Large Food Items Research Articles

Whole versus chopped food: the bintu-right way to do it?

It remains common practice for zoos to chop animal diets into small pieces, even though there is limited evidence to support this practice. It is important that the purported benefits of chopping food are investigated, to determine whether there are any benefits for animal welfare. This study investigates the impact of food presentation on the behaviour of the binturong (Arctictis binturong), a large Asian viverrid, at Beale Wildlife Park in the United Kingdom. For this study, food was provided in three sizes: very finely chopped, chopped, and in whole pieces, and the behaviour and food preference of binturongs was investigated alongside the time taken for keepers to prepare diets. There were relatively few behavioural differences when binturongs were provided with the three food sizes. Only a few behaviours, namely feeding, food manipulation and locomotion with food were significantly more frequent when food was whole, whilst vocalisations were significantly less frequent in this condition. When food items are large, the binturongs appeared to take a large item and move elsewhere to eat, thus moving away from one another, which therefore reduces opportunities for aggression or stealing. This suggests that large food items may have benefits in terms of reduced food monopolisation, especially for binturongs housed in pairs or groups. Keepers saved almost five minutes when preparing whole food diets as opposed to the very chopped size. Given the potential benefits, plus the keeper time saved, whole diets are a viable option for feeding binturongs.

Two Types of Withdraw-to-Eat Movement Related to Food Size in Long-Tailed Macaques (Macaca fascicularis): Insights into the Evolution of the Visual Control of Hand Shaping in Anthropoid Primates

The details of the evolutionary steps in the transition from nonvisual guidance of hand movements for feeding, as displayed by many non-primate species, to visual guidance of hand movements in primates are sparse. Contemporary theory holds that a small-bodied stem primate evolved visual control of the reach to guide a hand to obtain small insects and fruit items from the terminal branches of trees. The subsequent evolution of the visual control of hand and finger shaping movements of the grasp of anthropoids is uncertain. The present study finds that Balinese long-tailed macaques (Macaca fascicularis), video recorded while spontaneously eating at the Sacred Monkey Forest Sanctuary in Ubud in Indonesia, displayed two types of hand movements associated with two types of withdraw movements to place food items in the mouth. Small food items were brought directly to the mouth with hand supination, often with no visual monitoring after grasping. Large food items that protruded from the hand were visually monitored to orient the food item on the initial part of the withdraw but visually disengaged with a head movement and often a blink before the item was placed in the mouth. The results are discussed in relation to the idea that visual information related to orientating food items of varying sizes to an appropriate position in the mouth contributed to the evolution of the visual control of hand shaping skills in anthropoid primates.

Remarkable multicuspid teeth in a new elusive skate (Chondrichthyes, Rajiformes) from the Mediterranean Pliocene

Here we report on four highly peculiar skate teeth from Arcille and Certaldo, two Pliocene localities of Tuscany (central Italy). While being attributable to Rajiformes and somewhat reminiscent of Dipturus and Rostroraja, these specimens display an unusual multicuspid tooth design that does not match any extinct or extant skate taxon known to date. The studied teeth are thus referred to a new genus and species of Rajiformes, Nebriimimus wardi gen. et sp. nov., which is here tentatively assigned to the family Rajidae. Based on pronounced morphological similarities between the rather large-sized teeth of the latter and those of extant nurse sharks, we hypothesise that N. wardi might have been capable of actively foraging upon relatively large food items compared to other rays. This extinct skate species was likely not a common component of the Pliocene Tuscan marine vertebrate assemblages. The palaeoenvironmental scenarios that N. wardi inhabited were marginal-marine and open shelf settings characterised by tropical climate conditions. As N. wardi is currently known only from lower to mid-Pliocene deposits of the Mediterranean Basin, it is tempting to speculate that its speciation dates back to an earliest Pliocene phase of diversification that also contributed to the emergence of the Mediterranean endemic stock of extant skate species.

