Exploring the effects of two-segment loop tunnels on termite food transport efficiency: a simulation study.

This study explores the food transport efficiency (E) in a termite tunnel consisting of a main tunnel and a 2-segment loop tunnel through a model simulation. Simulated termites navigate between the main and loop tunnels through branching nodes (a, b, c, d) with associated probabilities (P1, P2, P3, P4). The loop tunnel locations (δ) are considered: near the nest (δ = 1), at the center of the main tunnel (δ = 2), and close to the food site (δ = 3). The results reveal that for δ = 1, paths such as a → d → b → c and c → d → b → a exhibited high E values. Conversely, for δ = 2, P3 and P4 demonstrate elevated E values ranging from 0.4 to 0.6. For δ = 3, paths like c → d or c → b display high E values, emphasizing the significance of in-loop separation tunnels (characterized by P3 and P4) in alleviating traffic congestion. Partial rank correlation validates that P1 and P2 minimally influence E, while P3 and P4 significantly negatively impact E, regardless of δ. However, for δ = 2, the influence of P3 and P4 is notably reduced due to the positional symmetry of the loop tunnel. In the discussion, we address model limitations and propose strategies to overcome them. Additionally, we outline potential experimental validations to ensure a comprehensive understanding of the dynamics governing termite food transport within tunnels.

Hominin forager technology, food sharing, and diet breadth.

We propose a predator-prey model to explain diachronic changes in Palaeolithic diet breadth. The fraction of rapidly-reproducing hard-to-catch hares and birds among small animals in the hominin diet shows a significant increase between the Middle and Upper Palaeolithic in the Levant, with an associated decrease in slowly-reproducing easily-caught tortoises. Our model interprets this fraction in terms of foraging effort allocated to, and foraging efficiency for each of these two classes of resource, in addition to their abundances. We focus on evolutionary adjustments in the allocation of foraging effort. The convergence stable strategy (CSS) of foraging effort and the dietary fraction of hares/birds are both highly sensitive to variation in the foraging efficiencies, which may have been upgraded by advanced technology introduced from Africa or developed locally. A positive correlation (not necessarily a cause and effect relationship) is observed between this fraction and forager population when the foraging efficiency for hares/birds is varied. Overexploitation can however result in a reduction of both diet breadth and forager population, as can food sharing within the forager group. Food sharing is routine among recent (and perhaps also Palaeolithic) foragers. We speculate that some controversial issues regarding this public goods problem might be resolved if we could incorporate sexual selection into our model.

Multi-camera field monitoring reveals costs of learning for parasitoid foraging behaviour.

Dynamic conditions in nature have led to the evolution of behavioural traits that allow animals to use information on local circumstances and adjust their behaviour accordingly, for example through learning. Although learning can improve foraging efficiency, the learned information can become unreliable as the environment continues to change. This could lead to potential fitness costs when memories holding such unreliable information persist. Indeed, persistent unreliable memory was found to reduce the foraging efficiency of the parasitoid Cotesia glomerata under laboratory conditions. Here, we evaluated the effect of such persistent unreliable memory on the foraging behaviour of C. glomerata in the field. This is a critical step in studies of foraging theory, since animal behaviour evolved under the complex conditions present in nature. Existing methods provide little detail on how parasitoids interact with their environment in the field, therefore we developed a novel multi-camera system that allowed us to trace parasitoid foraging behaviour in detail. With this multi-camera system, we studied how persistent unreliable memory affected the foraging behaviour of C. glomerata when these memories led parasitoids to plants infested with non-host caterpillars in a semi-field set-up. Our results demonstrate that persistent unreliable memory can lead to maladaptive foraging behaviour in C. glomerata under field conditions and increased the likelihood of oviposition in the non-host caterpillar Mamestra brassica. Furthermore, these time- and egg-related costs can be context dependent, since they rely on the plant species used. These results provide us with new insight on how animals use previously obtained information in naturally complex and dynamic foraging situations and confirm that costs and benefits of learning depend on the environment animals forage in. Although behavioural studies of small animals in natural habitats remain challenging, novel methods such as our multi-camera system contribute to understanding the nuances of animal foraging behaviour.

Adjustment of fuel loads in stingless bees (Melipona subnitida).

