Daily Foraging Research Articles

Function of Notification in Papio hamadryas

Notification is a form of ritualized greeting behavior performed by adult male hamadryas baboons (Papio hamadryas). Originally observed in the wild when harem leaders signaled the direction of travel to their followers on daily foraging marches, its true function is unknown. Notification involves the approach of an adult male baboon to another male, the presentation of his hindquarters, then retreat. Researchers have previously linked notification to aggression avoidance, appeasement, and the dominance-subordination relationship between males. We observed instances of notification over 6 mo among 8 adult males in a troop of 61 captive-bred hamadryas baboons at Paignton Zoo Environmental Park, Devon, UK. We compared observation sessions in which notification occurred with matched control periods. We classified different forms of notification according to the recipient’s response: presenting, mounting, touching of the buttocks or genitals, or ignoring. Results suggest that different forms of notification may have different functions, including submission, alliance, and peacekeeping but not general greeting, recruitment, or appeasement.

Working the Post with Big Jim McKean

76 Working the Post with Big Jim McKean The animals in this neighborhood are waiting for someone to talk to them. Pretty soon they’ll get the picture: we no longer know enough to see ourselves in their daily foraging. Or in the red-tail hawk propped like a boy’s favorite toy on the top shelf of an old oak, peering longingly into the mute field of this ritzy campus. What’s this got to do with basketball, with four aging poets enacting a slowed-down, heat-drenched game of two-on-two? Nothing, everything. I’m down on the post, giving up seven inches and fifty pounds to Big Jim McKean, who keeps backing me down, putting me on his hip, rotating left, right, the eight-foot hook there every time. Lucky he’s rusty. Who cares if he’s twenty years my senior— he’s still got textbook moves he tried once on a young Cassie Russell, on Kareem when he was still Lew Alcindor. He times my shot and swats it at the release. This morning a rabbit blurred back into the bushes. Tiny brown squirrels darting under the trees. A house sparrow pecked at field-house garbage. Just once I get Jim, if not off his feet then off his balance, and take him left. When he reaches out, I show him my younger brother lefty scoop. for Jon Pineda, for Kym Ragusa Sebastian Matthews 77 Sebastian Matthews But only Alan’s in shape for all this stop and start; it’s up to him to hit his shots. Bob’s a natural but one step off the pick and roll. There’s nothing to do for the three pigeons caught inside the fenced-in power station but offer a small prayer; to transform the smoke alarm battery squawking all night into a dream hawk caught in a snare. This morning Alan used one of my poems to show a student how he might cut against the rhapsodic he wears like a Hawaiian shirt. And how to— unlike the poem’s last two lines—avoid falling off emotion’s cliff edge. Let me leave you not with the hawk, nor with Jim limping doggedly off court, but with Bob riding shotgun in someone’s car, grinning. Outside after a long, loud dinner, just beginning to feel sore, I stick out my thumb jokingly for a ride. As he floats by, Bob mouths, gleefully, “Fuck you!” then flips me the bird. Bill Matthews ...

Flower characteristics and visitors of Merremia macrocalyx (Convolvulaceae) in the Chapada Diamantina, Bahia, Brazil

Merremia macrocalyx (Ruiz & Pav.) O’ Donell (Convolvulaceae) is a common, native herb in open grasslands (Campos Gerais) of northeastern Brazil. At Pai Inácio Mountain, Chapada Diamantina, Bahia, Brazil (12º 27´41”S, 41º 28’ 34”W), we made daily observations from 6:30 a.m. until 5:30 p.m. from 25 April to 29 April, 2003 and on May 31, 2005. The stereomorphic corolla of the weakly scented flowers was 4.04 mm mean diameter, tube depth was 3.12 mm, and the mean diameter of the gullet was 1.17 mm. Anthesis is diurnal, between 06:30 a.m. and 07:45 a.m. and floral longevity varied between 9-10 h. Nectar secretion occurred from 7:00 a.m. to 11:00 a.m., and the standing crop of nectar per flower increased from 0.67 ml (7:00 a.m.) to 2.5 ml (09:00 a.m.) then declining. The nectar sugar concentration was low (22%). Bees were the most frequent visitors, and were classified into six morpho-functional categories. Their daily foraging pattern was synchronized with nectar availability, being concentrated between 8:30 and 10:30 a.m. The clumped distribution of the plants, flower size and easily accessible nectar all stimulate visitation, especially by generalist bee species. Eusocial bees (A. mellifera, Geotrigona mombuca and Bombus morio) and the solitary bee Euplusia nigrohirta (Friese, 1899) were the most frequent on the flowers and are the most likely potential pollinators, as suggested by their contact with floral reproductive structures and adhesion of pollen to their bodies.
 Keywords: Merremia macrocalyx, Apoidea, flower biology, pollination, bees.