Preliminary findings on the food and feeding dynamics of the anchovy Stolephorus commersonnii (Lacepède, 1803) and the Indian mackerel Rastrelliger kanagurta (Cuvier, 1817) from Tanga Region, Tanzania

Small pelagic fishes play an important role in the ecosystem by linking planktonic production and higher trophic level predators, and provide a livelihood to both the small-scale and commercial fisher communities. This study analyzed the food and feeding habits of Stolephorus commersonnii (Lacepède, 1803) and Rastrelliger kanagurta (Cuvier, 1817) from the ring-net fishery in Tanga, Tanzania. A total of 1 434 and 320 stomachs of S. commersonnii and R. kanagurta respectively were examined for gut contents using the relative volumetric method. S. commersonnii was found to be a planktivorous carnivore, feeding principally on planktonic penaeid shrimps (48.6%), fish larvae (33.2%) and zooplankton (12.3%). R. kanagurta was found to be carnivorous, feeding predominantly on fish (60.6%), mainly S. commersonnii, while penaeid shrimps, juvenile fish, and juvenile stages of squids formed 26.5% of the total number of food items in R. kanagurta guts. Both S. commersonnii and R. kanagurta exhibited ontogenic diet shifts, where they fed exclusively on small prey as juveniles and consumed larger food items as they grew. The index of vacuity was higher in S. commersonnii (46.1%) than in R. kanagurta (16.6%). This study revealed the importance of penaeid shrimps as food for S. commersonnii, that in turn formed the main food for R. kanagurta. This implied that the two species were able to coexist in the same niche by avoiding interspecific competition for food.

Morphology, histology and histochemistry of the digestive tract of the Banded tilapia, Tilapia sparrmanii (Perciformes: Cichlidae)

This study described anatomical, histological and histochemical features of the mucosal layer of the digestive tract of Tilapia sparrmanii Smith, 1840, an omnivorous freshwater fish endemic to Southern Africa. This species exhibited a short thick oesophagus with long deep longitudinal folds (466.68 ± 16.91 µm), and a thick (173.50 ± 10.92 µm) muscular layer that allow the passage of large food items. The mucosa was lined with stratified secretory epithelium rich in goblet cells that secreted neutral and acid mucins. The stomach was a sac-like structure with simple tubular glands surrounded by connective tissue. The mucosa was lined with simple columnar epithelium and the lamina propria exhibited a well-developed layer of gastric glands that occupied the entire length of the cardio-fundic region. The stomach mucosa consisted of epithelial cells with intense neutral mucin secretion which protects against gastric juice. Neck cells of gastric glands synthesized neutral and acid mucins. The intestine was highly coiled and presented a complex pattern of transversal folds internally (villi). Villi length decreased progressively from the anterior to the posterior intestine (p < 0.0001). Tunica muscularis of the mid-intestine had the thinnest thickness among all parts of the intestine (p < 0.0001). Goblet cells whose numbers increased towards the rectum secreted both acid and neutral mucins. The results indicate structural similarities of T. sparrmaniiGIT with other tilapia species and will be useful for understanding the physiology of the digestive systems as well as functional components of the GIT.

Incorporating indirect pathways in body size-trophic position relationships.

Body size, trophic position (TP), and trophic niche width are important elements of food webs; however, there is still debate regarding their interrelationships. Most studies have tested these correlations using datasets restricted to carnivores and bivariate models that disregard potential indirect effects of other factors, their interactions, and phylogeny. We analyzed relationships among TP, consumer size, maximum food item size, food item size variation (a proxy for trophic niche width), and two other traits (gut length and mouth width) using confirmatory path analysis of an extensive dataset for freshwater fishes that encompass both carnivorous and non-carnivorous species. Consumer size was associated with maximum food size, food size variation, mouth width, and gut length, all of which mediated indirect relationships between body size and TP. Mouth gape was associated with maximum food size, and consumers that fed on larger food items had higher TP. Consumers with relatively long guts generally fed on small and homogeneous food items near the base of the food web. Models were consistent whether or not accounting for phylogeny, but varied according to trophic guilds. However, the body size of both carnivorous and non-carnivorous was not directly associated with TP. Therefore, the incorporation of functional traits and their intermediate pathways is critical for understanding size-based trophic relationships of animals that encompass diverse feeding strategies. Our results caution approaches that rely on body size as a surrogate for TP, especially in systems where plants and detritus are consumed directly by a significant number of animals, such as in most freshwater ecosystems.