Eusocial bee foragers leave their nest with nectar as flight fuel, therewith reducing the risk of starvation during a foraging trip. Yet, the extra mass results in an increase of energetic expenditure for flight. Thus, bees should tune their fuel loads to the respective foraging situation. In the present study, we investigated the fuel adjustment in the Brazilian stingless bee Melipona subnitida (Apidae, Meliponini). Specifically, we examined whether foragers of this species increase their fuel loads when they have low expectation for nectar collection during a foraging trip. Crop load measurements revealed that nectar foragers carried significantly less fuel on departing the nest than foragers collecting either pollen, clay, or resin. Surprisingly, 75% of nectar foragers left the nest without any detectable amount of nectar, which suggests that the majority of bees collected at nearby nectar sources and avoided an increase in foraging costs. Moreover, foragers increased their fuel loading when repeatedly experiencing empty food sources that had previously been rewarding. These results support our hypothesis and demonstrate that the capability of fuel adjustment is not restricted to honey bees.

Oceans of stimuli: an individual-based model to assess the role of olfactory cues and local enhancement in seabirds' foraging behaviour.

Oceans are extremely dynamic environments, which poses challenges for top-predators such as seabirds to find food resources. Yet, seabirds evolved sensorial abilities (olfactory senses) along with complex behaviours (social information transfer through local enhancement) to improve foraging efficiency. Using the Cory's shearwater (Calonectris borealis) as a model species, we developed an individual-based model to explore the complementary role of different searching mechanisms (olfactory foraging and local enhancement) for the optimal foraging behaviour of pelagic seabirds during 1-day foraging trips around breeding colonies. Model outputs were compared with observed patterns of Cory's shearwaters distribution during local foraging trips. Also, the foraging efficiency of virtual individuals was analysed considering hypothetical scenarios of foraging conditions and densities of foraging individuals around breeding colonies. The results support the use of a combination of searching strategies by Cory's shearwaters, which produced representative patterns of space use from tracked individuals, including spatial foraging segregation of neighbouring sub-colonies. Furthermore, while the mechanisms underpinning local enhancement played a key role in mitigating sub-optimal foraging conditions, the use of olfactory senses conferred great adaptive foraging advantages over a wide range of environmental conditions. Our results also indicate a synergistic effect between the two strategies, which suggests that a multimodal foraging strategy is useful to forage in extremely dynamic environments. The developed model provides a basis for further investigation regarding the role of foraging mechanisms in the population dynamics of colonial animals, including the adaptive foraging behaviour of marine top predators to dynamic environmental conditions.

Foraging efficiency and size matching in a plant-pollinator community: the importance of sugar content and tongue length.

A long-standing question in ecology is how species interactions are structured within communities. Although evolutionary theory predicts close size matching between floral nectar tube depth and pollinator proboscis length of interacting species, such size matching has seldom been shown and explained in multispecies assemblages. Here, we investigated the degree of size matching among Asteraceae and their pollinators and its relationship with foraging efficiency. The majority of pollinators, especially Hymenoptera, choose plant species on which they had high foraging efficiencies. When proboscides were shorter than nectar tubes, foraging efficiency rapidly decreased because of increased handling time. When proboscides were longer than nectar tubes, a decreased nectar reward rather than an increased handling time made shallow flowers more inefficient to visit. Altogether, this led to close size matching. Overall, our results show the importance of nectar reward and handling time as drivers of plant-pollinator network structure.

Experimental disturbances reveal group-level costs of social instability.

In group-living species, social stability is an important trait associated with the evolution of complex behaviours such as cooperation. While the drivers of stability in small groups are relatively well studied, little is known about the potential impacts of unstable states on animal societies. Temporary changes in group composition, such as a social group splitting and recombining (i.e. a disturbance event), can result in individuals having to re-establish their social relationships, thus taking time away from other tasks such as foraging or vigilance. Here, we experimentally split socially stable groups of captive zebra finches (Taeniopygia guttata), and quantified the effects of repeated disturbance events on (1) group foraging efficiency, and (2) co-feeding associations when subgroups were recombined. We found that the efficiency of groups to deplete a rich, but ephemeral, resource patch decreased after just a single short disturbance event. Automated tracking of individuals showed that repeated disturbances reduced efficiency by causing social relationships to become more differentiated and weaker, resulting in fewer individuals simultaneously accessing the patch. Our experiment highlights how short-term disturbances can severely disrupt social structure and group functionality, revealing potential costs associated with group instability that can have consequences for the evolution of animal societies.

