Foraging behaviour of gregarious Mediterranean water shrew Neomys anomalus was investigated in 7 individuals. Shrews were tested individually and in a 4-animal-group in a terrarium. Shrew behaviour was recorded in darkness using 2 infra-red sensitive video-cameras. Two experimental variants, with and without natural structures in the terrarium, were established. When foraging individually, N. anomalus consumed only few food portions at the places of finding. Shrews hoarded most food in the nest and/or in hiding-places and ate it under cover. The presence of natural structures caused hoarding and eating of food in scattered hiding-places, instead of carrying it to the nest. During group foraging, N. anomalus did not hoard food communally, and preparation of individual stores almost ceased. In all tests, they ate successively more food items at the places of finding as the duration of foraging increased.

Time—energy budgets (TEB) of Gambel's Quail (Callipepla gambelii) were compiled during two summers in the Colorado Desert of California. Quail spent 6.77 h/d foraging, 6.2 h/d inactive during daylight hours, and 11.02 h/d inactive at night. Field metabolic rate (FMR) calculated from this activity budget was 81.8 kJ/d. Of this, 47.3 kJ/d was expended during foraging, 12.6 kJ/d in daytime inactivity, and 20.4 kJ/d in nighttime inactivity. Despite the extremely hot thermal environment (maximum ambient temperature °45°C), there was no energy cost above resting levels for thermoregulation. FMR was also measured simultaneously with doubly labeled water (DLW), and averaged 90.8 kJ/d. TEB and DLW values agreed to within 6% when differences in measurement period were taken into account. A laboratory validation study indicated that DLW and balance methods agreed to within 5%. The FMR of C. gambelii was only 40% of that predicted for a bird of its body mass. This low FMR is primarily the result of a low resting metabolic rate (RMR): 51% of the predicted basal rate in 1981, and 70% of predicted in 1982. The basis and significance of this low and variable RMR are unclear. Energy assimilation efficiency, measured in laboratory feeding experiments with a mixed seed and arthropod diet, was 60.3%. An individual quail in the field thus required 150.3 kJ/d in its diet, representing a dry matter intake of 8.1 g/d. A diet of seeds alone provides insufficient water for Gambel's Quail in summer, so they must either incorporate moist food items in their diet or drink free water. It was calculated that over the course of a year, a population of Gambel's Quail consumes seeds with a total energy content °15% as great as that in seeds consumed by a population of desert rodents or harvester ants in the same area. Gambel's Quail thus may be important factors in the competition for resources among desert granivores, particularly because they can eat one of their competitors (harvester ants).

Freshwater food webs are dominated by aquatic invertebrates whose trophic relationships are often poorly known. Here, I used laboratory experiments to study the role of a water bug, Sigara striata, as a potential predator and prey in food webs of stagnant waters. Multiple-choice predation experiment revealed that Sigara, which had been considered mostly herbivorous, also consumed larvae of Chironomus midges. Because they often occur in high densities and are among the most ubiquitous aquatic insects, Sigara water bugs may be important predators in fresh waters. A second experiment tested the role of Sigara as a potential prey for 13 common invertebrate predators. Mortality of Sigara inflicted by different predators varied widely, especially depending on body mass, foraging mode (ambush/searching) and feeding mode (chewing/suctorial) of the predators. Sigara was highly vulnerable to ambush predators, while searching predators caused on average 8.1 times lower mortality of Sigara. Additionally, suctorial predators consumed on average 6.6 times more Sigara individuals than chewing predators, which supports previous results hinting on potentially different predation pressures of these two types of predators on prey populations. The importance of these two foraging-related traits demonstrates the need to move from body mass based to multiple trait based descriptions of food web structure. Overall, the results suggests that detailed experimental studies of common but insufficiently known species can significantly enhance our understanding of food web structure.

Food selection by adult red foxes Vulpes vulpes was studied in a mountainous environment characterised by fluctuating populations of water voles. According to optimal foraging theory, the diets of adults and cubs should be similar during vole highs, with voles as staple prey. On the other hand, a difference should occur when water voles become scarce. Adults should then bring larger alternative prey to their cubs, and consume smaller prey at the capture site. Adult and cub scats were collected around breeding dens during a 6‐year period, from the peak to a near‐extinction phase of the water vole population, and analysed. As predicted by the optimal foraging theory, no significant difference was found between the diets of cubs and adults when voles were abundant. Furthermore, cubs consumed a higher proportion of large alternative prey, i.e. lagomorphs, than adults in the first year of low vole density. Unexpectedly, this difference did not persist the following years despite the water vole scarcity. The consumption of large alternative prey at the den decreased significantly, whereas the consumption of small alternative prey, i.e. invertebrates, increased. Consequently, the composition of prey brought to the den was similar to that consumed at the capture site. Food selection was probably affected by the unpredictability of large prey availability and accessibility. It is suggested that if small alternative prey proves less profitable to the cubs than large prey, a long‐lasting shortage of water voles could possibly become a factor regulating fox numbers in the area studied.

The availability of multiple sources of food and drink has a profound influence on choice behavior in rodents. It is not known how other taxa might respond to the same kind of variation in availability. We tested European starlings (Sturnus vulgaris) with various combinations of unadulterated and repellent-treated (0.025% citronellyl acetate) resources. In Experiment 1, birds drank more plain than repellent-treated water than when given (a) 2 bottles of plain water and 2 of repellent-water, or (b) 3 bottles of plain water and 1 of repellent-water. However, they drank more repellent than water when given 3 bottles of repellent-water and 1 of plain water. Thus, the aversion to the repellent became indifference when repellent-water was abundant. In Experiment 2, birds ate more untreated than treated food when given (a) 1 cup of untreated food and 1 cup of treated food or (b) 2 cups of untreated food and 1 of treated food. They ate equal amounts of untreated and treated food when given 1 cup of untreated food and 2 cups of treated food. These results demonstrate the effect of relative availability on choice, and imply that availability should be considered when using repellents.

1. Colonies of the social caterpillar Eutachyptera psidii (Sallé) (Hymenoptera: Lasiocampidae) occurring on oak (Quercus) in upland forests of Mexico endure periods as long as 6 weeks, with little or no food or water between the time host trees shed their leaves in April and produce new leaves in June. 2. By monitoring the activity of both field and laboratory colonies with infrared activity monitors and data loggers, it was found that although colonies remain active during the period of deprivation, their foraging activity shifts from once nightly when food is available to once every second night when food-deprived. 3. Over a period of absolute food and water deprivation of 18 days, caterpillars lost an average of 36% of their initial mass but none perished. On average, the caterpillars regained their pre-starvation mass within a few days after food was provided and continued to grow thereafter. During the period of starvation, caterpillars were observed to chew on dead and dried leaves in the field and on sheets of paper in the laboratory. 4. To the authors' knowledge, there is no other documented instance of a species of caterpillar that exhibits the physiological capacity to engage in a similar level of persistent activity when forced to endure a prolonged period with neither food nor water.

Anopheles gambiae larvae have frequently been observed to dive, but the ecology of this behavior has not been extensively examined. We manipulated food level, water depth, and temperature for individually-reared larvae and observed diving activity. Larvae dived more often under low food, which suggests that they dive to forage. There was only weak evidence for effects of water depth or temperature on diving. Experimental results are discussed in the context of energy budgets. Understanding larval ecology of this species is important for predicting how it will respond to environmental change. Further study is needed to assess the role that larval diving plays in both feeding ecology and thermal regulation of this and other medically important species.