steppe. These species overlap in diet and spatial use at medium distances from rocky outcrops in summer. We evaluated the spatial use through feces distribution in winter and determined seasonal foraging intensity in relation to the distances from rocky outcrops in order to elucidate how these herbivores use food and spatial resources in food scarcity periods. The vizcacha utilized the habitat close to rocky outcrops (<40 m) independent of season, while the hare exploited the space more widely, especially distances >40 m. However, in winter, at medium distances from rocky outcrops, there was partial spatial overlap because hares' activities were closer to rocky outcrops. Foraging intensity increased significantly in areas used by the vizcacha closer to rocky outcrops when food availability decreased, and the grasses Stipa speciosa, Poa sp., and Festuca pallescens were strongly foraged. In contrast, foraging intensity showed no changes in further distances to rocky outcrops and more use by the hare. The spatial and feeding behavior of the vizcacha, restricted to vicinity of rocky outcrops, showed high vulnerability to food availability changes. In resource scarcity situations, the spatial opportunistic behavior of the hare and the overlap in diet with the vizcacha constitutes a threat to this native herbivore. It is necessary to monitor populations of hare, since high densities could lead to food competition, impacting the small colonies of the southern vizcacha.     

Diet selection of the southern vizcacha (<Emphasis Type="Italic">Lagidium viscacia</Emphasis>): a rock specialist in north western Patagonian steppe,Argentina

The southern vizcacha (Lagidium viscacia) is a rock specialist that inhabits small colonies in isolated rocky outcrops of northwestern Patagonia. This study analyzes its diet selection in relation to food availability, establishes the degree of dietary specialization, and discusses the potential competition with exotic herbivores. Diet composition and food availability were determined in summer and winter in eight rocky outcrops by microhistological analysis of fecal pellets, and food availability was estimated by the Braun Blanquet cover abundance scale. Vegetation cover differences were detected by using a random analysis of variance (ANOVA) factorial block design, and dietary preferences were determined by the confidence interval of Bonferroni. The southern vizcacha showed a specialized feeding behavior despite the consumption of a wide variety of items. Their diet was concentrated on a few types of food, mainly grasses, and the trophic niche was narrow and without seasonal variations. In winter, when food was scarce and of lower quality than summer, diet was dominated by Stipa speciosa, suggesting a selection according to the selective quality hypothesis. Our results (narrow trophic niche, restricted activity near rocky outcrops, and a diet with high proportions of low-quality grasses) showed that the vizcacha is an obligatory dietary specialist, and these characteristics made it highly vulnerable to changes in food availability. In this scenario, overgrazing caused by alien species with similar diets, as the European hare and livestock, could negatively affect their colonies.     

Space use patterns of mountain hare (<Emphasis Type="Italic">Lepus timidus</Emphasis>) on the Alps

Populations on the limits of species’ distribution can show different behavioral adaptations to strong ecological pressure than in the central part of the range. We investigated space use patterns of alpine mountain hare (Lepus timidus) at two areas on the southern edge of the species’ range. We monitored 34 hares between 2005 and 2008, estimating home range size, overlap, and site fidelity, and compared our results with space use in Scottish and North-European populations. Home ranges of mountain hares did not differ between two study areas with different habitat types. Subadult animals used larger ranges than adults and both age groups reduced home range size in autumn, a period that might be critical for hares due to changes in diet and/or high energy expenditure during the previous breeding season. Home ranges in these alpine populations were smaller than in Scandinavian populations but within the range of populations in different habitat types in Scotland. Seasonal home ranges overlapped considerably, but differed among the sexes: male–female overlap was higher than same sex (male–male and female–female) spatial overlap. Seasonal shifts of home ranges were small, and site fidelity remained high over the seasons, suggesting that resource distribution remained constant throughout the year and that the knowledge of an intensively frequented area is an important element of habitat quality. We concluded that habitat structure and availability of mates interact in affecting mountain hare space use in alpine habitats.     

