Increase Encounter Rates Research Articles

LMC-driven Anisotropic Boosts in Stream–Subhalo Interactions

Dark matter subhalos are predicted to perturb stellar streams; stream morphologies and dynamics can, therefore, constrain the mass distribution of subhalos. Using FIRE-2 simulations of Milky Way–mass galaxies, we demonstrate that the presence of an LMC analog significantly changes stream–subhalo encounter rates. The LMC analog brings in many subhalos, increasing encounter rates for streams near the massive satellite by 10%–40%. Additionally, the LMC analog displaces the host from its center of mass (inducing reflex motion), which causes a north–south asymmetry in the density and radial velocity distributions of subhalos. This asymmetry, combined with the presence of LMC-analog subhalos, causes encounter rates at the same distance to vary by 50%–70% across the sky, particularly in regions opposite the LMC analog. Furthermore, the LMC analog induces a density wake in the host's dark matter halo, further boosting the encounter rates near the LMC analog. We also explore how stream orbital properties affect encounter rates, finding up to a 50% increase for streams moving retrograde to the LMC analog’s orbit in the opposite quadrant. Finally, we report the encounter rates for Milky Way streams within the context of our simulations, both with and without the presence of an LMC analog. The dependence of encounter rates on stream location, orbit, and their position relative to the LMC has important implications for where to search for streams with spurs and gaps in the Milky Way.

Cattle exclusion increases encounters of wild herbivores in Neotropical forests

Abstract Ongoing habitat loss and species extinctions require managers to implement and quantify the effectiveness of conservation actions for protecting biodiversity. Fencing, when done properly, is an important management tool for conservation in landscapes where wildlife and domestic animals co‐occur, potentially enhancing habitat use through selective exclusion of domestic species. For instance, the fencing of forest patches in the Neotropics is expected to reduce the degradation of understory vegetation by cattle, releasing these resources for the native community of browsers and fruit consumers. Here, we implemented an ecological experiment using a before‐after control‐impact design to quantify the effect of cattle exclusion on encounter probability of the native community of browsers and fruit consumers, and percent ground cover in multifunctional landscapes of the Colombian Orinoquía. We built 14 km of wildlife‐permeable fences along forest edges in four forest patches (i.e. blocks) containing control and fenced (treatment) sites. We installed 33 camera traps to obtain information about wildlife and cattle encounter probabilities, before and after the fences were constructed. We used Bayesian generalised linear mixed effects models to quantify the effect of fences via the interaction between the time period (before and after the fences were built) and treatment (control or fenced sites). Fencing was effective at reducing encounter probabilities of cattle in the treated sites, and it had a positive impact on relative encounter probabilities of four of seven studied wildlife species (herbivores including the black agouti [dry season only], lowland tapir [dry season only] and spotted paca [both seasons] and an omnivore, the South American coati [rainy season only]). The effect of fencing was negative for the collared peccary but only during the dry season. No statistically significant effect was detected for the white‐lipped peccary or white‐tailed deer. Synthesis and applications: We provide experimental evidence that fences are effective at selectively excluding cattle and increasing encounter rates of wild browsers and fruit consumers in forest patches where these species co‐occur with cattle. Our results highlight an important application of fencing ecology in Neotropical forests, where the implementation of wildlife‐permeable fences is feasible due to smaller body sizes of wildlife compared to domestic animals such as cattle.