Daily movement and territory use by badgers Meles meles in Białowieża Primeval Forest, Poland

We used radio-telemetry to study movement and territory use by 13 Eurasian badgers Meles meles in a well-preserved continuous woodland of Białowieża Primeval Forest (BPF), Poland. Daily movement distance (DMD) of badgers averaged 7 km, and daily range (DR) covered 2.1 km2, i.e. 19% of their total home-range size. DMD and DR varied seasonally, being largest in summer when the availability of food resources was lowest. DMD was positively correlated with home-range size of badgers and the duration of their daily activity. Badgers moved with an average speed of 0.9 km/hour (maximum 7.1 km/hour). Nevertheless, travel speed was more than twice as fast after the emergence and before the return to the sett than during the peak of badger activity. This behaviour suggests that badgers moved directly to well-known and well-defined feeding patches. Indeed, we also found that the lengths of daily foraging routes was positively correlated with the number of patches of oak Quercus robur-lime Tilia cordata-hornbeam Carpinus betulus forests in a territory (ranging within 1–11), habitat which presents the highest earthworm abundance in BPF. Adult badgers of both sexes visited territory boundaries significantly more often than subadult individuals. Consecutive nightly ranges of badgers overlapped by 24%, which may indicate a rotational way of area use in order to defend large territories. Review of available data on mobility of badgers showed that mean daily movement ranged from 1.2 km in England to 7.0 km in our study. DMDs were positively correlated with home-range size. Average speed of badger movement varied from 0.3 km/hour in Spanish badgers to 1.1 km/hour in Swiss badgers. Our local data as well as the review of other European studies suggest that it is the length of the daily foraging routes that links food resources and home-range size. In areas with low abundance of earthworms and/or widely dispersed foraging patches, badgers move longer distances, cover larger daily ranges and defend large territories.

Minimal diurnal change in foraging time in an Australian passerine, the white‐browed babbler Pomatostomus superciliosus

This paper describes the daily foraging pattern of the white‐browed babbler Pomatostomus superciliosus, a small passerine endemic to Australia. The percentage of time spent foraging as the day progressed increased by an average of only 9%. This contrasts markedly with studies of other passerines that have mostly shown a bimodal pattern, with a peak of foraging early in the day followed by a period of reduced activity and a second peak later in the day. The most likely explanation for the observed pattern of foraging time is that babblers experienced considerable diurnal certainty in their food supply mainly as a result of stable and predictable weather conditions. The lack of a marked increase in foraging towards the end of the day might also have resulted from an increase in predation risk at this time and a reduced need to build up food reserves at the end of the day because of the energetic advantages of communal roosting in an enclosed nest.

Does rock disturbance by superb lyrebirds (Menura novaehollandiae) influence habitat selection by juvenile snakes?

Abstract: Vertebrates that destroy or disturb habitats used by other animals may influence habitat selection by sympatric taxa. In south‐east Australian forests, superb lyrebirds (Menura novaehollandiae) displace soil, leaf litter and rocks during their daily foraging activities. We investigated whether superb lyrebirds disturb small sandstone rocks that endangered broad‐headed snakes Hoplocephalus bungaroides and common small‐eyed snakes Cryptophis nigrescens use as diurnal thermoregulatory sites. To estimate the frequency of lyrebird rock disturbance, and to assess whether lyrebirds also attack small snakes, we placed 900 plasticine snake replicas under stones on rock and soil substrates along transects on three sandstone plateaux. Because juvenile snakes must select retreat sites that simultaneously allow them to thermoregulate and minimize predation risk, we quantified the thermal environments underneath stones on rock and soil substrates. During the 6‐week experiment, animals disturbed rocks on soil substrates twice as often (16.9%) as rocks lying on rock substrates (8.2%). Disturbed rocks were significantly smaller and lighter than undisturbed rocks on both substrates. Lyrebirds were the major agents of disturbance, and attacked 40% of snake models under disturbed rocks. Rocks on soil substrates conferred the greatest thermal benefits to snakes, but both species of snake avoided these microhabitats in the field. Instead, juvenile snakes selected rocks on rock substrates, and sheltered under stones that were too heavy for superb lyrebirds to disturb. By disturbing rocks over millennia, superb lyrebirds not only have shaped the physical landscape, but also may have exerted strong selection on habitat selection by sympatric snakes.