The recent expansion of the brown hare (<Emphasis Type="Italic">Lepus europaeus</Emphasis>) in Sweden with possible implications to the mountain hare (<Emphasis Type="Italic">L. timidus</Emphasis>)

The brown hare (Lepus europaeus) expanded its Swedish distribution since the 1980s northwards and locally to new areas within its former range. Of 115 brown hare populations within the former range reported in a hunter enquiry, those established after 1980 were situated higher above the sea level than older ones and higher than neighbouring (<50 km) older populations. Reports on increased use of forest habitats by brown hares were equally frequent among recent and older populations, suggesting a process promoted solely by less harsh winters. Supposed hare hybrids were more often reported from hunting grounds with recent brown hare establishment, i.e. where the species expands in time and in space. In a 27-year dataset on brown hare observations, the recent increased use of forest habitats was supported in that maximum distances to agricultural land for brown hare sightings were higher in mild winters, whereas the proportions of the annual observations made during winter were lower. In 40-year bag records from two Swedish counties, the dynamics of the mountain hare (Lepus timidus) responded positively to snow parameters, whereas brown hares responded negatively. We suggest that the state of mountain hare populations primarily depends on winter conditions and predation pressure, whereas possible effects of hybridization are unclear. If winter conditions remain as in the last 15 years, mountain hare numbers are not likely to increase in southern Sweden, whereas the brown hare may expand even further. In either case, hybrids will occur in sympatric areas in frequencies probably related to the density of the respective true species.     

Hares in Corsica: high prevalence of <Emphasis Type="Italic">Lepus corsicanus</Emphasis> and hybridization with introduced <Emphasis Type="Italic">L. europaeus</Emphasis> and <Emphasis Type="Italic">L. granatensis</Emphasis>

The Italian hare, Lepus corsicanus, was first described in Corsica more than 100 years ago, but the knowledge on the status of the species in this island remains scarce. Moreover, frequent introductions of thousands of individuals from other hare species, namely Lepus europaeus and Lepus granatensis, into Corsica are known to have occurred and an updated assessment of the prevalence of L. corsicanus in Corsica is therefore of utmost importance. Here, to estimate the relative prevalence of the hare species present in Corsica, we conducted a molecular analysis on 67 samples collected by hunters between 2002 and 2007 in 36 Corsican communes. Sequencing of portions of the nuclear gene transferrin and of the control region of the mitochondrial DNA allowed classifying most of the collected samples as belonging to L. corsicanus (70.1%). Of the sampled Corsican communes, 86.1% contained this species, while only in 11.1%, L. europaeus was present. Three of the analyzed specimens showed an inconsistent molecular assignment between markers suggesting a hybrid origin: L. corsicanus × L. europaeus, L. corsicanus × L. granatensis, and L. europaeus × L. granatensis. The first two cases of hybridization had never been described in nature, even in studies focusing on hares from Italy where L. corsicanus and L. europaeus are often sympatric. These results stress the real risk of corrosion of the native gene pool of L. corsicanus via hybridization with introduced species. We highlight the need of urgently rethinking the management plan of hare populations in Corsica.     

Habitat selection and segregation by two sympatric lagomorphs: the case of European hares (<Emphasis Type="Italic">Lepus europaeus</Emphasis>) and Eastern cottontails (<Emphasis Type="Italic">Sylvilagus floridanus</Emphasis>) in northern Italy

In northern Italy, the native European hare (Lepus europaeus) and the introduced Eastern cottontail (Sylvilagus floridanus) can occur together at a local scale, as a result of cottontail introduction and expansion into the European hare range. Hare populations are limited in Italy by habitat loss, diseases, and most important by overhunting, and many areas within hare range in northern Italy are undergoing increasing anthropogenic impact. Therefore, quantitative studies on resource selection and exploitation by both species will be of great interest to evaluate the degree of habitat overlap and to search for exploitation competition evidences. We studied habitat selection during resting time by both species in two areas where they occur alone and in one area where they occur together. Habitat selection by the two species was examined at micro- and macro-habitat scales during autumn–winter and spring–summer. Both species selected ecotonal zones between arboriculture stands and crops and between arboriculture stands and spontaneous vegetation (i.e., herbaceous, bush, and woody permanent species), which were the less available in the area of sympatry. No habitat shifts were evident at macro-habitat level because the two species showed a differential micro-habitat use within patches. On the whole, it seems that habitat heterogeneity promoted daytime segregation between the two species. In particular, edges between crops and canopy habitats should be improved, thus reducing chance of intra- and inter-specific encounters.     