The effect of vorticity on the feeding of a freshwater grazer

AbstractThe transfer of energy through zooplankton grazing on phytoplankton is one of the most important interactions in aquatic ecosystems, yet the role of hydrodynamic forces is not fully understood. Factors that influence these interactions include algal size and shape and the interactions between grazer and alga dictated by hydrodynamic forces. Hydrodynamic forcing lead to unimodal relationships in grazer clearance rates (CR) because water motion and turbulence increases encounters but interferes with feeding at high levels. We expect higher CR on small algae due to increased encounter rates caused by vorticity generated in a horizontally oriented rotating cylinder to model increasing turbulence, whereas longer cells, tumbling in the flow, may be more difficult to handle. Ultimately, we expect that increased vorticity will interfere with zooplankton swimming. The CR of Daphnia magna followed the unimodal trend, with higher CR on the small, spherical Chlorella vulgaris than on larger, elongated, and colonial Scenedesmus quadricauda. This was likely due to lower handling time and higher concentration of the smaller cells in the feeding radius around D. magna. The normal hop‐sink swimming behavior of the Daphnia was affected by increasing vorticity; hop frequency decreased, displacement increased, and there was a loss of vertical orientation. This pattern in feeding and swimming were predicted by vorticity. These results for Daphnia differ from those obtained for copepods, which do not respond to vorticity. Given the importance of vorticity in nature, it is relevant to examine grazer feeding interactions under ecologically relevant hydrodynamic conditions.

Collisions among elongated settling particles: The twofold role of turbulence

We study the collision rates of settling spheres and elongated spheroids in homogeneous, isotropic turbulence by means of direct numerical simulations aiming to understand microscale-particle encounters in oceans and lakes. We explore a range of aspect ratios and sizes relevant to the dynamics of plankton and microplastics in water environments. The results presented here confirm that collision rates between elongated particles in a quiescent fluid are more frequent than those among spherical particles in turbulence due to oblique settling. We also demonstrate that turbulence generally enhances collisions among elongated particles as compared to those expected for a random distribution of the same particles settling in a quiescent fluid, although we also find a decrease in collision rates in turbulence for particles of the highest density and moderate aspect ratios (A=5). The increase in the collision rate due to turbulence is found to quickly decrease with aspect ratio, reach a minimum for aspect ratios approximately equal to 5, and then slowly increase again, with an increase up to 50% for the largest aspect ratios investigated. This non-monotonic trend is explained as the result of two competing effects: the increase in the surface area with aspect ratio (beneficial to increase encounter rates) and the alignment of nearby prolate particles in turbulence (reducing the probability of collision). Turbulence mixing is, therefore, partially balanced by rod alignment at high particle aspect ratios.

Testing presence of directionality information in female spider silk trails through male trail-following behavior

Mate search is challenging for solitary species. Trails represent a particularly potent, target-oriented means for finding mates, as trail-following increases encounter rates between individuals compared to random search. Embedding directionality information into the trail allows individuals to follow trails correctly to the source. Yet, directionality remains poorly understood. Spiders deposit trails during locomotion consisting of silk lines and substrate-borne chemicals. We conducted multiple experiments to test whether female silk trails convey directionality information, whether directionality is chemically or structurally encoded and depends on female phenotype. We also examined whether males interact with silk in a way that suggests information gathering. We exposed males of the cursorial spider Pisaura mirabilis to female trails deposited unidirectionally and scored their trail-following direction (i.e., same as or opposite to the females’). Tests were repeated after washing trails with a solvent to remove putative chemicals and by sourcing silk from females of different feeding regimes. While we found little evidence for male directional trail-following, we did find that unwashed trails were more likely to be followed than washed trails. Similarly, trails of relatively larger females were more likely to be followed correctly than those of smaller females. Males extensively probed and pulled on silk lines with their appendages, suggesting the gathering of chemical and tactile information. Taken together, results suggest that directional trail-following is selected only under specific contexts in this species. Chemical attributes of trails may convey information on female quality, with directional trail-following reflecting male mate choice in a system characterized by costly male nuptial gifts.Significance statementIn the context of male mate search, following conspecific trails increases the chances of encountering a mating partner, especially if trails provide information about the direction the conspecific went. Yet, trail directionality remains poorly understood. Female spiders deposit silk trails as they walk. We overall show that males follow trails directionally only under a specific context. Males were more likely to follow correctly when trails were unmanipulated (compared to being washed with solvents to remove chemicals) and when they were deposited by relatively larger females (compared to smaller ones). Chemical attributes of trails may potentially indicate directionality, while decoding movement direction from trails of larger females may reflect male preferences for females of higher reproductive value.

Logging, linear features, and human infrastructure shape the spatial dynamics of wolf predation on an ungulate neonate.

