Reduced Foraging Activity Research Articles

Local and global dynamics of a prey–predator system with fear, Allee effect, and variable attack rate

Fear prompts prey to adopt risk-averse behaviors, such as reduced foraging activity, increased vigilance, and avoidance of areas with high predator presence, which affects its reproduction. In a real scenario, a population requires a minimum density to avoid extinction, known as an Allee threshold. In light of these biological factors, we propose a predator–prey model with (i) a fear effect in a prey population, (ii) an Allee effect in a predator population, and (iii) a non-constant attack rate that modifies the functional response. We ensured the non-negativity and boundedness of the solutions and examined the local and global stability status for each existing steady state solutions. We investigated some deep dynamical properties of the system by varying different parameters, such as cost of fear in prey and strength of the Allee effect in predators and their mortality rate. In codimension one bifurcations, we observed saddle node, Hopf, homoclinic, and coalescence of two limit cycles. Additionally, codimension two bifurcations were observed, including Bautin and Bogdanov Takens bifurcations. To provide a clearer understanding of these bifurcations, we conducted biparametric analysis involving the fear and Allee parameters, as well as the fear parameter and predator mortality rate. Our investigation shows that cost of fear and strength of Allee strongly influences the survival status of the predator. Furthermore, bistability and tristability reveal that the survival and extinction of predator are dependent on the initial population level. Numerical simulations and graphical illustrations are provided to support and validate our theoretical findings.

The behavioural responses of bumblebees Bombus terrestris to simulated rain.

Bumblebee activity typically decreases during rainfall, putting them under the threat of the increased frequency of precipitation due to climate change. A novel rain machine was used within a flight arena to observe the behavioural responses of bumblebees (Bombus terrestris) to simulated rain at both a colony and individual level. During rainfall, a greater proportion of workers left the arena than entered, the opposite of which was seen during dry periods, implying that they compensate for their lack of activity when conditions improve. The proportion of workers flying and foraging decreased while resting increased in rain. This pattern reversed during dry periods, providing further evidence for compensatory activity. The increase in resting behaviour during rain is thought to evade the high energetic costs of flying while wet without unnecessarily returning to the nest. This effect was not repeated in individual time budgets, measured with lone workers, suggesting that the presence of conspecifics accelerates the decision of their behavioural response, perhaps via local enhancement. Bumblebees probably use social cues to strategize their energetic expenditure during precipitation, allowing them to compensate for the reduced foraging activity during rainfall when conditions improve.

Harvester ant colonies differ in collective behavioural plasticity to regulate water loss.

Collective behavioural plasticity allows ant colonies to adjust to changing conditions. The red harvester ant (Pogonomyrmex barbatus), a desert seed-eating species, regulates foraging activity in response to water stress. Foraging ants lose water to evaporation. Reducing foraging activity in dry conditions sacrifices food intake but conserves water. Within a year, some colonies tend to reduce foraging on dry days while others do not. We examined whether these differences among colonies in collective behavioural plasticity persist from year to year. Colonies live 20-30 years with a single queen who produces successive cohorts of workers which live only a year. The humidity level at which all colonies tend to reduce foraging varies from year to year. Longitudinal observations of 95 colonies over 5 years between 2016 and 2021 showed that differences among colonies, in how they regulate foraging activity in response to day-to-day changes in humidity, persist across years. Approximately 40% of colonies consistently reduced foraging activity, year after year, on days with low daily maximum relative humidity; approximately 20% of colonies never did, foraging as much or more on dry days as on humid days. This variation among colonies may allow evolutionary rescue from drought due to climate change.

Parasites either reduce or increase host vulnerability to fishing: a case study of a parasitic copepod and its salmonid host

Parasites generally increase host vulnerability to predators via host manipulation for trophic transmission and reduction of host activities. Predators also select prey depending on the parasite infection status. Despite such parasites' roles in prey-predator interactions in wild animals, how parasites affect human hunting probability and resource consumption remains unknown. We examined the effects of the ectoparasitic copepod Salmincola cf. markewitschi on fish vulnerability to angling. We found that infected fish were less vulnerable compared with non-infected fish when the fish body condition was low, which was probably due to reduced foraging activity. On the contrary, infected fish were more vulnerable when the host body condition was high, probably due to the compensation of parasites' negative effects. A Twitter analysis also suggested that people avoided eating fish with parasites and that anglers' satisfaction decreased when captured fish were parasitized. Thus, we should consider how animal hunting is affected by parasites not only for catchability but also for avoiding parasite infection sources in many local regions.

