Biology subjects

Rands, S. A.

Publications and source records attributed to Rands, S. A..

14 recordsLinked to original sources

bioRxiv2026

Camera trapping and passive acoustic monitoring as non-invasive techniques for the study of small mammals

Terrestrial small mammals are of significant importance worldwide in providing valuable ecosystem services and acting as invasive species, pests, and carriers of disease. Many species are under threat from anthropogenic stressors and non-invasive techniques are required to sustain long-term and large-scale monitoring of these animals. This research compares the application of camera trapping and passive acoustic monitoring for the study of terrestrial small mammals. We conducted a field study aiming to evaluate three camera trapping tunnel designs (Modified Littlewood, Mostela and a new design utilising readily available components), and compare the performance of passive acoustic monitoring to camera trapping for terrestrial small mammal surveying. The Modified Littlewood tunnel produced a higher number of shrew detections compared to the plastic tunnel. The Mostela tunnel produced the highest quality data by facilitating species identification and reducing non-target triggers. Passive acoustic monitoring and camera trapping detected different species, but there was no difference in species richness between the methods. Voles were better detected by camera trapping than passive acoustic monitoring. We consider the success of current machine learning classification for processing our acoustic data, and suggest that future developments in machine learning classification will likely speed up processing of both visual and acoustic data, and perhaps allow more detailed and accurate identification to species and individual level.

ecology↗

bioRxiv2025

Shoal cohesion and polarisation increase in turbid water and improve foraging performance

Group living can make animals more resilient or more susceptible to human-induced rapid environmental change, and whether animals demonstrate plasticity in their collective behaviour to mitigate the effects of environmental change is unknown. Freshwater and coastal habitats are becoming increasingly turbid as a result of human activity, which limits the availability of information and hence responses to critical stimuli such as food and predators. Here, we tested whether the well-documented improvement in foraging performance by larger groups is affected by moderate levels of water turbidity. Fish shoals were faster to attack the food stimulus in larger groups and slower in turbid water, effects which were independent of one another. However, shoals became more cohesive and coordinated (i.e. more polarised in direction) in turbid water, and this corresponded to more cohesive and polarised shoals being faster to attack the food stimulus in turbid water but slower in clear water. Our results demonstrate that fish shoals can increase cohesion and coordination in moderate levels of turbidity, that this plasticity improves their response to ecologically relevant ephemeral stimuli, and that collective behaviour, rather than group size, can mediate the response of groups to environmental change.

animal behavior and cognition↗

bioRxiv2025

A spatially explicit model of pollinator-plant-pathogen interactions

Flowers have long been suggested to be infection hotspots for pollinator diseases, as, during their brief lifespan, they are visited and handled by many individuals from a diverse range of species. Evidence that floral hotspots are an important point of contagion is building, but few models currently allow us to characterise these novel plant-pathogen-pollinator systems where horizontal infections occur from concentrated, short-lived sites of contagion. Infection success is going to depend heavily upon the behaviour of individual pollinators, alongside the structure of the floral landscape that they are foraging within. Here, we describe an individual-based model that considers the impact of environmental heterogeneity and individual differences in movement on the spread of a disease that is spread via floral hotspots, considering a centrally nesting social pollinator (such as a social bee). The biggest effects we saw were associated with the likelihoods of leaving and staying in the nest and the distances travelled by the pollinators, and so it is likely that social pollinators, most of which are constrained to return to a central nest, could be strongly impacted by the schedules they use for allocating foraging behaviour. We also considered the impact of the pollinators being able to deposit and detect temporary scent-marks, which could inform an uninfected pollinator of a potentially infected site. Scent marks have a negative impact on pathogen transmission, and their effect may be dependent on both the longevity of the scent mark, the turnover of flowers in the environment, and the factors affecting pathogen viability and infectivity. Overall, although the structure of the landscape may have limited impact on pathogen spread, the behaviour of the pollinators is important, and needs further consideration within models of this pathogen system. AUTHOR SUMMARYFlowers have long been suggested to be infection hotspots for pollinator diseases, as, during their brief lifespan, they are visited and handled by many individuals from a diverse range of species. Evidence that floral hotspots are an important point of contagion is building, but we currently know little about the environmental biology of these infections. We describe a model that considers how pathogens caught at floral infection hotspots might spread in populations of social pollinators (such as a bumblebee or honeybee), and show that both pollinator behaviour and how flowers are distributed through the landscape can have a big impact on the spread of the pathogen. Pollinators can leave temporary detectable scent marks on the surfaces of the flowers that they visit: our model demonstrates that being able to detect these marks reduces the spread of the pathogen, as the pollinator is better able to avoid potential hotspots.

