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Making fast and accurate group decisions under uncertain and risky conditions is a fundamental problem for groups. Currently, there is little empirical evidence of how natural selection (such as environmental predation risk) has shaped the mechanisms of group decision making. We repeatedly tested individually marked guppies, Poecilia reticulata, from the upper and lower reaches of the Aripo and Turure rivers in a Y-maze and found that populations that had evolved under different predation regimes differed in their decision-making speed. All groups decreased decision time over successive trial rounds, but fish from low-predation environments did so at a greater rate than fish from high-predation environments. This effect was only significant when fish were tested in groups of eight, not when tested individually. Decision-making accuracy was not significantly different between high- and low-predation populations. Group behaviour differed according to predation risk and trial round, most notably with low-predation groups reducing the amount of positional switching over successive trial rounds at a greater rate than high-predation groups. While fish from both predator risk environments had repeatable within-shoal positioning behaviour as they swam down the maze, only fish from the high-predation groups had repeatable finishing positions. Meaningful measures of information transfer (mean pairwise transfer entropy) were only recorded in low-predation groups, and here there was a significant effect of source river on information flow within groups. Aripo groups increased information flow over successive trial rounds, while Turure groups did not. Variation in mean pairwise transfer entropy increased over successive trial rounds for both low-predation populations, suggesting that information used to make movement decisions became less homogeneously distributed and increasingly directed through a subset of individuals. Predation pressure is a ubiquitous selection force, and these findings may apply to a variety of natural social groups.

Author(s): Davis, BE; Hansen, MJ; Cocherell, DE; Nguyen, TX; Sommer, T; Baxter, RD; Fangue, NA; Todgham, AE | Abstract: The effects of water temperature on individual and group movement behaviour in prey fish can affect ecological interactions such as competition and predation, but how variability in temperature influence fish behaviour is less understood. Of particular concern is how increased warming in tidally fluctuating estuaries may impact the native and endangered delta smelt (Hypomesus transpacificus, Osmeridae). To help address this issue, we tested the effects of increased water temperature (fluctuating [17–21°C] and warm [21°C] acclimated treatments) on juvenile delta smelt individual and group behaviour, response to chemical alarm and predator cues, as well as capacity to evade predation. In addition, predation of delta smelt was tested in the presence of a dominant invasive competitor, Mississippi silversides (Menidia beryllina, Atherinopsidae), as well as comparative predation mortality on Mississippi silversides when isolated. After 7ndays of increased temperature treatments, delta smelt in the warm treatment increased swimming velocity, decreased turning angle, and altered group structure with larger inter-individual distances compared to fish in the control (17°C) and fluctuating temperature treatments. Following conspecific and predator chemical alarm cues, delta smelt showed anti-predator responses. Control and fluctuating treatment fish responded to conspecific cues with increased swimming speeds, decreased inter-individual distances and near-neighbour distances, and, after 15nmin, fish recovered back to baseline behaviours. In contrast, fish in the warm treatment had not recovered after 15nmin, and swimming speeds were maintained at roughly 25ncm/s, close to maximum capabilities. Fish in control and fluctuating treatments showed minimal responses to predator cues, whereas delta smelt exposed to warm conditions significantly increased swimming speeds and decreased turning angle. Predation of delta smelt by largemouth bass (Micropterus salmoides, Centrarchidae) was greatest under the warm treatment, correlating with altered behaviours of delta smelt; however, predation of Mississippi silversides was greater than delta smelt, independent of temperature. This study provides novel insight into the group behaviour of delta smelt, their response to predation, and how prolonged exposure to elevated temperature may induce negative individual and group behaviours causing alterations in predator–prey dynamics. This work highlights the importance of testing ecologically realistic temperature fluctuations in experiments as delta smelt had significantly altered responses to elevated temperature, dependent on variability of warming.

The entrainment and impingement of fish into water diversion infrastructure is one of the several factors contributing to their decline. Here, controlled experiments assessed the potential for a behavioral guidance device [a light-emitting diode (LED) light array] strobing at various spectra to reduce the entrainment of juvenile Chinook salmon (Oncorhynchus tshawytscha) into a water diversion pipe. Fish were tested during the day and night, and under control conditions (light off) and red, blue, and white spectra strobing at 2 Hz. Fish entrainment into the diversion pipe was evaluated. Results indicated greater entrainment at night compared to day. All trials at night with the LED light strobing had higher entrainment than the control, with blue and white spectra corresponding to greater entrainment than red spectra. During the day, the white spectra treatment was different from the red treatment, with lower entrainment. LED lights employed to repel migratory juvenile salmon away from water intake structures may be ineffectual but there is potential for the light to be used as an attractant to guide fish towards desirable features such as “safe” areas (bypass channels or fishways).