Seed-coating of rapeseed (Brassica napus) with the neonicotinoid clothianidin affects behaviour of red mason bees (Osmia bicornis) and pollination of strawberry flowers (Fragaria × ananassa).

Neonicotinoid insecticides applied to flowering crops can have negative impacts on bees, with implications for crop pollination. To assess if exposure to the neonicotinoid clothianidin via a treated crop (rapeseed) affected bee behaviour, pollination performance (to strawberry), and bee reproduction, we provided each of 12 outdoor cages with rapeseed (autumn-sown plants complemented with a few spring-sown plants to extend the flowering period) grown from either clothianidin-treated or untreated (control) seeds, together with strawberry plants and a small population of red mason bees (Osmia bicornis). We expected clothianidin to reduce bee foraging activity, resulting in impaired strawberry pollination and bee reproduction. During the early stage of the experiment, we observed no difference between treatments in the length of entire foraging trips, or the combined number of rapeseed and strawberry flowers that the bees visited during these trips. During the later stage of the experiment, we instead determined the time a female took to visit 10 rapeseed flowers, as a proxy for foraging performance. We found that they were 10% slower in clothianidin cages. Strawberries weighed less in clothianidin cages, suggesting reduced pollination performance, but we were unable to relate this to reduced foraging activity, because the strawberry flowers received equally many visits in the two treatments. Clothianidin-exposed females sealed their nests less often, but offspring number, sex ratio and weight were similar between treatments. Observed effects on bee behaviour appeared by the end of the experiment, possibly because of accumulated effects of exposure, reduced bee longevity, or higher sensitivity of the protocols we used during the later phase of the experiment. Although the lack of a mechanistic explanation calls for interpreting the results with cautiousness, the lower strawberry weight in clothianidin cages highlights the importance of understanding complex effects of plant protection products, which could have wider consequences than those on directly exposed organisms.

Seismic surveys near gray whale feeding areas off Sakhalin Island, Russia: assessing impact and mitigation effectiveness

In 2015, two oil and gas companies conducted seismic surveys along the northeast coast of Sakhalin Island, Russia, near western gray whale (Eschrichtius robustus) feeding areas. This population of whales was listed as Critically Endangered at the time of the operations described here but has been reclassified as Endangered since 2018. The number and duration of the 2015 seismic surveys surpassed the level of previous seismic survey activity in this area, elevating concerns regarding disturbance of feeding gray whales and the potential for auditory injury. Exxon Neftegas Limited (ENL) developed a mitigation approach to address these concerns and, more importantly, implemented a comprehensive data collection strategy to assess the effectiveness of this approach. The mitigation approach prioritized completion of the seismic surveys closest to the nearshore feeding area as early in the season as possible, when fewer gray whales would be present. This was accomplished by increasing operational efficiency through the use of multiple seismic vessels and by establishing zones with specific seasonal criteria determining when air gun shutdowns would be implemented. These zones and seasonal criteria were based on pre-season modeled acoustic footprints of the air gun array and on gray whale distribution data collected over the previous 10 years. Real-time acoustic and whale sighting data were instrumental in the implementation of air gun shutdowns. The mitigation effectiveness of these shutdowns was assessed through analyzing short-term behavioral responses and shifts in gray whale distribution due to sound exposure. The overall mitigation strategy of an early survey completion was assessed through bioenergetics models that predict how reduced foraging activity might affect gray whale reproduction and maternal survival. This assessment relied on a total of 17 shore-based and 5 vessel-based teams collecting behavior, distribution, photo-identification, prey, and acoustic data. This paper describes the mitigation approach, the implementation of mitigation measures using real-time acoustic and gray whale location data, and the strategy to assess impacts and mitigation effectiveness.

