Biology subjects

Lihoreau, M.

Publications and source records attributed to Lihoreau, M..

28 records · Page 2Linked to original sources

bioRxiv2022

Automated detection of sow posture changes with millimeter-wave radars and deep learning

Automated behavioural monitoring is increasingly required for animal welfare and precision agriculture. In pig farming, detailed analyses of sow activity are essential to identify and reduce the risks of piglets being crushed during postural changes of their mothers. Here we introduce a new, non-invasive, fast and accurate method for monitoring sow behaviour based on millimeter-wave radars and deep learning analysis. We used our method to predict postural changes in crated sows and distinguish the dangerous one that lie down abruptly from those that lie down carefully using transient postures. Two radars were placed on a metal backing above the head and the upper part of the back of each of ten sows to monitor their activity during 5 hours. We analysed the radar data with a convolutional neural network and identified five postures. The average sensitivity was 96.9% for standing, 90.8% for lying, 91.4% for nursing, 87.6% for sitting, but only 11.9% for kneeling. However, the average specificity and accuracy were greater than 92% for the five postures. Interestingly, two of the ten sows occasionally moved directly from standing to lying, without using the transient postures sitting and kneeling, thereby displaying risky behaviours for their piglets. Our radar-based classifier is more accurate, faster and require less memory than current computer vision approaches. Using more sows will improve the algorithm performance and facilitate future applications for large scale deployment in animal farming. HighlightsO_LIAutomated behavioural analysis is a major challenge for precision farming. C_LIO_LIWe developed automated detection of lactating sow postures with radars and deep learning. C_LIO_LIWe identified five postures, including transitions risky for the piglets. C_LIO_LIOur method is accurate, fast and requires less memory than computer vision. C_LIO_LIRadars thus hold considerable promises for high through-put recording of livestock activity. C_LI

animal behavior and cognition↗

bioRxiv2021

Considering variance in pollinator responses to stressors can reveal potential for resilience

O_LIEnvironmental stressors have sublethal consequences on animals, often affecting the mean of phenotypic traits in a population. However, potential effects on variance are poorly understood. Since phenotypic variance is the basis for adaptation, any influence of stressors may have important implications for population resilience. C_LIO_LIHere we explored this possibility in insect pollinators by analysing raw datasets from 24 studies (6,913 bees) in which individuals were first exposed to stressors and then tested for cognitive tasks. C_LIO_LIWhile all types of stressors decreased the mean cognitive performance of bees, their effect on variance was complex. Focusing on 15 pesticide studies, we found that the dose and the mode of exposure to stressors were critical. At low pesticide doses, cognitive variance decreased following chronic exposures but not for acute exposures. Acute exposure to low doses thus seems less damaging at the population level. In all cases however, the variance decreased with increasing doses. C_LIO_LIPolicy implications. Current guidelines for the authorization of plant protection products on the European market prioritize acute over chronic toxicity assessments on non-target organisms. By overlooking the consequences of a chronic exposure, regulatory authorities may register new products that are harmful to bee populations. Our findings thus call for more research on stress-induced phenotypic variance and its incorporation to policy guidelines to help identify levels and modes of exposure animals can cope with. C_LI

animal behavior and cognition↗

bioRxiv2021

Nutrigonometry I: using right-angle triangles to quantify nutritional trade-offs in multidimensional performance landscapes