Constraints of feeding on Salicornia ramosissima by wigeon Anas penelope: an experimental approach

The coastal marshes of the Charente-Maritime (western France) are a major wintering area for wigeon Anas penelope. In these marshes, wigeon feed mainly on grasses, while foraging on Salicornia (a fleshy, succulent halophyte) is uncommon. In order to understand the reason for this under-exploitation, an experimental study was carried out with captive wigeon in autumn 1998 on a Salicornia ramosissima marsh in the Charente- Maritime. Birds were unable to maintain their body weight when feeding on Salicornia. Measurements of food chemical composition and metabolisability, as well as instantaneous intake rate of the birds (g/min) could not explain these weight losses. However, the time budget of wigeon revealed that they spent a maximum of 10-11 h per 24 h consuming Salicornia, whereas 18-19 h would have been needed to meet their daily energy requirements. The daily foraging time on Salicornia may have been limited by physiological constraints due to: (1) a high ash content (mainly salt, about 34% of dry matter), and/or (2) a digestive bottleneck, because of the waxy cuticle covering the leaves, which is likely to have constrained processing rate of Salicornia ears in the gut of birds. In the discussion, we address the question of the potential geographical differences in the use of Sal- icornia by birds.

Diet switching in a generalist mammalian folivore: fundamental to maximising intake

Generalist mammalian herbivores exploit a diverse diet. A generalised feeding strategy utilises a mixed diet to obtain a range of nutrients and to reduce the detoxication load of similar groups of plant secondary metabolites (PSMs). There is limited research investigating how mammalian herbivores achieve this dietary mixing in their daily foraging activities. We investigated the patterns of, and behaviours associated with, dietary mixing in a generalist mammalian folivore, the common brushtail possum (Trichosurus vulpecula). Possums were offered foliage of two eucalypt species (Eucalyptus globulus and E. regnans) as either (a) Full choice: both species offered for 8 h; (b) Restricted choice: both species offered for 2x2 h blocks; (c) G-R no choice: E. globulus offered for the first 4 h, E. regnans offered for next 4 h; and (d) R-G no choice: E. regnans offered for first 4 h, E. globulus offered for next 4 h. We hypothesised that possums would maximise intake on the Full choice diet, where time availability was greatest in combination with a choice of foliage. We also hypothesised that diet switching, defined as the frequency of changing between food types while feeding, would play a fundamental role in maximising intake. Possums achieved maximum intake on the Full choice diet and minimum intake on the No choice diets. Although intake was similar between the Restricted choice and No choice diets, possums achieved this intake in half the amount of time when able to switch regularly between foliage on the Restricted choice diet. We conclude that a generalist herbivore's ability to effectively switch diets when foraging is fundamental to maximising intake. Hence, the degree of plant heterogeneity in an environment, and the spatial scale at which it occurs, may affect an herbivore's foraging decisions and, ultimately, influence its foraging efficiency.

Foraging ecology of the thermophilic Australian desert ant, Melophorus bagoti

The paper describes the foraging ecology of the Australian desert ant, Melophorus bagoti, a thermophilic, diurnal scavenger with ground-nesting colonies. Overlapping foraging ranges, low foraging success rates, and intercolony aggression suggest intense competition for food between colonies. Daily foraging starts when soil surface temperatures approach 50°C. Workers search individually and collect predominantly dead insects. Occasionally, they consume plant secretions. Foraging activity peaks on mid-summer days. On cloudy days the onset of foraging is delayed, and the foraging activity is low. Ants do not forage on rainy days. Typically, workers start their above-ground activities with a few short exploration runs. On average, they perform one foraging run on the first day of their outdoor lives. With age they gradually increase foraging site fidelity and daily foraging effort. Individual foraging efficiency is low at the beginning but grows with experience. However, due to a high mortality rate and, hence, high forager turnover, average rates of foraging success for a colony remain rather low. The outdoor activity gradually decreases towards the end of summer and appears to stop completely during the winter months.