Staying cool and eating junk: Influence of heat dissipation and anthropogenic food on foraging and body condition in an urban passerine

Climate change and urbanization are two of the most important current global change drivers. However, most studies have focused on these issues in isolation, limiting our ability to predict the impacts of the two in tandem. During hot conditions, many birds reduce foraging activity to minimise heat gain, which can result in costly trade-offs, affecting their ability to maintain body mass. In urban environments however, higher anthropogenic food or water availability could buffer individuals from these potential costs. In this study, we explore the impacts of air temperature on the foraging behaviour and body mass of an urban passerine, the Red-winged Starling, Onychognathus morio in Cape Town, South Africa. In our study system (a university campus), anthropogenic food abundance fluctuates over short timescales, with food being more abundant on weekdays and less abundant on weekends. This system allows us to explore how birds respond to elevated temperatures during days of varying availability of anthropogenic food. We found that individuals increased heat dissipation behaviours with temperature, leading to an apparent trade-off between foraging and heat dissipation. However, despite reduced foraging time, starlings were able to maintain constant food intake rate and body mass with rising temperatures irrespective of the short-term food fluctuations. This suggests that overall food and water abundance in this urban environment buffered individuals from the effects of elevated air temperature, at least within the current range experienced in this system and outside of the breeding season.

Artificial light at night and anthropogenic noise alter the foraging activity and structure of vertebrate communities

Light and noise pollution from human activity are increasing at a dramatic rate. These sensory stimuli can have a wide range of effects on animal behavior, reproductive success, and physiology. However, less is known about the functional and community-level consequences of these sensory pollutants, especially when they co-occur. Using camera traps in a manipulative field experiment, we studied the effects of anthropogenic light and noise, singularly and in tandem, on richness and community turnover at both the taxa and functional group level as well as foraging activity. We showed that both light and noise pollution did alter taxonomic richness and that these effects can differ depending on the scale of observation. Increases in light levels had a negative effect on richness at the camera-level scale, but light-treated sites had the highest pooled (i.e., cumulative) richness of all treatment types. In contrast, noise was found to have a negative effect on cumulative richness; however, when both stimuli were present, the addition of night-lighting mitigated the effects of noise. Artificial light and moonlight had the strongest influence on community turnover, and results remained consistent at both the taxa and functional group level. Additionally, increases in ambient noise and moonlight, but not artificial light, reduced foraging activity. Our study provides evidence that alterations to the sensory environment can alter the richness and composition of communities and that effects can be scale-dependent and also alter foraging behavior. Unexpectedly, the addition of artificial light may have mitigated the negative effects of noise on cumulative taxonomic richness. This highlights the importance of researching the consequences of co-exposure to these globally common pollutants.

Novel object test in farmed fallow deer (Dama dama) – The impact on appearance, diurnal rhythm and behaviour in the foraging area

The fallow deer (Dama dama) represents a typical example of a species in the early stage of domestication, where selection for tameness is not yet complete. In contrast to fully domesticated species, there is still a lack of studies on the behaviour of deer under farm conditions and their response to changes in their environment. Therefore, this study aimed to investigate the behaviour of fallow deer after the introduction of the novel object (NO) into the enclosure. The herd was observed at the most frequently visited part of the enclosure, i.e. the foraging area near the feeding station. We installed several different Non-animal NOs (abstract object/installation, camping chair, colourful boxes) and Animal NO (animal-shaped toy) with intervening Controls (periods without NO). Results generally showed that time spent at the foraging area decreased in the presence of NO (p < 0.05). This effect was significantly stronger when NO had an animal shape (horse-shaped toy), with the frequency of animal appearance also being lower with frequent complete absence of animals at the foraging area. However, diurnal rhythm of animal appearance did not differ, nor did group size. When looking at the ratio among different behaviours that animals performed in the foraging area (movement, stationary, feeding), we found no differences between the Control and Non-animal NO (feeding 42−43 %, stationary 38–39 %). However, in the presence of Animal NO, feeding behaviours increased significantly (57 %), while the stationary behaviours decreased significantly (24 %). While resting predominated among stationary behaviours in the Control and Non-animal NO treatments (72–75 %), vigilance represented the most stationary behaviours in the presence of Animal NO (58 %). Movement was consistently performed to the same extent (18–20 %). Therefore, the presence of the novel object reduced foraging activity and increased vigilance in fallow deer, and deer breeders should consider this. Avoidance of the foraging area within the enclosure, where animals have fewer alternative food sources, can be particularly problematic. Therefore, preventing or disturbing their regular foraging routine should be minimized to meet basic welfare requirements.