Author(s): Singer, GP; Hansen, MJ; Ho, KV; Lee, KW; Cocherell, DE; Peter Klimley, A; Rypel, AL; Fangue, NA | Abstract: Acoustic telemetry, a commonly used tool for examining movements and survival of aquatic species, is often applied without a comprehensive understanding of transmitter implantation effects. This can be problematic when the goal of the study is to use telemetry results to make inferences regarding broader populations. Here, we examined juvenile Chinook Salmon Oncorhynchus tshawytscha at varying time intervals after transmitter implantation to assess the behavioral implications of tagging. The following behavioral metrics in response to a novel environment were compared across treatment and control groups: time to emergence from shelter into the open portion of the test arena, rheotactic response, total activity, and rates of exploration. Tagged fish (114–132nmm FL) were tested at 0, 1, or 4nd postsurgery (day-0, day-1, and day-4 groups, respectively), and their behavior was compared to that of similarly handled control fish. Emergence from refuge was the only metric that differed significantly between treatment and control groups. Fish tested on the same day as the surgery were less likely to emerge from the refuge, with only 46% of the day-0 tagged fish emerging compared to 88, 93, and 80% of the day-1, day-4, and control groups, respectively. However, day-0 fish that did emerge from the refuge had rheotactic responses, total activity, and exploration rates similar to those of fish from the other treatment and control groups. This study may have fisheries research and management implications, especially for telemetry studies and monitoring efforts. We encourage researchers using this technology to consider (1) observing a post-transmitter-implantation recovery period of at least 24nh prior to release, adjusting study plans and logistics accordingly; (2) applying sufficient scientific rigor to emerging tagging technology prior to wide-scale adoption; and (3) when possible, conducting concurrent battery life and tag effects studies with any field release of tagged fishes, as differing relationships between fish size, tag size, and tagging techniques may yield variable results.

© 2020. Published by The Company of Biologists Ltd. Billfishes are well known for their distinctive elongated rostra, i.e. bills. The functional significance of billfish rostra has been frequently discussed and the recent discovery of an oil gland (glandula oleofera) at the base of the rostrum in swordfish, Xiphias gladius, has added an interesting facet to this discussion regarding the potential co-evolution of gland and rostra. Here, we investigated the oil gland and oil pores (through which the oil is brought to the skin surface) of four billfish species - swordfish, Atlantic blue marlin (Makaira nigricans), Indo-Pacific sailfish (Istiophorus platypterus) and striped marlin (Kajikia audax) - and provide detailed evidence for the presence of an oil gland in the last three. All four species had a high density of oil pores on the forehead which is consistent with the hypothesis of hydrodynamic benefits of the oil. The extension of the pores onto the front half of the rostrum in sailfish and striped marlin, but not in swordfish or blue marlin, suggests that the oil may have additional functions. One such function could be linked to the antibacterial and anti-inflammatory properties of the oil. However, the available evidence on predatory rostrum use (and hence the likelihood of tissue damage) is only partly consistent with the extension of pores on rostra across species. We conclude that the oil gland probably serves multiple, non-mutually exclusive functions. More detailed information on rostrum use in blue marlin and swordfish is needed to better link behavioural and morphological data with the aim of accomplishing a full comparative analysis.

Linking morphological differences in foraging adaptations to prey choice and feeding strategies has provided major evolutionary insights across taxa. Here, we combine behavioural and morphological approaches to explore and compare the role of the rostrum (bill) and micro-teeth in the feeding behaviour of sailfish ( Istiophorus platypterus ) and striped marlin ( Kajikia audax ) when attacking schooling sardine prey. Behavioural results from high-speed videos showed that sailfish and striped marlin both regularly made rostrum contact with prey but displayed distinct strategies. Marlin used high-speed dashes, breaking schools apart, often contacting prey incidentally or tapping at isolated prey with their rostra; while sailfish used their rostra more frequently and tended to use a slower, less disruptive approach with more horizontal rostral slashes on cohesive prey schools. Capture success per attack was similar between species, but striped marlin had higher capture rates per minute. The rostra of both species are covered with micro-teeth, and micro-CT imaging showed that species did not differ in average micro-tooth length, but sailfish had a higher density of micro-teeth on the dorsal and ventral sides of their rostra and a higher amount of micro-teeth regrowth, suggesting a greater amount of rostrum use is associated with more investment in micro-teeth. Our analysis shows that the rostra of billfish are used in distinct ways and we discuss our results in the broader context of relationships between morphological and behavioural feeding adaptations across species.