<Emphasis Type="Italic">In vitro</Emphasis> propagation of <Emphasis Type="Italic">Zingiber petiolatum</Emphasis> (Holttum)

Summary We describe an in vitro propagation protocol for Zingiber petiolatum (Holttum), I. Theilade, a rare species from the southern part of Thailand. Fruits were surface-sterilized and seeds germinated on Murashige and Skoog medium (MS) medium supplemented with 3% sucrose. Three-month-old seedlings were used as initial plant material for in vitro propagation. Terminal buds of the plants were inoculated on MS medium containing 6-benzylaminopurine (BA; 2.2–35.5 μM) alone or in combination with 1-naphthaleneacetic acid (0.5 μM). Eight weeks after inoculation, the cultures were transferred to MS medium without plant growth regulators for 4wk. The cultures transferred from MS medium with 17.8 μM BA revealed the highest shoot induction rate of 6.1±0.7 shoots per explant. Rooting was spontaneously achieved in MS medium without plant growth regulators. Rooted plants were successfully transplanted to soil.     

<Emphasis Type="Italic">In vitro</Emphasis> propagation of <Emphasis Type="Italic">Decalepis arayalpathra</Emphasis>, a critically endangered ethnomedicinal plant

Summary This study reports a protocol for successful micropropagation of Decalepis arayalpathra (Joseph and Chandras) Venter. (Janakia arayalpathra Joseph and Chandrasekhran; Periplocaceae), a critically endangered and endemic ethnomedicinal plant in the southern forests of the Western Ghats which is overexploited for its tuberous medicinal roots by the local Kani tribes. Natural regeneration is rare and conventional propagation is difficult. Conservation of the species through micropropagation was attempted. The nodal explants of greenhouse-raised plants, were more desirable than cotyledonary nodal explants of aseptic seedlings. The basal nodes (73%) of 12–16-wk-old greenhouse-grown plants cultured in Murashige and Skoog (MS) medium containing 12.96 μM 6-benzyladenine (BA), 2.48 μM 2-isopentenyladenine (2-ip) and 2.68 μM α-naphthaleneacetic acid (NAA) formed 16–17 cm long unbranched robust solitary shoots in 8 wk. Cotyledonary nodal explants cultured in the same medium showed multiple shoot formation and axillary branching. But the shoots were thin, fragile and not suitable for mass propagation. Single nodes of a solitary shoot subcultured on MS medium containing 2.22 μM BA and 0.24 μM 2-ip together produced 9.8±0.3 nodes from 18.0±0.6 cm long shoots within 5–6 wk. The basal nodes of the shoots so formed were repeatedly subcultured to increase the stock of propagules while the 2.5–3.0 cm terminal cuttings were used for rooting. The best root induction (68%) and survival (86%) was achieved on half-strength MS medium supplemented with 1.07 μM NAA. Field-established plants showed uniform growth and phenotypic similarity to parental stock.     

Reclassification of Two <Emphasis Type="Italic">Peronospora</Emphasis> Species Parasitic on <Emphasis Type="Italic">Draba</Emphasis> in <Emphasis Type="Italic">Hyaloperonospora</Emphasis> Based on Morphological and Molecular Phylogenetic Data

On the family Brassicaceae, the causal agent responsible for downy mildew disease was originally regarded as a single species, Peronospora parasitica (now under Hyaloperonospora), but it was recently reconsidered to consist of many distinct species. In this study, 11 specimens of Peronospora drabae and P. norvegica parasitic on the genus Draba were investigated morphologically and molecularly. Pronounced differences in conidial sizes (P. drabae: 14–20 × 12.5–15.5 μm; P. norvegica: 20–29 × 15.5–22 μm) and 7.8% sequence distance between their ITS1-5.8S-ITS2 rDNA sequences confirmed their status as distinct species. Based on ITS phylogeny and morphology (monopodially branching conidiophores, flexuous to sigmoid ultimate branchlets, hyaline conidia and lobate haustoria), the two species unequivocally belong to the genus Hyaloperonospora and not to Peronospora to which they were previously assigned. Therefore, two new combinations, Hyaloperonospora drabae and H. norvegica, are proposed. The two taxa are illustrated and compared using the type specimen for H. norvegica and authentic specimens for H. drabae, which is lectotypified.     