Food choice by Messor arenarius ants in different distances from their nest: testing increased selectivity theory

Abstract According to central-place-foraging theory, selectivity of central-place foragers to larger or more profitable food items should increase as the distance from their nest to the food increases. In this research it was checked, if the selectivity of ants of the species Messor arenarius (Fabricius) to larger food items increases as a function of the distance from their nest entrance to the food site. In food choice experiments, whole wheat seeds and halves of wheat seeds cut longitudinally were offered to M. arenarius ants at the same points. These ants preferred halves of wheat seeds cut longitudinally over whole wheat seeds, in all the distances from nest entrance that were checked in this research - 1m, 5m or 10m from nest entrance. According to these findings, M. arenarius ants did not show increased selectivity to different wheat particles within a distance range of 1m – 10m from their nest entrance. It is possible that since the nutritional value of wheat is relatively high, these ants could not evaluate the nutritional value of wheat particles that were offered to them.

Diet and prey preferences of larval and pelagic juvenile Faroe Plateau cod (Gadus morhua)

The availability of suitable prey during the early life of fish may determine recruitment to the adult population. Since larval and juvenile feeding can be highly selective, their preferences for certain prey species and sizes should be considered when estimating the availability of prey. In this study, diet composition (and prey preferences) of 4984 (1366) Faroe Plateau cod (Gadus morhua) larvae and juveniles between 3 and 63 mm sampled on the central Faroe shelf (62°N, 6.8°W) over an 8-year period was investigated. Cod preyed on successively larger food items as they grew. Yolk-sac larvae consumed phytoplankton, copepod eggs and nauplii before the yolk sac was exhausted. Copepod eggs followed by calanoid nauplii were the predominant and preferred food items in the early larval stage. In the late larval stage these were replaced by small to medium sized (0.6–1.2 mm) copepod species mainly Pseudocalanus sp., Acartia sp. and early stage Calanus finmarchicus, of which the two former species appeared most preferred. Temora longicornis was highly abundant in juvenile cod, but the preference for this species was neutral. Positive selection and high abundance of late stage (≥ 1.5 mm) C. finmarchicus was observed in early juveniles, but C. finmarchicus was replaced by decapod larvae in late juveniles. Other abundant prey species such as Oithona sp. and barnacle larvae occurred in varying numbers in the guts, but were generally not positively selected at any stage. Late larval and early juvenile cod appeared to suffer from unfavourable feeding conditions as they fed on smaller prey than what they prefer potentially indicating bottle necks in the feeding at these development stages.

Effects of Aquatic Macrophytes on Spatial Distribution and Feeding Habits of Exotic Fish Species Lepomis macrochirus and Micropterus salmoides in Shallow Reservoirs in South Korea

Aquatic macrophytes determine the physical complexity of aquatic environments and may influence the distribution and feeding habits of fish species. We explored the influence of different microhabitats, including vegetated beds (VB), edges of vegetated beds (EVB), and open water zones (OW), on two exotic fish species (Lepomis macrochirus and Micropterus salmoides) in shallow reservoirs. Lepomis macrochirus was more abundant in VB than in other zones and M. salmoides was mainly distributed in EVB. In VB, L. macrochirus mainly consumed branchiopods and isopods, while M. salmoides in EVB relied on relatively larger food items, such as dipterans, odonatans, and young fish. The consumption of young fish by M. salmoides, including L. macrochirus, showed little difference between winter and summer. Based on these findings, we suggest that young L. macrochirus (~20 cm) utilize VB as a refuge to avoid predation by M. salmoides. Meanwhile, M. salmoides mainly occupied in areas surrounding VB, preying on animals at these edges. As such, the presence of aquatic macrophytes appears to plays a key role in the survival and population growth of L. macrochirus. Proper management of aquatic macrophytes can help reduce populations of exotic fish and support native fish species.

Morphology of the feeding apparatus in the herbivorous mudskipper, Boleophthalmus pectinirostris (Linnaeus, 1758)

Gaining the ability to feed in terrestrial environment allows fish to exploit novel food resources. However, the difference in physical characteristics between air and water, i.e., much lower density and viscosity of the former, would dictate a change in feeding mechanisms: suction feeding, the dominant feeding mode of aquatic vertebrates, hardly works in the air. There are some extant amphibious fishes that feed on land. However, most published studies have dealt with the feeding mechanisms of carnivorous amphibious fishes that prey on relatively large food items, and little is known about herbivorous fishes grazing on land. In this study, we investigated the morphology of the feeding apparatus of Boleophthalmus pectinirostris, a herbivorous mudskipper, to understand how feeding apparatus is modified for grazing on land. Dentition, and the skeletal and muscular systems of the branchial basket were examined through macroscopic and microscopic dissection, scanning electron microscopy, and micro-computed topography scanning. The results show that the feeding apparatus of the fish has been modified presumably to transport diatom cells from the mudflat surface to the digestive tract with minimum admixture of mud particles. The modifications include horizontal orientation of the lower jaw teeth, horizontally aligned, high-density gill rakers on the third (only on the posterior raw) and fourth (both rows) gill arches, large pharyngeal plates bearing numerous fine teeth, and the musculoskeletal system of the branchial basket.