Animals regulate their diet in order to maximise the expression of fitness traits that often have different nutritional needs. These nutritional trade-offs have been experimentally uncovered using the Geometric framework for nutrition (GF). However, current analytical methods to measure such responses rely on either visual inspection or complex models applied to multidimensional performance landscapes, making these approaches subjective, or conceptually difficult, computationally expensive, and in some cases inaccurate. This limits our ability to understand how animal nutrition evolved to support life-histories within and between species. Here, we introduce a simple trigonometric model to measure nutritional trade-offs in multidimensional landscapes ( Nutrigonometry). Nutrigonometry is both conceptually and computationally easier than current approaches, as it harnesses the trigonometric relationships of right-angle triangles instead of vector calculations. Using landmark GF datasets, we first show how polynomial (Bayesian) regressions can be used for precise and accurate predictions of peaks and valleys in performance landscapes, irrespective of the underlying structure of the data (i.e., individual food intakes vs fixed diet ratios). Using trigonometric relationships, we then identified the known nutritional trade-off between lifespan and reproductive rate both in terms of nutrient balance and concentration. Nutrigonometry enables a fast, reliable and reproducible quantification of nutritional trade-offs in multidimensional performance landscapes, thereby broadening the potential for future developments in comparative research on the evolution of animal nutrition.

evolutionary biology↗

bioRxiv2021

The gut parasite Nosema ceranae impairs olfactory learning in bumblebees

Pollinators are exposed to numerous parasites and pathogens when foraging on flowers. These biological stressors may affect critical cognitive abilities required for foraging. Here, we tested whether exposure to Nosema ceranae, one of the most widespread parasite of honey bees also found in wild pollinators, impacts cognition in bumblebees. We investigated different forms of olfactory learning and memory using conditioning of the proboscis extension reflex. Seven days after feeding parasite spores, bumblebees showed lower performance in absolute and differential learning, and reversal learning than controls. Long-term memory was also slightly reduced. The consistent effect of N. ceranae exposure across different types of olfactory learning indicates that its action was not specific to particular brain areas or neural processes. We discuss the potential mechanisms by which N. ceranae impairs bumblebee cognition and the broader consequences for populations of pollinators.

animal behavior and cognition↗

bioRxiv2021

Poor adult nutrition impairs learning and memory in a parasitoid wasp

Animals have evolved cognitive abilities whose impairment can incur dramatic fitness costs. While malnutrition is known to impact brain development and cognitive functions in vertebrates, little is known in insects, whose small brain appears particularly vulnerable to environmental stressors. Here, we investigated the influence of diet quality on learning and memory in the parasitoid wasp Venturia canescens. Newly emerged adults were exposed for 24h to either honey, sucrose solution 20%, sucrose solution 10%, or no food, before being conditioned in an olfactory associative learning task in which an odor (orange) was associated to a reward (host larvae). Wasps fed honey showed 3.5 times higher learning performances and 1.5 times longer memory retention times than wasps fed sucrose solutions and starved wasps. Poor diets also reduced longevity and fecundity. Our results demonstrate the importance of early adult nutrition for optimal cognitive function in these parasitoid wasps that must quickly develop olfactory memories for choosing high quality hosts for their progeny.

animal behavior and cognition↗

bioRxiv2020

Bumblebees develop more efficient traplines than honey bees

Central place foraging pollinators, such as bees, tend to learn multi-destination routes (traplines) to efficiently visit known feeding locations and return to their nest. To what extent these routing behaviours are shared across species is unknown. Here we ran laboratory experiments to compare trapline formation and efficiency by foragers of two social bee species that differ in their collective foraging strategies: the solo foraging bumblebee Bombus terrestris and the mass foraging honey bee Apis mellifera. In a simple routing task with four artificial flowers, both bumblebees and honey bees developed a stable route, although honey bees were slower and less efficient to do so. In a more complex routing task with six flowers, only bumblebees developed a stable route. Honey bees took a longer time to discover all flowers and never integrated them in a single route. Simulations of a model of trapline formation show that these inter-specific differences can be replicated by adjusting the strength of a single learning parameter. Comparing bumblebees and honey bees in the same experimental conditions thus revealed key differences in their spatial foraging strategies, potentially driven by social constraints.