Comparative Feeding Ecology of Two Sympatric Greenling Species, <Emphasis Type="Italic">Hexagrammos otakii</Emphasis> and <Emphasis Type="Italic">Hexagrammos agrammus</Emphasis> in Eelgrass <Emphasis Type="Italic">Zostera marina</Emphasis> Beds

Synopsis Feeding ecology was compared between sympatric greenling species, Hexagrammos otakii and H. agrammus in the eelgrass beds in Jindong Bay, Korea, from January to December. These two species had similar diets composed of crustaceans, polychaetes, gastropods and fishes; both species consumed primarily crustaceans throughout study periods. H. otakii, however, fed a greater proportion of polychaetes and fishes than H. agrammus. H. agrammus had a greater proportion of gastropods in their diets. The diet of both species underwent size-related changes; smaller individuals of H. otakii and H. agrammus consumed amphipods (gammarid amphipods and caprellid amphipods), while larger individuals of H. otakii ate polychaetes and fishes and those of H. agrammus fed mainly on gastropods and crabs. The diet of H. otakii underwent seasonal changes; H. otakii consumed mainly polychaetes and fishes during January and February 2002 but amphipods during March and May 2002. H. agrammus, however, ate mainly gastropods and crabs all seasons. H. otakii underwent also a significant diel changes that could be related to difference of prey availability. Thus the nocturnal emergence of gammarid amphipods, polychaetes and fishes explained their greater consumption by H. otakii. Dietary breadth of both species was lower in the smallest individuals (<5 cm SL) and in March and April 2002. This was due to the disproportionate dry mass attributable to the consumption of amphipods by both H. otakii and H. agrammus. Dietary overlap of both species was relatively moderate to high, in particular in <9.9 cm SL (0.62 – 0.71) from May to July 2002 (0.63 – 0.71). This is coincident with higher abundances of crabs, caridean shrimps and polychaetes in the study area, and it was assumed that these prey species were not limited resources. Higher dietary overlap was correlated with an abundance of a shared resource and did not indicate the interspecific competition between H. otakii and H. agrammus.     

Redescriptions of the Indo-Pacific atherinid fishes <Emphasis Type="Italic">Atherinomorus forskalii</Emphasis>, <Emphasis Type="Italic">Atherinomorus lacunosus</Emphasis>, and <Emphasis Type="Italic">Atherinomorus pinguis</Emphasis>

The Indo-Pacific marine atherinid fishes Atherinomorus forskalii (Rüppell, 1838), Atherinomorus lacunosus (Forster, 1801), and Atherinomorus pinguis (Lacepède, 1803) are redescribed as valid species based on the types and non-type specimens collected throughout the Indo-Pacific. They are similar to each other chiefly in having a wide midlateral band (almost the same or greater than the midlateral scale width), large mouth (posterior tip of upper jaw reaching to or beyond a vertical through anterior margin of pupil), and no distinct tubercle at the posterior end of the dentary. All three species are distinguishable from congeners by those characters. The three species have long been confused with each other or synonymized erroneously as a single species. Atherinomorus forskalii, known from the Red Sea and eastern Mediterranean, differs from Atherinomorus lacunosus and Atherinomorus pinguis in having conspicuous, large endopterygoid teeth, forming obvious tooth ridges. Atherinomorus lacunosus, widely distributed in almost the entire Indo-Pacific, from East Africa to Tonga, north to southern Japan, and south to northern Australia, differs from Atherinomorus pinguis in having a wider midlateral band (the lower margin reaching to almost the center of the fourth scale row at level of the anal fin origin vs. the lower margin reaching to the ventral end of the third scale row in Atherinomorus pinguis) and more numerous midlateral scales (40–44 vs. 38–41 in Atherinomorus pinguis). Atherina morrisi Jordan and Starks, 1906, Hepsetia pinguis mineri Nichols and Roemhild, 1951, Pranesus capricornensis Woodland, 1961, Pranesus maculatus Taylor, 1964, and Pranesus pinguis ruppelli Smith, 1965, are regarded as junior synonyms of Atherinomorus lacunosus. Atherinomorus pinguis is also widely distributed in the Indo-West Pacific, from East Africa to northern Australia and north to southern Japan. Atherina pectoralis Valenciennes, 1835, is considered a junior synonym of Atherinomorus pinguis. Supplementary material to this paper is available in electronic format at     

<Emphasis Type="Italic">Agrobacterium</Emphasis><Emphasis Type="Italic">tumefaciens</Emphasis>-mediated transformation of callus cells of <Emphasis Type="Italic">Crataegus</Emphasis><Emphasis Type="Italic">aronia</Emphasis>