Morphological and histochemical characterisation of the mucosa of the digestive tract in matrinxã Brycon amazonicus (Teleostei: Characiformes).

This study describes anatomical, histological and histochemical features of the digestive tract mucosal layer of the matrinxã Brycon amazonicus, an omnivorous freshwater fish endemic from the Amazon basin. This species presents short thick oesophagus with longitudinal folds, that allow the passage of large food items. The mucosa is lined with a stratified secretory epithelium rich in goblet cells that secrete neutral and acid mucins. The two mucin types provide different viscosity in anterior and posterior oesophagus related to the protective and lubricant functions, respectively. The stomach is a highly distensible Y-shaped saccular organ. Here, it is proposed that this anatomical shape plays an essential role in food storage when food availability is abundant. The stomach mucosa is composed of epithelial cells with intense neutral mucin secretion to protects against gastric juice. The intestine is slightly coiled and presents internally a complex pattern of transversal folds that increases the absorption surface and the retention time of food. Goblet cells in the intestine secrete acid and neutral mucins that lubricate the epithelium and aid in the digestive processes. In the rectum, an increase in goblet cells population occurs that may be related to better lubrication.

Molecular sexing and intersexual differences in the morphometry of the Hangnest Tody-Tyrant Hemitriccus nidipendulus (Passeriformes: Rhynchocyclidae)

Variation in the morphometry of individuals in a population may result from natural or sexual selection. In the present study we investigated morphometric differences between males and females of a bird species endemic to the Brazilian Atlantic Forest, the Hangnest Tody-Tyrant,Hemitriccus nidipendulus(Wied, 1831), with no apparent sexual dimorphism. All individuals (n = 56) were sexed by PCR amplification of the intronic fragments of theCHDZ/CHDWalleles obtained from blood samples, and 12 morphometric measurements were recorded. The molecular configuration was similar to that described for other species of Passeriformes, with males presenting a single band of approximately 360 base pairs (bp), and females with two bands of 360 and 400 bp. Males had significantly larger tarsi and wings than the females, while the females had two larger beak measurements. This indicates that differential selection pressures may be modeling the morphometry of the Hangnest Tody-Tyrant. In the males, larger tarsi and wings may be beneficial for the exploration of the habitat or the acquisition of potential mates, while females with larger beaks may be able to exploit larger food items and forage more efficiently. However, these hypotheses need to be tested empirically in future studies.

Meiofauna versus macrofauna as a food resource in a tropical intertidal mudflat

Evaluations of the functioning of benthic marine food webs could be improved by quantifying organic matter fluxes from the meiofauna to higher trophic levels. In this study, we measured the simultaneous ingestion of meiofauna and macrofauna by common dwellers of a tropical intertidal mudflat on the coast of Amazonia. The meiofauna and macrofauna (tanaid) communities of a tropical intertidal mudflat of French Guiana were separately enriched with 15N and 13C, respectively. The enriched preys were then used as tracers during feeding experiments with common predators of different sizes and feeding mechanisms: a Portunidae crab (Callinectes bocourti), a Penaeidae shrimp (Farfantepenaeus subtilis), and a Gobiidae fish (Gobionellus oceanicus). In feeding experiments with all predators except crabs, feeding rates increased with the availability of meiofauna and macrofauna food sources. The ability of consumers to ingest their food selectively was evaluated by calculating the differences in the ratio of macrofauna to meiofauna between the (1) ingested material and (2) that available in the environment. Larger predators showed a higher degree of preferential macrofauna ingestion than smaller predators, consistent with the optimal foraging theory. For large predators, the meiofauna would be important only during early life or in the absence of large food items.

