From breeding pairs to fox towns: the social organisation of arctic fox populations with stable and fluctuating availability of food

Food availability can impact group formation in Carnivora. Specifically, it has been suggested that temporal variation in food availability may allow a breeding pair to tolerate additional adults in their territory at times when food abundance is high. We investigate group occurrence and intraspecific tolerance during breeding in a socially flexible canid, the arctic fox (Vulpes lagopus). We compare Iceland and Sweden where resource conditions differ considerably. A breeding pair was the most common social unit in both populations, but as predicted, groups were more frequent where food abundance varied substantially between years (Sweden: 6 %) than where food availability was stable (Iceland: ≤2 %). Within Sweden, supplemental feeding increased group occurrence from 6 to 21 %, but there was no effect of natural variation in lemming (Lemmus lemmus) availability since group formation was rare also at lemming highs. Thus, additional factors appeared to influence the trade-off between intraspecific territoriality and tolerance. We report two cases where related females showed enduring social relationships with good-neighbour strategies. Related females also engaged in alloparental behaviour in a ‘fox town’ with 31 foxes (4 adults, 3 litters). In contrast, when unrelated foxes bred close to each other, they moved or split their litters during summer, presumably because of territorial conflict. We suggest that fluctuating food availability is linked to group formation in this Arctic carnivore, but also when food availability increases, additional factors such as relatedness, alloparental benefits, competition and predator defence appear necessary to explain group formation.     

Fitness consequences of cannibalism in the fall armyworm, Spodoptera frugiperda

We investigated the consequences of cannibalism for some correlatesof fitness in the fall armyworm, Spodoptera frugiperda (Lepidoptera: Noctuidae).The benefits gained by cannibals were ascertained by comparing survival,development rate, and pupal weight of larvae that had the opportunityto cannibalize with those that did not, at two levels of food availability.Larvae in the cannibalism treatments were provided with a conspecificone instar younger than themselves on five dates throughoutlarval development. Cannibalism was frequent; given the opportunityall larvae predated at least one younger conspecific. The frequencyof cannibalism was not affected by the sex of the cannibal orby the availability of alternative food. However, cannibalssuffered a significant reduction in survival at both high andlow food availability. Furthermore, cannibals had a lower pupal weightin the high food treatment and a reduced development rate inthe low food treatment. The only detectable fitness benefitassociated with cannibalism was a positive correlation betweenthe number of victims consumed and development rate under conditionsof low food availability. On balance, cannibalism appears tobe costly; alternative explanations for its occurrence in thisspecies are discussed.     

Effects of food availability and ambient temperature on hibernation in the Japanese dormouse,Glirulus japonicus

The effects of food availability and ambient temperature (Ta) on hibernation in the Japanese dormouse,Glirulus japonicus, were examined. When the dormice were deprived of food under natural environmental conditions in midwinter, they showed typical hibernation patterns; in contrast, the animals given ad lib food did not show continuous long-term torpor. Furthermore, exposure to constant low temperature did not affect the torpor patterns in the animals receiving adequate food. These results suggest that food availability plays a decisive role in the onset and maintenance of hibernation in this species, and that low Ta does not have a great influence on the torpor patterns in animals with access to food. This differs from the previous study that emphasized the importance of Ta in the occurrence of torpor and discounted the effects of food shortage.     

Dry Season Diet of the Sloth Bear (Melursus ursinus) in Hadagarh Wildlife Sanctuary,Eastern India

Dry season food habit of sloth bear (Melursus ursinus) in Hadagarh Wildlife Sanctuary was characterized by scat analysis. Importance value index (IVI) of contribution of different food items in the diet of sloth bear was estimated from the undigested food remnants. Percentage of dry weight and IVI score of Ziziphus fruits was highest, termites were the most frequently occurring food item in the diet and percentage of frequency occurrence was equal for both fruits and insects. The present study, as compared to previous studies, suggests that the dietary preference of sloth bear varies according to availability of food and the habitat quality.     