The relationship between individual physiological traits and social behaviour is an important research area because it can examine how mechanisms of behaviour link to functional outcomes. It is hypothesised that correlative and causative links between physiology and individual behaviour may be altered by social interactions. Here, we assess how nutritional stress (20-h starved, 90-h starved) and routine metabolic rate (RMR) determine the movement and foraging behaviour of threespine sticklebacks (Gasterosteus aculeatus), both individually and in a social context. Results showed that there was no statistically significant relationship between RMR and behaviour. The nutritional stress treatment had significant opposite effects on voluntary swim speed, dependent on whether fish were assayed asocially (alone) or socially (in shoals of three). Greater nutritional stress caused voluntary swimming speeds to reduce in an asocial context but increase in a social context, although both relationships were not significant. Additional results exploring social behaviour parameters such as the frequency and duration of shoaling interactions suggests that alterations in fish swim speed between the two nutritional stress treatments may be due to competition effects. This study links state-dependent individual behaviour to social foraging performance and reinforces the theory that social context is an important modulator of the relationships between physiology and behaviour. Recent research has highlighted that the social environment may shape how physiology and behaviour are linked. This area of research, however, requires data from empirical studies that measure and experimentally manipulate physiological traits of individually identifiable animals and tests them under asocial and social conditions. Using threespine sticklebacks foraging for bloodworms, we show that routine metabolic rate did not have a statistically significant effect on fish locomotion or risk-taking. Greater nutritional deprivation caused fish to decrease their swimming speed when they were alone (likely in an effort to reduce energy expenditure); however, when assayed in groups, competitive forces between shoal mates caused them to swim at faster voluntary speeds. Nutritional stress therefore had a significant socially dependent effect on fish locomotion.

© 2019, Springer Nature B.V. Predation and reduced energetic intake have been highlighted as potential mechanisms of recruitment failure in sturgeon populations. These two factors may interact, as foraging carries with it costs of increased predation risk, requiring behavioral trade-offs. We expect that juvenile sturgeon should express predator avoidance behaviors while they are within vulnerable size ranges, yet these behaviors should be modified by nutritional state. To evaluate behavioral trade-offs of juvenile white sturgeon, we designed an experiment to test the interacting effects of acute nutritional state and predation risk on the spatial distribution and movement of small groups (n = 6). Groups were assigned to one of four treatments, designed as a full factorial of nutritional state (well-fed or starved 24-h) and predation risk (largemouth bass present or absent), and eight replicates were conducted for each treatment. Juvenile sturgeon displayed a predicted and adaptive response to predation risk and predator aggression levels by reducing activity levels and displaying marked freezing behavior. Sturgeon responded strongly to nutritional deprivation through increased activity and increased near-neighbor distance, which was likely an adaptive response to increase encounter rates with benthic food items. Both of these responses to starvation were suppressed in the presence of predators. This study has provided experimental evidence that predators can abruptly reduce the foraging activity of white sturgeon, possibly reducing growth rates and extending the period of juvenile vulnerability. Future conservation planning should consider the interacting effects of multiple stressors experienced by sturgeon at early life-stages, as introduced predators and degraded foraging habitats may have interacting effects.

This study employed community analysis and behavioural field observations to explore the inter-specific interactions between fangblenny species (Plagiotremus spp.), the cleaner wrasse Labroides dimidiatus and their target species and found that the presence of Plagiotremus spp. did not affect the total amount that L. dimidiatus cleaned but it did reduce the amount L. dimidiatus cleaned key prey species of the Plagiotremus spp. The behavioural interactions between adult L. dimidiatus and their clients changed in response to the presence of Plagiotremus spp., but the results suggested the potential cost of Plagiotremus spp. on L. dimidiatus may be offset by behavioural niche partitioning.