Combined measurements of prey availability explain habitat selection in foraging seabirds.

Understanding links between habitat characteristics and foraging efficiency helps predict how environmental changes influence populations of top predators. This study examines whether measurements of prey (clupeids) availability varied over stratification gradients, and determined if any of those measurements coincided with aggregations of foraging seabirds (common guillemot Uria aalge and Manx shearwater Puffinus puffinus) in the Celtic Sea, UK. The probability of encountering foraging seabirds was highest around fronts between mixed and stratified water. Prey were denser and shallower in mixed water, whilst encounters with prey were most frequent in stratified water. Therefore, no single measurement of increased prey availability coincided with the location of fronts. However, when considered in combination, overall prey availability was highest in these areas. These results show that top predators may select foraging habitats by trading-off several measurements of prey availability. By showing that top predators select areas where prey switch between behaviours, these results also identify a mechanism that could explain the wider importance of edge habitats for these taxa. As offshore developments (e.g. marine renewable energy installations) change patterns of stratification, their construction may have consequences on the foraging efficiency of seabirds.

Structural complexity and fish body size interactively affect habitat optimality.

Predator-prey interactions are strongly influenced by habitat structure, particularly in coastal marine habitats such as seagrasses in which structural complexity (SC) may vary over small spatial scales. For seagrass mesopredators such as juvenile fishes, optimality models predict that fitness will be maximized at levels of SC that enhance foraging but minimize predation risk, both of which are functions of body size. We tested the hypothesis that in eelgrass (Zostera marina) habitat, optimal SC for juvenile giant kelpfish (Heterostichus rostratus), an abundant eelgrass mesopredator in southern California, changes through ontogeny. To do this, we quantified eelgrass SC effects on habitat associations, relative predation risk, and foraging efficiency for three size classes of juvenile giant kelpfish. We found that habitat selection differed with fish size: small fish selected dense eelgrass, whereas larger fish selected sparse eelgrass. Small kelpfish experienced the lowest relative predation risk in dense eelgrass but also had higher foraging efficiency in dense eelgrass, suggesting that dense eelgrass is selected by these fish because it minimizes risk and maximizes potential for growth. Surprisingly, larger kelpfish did not experience lower predation risk than small kelpfish. However, larger kelpfish experienced higher foraging efficiency in sparse eelgrass vs. dense eelgrass, suggesting that they select sparse eelgrass to maximize foraging efficiency. Our study highlights that trade-offs between predation risk and foraging can occur within a single habitat type, that studies should consider how habitat value changes through ontogeny, and that seagrass habitat value may be maximal when within-patch variability in SC is high.

Temporal effects of hunting on foraging behavior of an apex predator: Do bears forego foraging when risk is high?

Avoiding predators most often entails a food cost. For the Scandinavian brown bear (Ursus arctos), the hunting season coincides with the period of hyperphagia. Hunting mortality risk is not uniformly distributed throughout the day, but peaks in the early morning hours. As bears must increase mass for winter survival, they should be sensitive to temporal allocation of antipredator responses to periods of highest risk. We expected bears to reduce foraging activity at the expense of food intake in the morning hours when risk was high, but not in the afternoon, when risk was low. We used fine-scale GPS-derived activity patterns during the 2 weeks before and after the onset of the annual bear hunting season. At locations of probable foraging, we assessed abundance and sugar content, of bilberry (Vaccinium myrtillus), the most important autumn food resource for bears in this area. Bears decreased their foraging activity in the morning hours of the hunting season. Likewise, they foraged less efficiently and on poorer quality berries in the morning. Neither of our foraging measures were affected by hunting in the afternoon foraging bout, indicating that bears did not allocate antipredator behavior to times of comparably lower risk. Bears effectively responded to variation in risk on the scale of hours. This entailed a measurable foraging cost. The additive effect of reduced foraging activity, reduced forage intake, and lower quality food may result in poorer body condition upon den entry and may ultimately reduce reproductive success.

Does moonlight increase predation risk? Meta-analysis reveals divergent responses of nocturnal mammals to lunar cycles.