A Tasmanian devil call encodes identity and decreases agonistic behaviour

ABSTRACT Tasmanian devils (Sarcophilus harrisii), the largest extant carnivorous marsupials, often congregate at carcasses when feeding, where they produce vocalisations onomatopoetically termed ‘arffs’. Our aims were to quantify and determine: 1) arff acoustic structure, 2) if arffs are associated with feeding success, agonistic behaviours, and/or cooperation, c) if arffs encode identity. We observed 26 captive adults and measured the acoustic structure of 298 arff calls from 10 devils. Arffs are low amplitude, short duration, low frequency calls with tonal and harsh forms. During group-feeding events, increased utterances of arffs were associated with increased individual feeding success, decreased agonistic behaviours and increased cooperation (n = 16 devils). Arffs increased when devils were tugging in synchrony on a large food item, apparently to reduce it into manageable portions. Thus, arffs may play a role in this form of by-product mutualism. We classified 90–91% of arffs to the correct individual (nine acoustic characteristics and PCA; n = 9 devils), indicating that arffs encode identity. Devil Facial Tumour Disease is transmitted through bite wounds from bitten to the biter. Tumours that form inside the mouths of infected devils, eventually causing death by starvation, may prevent devils from uttering recognisable arffs, resulting in them being bitten, thereby transmitting the disease.

Food Transport of Red Imported Fire Ants (Hymenoptera: Formicidae) on Vertical Surfaces

Many ants can cooperatively transport large food items (either coordinated or uncoordinated during transportation), which can be rarely observed in other animals besides humans. Although these behaviors have been extensively investigated on horizontal surfaces, few studies dealt with food transport on vertical surfaces. The red imported fire ant, Solenopsis invicta Buren, is an invasive ant species that commonly forages on trees. Our studies showed that S. invicta used multiple strategies to transport food items on vertical surfaces (tree trunks). Small food items (1 × 1 × 1 mm sausage) were carried and transported by individual ants, and larger food items were either collectively and directly transported or cut collaboratively first and small particles were then transported individually or collectively. Competition and deadlocks were frequently observed during individual and collective transport respectively. During cutting, groups of ants tightly fixed the food on the tree trunks by holding the edges of the food item, while other ants cut the food into smaller particles. All food items and particles were moved downward. We investigated the effects of food placement (placed on a platform or fixed on tree trunk), food shape (cuboid or flattened), particle sizes (0.45–1, 1–2, 2–3, or 3–4 mm), and placement height (20, 80, or 150 cm) on the food transport on tree trunks. Our studies are the first to show how fire ants transport food on a vertical surface, and may provide insights into the development of novel fire ant baiting systems that can be placed on tree trunks.

The physics of cooperative transport in groups of ants

Collective motion by animal groups is affected by internal interactions, external constraints and the influx of information. A quantitative understanding of how these different factors give rise to different modes of collective motion is, at present, lacking.} Here, we study how ants that cooperatively transport a large food item react to an obstacle blocking their path. Combining experiments with a statistical physics model of mechanically coupled active agents, we show that the constraint induces a deterministic collective oscillatory mode that facilitates obstacle circumvention. We provide direct experimental evidence, backed by theory, that this motion is an emergent group effect that does not require any behavioral changes at the individual level. We trace these relaxation oscillations to the interplay between two forces; informed ants pull the load towards the nest while uninformed ants contribute to the motion's persistence along the tangential direction. The model's predictions that oscillations appear above a critical system size, that the group can spontaneously transition into its ordered phase, and that the system can exhibit complete rotations are all verified experimentally. We expect that similar oscillatory modes emerge in collective motion scenarios where the structure of the environment imposes conflicts between individually held information and the group's tendency for cohesiveness.

Bi-stability in cooperative transport by ants in the presence of obstacles.

To cooperatively carry large food items to the nest, individual ants conform their efforts and coordinate their motion. Throughout this expedition, collective motion is driven both by internal interactions between the carrying ants and a response to newly arrived informed ants that orient the cargo towards the nest. During the transport process, the carrying group must overcome obstacles that block their path to the nest. Here, we investigate the dynamics of cooperative transport, when the motion of the ants is frustrated by a linear obstacle that obstructs the motion of the cargo. The obstacle contains a narrow opening that serves as the only available passage to the nest, and through which single ants can pass but not with the cargo. We provide an analytical model for the ant-cargo system in the constrained environment that predicts a bi-stable dynamic behavior between an oscillatory mode of motion along the obstacle and a convergent mode of motion near the opening. Using both experiments and simulations, we show how for small cargo sizes, the system exhibits spontaneous transitions between these two modes of motion due to fluctuations in the applied force on the cargo. The bi-stability provides two possible problem solving strategies for overcoming the obstacle, either by attempting to pass through the opening, or take large excursions to circumvent the obstacle.