Animals that forage in groups have access to social information concerning the quality and location of food resources available. The degree to which individuals rely on social information over their own private information depends on a myriad of ecological and social factors. In general, where resources are patchy in space and/or time, individuals that use social information and join others at previously identified food patches can reduce both search times and the variance in finding food. Here, we explore social foraging dynamics of shoals of three-spined sticklebacks (Gasterosteus aculeatus) and investigate when fish tend to use private information and find food themselves, or rely on social information and attend to the food discoveries of others. We show that fish’s allocation to alternative foraging tactics (i.e. finding or joining) can be explained by environmental quality. In environments with large food patches, fish experience a reduced finder’s share and tend to adopt joining foraging tactics; in environments with small food patches, fish rely on private information and tend to discover their own food patches. However, we found that finding and joining do not result in equal foraging returns as predicted by theory, and instead payoffs were higher for fish adopting finding tactics in all environments we studied. These unequal payoffs may be explained, in part, by consistent inter-individual differences in the amount of food fish consumed per foraging event and by heavier fish consuming more food. Overall, our simple experimental approach suggests that socially foraging three-spined sticklebacks do show a degree of behavioural flexibility that enables them to efficiently exploit food patches under a range of environmental conditions. Animals must continually make decisions to secure resources to survive and reproduce; however, inherent variability in the spatio-temporal distribution of resources means that the best decision is not fixed. How do animals ensure they respond effectively to variation? For animals that live and forage in groups, how do environmental conditions determine whether they use private information or social information to meet these challenges? These are important questions in behavioural ecology and have great significance to animals’ ability to deal with unheralded environmental change. Here, we show empirically that three-spined sticklebacks flexibly and adaptively switch between behavioural tactics to acquire foraging resources in accordance with the abundance and distribution of forage in their environment, establishing a new model system to extend and build our understanding of social foraging dynamics and how animal groups optimally function in a variable world.

Summary Foraging behaviour must be flexible enough to adapt to heterogeneities in the distribution and quality of food resources. Accurate models of optimal foraging behaviour should acknowledge the extent to which animals can detect and regulate their intake of food based on smaller scale differences in food types. In particular, consideration of macro-nutrient distribution and how animals perceive this is limited in studies of optimal foraging, particularly in vertebrates and for animals that forage in groups. Here, we track shoals of eight mosquitofish as they forage in two environments that contain equal amounts of available energy but differ in their distribution of macro-nutrients. We provide empirical evidence that fish will distribute themselves within an environment in relation to the distribution of specific macro-nutrients. Also, fish make foraging decisions based on the macronutrient composition of patches, such that their durations on patches are longer when they have a higher concentration of protein and lower concentration of carbohydrate. The ratio of protein to carbohydrate does not affect the probability of a fish joining a patch, however, with low numbers of fish on the patch the probability of a fish leaving is greater per unit time step in the patches with a low protein to carbohydrate ratio than the patches with a high protein to carbohydrate ratio. This study confirms the importance of considering the macro-nutrient composition of foods when considering the movement decisions of foraging groups and thus has important consequences for developing more accurate foraging models that take into account the distribution of macro-nutrients in the environment. The results suggest the spatial distribution of nutrients on a landscape scale could influence grouping patterns and social interactions, thus affecting population dynamics.

How animals trade-off food availability and predation threats is a strong determinant of animal activity and behavior; however, the majority of work on this topic has been on individual animals, despite the modulating effect the presence of conspecifics can have on both foraging and predation risk. Although these environmental factors (food and predation threat) vary spatially within habitats, they also vary temporally, and in marine habitats, this can be determined by not only the diel cycle but also the tidal cycle. Humbug damselfish, Dascyllus aruanus, live in small groups of unrelated individuals within and around branching coral heads, which they collectively withdraw into to escape a predation threat. In this study, we measured the proportion of individuals in the colony that were outside the coral head before and after they were scared by a fright stimulus and compared the responses at high tide (HT) and low tide (LT). We found that a greater proportion of the shoal emerged after the fright stimulus at HT and in larger groups than at LT or in smaller groups. We also quantified the pattern of emergence over time and discovered the rate of emergence was faster in larger shoals as time progressed. We show that shoals of fish change their behavioral response to a predation threat in accordance with the tide, exemplifying how temporally variable environmental factors can shape group movement decisions.