CORRELATES OF FALL–SPRING MASS DYNAMICS OF NORTHERN BOBWHITES

We examined the relationship of trends in fall–spring mass of 330 Northern Bobwhites (Colinus virginianus) with photoperiod, air temperature, energy requirements, and supplemental feeding in the Texas Panhandle during 2000–2003. Mass of bobwhites increased from September to December, at which point it peaked and then decreased through March. Mean monthly mass was negatively correlated with photoperiod (r =−0.89) and temperature (r =−0.79) and positively correlated with energy required (r = 0.79; estimated using air temperature). From September to March, bobwhites occupying areas where supplemental feed was provided (n = 246) were greater in mass (x̄ = 193.4 g, 95% CL = 191.6–195.1) than bobwhites in areas without supplemental feed (x̄ = 186.5 g, 95% CL = 184.0–189.0, n = 84), but mean monthly mass was different only during November (x̄ = 197.8 g, 95% CL = 195.3–200.3 for food-supplemented; x̄ = 188.0 g, 95% CL = 185.0– 191.0 for unsupplemented). Abiotic factors, such as photoperiod and temperature, are confounding factors when attempting to explain fall and winter trends of bobwhite mass. Temporal changes in activities (daily foraging, nocturnal roosting) and their energetic costs (e.g., thermoregulation) also complicate issues of trends in mass.

All-day foraging characteristics of successful underground colonies of Vespula vulgaris (Hymenoptera, Vespidae) in England

Thirteen days of foraging studies, on normally developing colonies of Vespula vulgaris, were carried out between 5 July and 7 October over several years. Seven categories of workers were considered: two of outgoers – earth carriers and non-earth outgoers, and five of incomers – pulp, flesh, full fluid, and partial fluid carriers, and empty incomers. The pre-exponential small-cell colony is characterised by a more-or-less equal frequency of pulp and flesh carriers and a relatively high frequency of non-earth outgoers. These characteristics are related to the needs of a colony rapidly to build its worker population. The exponential small-cell colony is characterised by an increased frequency of earth and pulp carriers, with the latter being more frequent than flesh carriers. These characteristics are related to the enlargement of the nest cavity, the building of small cells and the decreasing weight of workers. The large-cell colony is characterised by a relative lack of earth and pulp carriers, with flesh carriers being more frequent than pulp carriers. The relative lack of earth carriers is probably because the large-celled combs occupy the nest cavity created during the exponential small-cell colony. The relative lack of pulp carriers is probably due to the re-use of pulp from discarded small cells for large cells. The percentage differences between early morning and evening worker categories compared with normal daily foraging (from Archer, 2000) are determined. Despite much variation, during the early morning there were relatively more full fluid carriers and relatively fewer flesh carriers. During the evening, there were relatively more partial fluid carriers and relatively fewer solid carriers. The dissolved component of the fluid is hypothesised to provide a food source to maintain a high, stable nest temperature.

Changes in vigilance with group size under scramble competition.

Animals often interrupt foraging to scan the surrounding environment. In several taxa, such vigilance decreases with group size (Elgar 1989). The decline in vigilance is usually interpreted as a decrease in the predation risk to an individual in large groups. Mechanisms such as increased detection ability and numerical dilution of risk may provide more protection to foragers in large groups, thus leading to lower vigilance (Pulliam 1973; Roberts 1996; Bednekoff and Lima 1998). Nevertheless, recent work indicates that the decrease in vigilance with group size may be mitigated against if individuals in large groups scan more to avoid displacements by aggressive companions (Slotow and Coumi 2000; Treves 2000) or to locate the food discoveries of other group members (Beauchamp 2001). We explore the role of resource availability on vigilance patterns. In earlier vigilance models, a decrease in vigilance would allow foragers either to decrease the total amount of time needed to accumulate a fixed amount of resources (Pulliam et al. 1982) or to increase feeding rate over a given time horizon (McNamara and Houston 1992). In either case, no competition for resources is assumed to take place. However, when resources are limited, a reduction in vigilance may allow individuals to allocate more time to foraging and so obtain a greater share of the re-

Foraging strategies of granivorous dabbling ducks wintering in protected areas of the French Atlantic coast