Behavioral changes in host foraging: Experiments with Clinostomum (Trematoda, Digenea) parasitizing Loricariichthys platymetopon (Loricariidae)

Complex life cycle parasites can manipulate the behavior of intermediate hosts in order to reduce their fitness and increase the chance of completing life cycle. In order to understand the effects of the trematode parasites of the genus Clinostomum on host fish Loricariichthys platymetopon, a filmed experiment was carried out to quantify the foraging activity of hosts with different intensities of infection. The results suggest that hosts with higher parasite intensities reduced foraging activity early in the morning when compared to hosts with low intensities. This period may be critical for hosts since birds, the target hosts of such trematodes, forage intensively at dawn.

Cue recognition and behavioural responses in the three-spined stickleback (Gasterosteus aculeatus) under risk of fish predation

To effectively respond to predation risk, prey must assess the risk associated with different predation cues. Predation cues can stem either from the predator or from conspecifics and indicate different predation risk levels, thus eliciting different anti-predation responses. The three-spined stickleback is a well-studied fish species often found in gregarious formations. Previous studies show that sticklebacks perform a variety of anti-predation behaviours; however, little is known about how they respond to multiple simultaneous predator cues, characteristic of heterogeneous natural habitats. Here, we experimentally compare the relative importance of three types of predation cues (visual predator cue, chemical predator odour cue and chemical alarm cue from injured conspecifics) and their interactions, on anti-predation and foraging behaviour of sticklebacks. Results showed that (1) individual sticklebacks responded most strongly to visual predator cues, which resulted in reduced foraging activity, increased spine erection and increased predator inspection; (2) the presence of chemical cues (predator odour and/or conspecific alarm cues) stimulates freezing behaviour to a minor extent; and (3) anti-predation behaviour manifests as a trade-off with foraging-related activities. Overall, the results indicate that sticklebacks could assess risk and modify their behavioural responses depending on which cues are present in the environment. The experimental approach of using factorial combinations of different predatory cues can increase our understanding of the role of multimodal cues in aquatic ecosystems.

Fungicides chlorothanolin, azoxystrobin and folpet induce transcriptional alterations in genes encoding enzymes involved in oxidative phosphorylation and metabolism in honey bees (Apis mellifera) at sublethal concentrations

Fungicides are highly used for plant protection but their molecular and chronic effects are poorly known. Here, we analyse transcriptional effects in the brain of honey bees of three frequently applied fungicides, azoxystrobin, chlorothanolin and folpet, after oral exposure for 24, 48 and 72 h. Among transcripts assessed were genes encoding proteins for immune and hormone system regulation, oxidative phosphorylation, metabolism, and acetylcholine receptor alpha 1. Azoxystrobin and folpet induced minor alterations, including down-regulation of hbg-3 by azoxystrobin and induction of ndufb-7 by folpet. Chlorothanolin induced strong transcriptional down-regulation of genes encoding enzymes related to oxidative phosphorylation and metabolism, including cyp9q1, cyp9q2 and cyp9q3, acetylcholine receptor alpha 1 and hbg-3 and ilp-1, which are linked to hormonal regulation and behavioural transition of honey bees. Exposures to chlorothanolin in different seasonal times showed different responsiveness; responses were faster and often stronger in April than in June. Chlorothanolin caused the strongest effects and affected transcriptional abundance of genes related to energy production, metabolism and the endocrine system. Disturbed energy production may reduce foraging activity and hormonal dysregulation, such as the transition of nurse bees to foragers. Further analyses are needed to further substantiate potential adverse effects of chlorothanolin in bees on the physiological level.