A genetic transformation system has been developed for callus cells of Crataegus aronia using Agrobacterium tumefaciens. Callus culture was established from internodal stem segments incubated on Murashige and Skoog (MS) medium supplemented with 5 mg l⁻¹ Indole-3-butyric acid (IBA) and 0.5 mg l⁻¹ 6-benzyladenine (BA). In order to optimize the callus culture system with respect to callus growth and coloration, different types and concentrations of plant growth regulators were tested. Results indicated that the best average fresh weight of red colored callus was obtained on MS medium supplemented with 2 mg l⁻¹ 2,4-dichlorophenoxyacetic acid (2,4-D) and 1.5 mg l⁻¹ kinetin (Kin) (callus maintenance medium). Callus cells were co-cultivated with Agrobacterium harboring the binary plasmid pCAMBIA1302 carrying the mgfp5 and hygromycin phosphotransferase (hptII) genes conferring green fluorescent protein (GFP) activity and hygromycin resistance, respectively. Putative transgenic calli were obtained 4 weeks after incubation of the co-cultivated explants onto maintenance medium supplemented with 50 mg l⁻¹ hygromycin. Molecular analysis confirmed the integration of the transgenes in transformed callus. To our knowledge, this is the first time to report an Agrobacterium-mediated transformation system in Crataegus aronia.     

Micropropagation of <Emphasis Type="Italic">Pseudoxytenanthera stocksii</Emphasis> Munro

Summary An efficient and reproducible procedure for the large-scale propagation of Pseudoxytenanthera stocksii is described. High-frequency multiple shoot induction was achieved from nodal shoot segments collected from superior/elite genotypes on Murashige and Skoog (MS) liquid medium supplemented with 1-naphthaleneacetic acid (NAA; 2.68 μM) and 6-benzylaminopurine (BA; 4.40 μM) at 28±1°C and 60 μmol m⁻² s⁻¹ light intensity under 12h photoperiod. In vitro-differentiated shoots were multiplied on MS liquid medium fortified with NAA (2.68 μM), BA (2.21 μM) and additives: ascorbic acid (283.93 μM), citric acid (118.10 μM), cysteine (104.04 μM), and glutamine (342.24 μM). Subculturing was carried out every 2wk on fresh shoot multiplication medium. About 125–150 shoots per culture flask were harvested within 45–50d. In vitro-differentiated shoot clumps (three or four shoots) were successfully rooted on half-strength MS basal liquid medium with indole-3-butyric acid (4.90 μM), BA (0.44 μM), and additives. This is the first report where in vitro- and in vivo-(through tillers) raised clonal plants were acclimatized and established in the field, where they exhibited normal growth.     

<Emphasis Type="Italic">Democricetodon</Emphasis> and <Emphasis Type="Italic">Megacricetodon</Emphasis> (Mammalia,Cricetidae) from the Miocene of Sandelzhausen,Southern Germany

The cricetid species Democricetodon gracilis (Fahlbusch, 1964), Democricetodon mutilus (Fahlbusch, 1964), Megacricetodon bavaricus (Fahlbusch, 1964), and Megacricetodon minor (Lartet, 1851) from Sandelzhausen (Early/Middle Miocene boundary, MN5, Southern Germany) are represented by more than 2,000 molars providing substantial data on the variability in sizes and on variation in morphologies. Temporal and spatial distributions of these species indicate that they are probably immigrants in SE Germany, originating from south-eastern or more southern areas. Except for M. minor, whose origin is not clear and could be regarded as an immigrant from more eastern areas. Using the length of the mesoloph in the second upper molars as an indicator of habitat, D. gracilis and M. minor had a preference for a humid habitat, D. mutilus and M. bavaricus a preference for drier habitats.      

<Emphasis Type="Italic">In vitro</Emphasis> multiplication of heavy metals hyperaccumulator <Emphasis Type="Italic">Thlaspi caerulescens</Emphasis>

A micropropagation protocol through multiple shoot formation was developed for Thlaspi caerulescens L., one of the most important heavy metals hyperaccumulator plants. In vitro seed-derived young seedlings were used for the initiation of multiple shoots on Murashige and Skoog (MS) medium with combinations of benzylaminopurine (BA; 0.5–1.0 mg dm⁻³), naphthaleneacetic acid (NAA; 0–0.2 mg dm⁻³), gibberellic acid (GA₃; 0–1.0 mg dm⁻³) and riboflavin (0–3.0 mg dm⁻³). The maximum number of shoots was developed on medium containing 1.0 mg dm⁻³ BA and 0.2 mg dm⁻³ NAA. GA₃ (0.5 mg dm⁻³) in combination with BA significantly increased shoot length. In view of shoot numbers, shoot length and further rooting rate, the best combination was 1.0 mg dm⁻³ BA + 0.5 mg dm⁻³ GA₃ + 1.0 mg dm⁻³ riboflavin. Well-developed shoots (35–50 mm) were successfully rooted at approximately 95 % on MS medium containing 20 g dm⁻³ sucrose, 8 g dm⁻³ agar and 1.0 mg dm⁻³ indolebutyric acid. Almost all in vitro plantlets survived when transferred to pots.     