Most important day-roosts for wintering ducks are protected, but the useof such sites as foraging habitats by Anatidae has received little attention. Westudied the foraging activity of wintering mallard (Anasplatyrhynchos) and teal (A. crecca) at fourprotected areas of the Marshes of Rochefort, western France. These species aregenerally nocturnal feeders, but they may expand their foraging time into thedaylight hours if they have high energy requirements. Our goal was to identifythe factors that lead dabbling ducks to increase their daily foraging time, sothat the management of protected sites used by ducks diurnally could be adjustedaccordingly. We demonstrate for the first time that, at the holarctic scale,granivorous ducks in colder habitats have longer diurnal foraging times. Inwestern France, foraging represented 37–60% of ducks' daily time-budget:16% of daylight hours and 85% of the night were spent foraging on average. Teal(350 g) fed longer per day than mallard (1100 g), andthis seemed to result from different migration strategies rather thandifferences in body mass. This study suggests that management of protected areasshould be adjusted to the climatic conditions of a wintering quarter and to themigration status of species in the duck community, so that adequate foragingsites are available for energetically stressed individuals to fulfil their dailyrequirements.

Foraging strategies of Great Cormorants Phalacrocorax carbo carbo wintering north of the Arctic Circle

This study describes how 30 Great Cormorants Phalacrocorax carbo carbo managed to catch sufficient food for their daily energetic needs under conditions of reduced daylight and cold while wintering north of the Arctic Circle. Activity observations showed that the Great Cormorants' daily foraging pattern was generally bimodal, with morning and evening feeding peaks. They compensated for shorter daylengths in midwinter by starting to forage later and ending progressively earlier at lower light intensities. Fishing constituted only a minor part of their time–activity budget, and was one of the most efficient reported in marine birds. The Great Cormorants spent less than 60 minutes a day fishing in midwinter. Although subzero ambient temperatures and blizzards contributed to increased heat loss in midwinter, this potential energy loss did not seem to be compensated for by an increase in fish intake. Instead the Great Cormorants seemed to economize energy expenditure by halving the time spent at sea, and halving the number but doubling the mass of each fish taken.

Consequences of Diet Choice by a Small Generalist Herbivore

We examined the energy, nutrient, time, and habitat consequences of diet choice by a generalist herbivore, the hispid cotton rat (Sigmodon hispidus) on the Texas coastal prairie. Benefit–cost and linear programming models were developed and used to test several specific hypotheses about diet choice, foraging strategy, and habitat use by cotton rats. Within cotton rat habitat, there were significant differences among both seasons and habitat patches in the abundance and biomass of foods available. Monocot patches typically were higher in standing crops of energy and nutrients than were either dicot or mixed patches. Relative to available biomass and nutrients in dicot foods, this cotton rat habitat was both spatially and temporally heterogeneous and dynamic. Although the abundance of dicot foods in a habitat patch did influence costs of foraging time, time costs of cotton rats foraging for suitable foods did not decrease when standing crops of energy and nutrients in these habitats increased. Higher requirements for energy and nutrients needed for lactation by reproductive cotton rats resulted in higher foraging costs than for nonreproductive female rats. A mixed diet incorporating both monocot and dicot foods was nutritionally superior to either a monocot-only diet or a dicot-only diet. A diet of only monocots would meet minimum daily energy requirements and would not exceed either maximum daily digestive capacity or maximum daily foraging time, but it would not meet minimum daily requirements for protein and phosphorus during reproduction. Conversely, a diet of only dicots would meet nutrient requirements for reproduction but would exceed maximum daily foraging time. Mixing of monocot and dicot plant parts in the diet met both net energy and nutritional requirements, and increased foraging time, as compared to a diet of only monocots. Diets of cotton rats foraging to maximize net energy intake each season differed from the observed diets. Likewise, diets of cotton rats foraging to minimize total daily foraging time differed from the observed diets. Thus, we conclude that reproductive females of this generalist herbivore neither maximized their energy nor minimized their time, but rather, consumed a mixed diet to balance intake of requisite nutrients. Accordingly, a diet choice that included a mixture of monocot and dicot foods was most efficient when foraging occurred in a habitat having a mixture of monocot and dicot plants. Mixed patches provided higher energy and nutrient benefits to foraging cotton rats than did either monocot or dicot patches. Finally, we observed that reproductive female cotton rats concentrated their activities in mixed-patch habitats.