The risk of predation strongly affects mammalian population dynamics and community interactions. Bright moonlight is widely believed to increase predation risk for nocturnal mammals by increasing the ability of predators to detect prey, but the potential for moonlight to increase detection of predators and the foraging efficiency of prey has largely been ignored. Studies have reported highly variable responses to moonlight among species, calling into question the assumption that moonlight increases risk. Here, we conducted a quantitative meta-analysis examining the effects of moonlight on the activity of 59 nocturnal mammal species to test the assumption that moonlight increases predation risk. We examined patterns of lunarphilia and lunarphobia across species in relation to factors such as trophic level, habitat cover preference and visual acuity. Across all species included in the meta-analysis, moonlight suppressed activity. The magnitude of suppression was similar to the presence of a predator in experimental studies of foraging rodents (13.6% and 18.7% suppression, respectively). Contrary to the expectation that moonlight increases predation risk for all prey species, however, moonlight effects were not clearly related to trophic level and were better explained by phylogenetic relatedness, visual acuity and habitat cover. Moonlight increased the activity of prey species that use vision as their primary sensory system and suppressed the activity of species that primarily use other senses (e.g. olfaction, echolocation), and suppression was strongest in open habitat types. Strong taxonomic patterns underlay these relationships: moonlight tended to increase primate activity, whereas it tended to suppress the activity of rodents, lagomorphs, bats and carnivores. These results indicate that visual acuity and habitat cover jointly moderate the effect of moonlight on predation risk, whereas trophic position has little effect. While the net effect of moonlight appears to increase predation risk for most nocturnal mammals, our results highlight the importance of sensory systems and phylogenetic history in determining the level of risk.

Variation in harbour porpoise activity in response to seismic survey noise.

Animals exposed to anthropogenic disturbance make trade-offs between perceived risk and the cost of leaving disturbed areas. Impact assessments tend to focus on overt behavioural responses leading to displacement, but trade-offs may also impact individual energy budgets through reduced foraging performance. Previous studies found no evidence for broad-scale displacement of harbour porpoises exposed to impulse noise from a 10 day two-dimensional seismic survey. Here, we used an array of passive acoustic loggers coupled with calibrated noise measurements to test whether the seismic survey influenced the activity patterns of porpoises remaining in the area. We showed that the probability of recording a buzz declined by 15% in the ensonified area and was positively related to distance from the source vessel. We also estimated received levels at the hydrophones and characterized the noise response curve. Our results demonstrate how environmental impact assessments can be developed to assess more subtle effects of noise disturbance on activity patterns and foraging efficiency.

The presence of informed conspecifics improves individual foraging efficiency in naïve sheep.

Knowledge about the environment is fundamentally important to move, find resources and forage efficiently. This information can either be acquired through individual exploration (personal information) or from other group members (social information). We experimentally assessed the use of social information and its influence on foraging efficiency in sheep, Ovis aries. Naïve individuals paired with an informed partner that knew the food patch location, found the patch significantly faster compared to naïve individuals paired with another naïve individual. Similarly, they spent a significantly lower proportion of time exploring areas away from the food patch. We further found that the outcome of using social information in one directly previous trial (success = access to feed vs failure = no access to feed) had no impact and sheep continued to use social information in the subsequent foraging trial and foraged similarly efficient. Our results suggest, naïve sheep that are unfamiliar with resource locations, forage more efficiently when informed individuals are present compared to when all individuals are naïve. If informed individuals play a similar role in larger groups, new management practices that integrate informed sheep could be developed to improve foraging efficiency when sheep are moved to new paddocks or in paddocks with heterogenous and dynamic resource distribution.

Movement ecology of an endangered mesopredator in a mining landscape.