<Emphasis Type="Italic">In vitro</Emphasis> flowering of <Emphasis Type="Italic">Perilla frutescens</Emphasis>

This study investigated the factors affecting in vitro flowering of Perilla frutescens. The shoots regenerated from cotyledonary and hypocotyl explants cultured on Murashige and Skoog (MS) medium supplemented with benzyladenine (BA) and indole-3-acetic acid, each at 0.5 mg l⁻¹, were excised and transferred to MS medium containing 30 g l⁻¹ of sucrose, 8.25 g l⁻¹ of ammonium nitrate, and 1.0 mg l⁻¹ of BA. After 40 d of culture, 86.2% of shoots flowered and most of which self-fertilized in vitro and produced mature fruits with viable seeds. These seeds were germinated and plants were grown to maturity and flowered in soil under greenhouse conditions. The in vitro flowering system reported in this study may facilitate rapid breeding of P. frutescens and offers a model system for studying the physiological mechanism of flowering.     

Goldenseal (<Emphasis Type="Italic">Hydrastis canadensis</Emphasis> L.): <Emphasis Type="Italic">In vitro</Emphasis> regeneration for germplasm conservation and elimination of heavy metal contamination

Summary Hydrastis canadensis L. (Goldenseal) is an endangered medicinal plant used in the treatment of many ailments, such as gastrointestinal disturbances, urinary disorders, hemorrhage, skin, mouth and eye infections, and inflammation. Commercial preparations of wild-harvested goldenseal were found to contain heavy metal contaminants including aluminum (848 μgg⁻¹), cadmium (0.4μgg⁻¹), lead (18.7μgg⁻¹), and mercury (0.1 μgg⁻¹). As well, goldenseal is an endangered species listed in the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) Appendix II. Therefore, the practice of wild-harvest is actually decimating natural populations of goldenseal and endangering its genetic diversity. In vitro propagation protocol by tissue culture was developed for producing high-quality tissues of goldenseal. Significantly more de novo regeneration was induced on stem explants of 3-mo.-old plants cultured on a medium containing 10 μM 6-benzylaminopurine (BA) (22 regenerants per explant) than any other treatment. Subculture of the regenerants on a medium devoid of growth regulators resulted in the development of complete plants that were acclimatized and thrived in standard greenhouse conditions. The plants regenerated in vitro contained the lowest levels of heavy metals. The findings of this study provide the first evidence that heavy metal contaminants bioaccumulate in goldenseal tissues and also provide a method for germplasm conservation, mass multiplication, and production of goldenseal tissues free from abiotic contamination.     

Foraging behavior by <Emphasis Type="Italic">Daphnia</Emphasis> in stoichiometric gradients of food quality

Mismatches in the elemental composition of herbivores and their resources can impact herbivore growth and reproduction. In aquatic systems, the ratio of elements, such as C, P, and N, is used to characterize the food quality of algal prey. For example, large increases in the C:P ratio of edible algae can decrease rates of growth and reproduction in Daphnia. Current theory emphasizes that Daphnia utilize only assimilation and respiration processes to maintain an optimal elemental composition, yet studies of terrestrial herbivores implicate behavioral processes in coping with local variation in food quality. We tested the ability of juvenile and adult Daphnia to locate regions of high-quality food within a spatial gradient of algal prey differing in C:P ratio, while holding food density constant over space. Both juveniles and adults demonstrated similar behavior by quickly locating (i.e., <10 min) the region of high food quality. Foraging paths were centred on regions of high food quality and these differed significantly from paths of individuals exposed to a homogeneous environment of both food density and food quality. Ingestion rate experiments on algal prey of differing stoichiometric ratio show that individuals can adjust their intake rate over fast behavioral time-scales, and we use these data to examine how individuals choose foraging locations when presented with a spatial gradient that trades off food quality and food quantity. Daphnia reared under low food quality conditions chose to forage in regions of high food quality even though they could attain the same C ingestion rate elsewhere along a spatial gradient. We argue that these aspects of foraging behavior by Daphnia have important implications for how these herbivores manage their elemental composition and our understanding of the dynamics of these herbivore–plant systems in lakes and ponds where spatial variation in food quality is present. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.