CONSEQUENCES OF DIET CHOICE BY A SMALL GENERALIST HERBIVORE

We examined the energy, nutrient, time, and habitat consequences of diet choice by a generalist herbivore, the hispid cotton rat (Sigmodon hispidus) on the Texas coastal prairie. Benefit-cost and linear programming models were developed and used to test several specific hypotheses about diet choice, foraging strategy, and habitat use by cotton rats. Within cotton rat habitat, there were significant differences among both seasons and habitat patches in the abundance and biomass of foods available. Monocot patches typically were higher in standing crops of energy and nutrients than were either dicot or mixed patches. Relative to available biomass and nutrients in dicot foods, this cotton rat habitat was both spatially and temporally heterogeneous and dynamic. Although the abun- dance of dicot foods in a habitat patch did influence costs of foraging time, time costs of cotton rats foraging for suitable foods did not decrease when standing crops of energy and nutrients in these habitats increased. Higher requirements for energy and nutrients needed for lactation by reproductive cotton rats resulted in higher foraging costs than for non- reproductive female rats. A mixed diet incorporating both monocot and dicot foods was nutritionally superior to either a monocot-only diet or a dicot-only diet. A diet of only monocots would meet minimum daily energy requirements and would not exceed either maximum daily digestive capacity or maximum daily foraging time, but it would not meet minimum daily requirements for protein and phosphorus during reproduction. Conversely, a diet of only dicots would meet nutrient requirements for reproduction but would exceed maximum daily foraging time. Mixing of monocot and dicot plant parts in the diet met both net energy and nutritional requirements, and increased foraging time, as compared to a diet of only monocots. Diets of cotton rats foraging to maximize net energy intake each season differed from the observed diets. Likewise, diets of cotton rats foraging to minimize total daily foraging time differed from the observed diets. Thus, we conclude that repro- ductive females of this generalist herbivore neither maximized their energy nor minimized their time, but rather, consumed a mixed diet to balance intake of requisite nutrients. Accordingly, a diet choice that included a mixture of monocot and dicot foods was most efficient when foraging occurred in a habitat having a mixture of monocot and dicot plants. Mixed patches provided higher energy and nutrient benefits to foraging cotton rats than did either monocot or dicot patches. Finally, we observed that reproductive female cotton rats concentrated their activities in mixed-patch habitats.

Foraging behaviour of Atta cephalotes (leaf-cutting ants): an examination of two predictions for load selection

Two mechanisms have been proposed to explain how colony-level foraging performance of leaf-cutting ants can be maximized when workers harvest leaf fragments of a size that does not maximize their individual performance. Each mechanism predicts that ants will adjust the size of leaf fragments between starting a foraging bout and establishing full traffic between the nest and foraging site, but the two models predict shifts in opposite directions. I examined fragment sizes at the start of daily foraging in five field colonies of Atta cephalotes in Costa Rica and detected an obvious shift in only one case. More shifts were detected when the small and large ends of the worker body size range were considered separately, but the direction was inconsistent among colonies. I also examined the role of returning laden workers in recruitment of nestmates by intercepting all laden workers for the first 2h of foraging, and measuring the effect on the arrival of recruits at the foraging site. In two cases, the flow of recruits was not diminished by the interception of returning workers. The results suggest that neither mechanism correctly and consistently accounts for load size selection by leaf-cutting ants.

Ingestion d'herbe au pâturage par le cheval de selle en croissance : effet de l'âge des poulains et de la biomasse d'herbe