High air temperatures induce temporal, spatial and social changes in the foraging behaviour of wild zebra finches

Understanding how heatwaves affect organisms is becoming an important issue in animal behaviour, given the changing climate. Exposure to high air temperatures can lead to lethal hyperthermia, when individuals are no longer able to maintain body temperature within their optimal physiological range. Animals will rapidly adjust their behaviour, prioritizing heat dissipation through activities such as drinking and sitting in shade to maintain their body temperature over other activities, such as foraging. Here, we used an automated logging system to consider both the spatial and temporal foraging patterns under a range of different air temperatures at an individual level, in a strictly granivorous species in the wild. We continuously monitored individual foraging activity of wild zebra finches, Taeniopygia guttata, a species well adapted to arid conditions, in an Australian arid area across two heatwave events. High air temperatures significantly reduced foraging activity, with the extent of this effect depending on the time of day. They also led to a significant decrease in the number of birds foraging together and to birds spending a higher proportion of their foraging activity close to a water supply. As temperatures exceeded 35 °C we saw a significant escalation of heat dissipation behaviour. Our results indicate that extreme air temperatures significantly affected temporal, social and spatial characteristics of zebra finch foraging behaviour and these are likely to adversely reduce an individual's capacity to forage efficiently, and consequently its food intake in the short term, while also potentially having implications for both reproduction and survival in the long term.

Viral infections in fire ants lead to reduced foraging activity and dietary changes

Despite the presence of conserved innate immune function, many insects have evolved a variety of mechanical, chemical, and behavioral defensive responses to pathogens. Illness-induced anorexia and dietary changes are two behavioral defensive strategies found in some solitary insects, but little is known regarding the role of such behaviors in social insects, especially in ants. In the present study we examined if such reduced foraging activity exists for a social insect, the invasive fire ant Solenopsis invicta, and its viral pathogen, Solenopsis invicta virus 1 (SINV-1). Virus-free fire ant colonies were split into two colony fragments, one of which subsequently was inoculated with SINV-1. Four food resources with different macronutrient ratios were presented to both colony fragments. SINV-1-inoculated colony fragments consistently displayed reduced foraging performance (e.g., foraging intensity and recruitment efficiency), a decline in lipid intake, and a shift in dietary preference to carbohydrate-rich foods compared with virus-free fragments. These findings provide the first evidence for virus-induced behavioral responses and dietary shifts in shaping the host-pathogen interactions in fire ants. The findings also suggest a possible mechanism for how fire ant colonies respond to viral epidemics. Potential implications of these behavioral differences for current management strategies are discussed.

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.Electronic supplementary materialThe online version of this article (doi:10.1007/s00442-016-3729-8) contains supplementary material, which is available to authorized users.

Size-related habitat use in juvenile Atlantic salmon: the importance of intercohort competition

In stream-living salmonids, an underlying mechanism for the critical period after emergence has generally been assumed to be size-dependent swimming capacity constraining fry (age-0) to low-velocity habitats with reduced food availability and intense competition. A further plausible mechanism is that intercohort habitat exclusion confines fry to marginal habitats. This possibility was tested using a seminatural stream with 16 test arenas, each comprising one high-velocity, deep habitat and one low-velocity, shallow habitat. We observed groups of newly emerged Atlantic salmon (Salmo salar) fry, either alone or in sympatry with one or two age-1 salmon. Salmon fry used high-velocity areas (42.2 ± 0.4 cm·s−1) most extensively in the absence of intercohort competition, where they obtained more food than in low-velocity areas (3.3 ± 0.3 cm·s−1), even though foraging efficiency was lower (though not significantly so). In sympatry with older cohorts, fry increased their use of the low-velocity habitat, with a reduced foraging activity, suggesting that strong older cohorts in natural populations may have the potential to influence the strength of the recruiting cohort by negative density dependence due to interference competition for habitat.

Foraging differences between the native snail, Fossaria sp. and the invasive New Zealand mudsnail (Potamopyrgus antipodarum) in response to phosphorus limitation