Humans are increasingly recognized as important players in predator-prey dynamics by modifying landscapes. This trend has been well-documented for large mammal communities in North American boreal forests: logging creates early seral forests that benefit ungulates such as white-tailed deer (Odocoileus virginianus), while the combination of infrastructure development and resource extraction practices generate linear features that allow predators such as wolves (Canis lupus) to travel and forage more efficiently throughout the landscape. Disturbances from recreational activities and residential development are other major sources of human activity in boreal ecosystems that may further alter wolf-ungulate dynamics. Here, we evaluate the influence that several major types of anthropogenic landscape modifications (timber harvest, linear features, and residential infrastructure) have on where and how wolves hunt ungulate neonates in a southern boreal forest ecosystem in Minnesota, USA. We demonstrate that each major anthropogenic disturbance significantly influences wolf predation of white-tailed deer fawns (n = 427 kill sites). In contrast with the "human shield hypothesis" that posits prey use human-modified areas as refuge, wolves killed fawns closer to residential buildings than expected based on spatial availability. Fawns were also killed within recently-logged areas more than expected. Concealment cover was higher at kill sites than random sites, suggesting wolves use senses other than vision, probably olfaction, to detect hidden fawns. Wolves showed strong selection for hunting along linear features, and kill sites were also closer to linear features than expected. We hypothesize that linear features facilitated wolf predation on fawns by allowing wolves to travel efficiently among high-quality prey patches (recently logged areas, near buildings), and also increase encounter rates with olfactory cues that allow them to detect hidden fawns. These findings provide novel insight into the strategies predators use to hunt ungulate neonates and the many ways human activity alters wolf-ungulate neonate predator-prey dynamics, which have remained elusive due to the challenges of locating sites where predators kill small prey. Our research has important management and conservation implications for wolf-ungulate systems subjected to anthropogenic pressures, particularly as the range of overlap between wolves and deer expands and appears to be altering food web dynamics in boreal ecosystems.

Ecological and anthropogenic drivers of leopard (Panthera pardus fusca) attack occurrence on humans in Nepal

Abstract The negative impact of large carnivore presence in human‐dominated landscapes manifests as livestock depredation and in extreme cases as attacks on humans. In the case of conflict with leopards in Nepal, attacks resulting in human fatality have become more frequent over time, thus creating an urgent socio‐ecological and management issue. We estimated the occurrence of leopard attacks in Nepal from human‐leopard conflict cases reported in the media. We used occupancy models to analyse data collected from online news reports on incidents of leopard attacks on humans to explore drivers of leopard attacks on a landscape scale. Our results suggest that the probability of occurrence of leopard attack is associated with human population density, terrain ruggedness and livestock density. The human population density effect may be indicative of a density‐dependent relationship, where attacks are more likely in areas where an increased abundance of humans increases encounter rates with leopards. The positive effect of livestock density suggests that livestock may be drawing leopards into human settlements, and consequently increasing the likelihood of attacks on humans. Terrain ruggedness might be offering ideal conditions to facilitate attacks on humans, for example remoteness and high amounts of cover to launch ambush attacks. We provide inference and insights into key determinants of leopard attacks on humans on a landscape scale. These insights can be used to guide future research, inform mitigation measures to reduce leopard attacks and foster a better understanding of the interaction between people and leopards. This study demonstrates the applicability and novelty of using a hierarchical modelling framework applied to freely and publicly available media reports to inform the applied management of human‐wildlife conflict at a national scale. Read the free Plain Language Summary for this article on the Journal blog.

Increased fishery-independent sampling effort results in improved population estimates for multiple target species