The effects of food presentation at regular or irregular times on the development of activity-based anorexia in rats

Activity-based anorexia occurs when food availability is restricted to 1 h of the day and a wheel is freely available to the rest of the time. Under such conditions rats run excessively and stop eating even during periods in which food is available. A defining characteristic of the excessive activity is that there is a peak of running in the anticipation of food availability. The present study was designed to test whether the occurrence of the food period at different times of the light phase of the light-dark cycle (from 08:00 to 20:00 h) could impede or postpone the normal development of activity anorexia. We compared the effect of presenting the food at a fixed time of the light period with presenting it on a variable schedule. Far from impeding or postponing the development of activity-based anorexia, presenting food at irregular times resulted in a pronounced body-weight loss, a low food intake and an increase in locomotor activity. Animals ran excessively, with a peak at the start of the dark period, and again when lights were turned on in the experimental room (running in the anticipation of food). Both fixed and variable schedules of food availability resulted in the development of activity-based anorexia in rats.     

Effect of hunger on the drinking behaviour of rodents adapted for mesic and xeric environments

Observations of drinking behaviour were taken on six rodent species during fasting. Four of these species were wild-caught and had not previously been examined for food deprivation polydipsia (FDP). These data support an hypothesis that a negative correlation exists between water availability in the natural habitat and the occurrence of FDP. Namely, xerophilous species exhibit an absolute polydipsia during food deprivation while mesically adapted species evidence depressed water consumption. Urine analyses during food deprivation indicated substantial decreases in electrolyte and osmotic pressure concentrations in all species. The drinking patterns of the three desert species investigated are discussed with reference to the availability of green vegetation in the natural habitat; however, there is presently no explanation for the observed polydipsia.     

Flowers, fruits, and the abundance of the yellow-chevroned parakeet (Brotogeris chiriri) at a gallery forest in the South Pantanal (Brazil).

Parakeets usually forage for massive and ephemeral plant resources at forest canopies. Fruit pulp is widely cited as a major food resource for these birds, which often eat seeds and nectar. In this study, I assessed flower and fruit production at a gallery forest in the Pantanal flood plain (Brazil) in order to evaluate the relationship between food resource production and abundance of a common parakeet, Brotogeris chiriri. Also, I evaluated the relationship between food resource production and foraging activity. Parakeet abundance varied markedly along the year, coinciding with massive episodes of flower and fleshy fruit availability. Inga vera nectar, intensely used during the latter part of dry season, was by far the most exploited food item by parakeets when they were very abundant. The nectar comprised 34% of the parakeets' diet (N = 131 feeding records) at the gallery forest, while fleshy fruits made up the rest. Parakeets principally exploited fruits of Cecropia pachystachya and Ficus luschnathiana, besides palm fruits and Inga vera arils. The consistent relationship between foraging activity and parakeet abundance, as well as the coincidence between fluctuations of these parameters and availability of major food resources, suggests that food availability mostly influenced B. chiriri occurrence in the gallery forest. Furthermore, I found no evidence for gallery forest use for roosting and/or breeding, in spite of the fact that such factors usually influence local parakeet abundance.     

Seasonal variations in feeding range and flock structure of the Rook Corvus frugilegus in eastern Ireland

The feeding range and flock structure of Rooks showed temporal variations caused mainly by the dispersion of food and reproductive behaviour.
Feeding range was restricted in spring, autumn and early winter when food availability was high and Rooks were reproductively active. A large feeding range occurred in late summer and late winter, when food availability was either generally low or locally distributed and when Rooks were reproductively inactive. The occurrence of flocks common to several rookeries mirrored variations in feeding range; mixed rookery flocks were more common in late summer and late winter. Similarly, the size of the rookery (as measured by the number of nests) was related to feeding range only when Rooks were reproductively inactive and at such times larger rookeries had greater feeding ranges.
Flock structure showed similar seasonal variations; small widely spaced flocks predominated in summer, autumn, early winter and spring, whereas large dense flocks occurred in late winter. Diurnal variations in flock structure occurred within any one season. Both seasonal and diurnal variations in flock structure may be determined by the dispersion of the prey and the feeding strategy used to obtain it, reproductive behaviour and the risk of predation.     

Feeding biology of a habitat-forming antipatharian in the Azores Archipelago

Coral Reefs - Benthic suspension feeders have developed a variety of feeding strategies and food availability has often proven to be a key factor explaining their occurrence and distribution. The...     