We tested Chinook smolt response to combinations of spectra and strobing frequencies emitted from an underwater LED light, designed to guide fish near water diversion infrastructure. Whilst strobing did not alter fish behaviour when compared to constant light, the red light had a repulsive effect during the day, but not at night., Exploiting species-specific behavioural responses of fish to light is an increasingly promising technique to reduce the entrainment or impingement of fish that results from the diversion of water for human activities, such as hydropower or irrigation. Whilst there is some evidence that white light can be an effective deterrent for Chinook salmon smolts, the results have been mixed. There is a need to test the response of fish to different spectra and strobing frequencies to improve deterrent performance. We tested the movement and spatial response of groups of four fish to combinations of light-emitting diode (LED) spectra (red, green, blue and white light) during the day and night, and strobing frequencies (constant and 2Hz) during the day, using innovative LED technology intended as a behavioural guidance device for use in the field. Whilst strobing did not alter fish behaviour when compared to constant light, the red light had a repulsive effect during the day, with fish under this treatment spending significantly less time in the half of the arena closest to the behavioural guidance device compared to both the control and blue light. Importantly, this effect disappeared at night, where there were no differences in movement and space use found between spectra. There was some evidence of a potential attractive response of fish to the blue and green light during the day. Under these light treatments, fish spent the highest amount of time closest to the behavioural guidance device. Further tests manipulating the light intensity in the different spectra are needed to verify the mechanistic determinants of the observed behaviours. Results are discussed in reference to the known spectral sensitivities of the cone and rod photopigments in these fish, and further experiments are suggested to better relate the work to mitigating the effects on fish of infrastructure used for hydropower and irrigation.

The present study showed short-term elevations in cellular metabolism, alterations in behavior and susceptibility to predation in juvenile rockfish after acute acclimation to CO2-acidification and hypoxic conditions. Physiological and behavioral alterations were restored after 3 weeks suggesting that rockfish possess mechanisms to defend rapid changes in PCO2 and oxygen conditions., California’s coastal ecosystems are forecasted to undergo shifting ocean conditions due to climate change, some of which may negatively impact recreational and commercial fish populations. To understand if fish populations have the capacity to respond to multiple stressors, it is critical to examine interactive effects across multiple biological scales, from cellular metabolism to species interactions. This study examined the effects of CO2-acidification and hypoxia on two naturally co-occurring species, juvenile rockfish (genus Sebastes) and a known predator, cabezon (Scorpaenichthys marmoratus). Fishes were exposed to two PCO2 levels at two dissolved oxygen (DO) levels: ~600 (ambient) and ~1600 (high) μatm PCO2 and 8.0 (normoxic) and 4.5 mg l−1 DO (hypoxic) and assessments of cellular metabolism, prey behavior and predation mortality rates were quantified after 1 and 3 weeks. Physiologically, rockfish showed acute alterations in cellular metabolic enzyme activity after 1 week of acclimation to elevated PCO2 and hypoxia that were not evident in cabezon. Alterations in rockfish energy metabolism were driven by increases in anaerobic LDH activity, and adjustments in enzyme activity ratios of cytochrome c oxidase and citrate synthase and LDH:CS. Correlated changes in rockfish behavior were also apparent after 1 week of acclimation to elevated PCO2 and hypoxia. Exploration behavior increased in rockfish exposed to elevated PCO2 and spatial analysis of activity indicated short-term interference with anti-predator responses. Predation rate after 1 week increased with elevated PCO2; however, no mortality was observed under the multiple-stressor treatment suggesting negative effects on cabezon predators. Most noteworthy, metabolic and behavioral changes were moderately compensated after 3 weeks of acclimation, and predation mortality rates also decreased suggesting that these rockfish may be resilient to changes in environmental stressors predicted by climate models. Linking physiological and behavioral responses to multiple stressors is vital to understand impacts on populations and community dynamics.

Groups of animals are often heterogeneously structured and may be composed of selfish individuals responding to different internal stimuli. Group-level behaviour can be determined by the slight differences in simple behavioural movement parameters structuring local interactions between conspecifics. To accurately understand individual behaviour within groups and how it affects whole-group behaviour, we need to measure the responses of individuals in groups to changes in internal state and examine the outcome of these responses within the social context. Therefore, we quantified the influence of nutritional state on the individual and group movement parameters of free swimming shoals of eight rainbow fish, Melanotaenia duboulayi. Individual fish were experimentally manipulated to be in one of two nutritional states, hungry or satiated, and were assayed in three group compositions: all-hungry (8:0 hungry/satiated), mixed (4:4) or all-satiated (0:8). We showed that the internal nutritional state of individual fish affected basic behaviours relating to spatial positioning. The interaction between pairs of fish was dependent on the nutritional state of both fish, and there was an additive effect of individual behaviour on group behaviour, which meant that group behaviour reflected the motivations of its individual members in such a way that allowed individuals to fulfil their own behavioural needs whilst still attaining the benefits of grouping.