The power of fishery-independent surveys for stock assessments and management decisions is in their consistency over time and space. Although the preference is to limit change to survey execution, such changes may be necessary. In multi-species surveys, changes that improve metrics for one species may be a detriment to survey performance for others. In 2010, the Southeast Reef Fish Survey (SERFS) was formed to better address sampling needs off the U.S. Southeast Atlantic coast by intensifying a historical chevron trap survey (MARMAP), especially at the northern and southern extent of the sampling range. We used several performance metrics (encounter rate, annual coefficient of variability, standard error, and relative abundance index values) to determine the impact of this change in survey coverage on trend estimates for three commonly encountered species with varying centers of distribution in the survey region. Gray Triggerfish (Balistes capriscus) is found throughout the range of both surveys (i.e. centrally-distributed), while White Grunt (Haemulon plumierii) and Red Snapper (Lutjanus campechanus) are centered near the northern and southern extent of the sampling range, respectively. For Gray Triggerfish, the survey intensification had no effect on encounter rate, but reduced the coefficient of variation and indicated that the historical index of relative abundance may have been overestimated. For White Grunt, the survey intensification slightly improved CV but did not affect the index of relative abundance value or encounter rate. For Red Snapper, SERFS increased encounter rates, reduced CV overall, and detected a population increase 5 years earlier than MARMAP. Overall, the intensification of the survey improved at least one performance metric for each species and showed few deleterious effects on performance, suggesting that intensification of the survey was a net-positive for the accurate estimation of population trends in several species of interest.

Immature hard ticks infected with Rickettsia amblyommatis on breeding birds from Pantanal

Immature hard ticks from the genus Amblyomma feed on blood from a wide range of Neotropical avian hosts. They serve as vectors for pathogens of medical and veterinary importance, such as Rickettsia agents of the spotted fever group (SFG). Hence, determining ecological factors that increase encounter rates between immature ticks and their avian hosts may contribute to the understanding of tick-borne diseases transmission. Here, we used 720 individual birds from 96 species surveyed in the Brazilian Pantanal to test whether host breeding season influenced tick infestation probabilities. Additionally, collected ticks were screened for Rickettsia agents to describe new avian-tick-bacteria associations. Our models revealed that the probability of an individual bird being infested with immature ticks was similar during the breeding and pre-breeding season, but higher loads of immature tick stages were found during the breeding season. Host sex did not predict infestation probability, but Rickettsia agents recovered from ticks were more prevalent during the pre-breeding season. The new records of host usage by larvae and nymphs of Amblyomma in Pantanal and the growing body of tick surveys in Neotropical avian communities, suggest that immature ticks may benefit from avian blood sources during their annual cycle. The low number of infected ticks with Rickettsia agents on Pantanal birds suggest that this vertebrate group are likely not acting as reservoirs for these microorganisms. However, long-term surveys at the same site are imperative to determine which tick species are acting as reservoirs for Rickettsia agents in Pantanal and determine whether birds are playing a role in dispersing ticks and tick-borne pathogens.

Feral pig (Sus scrofa) activity and landscape feature revisitation across four sites in eastern Australia

Quantifying feral pig movements and understanding the fine-scale ecological drivers of feral pig landscape use are important factors for optimising pest management programs. We tracked 59 GPS-collared feral pigs at four sites in eastern Australia between 2017 and 2021, for a mean of 375 ± 277 (s.d.) days. The mean number of successful GPS fixes was 15 577 ± 11 833 (s.d.) and these were recorded at 30-min intervals. We calculated mean hourly and daily distances travelled to determine feral pig activity and investigated the influence of sex, site, season and time of day on this activity. We also investigated the proximity of highly active sites to habitat covariates, along with intensity and frequency of site use. Male daily movement, 4.9 km (95% CI = 4.2, 5.6 km), was significantly greater than it was for females, 3.6 km (95% CI = 3.0, 4.1 km) and males maintained a high level of activity all night, while female activity was predominantly crepuscular. Study site was a significant determinant of daily movement, but season was not, across either sex or site. Highly-visited site selection was negatively associated with distance from creeks, dams, cultivation, open herbaceous vegetation and medium woody vegetation. Both medium woody vegetation and dam sites had the longest duration of use (3 and 2.7 h respectively) and the shortest time between visitations (14.5 and 13 h respectively). Quantifying feral pig activity and key habitat feature preference are important steps in improving management programs. Better prediction of feral pig movement and behaviour allows for more targeted placement of control tools, potentially increasing encounter rates.

Protection from fishing improves body growth of an exploited species.