ecology↗

bioRxiv2024

Variations of floral temperature in changing weather conditions

O_LIFloral temperature is a flower characteristic that has the potential to impact the fitness of flowering plants and their pollinators. Likewise, the presence of floral temperature patterns, areas of contrasting temperature across the flower, can have similar impacts on the fitness of both mutualists. C_LIO_LIIt is currently poorly understood how floral temperature changes under the influence of different weather conditions, and how floral traits may moderate these changes. Such weather dependency will impact how stable floral temperatures are over time and their utility to plant and pollinator. The stability of floral temperature cues is likely to facilitate effective plant-pollinator interactions and play a role in the plants reproductive success. C_LIO_LIWe use thermal imaging to monitor how floral temperatures and temperature patterns of four plant species (Cistus snow fire and snow white, Coreopsis verticillata and Geranium psilostemon) change with several weather variables (illumination, temperature; windspeed; cloud cover; humidity and pressure) during times that pollinators are active. C_LIO_LIAll weather variables influenced floral temperature in one or more species. The directionality of these relationships were similar across species. In all species light conditions (illumination) had the greatest influence on floral temperature overall, and in generation of contrasting temperatures between parts of the flower, temperature patterns. The effect sizes of other weather variables were lower and more varied across the four species. Most likely, floral traits such as pigmentation and structure influence these relationships between weather conditions and generation of floral temperature. C_LIO_LISynthesis: Floral temperature and the extent to which flowers showed contrasting temperature patterns were influenced predominantly by light conditions. However, several weather variables had additional, lesser, influences. Furthermore, differences in floral traits, pigmentation and structure, likely resulted in differences in temperature responses to given conditions between species and different parts of the same flower. However, floral temperatures and contrasting temperature patterns that are sufficiently elevated for detection by pollinators were maintained across most conditions if flowers received moderate illumination. This suggests the presence of elevated floral temperature and contrasting temperature patterns are fairly constant and may have potential to influence plant-pollinator interactions across weather conditions. C_LI

plant biology↗

bioRxiv2024

Blinking as a measurement of group vigilance in red deer Cervus elaphus and fallow deer Dama dama

The group vigilance hypothesis suggests animals within a group have a lower overall vigilance level than solitary individuals due to the collective responsibility of predator detection. Previous methods of studying vigilance have used head position as a proxy to indicate a state of vigilance, but it has been suggested that this method is too ambiguous, and the observer cannot accurately ascertain the exact behavioural state of the focal animal. Here, we consider blinking as a proxy for vigilance, as the eye-closure during a blink momentarily reduces the animals information about the environment, increasing the risk of unanticipated predator attack. We videoed semi-captive herds of red deer Cervus elaphus and fallow deer Dama dama, and quantified their blinking behaviour using behavioural logging software. We show that blink rate decreased with increasing group size in both species, suggesting that blinking may be tied with social vigilance rather than anti-predator vigilance. Similarly, the length of the inter-blink interval increased with increasing group size in red deer. We discuss the suitability of blinking measures for assessing vigilance behaviour.

animal behavior and cognition↗

bioRxiv2023

The behavioural responses of bumblebees Bombus terrestris in response 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 whilst 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 likely use social cues to strategise their energetic expenditure during precipitation, allowing them to compensate for the reduced foraging activity during rainfall when conditions improve.

animal behavior and cognition↗

bioRxiv2023

The cuticular wax compositions and crystal coverage of leaves and petals differ in a consistent manner between plant species

1Both leaves and petals are covered in a cuticle, which itself contains and is covered by, cuticular waxes. The waxes perform various roles in plants lives, and the cuticular composition of leaves has received much attention. To date, the cuticular composition of petals has been largely ignored. Being the outermost boundary between the plant and the environment, the cuticle is the first point of contact between a flower and a pollinator, yet we know little about how plant-pollinator interactions shape its chemical composition. Here, we investigate the general structure and composition of floral cuticular waxes by analysing the cuticular composition of leaves and petals of 49 plant species, representing 19 orders and 27 families. We show that the flowers of plants from across the phylogenetic range are nearly devoid of wax crystals, and that the total wax load of leaves in 90% of the species is higher than that of petals. The proportion of alkanes is higher, and the chain-lengths of the aliphatic compounds are shorter in petals than in leaves. We argue these differences are a result of the adaptation to the different roles leaves and petals play in plant biology.