Nectar-feeding by suburban Blue Tits: contribution to the diet in spring

The incidence of nectar feeding by 2 pairs of Blue Tits Parus caeruleus was investigated in relation to the availability of nectar and alternative food. Nectar was not the most preferred food and the occurrence of nectar feeding did not correlate significantly with most measures of nectar availability, but the Blue Tits selected the most productive flowers. Nectar feeding frequently occurred when the preferred peanuts were unavailable due to interspecific competition. The nectar resource was under-utilized by the Blue Tits except at the beginning of the flowering period. Despite this, nectar was a highly profitable food source, yielding 0.33-0.38 kJ min^?1 foraging. During the flowering period nectar was estimated to contribute up to 32.7% of the average daily metabolic rate (ADMR) of the male and up to 49.3% of the ADMR of the female, with means over the 2 years of 7.4% and 13.2% per day for the male and female, respectively. The importance of nectar in the ecology of Blue Tits is discussed.     

Variation in the feeding pattern of red foxes in relation to changes in anthropogenic resource availability in a rural habitat of western Poland

The feeding pattern of red foxes Vulpes vulpes, i.e., the composition of their diet and dietary responses to fluctuations in the abundance of common voles Microtus arvalis were compared in the periods before and after the limitation of anthropogenic food availability in a rural area in western Poland. During the winter seasons of 1996/97–2014/15, the diet of the foxes was estimated by analysing the stomach contents of individuals shot from November to March and the index of vole abundance was obtained by counting their burrow entrances. The major component of the fox diet over the entire study period was anthropogenic food (mainly, the remains of farm animals) that showed both the highest average proportion in the stomach content volume (53.4%) and the highest average frequency of occurrence in the stomachs (62.7%), whereas small mammals were the second important component (27.5% and 54.2%, respectively). The frequency of anthropogenic food decreased and the frequencies of wild ungulate carrion and other wild vertebrates (mainly birds) increased after the limitation of anthropogenic resources. The observed fluctuations in the index of vole abundance resulted in positive changes in the small mammal frequency and negative changes in the anthropogenic food frequency, but the course of these relationships did not significantly differ between the two periods. The frequency of hares in fox stomachs did not change significantly between these periods, but recently the occurrence of hares in the diet of foxes increased with vole abundance. This study indicated that the reduction of anthropogenic food availability for carnivorous mammals may result in their switching to other prey species and potentially may have a negative influence on the demography of such prey species.     

Annual and seasonal trends in the use of garden feeders by birds in winter

Provision of bird food in gardens is a common activity that may provide an alternative food source to birds in winter. Long-term survey data recording the weekly presence of all bird species using garden feeders in the winter were analysed to see if there was any evidence of trends in feeder use between 1970 and 2000 and whether these trends were correlated with breeding bird population trends. Of 41 species analysed, 21 showed significant increases in occurrence at garden feeders between 1970 and 2000. Many of these increases were evident only in the last 10 years. Several species showed significant positive correlations between trends in winter garden use and trends in relative population size in the previous breeding season. This was especially the case for species with population change (either increase or decrease) of the greatest magnitude. There was no evidence that seasonal shifts in garden feeder use were associated with population change in any species. Temperature was an important predictor of garden use but could not explain the year-to-year trends. However, as the number of feeding stations had increased over time the response of birds to the greater food availability in gardens may have been responsible for the widespread increases in occurrence of several species.     

Habitat-mediated cannibalism and microhabitat restriction in the stream invertebrate <Emphasis Type="Italic">Gammarus pulex</Emphasis>

In cannibalistic species, small individuals often shift habitats to minimize risk of predation by larger conspecifics. The availability of diverse size-structured habitats may mediate the incidence of cannibalism by larger individuals on smaller individuals and increase fitness of smaller individuals. We tested these hypotheses in a series of laboratory studies with Gammarus pulex, a freshwater amphipod inhabiting substrates with varying interstitial pore space sizes. In the absence of larger, potentially cannibalistic individuals, small Gammarus actively used all pore space sizes offered. They used only substrates containing food and preferred food items that provided cover to food items that did not. In the presence of larger G. pulex, small individuals almost exclusively used smaller pore spaces from which larger individuals were excluded. Small individual survival was significantly lower in the presence of larger Gammarus than in controls without larger individuals regardless of substrate size, but availability of mixed pore sizes significantly increased survival. Food consumption and growth per individual were not affected by the presence of larger individuals or substrate composition. Our results suggest that the distribution and availability of complex and high-quality habitats may affect the occurrence and significance of cannibalism in size-structured populations. Handling editor: K. Martens     