BACKGROUND: Efficient movement and energy expenditure are vital for animal survival. Human disturbance can alter animal movement due to changes in resource availability and threats. Some animals can exploit anthropogenic disturbances for more efficient movement, while others face restricted or inefficient movement due to fragmentation of high-resource habitats, and risks associated with disturbed habitats. Mining, a major anthropogenic disturbance, removes natural habitats, introduces new landscape features, and alters resource distribution in the landscape. This study investigates the effect of mining on the movement of an endangered mesopredator, the northern quoll (Dasyurus hallucatus). Using GPS collars and accelerometers, we investigate their habitat selection and energy expenditure in an active mining landscape, to determine the effects of this disturbance on northern quolls. METHODS: We fit northern quolls with GPS collars and accelerometers during breeding and non-breeding season at an active mine site in the Pilbara region of Western Australia. We investigated broad-scale movement by calculating the movement ranges of quolls using utilisation distributions at the 95% isopleth, and compared habitat types and environmental characteristics within observed movement ranges to the available landscape. We investigated fine-scale movement by quolls with integrated step selection functions, assessing the relative selection strength for each habitat covariate. Finally, we used piecewise structural equation modelling to analyse the influence of each habitat covariate on northern quoll energy expenditure. RESULTS: At the broad scale, northern quolls predominantly used rugged, rocky habitats, and used mining habitats in proportion to their availability. However, at the fine scale, habitat use varied between breeding and non-breeding seasons. During the breeding season, quolls notably avoided mining habitats, whereas in the non-breeding season, they frequented mining habitats equally to rocky and riparian habitats, albeit at a higher energetic cost. CONCLUSION: Mining impacts northern quolls by fragmenting favoured rocky habitats, increasing energy expenditure, and potentially impacting breeding dispersal. While mining habitats might offer limited resource opportunities in the non-breeding season, conservation efforts during active mining, including the creation of movement corridors and progressive habitat restoration would likely be useful. However, prioritising the preservation of natural rocky and riparian habitats in mining landscapes is vital for northern quoll conservation.

Long-term home range stability provides foraging benefits in western gorillas.

OBJECTIVES: Long-term home range stability presumably emerges because familiarity with an area improves fitness through increased foraging efficiency, reduced predation risk, or reduced costs of intergroup aggression. While the use of spatial memory by primates has been widely demonstrated, few studies have examined whether long-term space use creates opportunities for interannual reuse of spatial knowledge. Here we examine the ranging behavior of western gorillas (Gorilla gorilla) to assess the degree of long-term site fidelity and the foraging consequences of reuse of space. METHODS: We measured interannual home range overlap over a 10-year period for a single group of gorillas at the Mondika Research Center, using both grid-based and kernel density estimation. By plotting the total area used over time, we identified periods of home-range stability and expansion. We compared foraging and ranging behavior in familiar versus unfamiliar areas, considering fruit trees visited, dietary diversity, and daily path length, to determine whether the lack of spatial knowledge in unfamiliar areas was associated with foraging costs. RESULTS: Average interannual home range overlap by the group remained high throughout the study. During periods of home range expansion, daily path lengths increased but not the number of fruit trees visited, suggesting that reduced familiarity with the area led to decreased foraging efficiency because individuals lacked prior knowledge of where to find resources. DISCUSSION: Western gorillas at Mondika exhibit long-term home range stability, presumably reflecting a strategy that relies on the use of spatial memory to increase foraging efficiency that is favored by their reliance on ephemeral fruit resources.

Exploring the effects of high curvature section distribution and density in termite tunnels on food transport efficiency: A simulation study.

This study explores the food transport efficiency of termite using an individual-based model. Termites are believed to have evolved tunneling patterns that optimize food search and transport efficiency. However, few studies have investigated transport efficiency due to the difficulty of field observations. The model is characterized by four control variables: the number of simulated termites participating in transport (k1), the distribution of high curvature sections of the termite tunnel (k2), a quantity related to the density of the tunnel sections (k3), and the duration of traffic jams (k4). As k3 increases, the total length of the high curvature section decreases. Our simulation results show that the E(k1, k2) maps for k3 and k4 contain two modes: Mode A shows that E decreases with increasing k1 due to an increase in traffic jams, while Mode B shows E increasing with increasing k1 due to a decrease in the density of curved sections and an increase in jamming resolution time. The partial rank correlation coefficient analysis reveals that k1 and k2 have a negative effect on E, while k3 and k4 have a positive effect, with k1 having the greatest influence on E, followed by k3, k4, and k2. The ecological implications of the simulation results are briefly described, and the limitations of the model are discussed.

The costs of keeping cool in a warming world: implications of high temperatures for foraging, thermoregulation and body condition of an arid-zone bird.