plant biology↗

bioRxiv2022

Personality variation is eroded by simple social behaviours in collective foragers

The movement of groups can be heavily influenced by leader individuals who differ from the others in some way. A major source of differences between individuals is the repeatability and consistency of their behaviour, commonly considered as their personality, which can influence both position within a group as well as the tendency to lead. However, links between personality and behaviour may also depend upon the immediate social environment of the individual; individuals who behave consistently in one way when alone may not express the same behaviour socially, when they may be conforming with the behaviour of others. Experimental evidence shows that personality differences can be eroded in social situations, but there is currently a lack of theory to identify the conditions where we would expect personality to be suppressed. Here, we develop a simple individual-based framework considering a small group of individuals with differing tendencies to perform risky behaviours when travelling away from a safe home site towards a foraging site, and compare the group behaviours when the individuals follow differing rules for aggregation behaviour determining how much attention they pay to the actions of their fellow group-members. We find that if individuals pay attention to the other members of the group, the group will tend to remain at the safe site for longer, but then travel faster towards the foraging site. This demonstrates that simple social behaviours can result in the repression of consistent inter-individual differences in behaviour, giving the first theoretical consideration of the social mechanisms behind personality suppression.

animal behavior and cognition↗

bioRxiv2021

The ability of bumblebees Bombus terrestris (Hymenoptera: Apidae) to detect floral humidity is dependent upon environmental humidity

Flowers produce local humidity that is often greater than that of the surrounding environment, and studies have shown that insect pollinators may be able to use this humidity difference to locate and identify suitable flowers. However, environmental humidity is highly heterogeneous, and is likely to affect the detectability of floral humidity, potentially constraining the contexts in which it can be used as a salient communication pathway between plants and their pollinators. In this study, we use differential conditioning techniques on bumblebees Bombus terrestris audax (Harris) to explore the detectability of an elevated floral humidity signal when presented against different levels of environmental noise. Artificial flowers were constructed that could be either dry or humid, and individual bumblebees were presented with consistent rewards in either the humid or dry flowers presented in an environment with four levels of constant humidity, ranging from low ([~]20% RH) to highly saturated ([~]95% RH). Ability to learn was dependent upon both the rewarding flower type and the environment: the bumblebees were able to learn rewarding dry flowers in all environments, but their ability to learn humid rewarding flowers was dependent on the environmental humidity, and they were unable to learn humid rewarding flowers when the environment was highly saturated. This suggests that floral humidity might be masked from bumblebees in humid environments, suggesting that it may be a more useful signal to insect pollinators in arid environments.

animal behavior and cognition↗

bioRxiv2021

The role of petal transpiration in floral humidity generation

Floral humidity, an area of elevated humidity in the headspace of flowers, has been detected across angiosperms and may function as a pollinator cue for insect pollinators. It is believed floral humidity is produced predominantly through a combination of evaporation of both liquid nectar and transpirational water loss from the flower. However, the role of transpiration in floral humidity generation has not been tested and is largely inferred by continued humidity production when nectar is removed from flowers. Understanding the extent that transpiration contributes to floral humidity has important implications for understanding the function of floral humidity. We test whether transpiration contributes to the floral humidity generation of two species previously identified to produce elevated floral humidity, Calystegia silvatica and Eschscholzia californica. Floral humidity production of flowers that underwent an antitranspirant treatment, petrolatum gel which blocks transpiration from treated tissues, is compared to flowers that did not receive such treatments. Gel treatments reduced floral humidity production to approximately a third of that produced by untreated flowers in C. silvatica, and half of that in E. californica. This confirms, the previously untested, inferences that transpiration has a large contribution to floral humidity generation and that this contribution may vary between species. HIGHLIGHTWe confirm, the previously untested, inferences that transpiration has a large contribution to floral humidity generation and show that this contribution may vary between species.