Seasonal change in the food habits of the Iriomote catFelis iriomotensis

The food habits of the Iriomote catFelis iriomotensis were studied by analyzing 177 feces collected monthly from 1987 to 1988. A total of 26 food items were identified. The frequency of lizards and frogs in the feces was higher than those of mammals and birds. The food habits changed greatly seasonally.Eumeces skinks were fed on most frequently, and found in the feces with a similar high frequency occurrence in March–April and July–September, while their proportion to the total number of food items was larger in March–April than in July–September. The cats fed on larg-sized skinks, adultEumeces kishinouyei, more in March–April than in other seasons. The number of skinks sighted in the course of a road census was greater from March to August, and large-sized skinks were sighted more in March–April than in July–August. The cats fed selectively on large-sized skinks in every season. Therefore, changes in the food habits depended on the food availability. Characteristics of food habits in the Iriomote cat are discussed in comparison with the food habits of other felids in temperate and tropical regions.     

Multi-annual variation in the diet composition and frugivory of the Japanese marten (Martes melampus) in western Tokyo,central Japan

To examine multi-annual variations in the food habits of the Japanese marten (Martes melampus), we analyzed the composition of marten feces in the Bonbori Forest Path in western Tokyo, central Japan, in two time periods a decade apart (1997–1998 and 2007–2008). The staple foods of martens in both periods were fruits/seeds and animal materials (mainly insects and mammals). The martens fed frequently on fruits/seeds and insects throughout the year in both periods, but the consumption of mammals, birds, and arthropods/other animals showed seasonal variations. The composition of fruits/seeds and the frequency of occurrence for each fruit-bearing species differed between the two periods. These results suggest that both the foraging strategy and role of martens as a seed dispersal agent changes yearly, presumably according to multi-annual variation in the availability of prey animals and/or fruits. We emphasize the importance of multi-annual studies both on food habits and to monitor food availability in the temperate region where the food environment changes among seasons, as well as years.     

Food niche overlap and ecological separation in a multi-species community of shrews in the Siberian taiga

An investigation of the feeding habits and prey availability in a community of seven species of shrew (Insectivora: Soricidae) inhabiting the taiga of Central Siberia was carried out with the aim of quantifying levels of niche overlap and elucidating modes of ecological separation amongst these coexisting species. All species took a wide range of invertebrate prey, and overlap in the numbers of shared prey taxa was high, but differences in dietary composition of certain taxa reduced overlap between most species. Small species fed almost exclusively on small arthropods, mostly Araneae, Chilopoda and Coleoptera, while medium and large-sized species took high proportions of oligochaetes. Prey were mostly taken in proportions approximately equal to their availability, although certain prey appeared to be selected. All shrews took prey in a range of sizes, and the high dietary occurrence of small invertebrates reflected their availability and high encounter rate in field samples. Dietary occurrence of small prey was negatively correlated, and large prey positively correlated, with body size of shrew. Smaller shrews were predominantly ground-surface foragers while larger species were more subterranean, with body size and dietary occurrence of soil prey being positively correlated. Differences in prey size and foraging mode reduced niche overlap between shrew species of widely differing sizes. Each shrew species did not occupy a separate, well-defined food niche. Instead, the community was sub-divided into three functional groups: large and small species which tended towards specialization with relatively low levels of overlap, and intermediate, generalist species with higher levels of overlap.     

Effect of resource gradient on age and size at maturity and their influence on early‐life fecundity in the predatory Asian lady beetle,Harmonia axyridis

Variation in food availability impacts the performance of insects in terms of their size and age to maturity and fecundity. Age at maturity determines how quickly individuals in a population can start to reproduce and how much they can reproduce. Results from studies on various insect species show that food availability influences the size and fecundity of adult females. It is predicted that under poor growth conditions, variation in size is low, but variation in age at maturity is considerable. This prediction was examined in a widely distributed lady beetle species, Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae), a predator of aphids and coccids. Using a food gradient from low to high aphid prey density, performance of females that were reared on excess food was recorded for pre‐reproductive duration, size at reproductive maturity, number of aphids consumed, and fecundity in the first 10 days of their reproductive period. Results suggested that female H. axyridis that were reared on surplus food when kept at low prey density (poor growth condition) took, on average, three times longer to attain maturity and produced, on average, 14 times fewer eggs than females that were also reared on surplus food, but kept at high prey density (good growth condition). Females performed best at a prey density of 30 aphids per female per 150 cm². Results suggested that the current food availability significantly influenced the age and size of females at maturity and their fecundity. Age and size at maturity of female lady beetles showed non‐linear responses to prey density as well as the occurrence of a minimum size of females, below which H. axyridis females fail to mature. The steep slope recorded at lower prey densities suggests relatively high variation in age at maturity but low variation in size.     