Hunting and fishing are often size-selective, which favours slow body growth. In addition, fast growth rate has been shown to be positively correlated with behavioural traits that increase encounter rates and catchability in passive fishing gears such as baited traps. This harvest-induced selection should be effectively eliminated in no-take marine-protected areas (MPAs) unless strong density dependence results in reduced growth rates. We compared body growth of European lobster (Homarus gammarus) between three MPAs and three fished areas. After 14 years of protection from intensive, size-selective lobster fisheries, the densities in MPAs have increased considerably, and we demonstrate that females moult more frequently and grow more during each moult in the MPAs. A similar, but weaker pattern was evident for males. This study suggests that MPAs can shield a wild population from slow-growth selection, which can explain the rapid recovery of size structure following implementation. If slow-growth selection is a widespread phenomenon in fisheries, the effectiveness of MPAs as a management tool can be higher than currently anticipated.

Contrasting phytoplankton-zooplankton distributions observed through autonomous platforms, in-situ optical sensors and discrete sampling.

Plankton distributions are remarkably 'patchy' in the ocean. In this study, we investigated the contrasting phytoplankton-zooplankton distributions in relation to wind mixing events in waters around a biodiversity-rich island (Runde) located off the western coast of Norway. We used adaptive sampling from AUV and shipboard profiles of in-situ phytoplankton photo-physiology and particle identification (copepods, fecal pellets and the dinoflagellate Tripos spp.) and quantification using optical and imaging sensors. Additionally, traditional seawater and net sampling were collected for nutrient and in-vitro chlorophyll a concentrations and phytoplankton and meso-zooplankton abundances. Persistent strong wind conditions (~5 days) disrupted the stratification in offshore regions, while stratification and a subsurface chlorophyll maximum (SCM) were observed above the base of the mixed layer depth (MLD ~30 m) in inshore waters. Contrasting phytoplankton and zooplankton abundances were observed between inshore (with the presence of a SCM) and offshore waters (without the presence of a SCM). At the SCM, phytoplankton abundances (Tripos spp., the diatom Proboscia alata and other flagellates) were half (average of 200 cell L-1) of those observed offshore. On the contrary, meso-zooplankton counts were ~6× higher (732 ind m-3 for Calanus spp.) inshore (where a SCM was observed) compared to offshore areas. In parallel, fecal pellets and ammonium concentrations were high (>1000 ind m-3 for the upper 20 m) at the SCM, suggesting that the shallow mixed layer might have increased encounter rates and promoted strong grazing pressure. Low nutrient concentrations (< 1μM for nitrate) were found below the MLD (60 m) in offshore waters, suggesting that mixing and nutrient availability likely boosted phytoplankton abundances. The size of the absorption cross-section (σPII') and yield of photosystem II photochemistry under ambient light (φPII') changed according to depth, while the depth-related electron flow (JPII) was similar between regions, suggesting a high degree of community plasticity to changes in the light regime. Our results emphasize the importance of using multiple instrumentation, in addition to traditional seawater and net sampling for a holistic understanding of plankton distributions.

Copepod interaction with small‐scale, dissipative eddies in turbulence: Comparison among three marine species

AbstractA physical model of a Burgers vortex was created in the laboratory with characteristics corresponding to dissipative‐scale eddies that copepods are likely to encounter in turbulent flows. The swimming behavior of three marine copepod species is assessed as a function of vortex strength in and around the flow structure with the vortex axis aligned vertically or horizontally in the water. The studied species are Acartia tonsa, an estuarine copepod with a hop‐sink swimming style; Temora longicornis, a coastal copepod with a cruise swimming style; and Calanus finmarchicus, an open‐ocean copepod with a cruise‐sink swimming style. The results show that copepods change their swimming behavior with the intensity of the Burgers vortex and reveal species‐specific responses in nearly all kinematic parameters. A. tonsa and C. finmarchicus exhibited the strongest behavioral response to increasing vortex strength and T. longicornis exhibited the weakest response. A. tonsa and T. longicornis showed no response to changes in vortex orientation, whereas the behavior of C. finmarchicus revealed some vortex orientation dependence. One common behavior among the species is that the swimming trajectory shape becomes increasingly curved and spiral around the vortex core with increasing vortex strength, which provides a means of local aggregation and increased encounter rate with food and mates. The results are interpreted in relation to differences in swimming style and setal morphology among the species.