plant biology↗

bioRxiv2021

Bumblebees can detect floral humidity

Floral humidity, a region of elevated humidity proximal to the flower, occurs in many plant species and may add to their multimodal floral displays. So far, the ability to detect and respond to floral humidity cues has been only established for hawkmoths when they locate and extract nectar while hovering in front of some moth-pollinated flowers. To test whether floral humidity can be used by other more widespread generalist pollinators, we designed artificial flowers that presented biologically-relevant levels of humidity similar to those shown by flowering plants. Bumblebees showed a spontaneous preference for flowers which produced higher floral humidity. Furthermore, learning experiments showed that bumblebees are able to use differences in floral humidity to distinguish between rewarding and nonrewarding flowers. Our results indicate that bumblebees are sensitive to different levels of floral humidity. In this way floral humidity can add to the information provided by flowers and could impact pollinator behaviour more significantly than previously thought. Summary statementWe demonstrate for the first time that bumblebees show a preference to elevated floral humidity and can learn to distinguish flowers that differ in floral humidity levels.

animal behavior and cognition↗

bioRxiv2020

Red deer Cervus elaphus blink more in larger groups

Most animals need to spend time being vigilant for predators, at the expense of other activities such as foraging. Group-living animals can benefit from the shared vigilance effort of other group members, with individuals reducing personal vigilance effort as group size increases. Behaviours like active scanning or head lifting are usually used to quantify vigilance, but may not be accurate measures as the individual could be conducting them for other purposes. We suggest that measuring an animals blinking rate gives a meaningful measure of vigilance: increased blinking implies reduced vigilance, as the animal cannot detect predators when its eyes are closed. We demonstrate that as group size increases in red deer, individuals increase their blink rate, confirming the prediction that vigilance should decrease. Blinking is a simple non-invasive measure, and offers a useful metric for assessing the welfare of animals experiencing an increase in perceived predation risk or other stressors.

animal behavior and cognition↗

bioRxiv2020

The neonicotinoid insecticide imidacloprid disrupts bumblebee foraging rhythms and sleep

Neonicotinoids have been implicated in the large declines observed in flying insects such as bumblebees, an important group of pollinators[1]. Neonicotinoids are agonists of nicotinic acetylcholine receptors that are found throughout the insect central nervous system, and are the main mediators of synaptic neurotransmission[2]. These receptors are important for the function of the insect central clock and circadian rhythms[3, 4]. The clock allows pollinators to coincide their activity with the availability of floral resources, favourable flight temperatures, as well as impacting learning, navigation and communication[5]. Here we show that exposure to the field relevant concentration of 10 {micro}g/L of imidacloprid can cause a reduction in foraging activity and reduce both locomotor and foraging rhythmicity in Bombus terrestris. Foragers showed an increase in daytime sleep and an increase in the proportion of activity occurring at night. This would likely negatively impact foraging and pollination opportunities, reducing the ability of the colony to grow and reproduce, endangering crop yields.

pharmacology and toxicology↗

bioRxiv2020

Neonicotinoids disrupt memory, circadian behaviour and sleep

Globally, neonicotinoids are still the most used insecticides, despite their well-documented sub-lethal effects on beneficial insects1. Neonicotinoids are agonists at the nicotinic acetylcholine receptors, the main mediator of synaptic transmission in the insect brain2-5, making them highly potent neurotoxins and insecticides6,7. Memory, circadian rhythmicity and sleep are essential for efficient foraging in many pollinating insects, and involve nicotinic acetylcholine receptor signalling2,4,8-10. The effect of field-relevant concentrations of European Union-banned neonicotinoids: imidacloprid, clothianidin and thiamethoxam, as well as the currently unbanned thiacloprid were tested on Drosophila memory, circadian rhythms and sleep. Field-relevant concentrations of imidacloprid, clothianidin and thiamethoxam disrupted learning, behavioural rhythmicity and sleep whilst thiacloprid exposure only affected sleep. Exposure to imidacloprid and clothianidin directly affected neurophysiology, preventing the day/night remodelling and accumulation of pigment dispersing factor neuropeptide in the dorsal terminals of clock neurons. Knockdown of the neonicotinoid susceptible D1 and D{beta}2 nicotinic acetylcholine receptor subunits in the mushroom bodies or clock neurons recapitulated the neonicotinoid like deficits in memory or circadian/sleep behaviour demonstrating that neonicotinoid effects are likely mediated in the mushroom body and clock circuitry. Disruption to learning, circadian rhythmicity and sleep are likely to have far-reaching detrimental effects on beneficial insects in the field.

pharmacology and toxicology↗