Animals require food adequate in quantity and quality to grow and reproduce. Therefore, environments limited in key nutrients may promote competitive interactions, with the organisms best equipped to exploit these resources gaining a competitive advantage. We compared the foraging behavior of the New Zealand mudsnail (Potamopyrgus antipodarum), a worldwide invader that can dominate secondary productivity to Fossaria (Bakerlymnaea) bulimoides which is native to western North America to determine whether either of these animals modify their behavior to compensate for nutrient limitation. We used the amount of dietary phosphorus (P) as a measure of food quality, because P is often a limiting resource in freshwater ecosystems. We compared the feeding rate and food preference of each snail species to food containing two levels of P. Because potential competitors can also affect foraging decisions, we conducted additional experiments comparing the effects of conspecifics and heterospecifics under low and high biomass. Consistent with predictions, both species increased feeding rate of low P food, and P. antipodarum consumed more food per unit mass than Fossaria. However, only Fossaria displayed a preference for high P food. The two snails also differed in their response to interacting snails. Fossaria significantly reduced foraging activity in the presence of both conspecifics and heterospecifics, while P. antipodarum spent more time feeding under high conspecific density. Although the presence of high densities of P. antipodarum may negatively impact Fossaria in its native habitat, Fossaria’s ability to locate and preferentially feed on higher quality resources may mitigate some of the impact, potentially facilitating coexistence between these two species.

Multiple stressors: using the honeybee model BEEHAVE to explore how spatial and temporal forage stress affects colony resilience

The causes underlying the increased mortality of honeybee Apis mellifera colonies observed over the past decade remain unclear. Since so far the evidence for monocausal explanations is equivocal, involvement of multiple stressors is generally assumed. We here focus on various aspects of forage availability, which have received less attention than other stressors because it is virtually impossible to explore them empirically. We applied the colony model BEEHAVE, which links within‐hive dynamics and foraging, to stylized landscape settings to explore how foraging distance, forage supply, and “forage gaps”, i.e. periods in which honeybees cannot find any nectar and pollen, affect colony resilience and the mechanisms behind. We found that colony extinction was mainly driven by foraging distance, but the timing of forage gaps had strongest effects on time to extinction. Sensitivity to forage gaps of 15 days was highest in June or July even if otherwise forage availability was sufficient to survive. Forage availability affected colonies via cascading effects on queen's egg‐laying rate, reduction of new‐emerging brood stages developing into adult workers, pollen debt, lack of workforce for nursing, and reduced foraging activity. Forage gaps in July led to reduction in egg‐laying and increased mortality of brood stages at a time when the queen's seasonal egg‐laying rate is at its maximum, leading to colony failure over time. Our results demonstrate that badly timed forage gaps interacting with poor overall forage supply reduce honeybee colony resilience. Existing regulation mechanisms which in principle enable colonies to cope with varying forage supply in a given landscape and year, such as a reduction in egg‐laying, have only a certain capacity. Our results are hypothetical, as they are obtained from simplified landscape settings, but they are consistent with existing empirical knowledge. They offer ample opportunities for testing the predicted effects of forage stress in controlled experiments.

European Roe Deer Increase Vigilance When Faced with Immediate Predation Risk by Eurasian Lynx

AbstractPrey animals must balance antipredatory behaviour with foraging behaviour. According to the risk allocation hypothesis, prey increase antipredatory behaviour and reduce foraging activity during pulses of high risk, but with continuous risk, other activities must continue and antipredatory behaviour decreases despite the risk. We studied the impact of lynx presence on the vigilance behaviour of wild roe deer under conditions of (i) a pulsed elevated risk by experimentally spreading lynx urine as an olfactory cue, and (ii) continuous risk by comparing an area where lynx was eradicated 160 years ago to an area where lynx has been re‐introduced 30 years ago. Roe deer were extremely vigilant in response to the predator olfactory cue; however, roe deer vigilance did not differ measurably among areas with or without potential lynx presence. Deer were more vigilant before sunset than during the night at both study areas, probably due to long‐term adaptation of roe deer to human hunting during daytime. Vigilance decreased from August to September even though activity of lynx increases in autumn, which may be a result either of increased foraging due to decrease in food quality in autumn, or of changes in social organization of the deer. Our results suggested that the degree of vigilance depends on environmental cues. We found that roe deer respond to lynx urine despite a long absence of lynx in the ecosystem. Our results support the risk allocation hypothesis for responses to pulses of high risk but not for responses to continuous elevated levels of risk.

Manipulators live better, but are they always parasites?

A recent study reports partner manipulation for an interaction that was considered a reward-for-defence mutualism. Secretions of lycaenid caterpillars altered ant locomotion and aggressiveness, likely by manipulating dopaminergic signalling. This study opens the question whether such manipulation is common and whether manipulation necessarily characterises an interaction as parasitism.