The question of how hunger affects locomotory behaviour, in particular how it affects the kinematics of movement and an animal’s interaction with the physical structures in its environment is of broad relevance in behavioural ecology. We experimentally manipulated the hunger levels of individual mosquitofish (Gambusia holbrooki) and recorded their swimming behaviour in shoals of 4 fish. We found that hungry individuals in shoals moved at greater speeds and had higher turning speeds than satiated individuals in shoals, as well as a greater variance in speed and turning speeds. We also found that hungry individuals explored more of the arena and used more of its internal space, away from the square arena’s walls and displayed less wall-following behaviour than satiated individuals. A functional explanation for this change in swimming behaviour and interaction with environmental heterogeneity is discussed in the context of social foraging, as is the consequence of these results for models of search patterns and collective movement.

Hansen, M. J., Owens, V. N., Beck, D. and Sexton, P. 2013. Suitability of cover crop monocultures for late-season forage in South Dakota. Can. J. Plant Sci. 93: 589–597. Cover crops provide many agronomic benefits and can produce large amounts of forage that is suitable for grazing. The objectives of this study were to determine (1) suitable cover crop forages based on yield and nutrient values; and (2) changes in feed value and yield of these crops through the late fall. Five cover crop monocultures consisting of lentil (Lens culinaris Medikus), cowpea (Vigna unguiculata L.), foxtail millet (Setaria italica L.), oats (Avena sativa L.), forage radish (Raphanus sativus L.), and a mixture of these crops were planted after winter wheat (Triticum aestivum L.) harvest in 2010 and 2011 in central and southeastern South Dakota. Forage data were collected on approximately Oct. 01, Nov. 01, and Dec. 01 each year. Yields increased after the first harvest date at both sites, both years. Oats, radish, and the cover crop mixture all yielded >4000 kg of dry matter per hectare on the second harvest date in 2011 in central South Dakota and radish and oats yielded >4000 kg ha−1 in southeastern South Dakota on the second and third harvest dates, respectively. Forage quality tended to decrease after each harvest date. Radish in central South Dakota in 2010 had the highest protein values for the study (194–313 g kg−1) whereas oats in southeastern South Dakota had the lowest protein concentrations (63–108 g kg−1), both years. All cover crops except cowpea were viable forages through the late fall when they had good establishment with the potential need for protein supplementation with oats, foxtail millet, and the cover crop mixture, depending on animal requirements.

Decision making in moving animal groups has been shown to be disproportionately influenced by individuals at the front of groups. Therefore, an explanation of state-dependent positioning of individuals within animal groups may provide a mechanism for group movement decisions. Nutritional state is dynamic and can differ between members of the same group. It is also known to drive animal movement decisions. Therefore, we assayed 6 groups of 8 rainbowfish foraging in a flow tank. Half of the fish had been starved for 24h and half had been fed 1h prior to experimental start. Groups were assayed again one week later but individuals were allocated to the opposite nutritional treatment. During the assay the positions of individually identified fish were recorded as were the number of food items they each ate and the position within the group they acquired them from. Food-deprived fish were more often found towards the front of the shoal; the mean weighted positional score of food-deprived fish was significantly larger than that of well-fed fish. Individuals were not consistent in their position within a shoal between treatments. There was a significant positive correlation between mean weighted positional score and number of food items acquired which displays an obvious benefit to front positions. These results suggest that positional preferences are based on nutritional state and provide a mechanism for state-dependent influence on group decision-making as well as increasing our understanding of what factors are important for group functioning.

Mass migration of locusts is an economically devastating and poorly understood phenomenon. Locust mass migration often follows rapid population growth because individuals must move to find new sources of locally depleted resources. In Mormon crickets and Desert locusts, cannibalistic interactions have been revealed as the driving force behind collective mass movement. Locusts are known to compensate for nutrient deficiencies and they themselves are a good source of nutrients such as protein. However, direct empirical evidence for an adaptive benefit of cannibalism in migratory bands has been lacking. Here, we first show that Australian plague locusts, Chortoicetes terminifera, will cannibalise vulnerable conspecifics to compensate for protein deprivation, supporting the notion that cannibalistic interactions among nutritionally deprived individuals drives collective mass movement. We then show that individuals in a group with the opportunity to cannibalise survive longer and move more than individuals without the opportunity to cannibalise. These results provide empirical support for the ‘lifeboat mechanism’, which proposes that cannibalism offers the dual benefits to individuals in a group of surviving longer and travelling farther than a solitary individual without the opportunity to cannibalise.