Comparison of head size and bite force in two sister species of parrotbills

BackgroundBrain size is associated with morphological evolution and behavioral flexibility because animals with large brain size tend to utilize new resources and colonize novel environments more successfully. Therefore, animals with larger brain size should possess larger distribution ranges. Brain size is strongly positively correlated with head size in birds, but also with prey size and vocalizations, because individuals with large heads eat large food items and produce high frequency calls.MethodsTo test if there exists an association between head morphology and bite performance, we compared head size and bite force in two sympatric sister species of parrotbills, Ashy-throated Parrotbill (Paradoxornis alphonsianus) and Vinous-throated Parrotbill (P. webbianus), which both originated from the Himalayan area, but differ significantly in their distribution ranges.ResultsIn Guizhou, southwestern China, the Ashy-throated Parrotbill with a restricted distribution range had smaller heads whilst the Vinous-throated Parrotbill with a large distribution range had larger heads. However, there were no differences in head size between Ashy-throated Parrotbills and allopatric populations of Vinous-throated Parrotbills (Jiangxi and Hebei). Furthermore, the tendency of variation in bite force was opposite to that in head size with populations with larger head size having weaker bite force.ConclusionsWe showed that there are no differences in head size between the Ashy-throated Parrotbill and allopatric populations of Vinous-throated Parrotbill, which provides evidence for the hypothesis that differences in head size in the Guizhou populations of two sister species are probably the result of local adaptation rather than species-specific. Our study has implications for avian dispersal and adaption related to head size such as diet ecology and vocalizations.

An ecomorphospace for the Ammonoidea

AbstractThe fossil conchs of ammonoids provide valuable information about the life habits of this extinct group. A new conch measurement, the apertural surface area (ASarea), is introduced here along with modeled sizes of the buccal mass and the hyponome, based on ratios of these organs in comparison with the aperture height from the RecentNautilus pompilius. A principal components analysis was performed using the three main characters: (1) apertural surface area index (i.e., the ratio of the apertural surface and the conch diameter), (2) buccal mass area index (i.e., the ratio between the buccal mass area and the ASarea), and (3) coiling rate of the conch. It revealed an ecomorphospace where life history traits can be tentatively assigned to species of the Ammonoidea. In this morphospace, RecentNautilushas a marginal position, being one of the ectocochleate cephalopods with best properties for active life (capacity for handling large food items, rather good mobility). In contrast, most ammonoids possessed, at comparable conch sizes, much smaller buccal apparatuses and hyponomes, suggesting a more passive life history with reduced mobility potential and reduced capacities for larger prey items.

Tandem Recruitment and Foraging in the Ponerine Ant Pachycondyla harpax (Fabricius).

Tandem running is a common recruitment strategy in ant species with small colony sizes. During a tandem run, an informed leader guides a usually naïve nestmate to a food source or a nest site. Some species perform tandem runs only during house hunting, suggesting that tandem running does not always improve foraging success in species known to use tandem running as a recruitment strategy, but more natural history information on tandem running under natural conditions is needed to better understand the adaptive significance of tandem recruitment in foraging. Studying wild colonies in Brazil, we for the first time describe tandem running in the ponerine ant Pachycondyla harpax (Fabricius). We asked if foragers perform tandem runs to carbohydrate- (honey) and protein-rich (cheese) food items. Furthermore, we tested whether the speed and success rate of tandem runs depend on the foraging distance. Foragers performed tandem runs to both carbohydrate food sources and protein-rich food items that exceed a certain size. The probability to perform a tandem run and the travelling speed increase with increasing foraging distances, which could help colonies monopolize more distant food sources in a competitive environment. Guiding a recruit to a food source is costly for leaders as ants are ~66% faster when travelling alone. If tandem runs break up (~23% of all tandem runs), followers do not usually discover the food source on their own but return to the nest. Our results show that tandem running to food sources is common in P. harpax, but that foragers modify their behaviour according to the type of food and its distance from the nest. Competition with other ants was intense and we discuss how tandem running in P. harpax might help colonies to build-up a critical number of ants at large food items that can then defend the food source against competitors.