Likely year-round presence of beaked whales in the Bay of Biscay

AbstractBeaked whales are cryptic and difficult to study species, often distributed in deep offshore waters and only briefly visible at the surface. A diverse range of cetacean species has been documented in the Bay of Biscay, including several species of beaked whales. However, little is known about how persistent their presence is. Citizen science data collected during ferry-based surveys between 2006 and 2018 were analysed to investigate how encounter rates varied across space and time, and their drivers for beaked whale species. Approximately 244,400 km were surveyed, and there were 419 encounters with beaked whales recorded including Cuvier’s beaked whales, (n = 260), Northern bottlenose whales (n = 19), Sowerby’s beaked whales (n = 13), and True’s beaked whales (n = 1). Generalized Additive Models revealed that encounters were generally more frequent in the southern bay, on northern facing slopes, with all species except Sowerby’s showing a preference for both deep waters and shallow shelf waters. Animals were recorded in each of the eight surveyed months, suggesting that beaked whales may be present year-round, with increased encounter rates in summer months. This study is the first to indicate that beaked whales may persist in this area throughout the year, which is key information for appropriate management.

DIVERSITY OF SNAKE RESCUED FROM RESIDENTIAL AREAS IN GREATER JAKARTA METROPOLITAN AREA, INDONESIA

Development and habitat loss in Greater Jakarta Metropolitan Area affected snakes and forced them to adapt in urban areas. Snakes in residential areas might increase encounter rate with humans which lead to human-snake conflict. The objectives of this research were to identify the diversity of snakes in residential areas based on rescue effort and to documents effort of those organizations on how to mitigate human-snake conflict through snake relocation. From 2015-2019, 37 snake species were reported found around residential areas in Jakarta Metropolitan Area. Javan spitting cobra Naja sputatrix and reticulated python Malayopython reticulatus are the most encountered snakes in residential areas. Jakarta has the highest total encounter of snakes compared to other area but Bogor has the highest diversity of snake species. Snake found in residential areas are sometimes “rescued” by snake reptile enthusiasts who formed a group. Most of these group does not have standard operating procedure when rescuing snake. Human-snake conflict can be mitigated by relocation of snakes, education, and translocation, although the impact of translocation should be evaluated further.&#x0D; &#x0D; Key words: Jakarta Metropolitan Area, human-snake conflict, Urban area, snake rescue

A fine‐scale analysis reveals microgeographic hotspots maximizing infection rate between a parasite and its fish host

Abstract For parasites, finding their hosts in vast and heterogeneous environments is a task that can be complex. Some parasite species rely on elaborate strategies to increase encounter rate with their hosts (e.g. behavioural modification of host), but others do not. For these parasites, a key issue is to reveal the processes that enable them to successfully find their hosts and complete their life cycles. Here, we tested the hypothesis that infective larvae of the freshwater ectoparasite Tracheliastes polycolpus are not homogeneously distributed along the river and preferentially occur in very specific microhabitats that maximize encounter rate, and hence infection rate, with their host fish. To do this, we combined an in situ experiment (caging) with an empirical survey carried out on the same sites to identify potential ‘hotspots’ of infection at the microgeographic scale and their environmental characteristics. Experimental and empirical results demonstrated that infections were not evenly distributed among microhabitats, and that infections were spatially aggregated in hotspots at a very fine spatial grain. We further found that certain combinations of environmental variables were consistently and nonlinearly associated with higher infection rate for both caged and wild‐caught fish. Microhabitats characterized by very low or high stream velocities, associated with medium or very small substrate, respectively, and a deep water column were strongly and repeatedly associated with higher infection rates. These microhabitats could concentrate parasites and/or promote physical contact with the hosts. We conclude that the characteristics of some microhabitats could facilitate contact between hosts and parasites and explain how some parasites manage to find their hosts in complex environments. A free Plain Language Summary can be found within the Supporting Information of this article.