We demonstrate that UV degradation can remove polymeric dispersants from the surface of colloidal pristine graphene. In particular, we investigated the irradiation of polyvinylpyrrolidone (PVP)-dispersed graphene in water; this polymer has been established as a versatile nanosheet dispersant for a range of solvents, and it undergoes photo-oxidative degradation when exposed to UV light. We find that the molecular weight of PVP decreases with irradiation time and subsequently desorbs from the graphene surface. This causes gradual destabilization of graphene and agglomeration in water. The amount of adsorbed PVP decreases by approximately 45% after 4 h of irradiation in comparison with the non-irradiated dispersion. At this point, the majority of the stable graphene nanosheets flocculate, likely because of insufficient surface coverage as indicated by thermogravimetric analysis. Graphene aggregates were characterized as a function of irradiation time by optical microscopy, UV-vis spectroscopy, Raman spectroscopy, and conductivity measurements; the data suggest that the agglomerates maintain a graphene-like (rather than graphite-like) structure. The effect is also observed for another graphene dispersant (sapogenin), which suggests that our findings can be generalized to the broader class of photodegradable dispersants.

Here we demonstrate through experiment and simulation the polymer-assisted dispersion of inorganic 2D layered nanomaterials such as boron nitride nanosheets (BNNSs), molybdenum disulfide nanosheets (MoS2), and tungsten disulfide nanosheets (WS2), and we show that spray drying can be used to alter such nanosheets into a crumpled morphology. Our data indicate that polyvinylpyrrolidone (PVP) can act as a dispersant for the inorganic 2D layered nanomaterials in water and a range of organic solvents; the effectiveness of our dispersion process was characterized by UV-vis spectroscopy, microscopy and dynamic light scattering. Molecular dynamics simulations confirm that PVP readily physisorbs to BNNS surfaces. Collectively, these results indicate that PVP acts as a general dispersant for nanosheets. Finally, a rapid spray drying technique was utilized to convert these 2D dispersed nanosheets into 3D crumpled nanosheets; this is the first report of 3D crumpled inorganic nanosheets of any kind. Electron microscopy images confirm that the crumpled nanosheets (1–2 μm in diameter) show a distinctive morphology with dimples on the surface as opposed to a wrinkled, compressed surface, which matches earlier simulation results. These results demonstrate the possibility of scalable production of inorganic nanosheets with tailored morphology.

We demonstrate three different techniques (dialysis, vacuum filtration, and spray drying) for removal of dispersants from liquid-exfoliated graphene. We evaluate these techniques for elimination of dispersants from both the bulk liquid phase and from the graphene surface. Thermogravimetric analysis (TGA) confirms dispersant removal by these treatments. Vacuum filtration (driving by convective mass transfer) is the most effective method of dispersant removal, regardless of the type of dispersant, removing up to ∼95 wt.% of the polymeric dispersant with only ∼7.4 wt.% decrease in graphene content. Dialysis also removes a significant fraction (∼70 wt.% for polymeric dispersants) of un-adsorbed dispersants without disturbing the dispersion quality. Spray drying produces re-dispersible, crumpled powder samples and eliminates much of the unabsorbed dispersants. We also show that there is no rapid desorption of dispersants from the graphene surface. In addition, electrical conductivity measurements demonstrate conductivities one order of magnitude lower for graphene drop-cast films (where excess dispersants are present) than for vacuum filtered films, confirming poor inter-sheet connectivity when excess dispersants are present.

Uroliths containing 70% or greater silica comprise approximately 1% of the canine uroliths submitted to the Minnesota Urolith Center. Male dogs are far more commonly affected than females. In our series, 84 different breeds were affected. Currently available data suggest dietary factors play a role in their formation. Diagnosis is facilitated by the characteristic jackstone configuration of silica uroliths, but must be confirmed by quantitative analysis. Voiding urohydropropulsion or surgery are currently the most practical methods of removal of silica uroliths.