animal behavior and cognition↗

bioRxiv2020

Heavy metal pollutants have additive negative effects on honey bee cognition

Environmental pollutants can exert sublethal deleterious effects on animals. These include disruption of cognitive functions underlying crucial behaviours. While agrochemicals have been identified as a major threat to pollinators, other compounds, such as heavy metals that are often found in complex mixtures, have largely been overlooked. Here, we assessed the impact of acute exposure to field-realistic concentrations of lead, copper, arsenic, and their combinations, on honey bee learning and memory. All treatments involving single metals slowed down appetitive learning and disrupted memory retrieval at 24 h. Importantly, combinations of these metals induced additive negative effects on both processes, suggesting common pathways of toxicity. Our results highlight the need to further assess the risks of heavy metal pollution on invertebrates and to their associated ecosystem services. Summary statementHoney bees displayed reduced learning and memory performances following acute exposure to arsenic, copper or lead. Exposure to combinations of these metals induced additive effects.

animal behavior and cognition↗

bioRxiv2020

A non-invasive radar system for automated behavioural tracking: application to sheep

Automated quantification of the behaviour of freely moving animals is increasingly needed in ethology, ecology, genetics and evolution. State-of-the-art approaches often require tags to identify animals, high computational power for data collection and processing, and are sensitive to environmental conditions, which limits their large-scale utilisation. Here we introduce a new automated tracking system based on millimetre-wave radars for real time robust and high precision monitoring of untagged animals. To validate our system, we tracked 64 sheep in a standard indoor behavioural test used for genetic selection. First, we show that the proposed radar application is faster and more accurate than conventional video and infrared tracking systems. Next, we illustrate how new behavioural estimators can be derived from the radar data to assess personality traits in sheep for behavioural phenotyping. Finally, we demonstrate that radars can be used for movement tracking at larger spatial scales, in the field, by adjusting operating frequency and radiated electromagnetic power. Millimetre-wave radars thus hold considerable promises for high-throughput recording of the behaviour of animals with various sizes and locomotor modes, in different types of environments.

animal behavior and cognition↗

bioRxiv2020

A model of resource partitioning between foraging bees

Central place foraging pollinators tend to develop multi-destination routes (traplines) to visit patchily distributed plant resources. While the formation of traplines by individual pollinators has been studied in details, how populations of foragers exploit resources in a common area is an open question, difficult to address experimentally. We explored conditions for the emergence of resource partitioning among traplining bees using agent-based models built from experimental data of bumblebees foraging on artificial flowers. In the models, bees learn to develop routes as a consequence of feedback loops that change their probabilities of moving between flowers. While a positive reinforcement of movements leading to rewarding flowers is sufficient for the emergence of resource partitioning when flowers are evenly distributed, addition of negative reinforcement of movements leading to unrewarding flowers is necessary when flowers are patchily distributed. In environments with more complex spatial structure, the negative experiences of individual bees on flowers favour spatial segregation and efficient collective foraging.

animal behavior and cognition↗

bioRxiv2020

Artificial diets modulate infection rates of bumblebees by Nosema ceranae

Parasites alter the physiology and behaviour of their hosts. In domestic honey bees, the microsporidia Nosema ceranae induces an energetic stress and impairs the behaviour of foragers, potentially leading to colony collapse. Whether this emerging parasite similarly affects wild pollinators is little understood because of the low success rates of experimental infection protocols. Here we established a new apporach for infecting bumblebees (Bombus terrestris) with controlled amounts of N. ceranae, by briefly exposing individual bumblebees to a sucrose solution containing parasite spores, before feeding them with artificial diets. We validated our protocol by testing the effect of two spore dosages and two diets varying in their protein to carbohydrate ratio, on the prevalence of the parasite (proportion of infected bees), the intensity of infection (spore count in the gut), and the survival of bumblebees. Insects fed a low-protein high-carbohydrate diet showed highest parasite prevalence (up to 70%) but lived longest, suggesting that immunity and survival of bumblebees are maximised at different protein to carbohydrate ratios. Spore dosage had no effect on parasite infection rate and host survival. The identification of experimental conditions for successfully infecting bumblebees with N. ceranae in the lab will facilitate investigations of the sub-lethal effects of this parasite on the behaviour and cognition of wild pollinators.

physiology↗