Grass intake by growing horses at pasture: a test of the effects of the horses' age and sward biomass. No data are currently available on the quantities of food ingested by young horses at pasture, in spite of the fact that pasture constitutes the main source of nutrients for these animals. In this study, three levels of sward mass were offered to animals (2.3; 2.9 and 3.5 T DM .ha -1 ), which correspond to grass heights of 6.6, 8.1 and 9.4 cm. Horses of the Cheval de Selle Francais breed were used (1 and 2 years old, live weight of 334 and 478 kg respectively) in a latin square design. The daily quantities of grass ingested at pasture were determined, and relationships between daily intake, and the characteristics of the pasture and animal were studied. Intake relative to metabolic live weight did not vary between yearlings and 2-year-old horses. Intake averaged 82 g OM .kg -1 LW 0.75.d -1 . Compared with yearlings, 2-year-old horses had a lower daily foraging time and a higher intake rate (9.9 vs. 7.6 g OM .min -1 ). Grass height had no effect on the food intake of growing horses for grass between 6 and 9 cm high. Compared with cattle and even sheep, horses maintain their lev- els of food intake even at low sward heights. horse / feeding / grass / intake Resume — Alors que le pâturage constitue l'alimentation principale des jeunes chevaux, il n'existe que tres peu de donnees sur les quantites d'herbe ingerees sur les prairies. Dans cette experimenta- tion, trois niveaux de biomasse relativement faibles ont ete proposes aux animaux (respectivement 2,3 ; 2,9 et 3,5 T MS.ha -1 ), ce qui correspond a des hauteurs d'herbe de 6,6 ; 8,1 et 9,4 cm respectivement. Deux categories de poulains de selle (un an et deux ans, respectivement 334 and 478 kg) ont ete integrees a l'etude. L'essai a ete conduit selon un dispositif en carre latin 3 〈 3. Les quantites d'herbe

Can a minority of informed leaders determine the foraging movements of a fish shoal?

There is no information on whether the daily foraging movements of fish shoals are the result of chance, the collective will of all shoalmates, or the leadership of a few individuals. This study tested the latter possibility. Shoals of 12 golden shiners, Notemigonus crysoleucas, were trained to expect food around midday in one of the brightly lit corners of their tank. They displayed daily food-anticipatory activity by leaving the shady area of their tank and spending more and more time in the food corner up to the normal time of feeding. Past this normal time they remained in the shade, even on test days when no food was delivered. Most of these experienced individuals were then replaced by naı̈ve ones. The resulting ratio of experienced:naı̈ve fish could be 5:7, 3:9 or 1:11. On their own, naı̈ve individuals would normally spend the whole day in the shade, but in all tests the experienced individual(s) were able to entrain these more numerous naı̈ve fish out of the shade and into the brightly lit food corner at the right time of day. Entrainment was stronger in the 5:7 than in the 1:11 experiment. The test shoals never split up and were always led by the same fish, presumably the experienced individuals. These results indicate that in a strongly gregarious species, such as the golden shiner, a minority of informed individuals can lead a shoal to food, either through social facilitation of foraging movements or by eliciting following behaviour.

A scientific note on the dynamics of labor devoted to nectar foraging in a honey bee colony: number of foragers versus individual foraging activity

entered the hive and both the departure and arrival times of the trips were recorded. A nectar forager was defined as a bee that, after a trip of 10 min or longer, unloaded at least once a day liquid to a receiver bee. Between 0 and 67% of the workers engaged in nectar foraging on a given day, with a mean of 34 ± 18% per day. The percent nectar foragers in the colony changed significantly between days in 5 of 6 observation periods (Fig. 1), most likely as a reaction to changing nectar availability. Overall, 66% of the nectar foragers made 1–4 foraging trips per day, 34% made 5–10 trips, and no bee made more than 10 foraging trips per day. The mean number of trips per nectar forager per day was 3.5 ± 1.3. The majority of the nectar foragers (over 70%) foraged for 4.5 h or less, even though there were approximately 15 h of daylight each day. The mean activity level (number of foraging trips.bee–1.day–1) of the nectar foragers in the colony changed significantly between days in only 1 of the 6 observation periods (Fig. 1). The results of this study suggest that the honey bee colony adjusted its daily foraging effort mainly by changing the number of nectar Division of labor is common to all insect societies and is regarded as one of the most important factors in their ecological success. A key feature of the division of labor in insect colonies is its plasticity. Changing the labor effort devoted to a task with regard to its urgency enables a colony to respond adaptively to changes in external and internal conditions [1, 2]. Honey bee colonies (Apis mellifera) can be expected to adjust the labor devoted to nectar foraging, because foraging conditions strongly fluctuate. The proportion of a colony’s workers engaged in nectar foraging and the activity of each nectar forager are two parameters that might be involved in the adjustment [2]. In this study we measured for the first time both the proportion and the activity of nectar foragers in a honey bee colony. From May to July 1999, 6 random samples of each 50 bees were taken from a colony with about 4 000 bees that was housed in a 3-frame observation hive. The bees in each sample were individually marked, and observed over a period of 3 successive days (except the first period lasting 2 days). Observations started at 05.00 and lasted without interruption until 19.00–21.00 or until foraging activity stopped. Scientific note