Predator abundance drives the association between exploratory personality and foraging habitat risk in a wild marine meso‐predator

Abstract In recent years, the incorporation of lower levels of organization to the understanding of population ecology, has led to an increase in interest for animal personality and individual foraging specialization. Despite these topics investigating comparable phenomena, that is, individual consistency in behaviour and in food resource use respectively, they have rarely been investigated together. Food resource use is thought to be at the interface between personality and life history. More explorative individuals in a population, for example, are thought to increase encounter rates with food resources and consequently have faster growth than less explorative conspecifics. Such hypotheses have so far only received partial support, and the link between personality and life history is increasingly speculated to be plastic and dependent on spatio‐temporal variation in ecological conditions. Intraspecific competition and/or predation risk, for example are known to influence foraging specialization. Here, we investigated the relationship between exploration personality of juvenile lemon sharks Negaprion brevirostris (measured in captivity) and foraging habitat use (high risk vs. low risk; measured via stable isotope analysis in the field) in relation to conspecific and predator abundance. We identified predator abundance as the main driver for the association between foraging habitat and exploration personality. When predators were less abundant, increased exploration was associated with foraging in riskier habitats. When predator abundance increased, an inverse relationship occurred, with less explorative individuals using more dangerous habitat. We conclude that the relationship between personality and resource use is plastic and context dependent, which could explain the inconclusive results of previous studies investigating links between personality and life history. A free Plain Language Summary can be found within the Supporting Information of this article.

Do fine-scale experiments underestimate predator consumption rates?

Understanding ecological processes across spatial scales helps link observations and predictions from experiments to ecological patterns occurring at coarser scales relevant to management and conservation. Using fish, we experimentally manipulated the size of arenas to test the spatial scaling of predator-prey interactions. We measured variation in predator consumption and prey behaviour (prey aggregation, spatial overlap with predators and movement) across arena sizes. Variation in prey behaviour across arena sizes was hypothesized to drive consumption patterns by altering prey vigilance and encounter rates with predators. Per capita consumption and movement were highest in the largest arena relative to the smallest and we observed a mismatch between where bass were present and the highest densities of prey across all arena sizes. We hypothesize more movement in largest arenas increased encounter rates and drove the observed increase in consumption with increasing arena size. Consumption estimates obtained in experimental studies may underestimate consumption, but understanding the mechanisms driving bias across scales helps predict the outcomes of predator-prey interactions in natural systems.

Spatially clustered resources increase male aggregation and mating duration in Drosophila melanogaster

In environments where females mate multiply, males should adjust their behaviour and physiology in response to the perceived level of sperm competition to maximize their fitness. Evidence of such plasticity has been found in several laboratory and field studies, but little is known about the cues stimulating these responses in natural populations. One way in which males appear to assess sperm competition risk is through encounter rates with conspecific males. Such encounter rates may be driven by the spatial distribution of resources required by males (i.e. food patches or potential mates), which in turn affects local density. However, explicit links between resource distribution, male encounter rates and shifts in behaviour related to sperm competition have not been demonstrated. We found that when group size of Drosophila melanogaster males was held constant, a small decrease in the distance between patches of food resources had striking effects on male behaviour. Compared to those from dispersed resources, males on clustered resources had a significantly reduced intermale distance (and hence encounter rate) and subsequently a longer noncompetitive copulation duration, previously shown to be a reliable indicator of male perception of sperm competition risk. The aggregation of resources, operating via increased encounter rate, can stimulate shifts in behaviour affecting male sperm competition performance. Given that the spatial distribution of resources is typically variable in natural populations (and often unpredictable), selection is likely to favour the evolution of plasticity in sexual behaviour where resource aggregation increases the probability of sperm competition.

Interaction between Epistylis sp. and copepods in tropical lakes: responses of epibiont infestation to species host density

Interaction between Epistylis sp. and copepods was investigated in 3 tropical lakes. Epibiont load was higher in Thermocyclops minutus compared to Notodiaptomus ssp. at light compensation depth. No difference was found at surface. Infestation of Epistylis sp. seems to respond to copepod species densities. Attaching to more abundant copepods may increase encounter rates of epibionts with its hosts, raising biological efficiency of it even if attaching to smaller hosts when rare larger ones are present.