Food supply and breeding occurrences: the West European population of the lekking great snipe Gallinago media (Latham, 1787) (Aves)

For species with very high energetic costs during reproduction we expect occurence during the reproduction season to be dramatically affected by the availability of energy. Recent studies have shown very high energetic costs of lekking for great snipe males, Gallinago media (Latham, 1787) and that breeding great snipes prefer to feed in soft soil with a high abundance of earthworms. We here evaluate the hypothesis that the breeding occurrence of great snipe is restricted to areas with very high availability of food. All the 125 registered great snipe leks in Scandinavia were situated in open habitats along the tree line. The occurrence of leks were analysed in relation to bedrock quality, soil chemistry and earthworm biomass. There was a strong positive relationship between soil pH and earthworm biomass. High pH values were found on or in the close vicinity of base-rich bedrocks. No great snipe leks were documented in areas with acid soil, even if the extent of acid bedrocks along the tree line predicts that 31% of the leks should be situated on acid soils. Hypotheses, including both natural and sexual selection, for why breeding occurrence of great snipe is restricted to areas with high abundance of high quality food are evaluated, and we find indications for this to be a consequence of the very high energetic costs for the lekking males. These costs have probably evolved through female mate choice and indicate that sexual selection may have important consequences for a species distribution. Population-level effects of sexual selection have previously received little attention. The stringent habitat demands here documented may also make great snipes vulnerable to environmental changes and can contribute to explain the dramatic reduction in breeding range of this species in western Europe during the past 150 years (Løfaldli et al ., 1989).     

Behavioral responses to combinations of timed light, food availability, and ultradian rhythms in the common vole (Microtus arvalis)

Light is the main entraining signal of the central circadian clock, which drives circadian organization of activity. When food is made available during only certain parts of the day, it can entrain the clock in the liver without changing the phase of the central circadian clock. Although a hallmark of food entrainment is a behavioral anticipation of food availability, the extent of behavioral alterations in response to food availability has not been fully characterized. The authors have investigated interactions between light and temporal food availability in the timing of activity in the common vole. Temporally restricted food availability enhanced or attenuated re-entrainment to a phase advance in light entrainment when it was shifted together with the light or remained at the same time of day, respectively. When light-entrained behavior was challenged with temporal food availability cycles with a different period, two distinct activity components were observed. More so, the present data indicate that in the presence of cycles of different period length of food and light, an activity component emerged that appeared to be driven by a free-running (light-entrainable) clock. Because the authors have previously shown that in the common vole altering activity through running-wheel availability can alter the effectiveness of food availability to entrain the clock in the liver, the authors included running-wheel availability as a parameter that alters the circadian/ultradian balance in activity. In the current protocols, running-wheel availability enhanced the entraining potential of both light and food availability in a differential way. The data presented here show that in the vole activity is a complex of individually driven components and that this activity is, itself, an important modulator of the effectiveness of entraining signals such as light and food.     

Variations in bark-stripping by red deer Cervus elaphus across Europe

• 1 The literature on bark‐stripping by red deer Cervus elaphus in Europe is reviewed to reveal quantitative variation in this behaviour and relate it to deer density and local characteristics such as dominant tree species, occurrence of artificial feeding, altitude, region and size of the study site. We also review the importance of bark in red deer diets over the seasons and discuss the causes of bark‐stripping, focusing on the significance of bark as food.
• 2 Over the 36 sites examined, the rate of bark‐stripping was highly variable (from 0 to 84% of susceptible trees debarked), with less damage in Scotland than in other European sites for which bark‐stripping rates were higher at high red deer density. Altitude, the size of the study site, the number of dominant tree species and the occurrence of artificial feeding do not significantly relate to the rate of bark‐stripping.
• 3 Bark sometimes made up a large proportion of red deer diet (> 10%), especially in areas with severe winters (high levels of snow), whereas in study sites with mild winters, bark was practically not eaten at all.
• 4 These results suggest that severe bark‐stripping could be related to a reduction in food resource availability. This food availability hypothesis needs to be better documented, dealing particularly with the possible interaction between food availability and red deer density.