Recent mass mortalities of bats, birds and even humans highlight the substantial threats that rising global temperatures pose for endotherms. Although less dramatic, sublethal fitness costs of high temperatures may be considerable and result in changing population demographics. Endothermic animals exposed to high environmental temperatures can adjust their behaviour (e.g. reducing activity) or physiology (e.g. elevating rates of evaporative water loss) to maintain body temperatures within tolerable limits. The fitness consequences of these adjustments, in terms of the ability to balance water and energy budgets and therefore maintain body condition, are poorly known. We investigated the effects of daily maximum temperature on foraging and thermoregulatory behaviour as well as maintenance of body condition in a wild, habituated population of Southern Pied Babblers Turdoides bicolor. These birds inhabit a hot, arid area of southern Africa where they commonly experience environmental temperatures exceeding optimal body temperatures. Repeated measurements of individual behaviour and body mass were taken across days varying in maximum air temperature. Contrary to expectations, foraging effort was unaffected by daily maximum temperature. Foraging efficiency, however, was lower on hotter days and this was reflected in a drop in body mass on hotter days. When maximum air temperatures exceeded 35.5 °C, individuals no longer gained sufficient weight to counter typical overnight weight loss. This reduction in foraging efficiency is likely driven, in part, by a trade-off with the need to engage in heat-dissipation behaviours. When we controlled for temperature, individuals that actively dissipated heat while continuing to forage experienced a dramatic decrease in their foraging efficiency. This study demonstrates the value of investigations of temperature-dependent behaviour in the context of impacts on body condition, and suggests that increasingly high temperatures will have negative implications for the fitness of these arid-zone birds.

Feeding behavior innovation increases foraging efficiency in the Amur falcon but may be a threat to Asian particolored bats.

Behavioral innovations are rare and infrequent in the natural world, but they are pivotal for animals to respond to environmental changes. The ecological benefits of these innovations remain unknown, especially in wild populations. Here, two foraging strategies and three eating behaviors of the Amur falcon (Falco amurensis) were observed during predation on Asian particolored bats (Vespertilio sinensis) across 3 years. We demonstrated that an eating behavioral innovation in F. amurensis increased the foraging efficiency of V. sinensis more than twofold during 3 consecutive years. This showed that changes in feeding behavior by a bird strongly influenced the rate of energy intake. Since predation on bats by falcons mainly occurred during the lactation and post-lactation of bats, this may have a certain level of negative effect on the bat population.

The cost of a meal: factors influencing prey profitability in Australian fur seals.

Knowledge of the factors shaping the foraging behaviour of species is central to understanding their ecosystem role and predicting their response to environmental variability. To maximise survival and reproduction, foraging strategies must balance the costs and benefits related to energy needed to pursue, manipulate, and consume prey with the nutritional reward obtained. While such information is vital for understanding how changes in prey assemblages may affect predators, determining these components is inherently difficult in cryptic predators. The present study used animal-borne video data loggers to investigate the costs and benefits related to different prey types for female Australian fur seals (Arctocephalus pusillus doriferus), a primarily benthic foraging species in the low productivity Bass Strait, south-eastern Australia. A total of 1,263 prey captures, resulting from 2,027 prey detections, were observed in 84.5 h of video recordings from 23 individuals. Substantial differences in prey pursuit and handling times, gross energy gain and total energy expenditure were observed between prey types. Importantly, the profitability of prey was not significantly different between prey types, with the exception of elasmobranchs. This study highlights the benefit of animal-borne video data loggers for understanding the factors that influence foraging decisions in predators. Further studies incorporating search times for different prey types would further elucidate how profitability differs with prey type.

Size-matching as an important driver of plant-pollinator interactions.

One of the greatest challenges in ecology is to understand and predict the functional outcome of interaction networks. Size-matching between plants and pollinators is one of the key functional traits expected to play a major role in structuring plant-pollinator interactions. However, the community-wide patterns of size-matching remain largely unexplored. We studied the association between the degree of size-matching and foraging efficiency, pollination efficiency and the probability of pairwise interactions in a community of Lamiaceae. Our study revealed that foraging efficiency is maximal when bee proboscis length corresponds to the corolla tube depth of the flower visited. Pollination efficiency was maximal when the bee body height corresponds to the corolla width of the flower visited. While the degree of size-matching did not influence the probability of interaction, it significantly influenced the strength of the interaction in terms of visitation frequency. We suggest a size-matching index as a reliable metric to predict the frequency of interactions as well as the effectiveness of visits in terms of foraging efficiency and pollination efficiency.