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The function of zebra stripes
Nature Communications
Abstract
Despite over a century of interest, the function of zebra stripes has never been examined systematically. Here we match variation in striping of equid species and subspecies to geographic range overlap of environmental variables in multifactor models controlling for phylogeny to simultaneously test the five major explanations for this infamous colouration. For subspecies, there are significant associations between our proxy for tabanid biting fly annoyance and most striping measures (facial and neck stripe number, flank and rump striping, leg stripe intensity and shadow striping), and between belly stripe number and tsetse fly distribution, several of which are replicated at the species level. Conversely, there is no consistent support for camouflage, predator avoidance, heat management or social interaction hypotheses. Susceptibility to ectoparasite attack is discussed in relation to short coat hair, disease transmission and blood loss. A solution to the riddle of zebra stripes, discussed by Wallace and Darwin, is at hand.
... Consequently, while in Figure 1a these structures may not be fully accessible to consciousness, in the subsequent figures, they become the primary perceptual focus, relegating the homogeneous global form to the background, resulting in its fragmentation. This phenomenon is analogous to certain forms of biological camouflage, such as the disruptive coloration observed in zebras [41,42]. The alternating black and white stripes serve to fragment the zebra's outline, impeding predator recognition of individual targets, particularly in group contexts or in environments characterized by high visual complexity, such as tall grasslands or during locomotion [43]. ...
... This phenomenon is analogous to certain forms of biological camouflage, such as the disruptive coloration observed in zebras [41,42]. The alternating black and white stripes serve to fragment the zebra's outline, impeding predator recognition of individual targets, particularly in group contexts or in environments characterized by high visual complexity, such as tall grasslands or during locomotion [43]. ...
... is true, as demonstrated by the Helmholtz square illusion [58]. However, this belief is partially validated when considering the groupings of elements like those illustrated in Figure 2. It is plausible that the horizontal stripes present on the rear (hindquarters) of prey species such as zebras and okapis serve to create an illusion of increased size in that area, which is typically the initial target for predators [42]. There is a common misconception that shirts with horizontal stripes make the body appear wider and heavier, while vertical lines have a slimming effect. ...
Background: This study investigates the complex relationship between accentuation and attention in visual perception, extending classical Gestalt principles by introducing dissimilarity as a complementary mechanism to similarity in perceptual organization. Objectives and Methods: Through a series of phenomenological experiments, we demonstrate how accentuation, driven by dissimilarity, plays a crucial role in shaping visual experience and guiding attention. Results: Our findings reveal that accentuation serves as a pre-attentive mechanism for highlighting salient features, influencing initial perceptual organization, and modulating the apparent shape and orientation of visual elements. We show that while accentuation operates rapidly and automatically, attention acts as a flexible, selective mechanism that can either reinforce or override accentuation-based percepts. This interplay suggests a two-stage process of visual perception, with implications for theories of consciousness and information processing in biological systems. This study also explores the evolutionary significance of accentuation in camouflage and sexual selection, providing insights into how perceptual mechanisms may have evolved to enhance adaptive fitness. Conclusions: Our results have broad implications for understanding visual cognition, design, and clinical applications related to attentional disorders.
... The physical characteristics of the skin and coat are important factors in the vulnerability of ungulates to flies (Caro et al. 2014, Kynkaanniemi et al. 2014, Scasta & Smith 2019. Bison spp. ...
... Areas on a moose with a lower density of hairs and shorter hairs are heavily targeted by feeding flies Caro et al. 2014;Scasta & Smith 2019); after molting, the caudal aspect of the legs, the perianal region, and the eyes are most vulnerable to flies . A moose's coat consists of guard hairs covering their entire body, wool hairs or underfur on their torso, and vibrissae around their eyes and nose (Rubenik 2007). ...
... In summary, our results indicate that the cause for the sores on the hindleg of moose is a previously unknown genetic lineageof Onchocerca, probably transmitted by black flies, in timing with the molt cycle of adult moose. These sores leave moose exposed to pathogens, making them vulnerable, and challenging their health and fitness.IntroductionA mammal's coat and integument is an important barrier between the animal and its environment, providing protection against pollutants, extreme temperatures, pathogens, and irritants such as insects(Caro et al. 2014;Mauldin & Peters-Kennedy 2015;. Hair and melanin in the integument offer thermoregulation and photoprotection. ...
I studied the responses of wild ungulates to harassment by flies (Diptera) by reviewing the literature on North American ungulates and studying the behavior and physiology of female moose (Alces alces) in a boreal forest in Alaska. Hair and skin provide morphological resistance to flies at low exposures, but behavioral and physiological responses are used to reduce and tolerate flies as exposure increases. Caribou (Rangifer tarandus) avoid flies, which displaces foraging and reduces body mass gain in summer. Moose tolerate flies through the summer. I found that flies do not trigger a release of glucocorticoid hormones in either moose calves or adult moose as a stress response. The dense hair of the neonatal coat resists flies, but calves still suffer morbidity and mortality from parasitic diseases carried by flies. Adult moose molt and lose their barrier of protection in June and July when flies are the most abundant, and sores appear on their hind legs. Leg sores of adult moose were infected with a parasitic nematode within the genus Onchocera, which is likely transmitted by black flies (Diptera: Simuliidae). The number of sores on the hind legs of an individual was positively correlated with total body fat, which suggests that tolerance of flies increases gain of energy from foraging over the summer. Conversely, the number of sores was negatively correlated with serum albumin, which indicates the use of body protein to repair injuries from flies and parasites. Moose altered daily movements in response to flies; on cool days (8°C), movement rates increased with the abundance of flies. However, on warm days (20°C), movement rates were not affected by flies probably because cooling takes priority. Time spent in black spruce forests increased with both air temperature and with counts of flies. Warm summer temperatures create an ecological trap for moose when heat gained while foraging is dissipated at rest in shady, wet habitats preferred by flies that adversely affect the fitness of moose.
... First, the presence of body striping in mammals reduces parasitism overall (reviewed in Caro et al., 2014), although ectoparasites are more likely to be found feeding on the black body stripes than they are on the lighter base body colouration. Similarly, our observation documents a mosquito feeding on one of the black bands of a female A. transversalis. ...
... Similarly, our observation documents a mosquito feeding on one of the black bands of a female A. transversalis. Second, the body stripes in A. transversalis are close in width (0.7-1.0 cm) to the most effective insect-deterrent striping width in mammals (1-5 cm; Caro et al., 2014). Third, these stripes are oriented horizontally when female A. transversalis are perched on tree trunks during the day. ...
Observations of mosquitoes feeding on anoles
... He discovered that a homogeneous steady-state solution of a reaction-diffusion PDE can develop instabilities owing to the disparity of diffusion coefficients of the two reacting species considered [5][6][7]. Recognized for its universality, the Turing instability has been invoked to explain a broad class of phenomenaparticularly in biological dynamics-such as the formation of striped patterns on zebras, and so on [8][9][10][11][12]. Interestingly, experimental evidence for such instability was found in the 1990s [13] spurring further advances [5,14,15]. ...
... Moreover, solving equations (12), and (13) involves the higher moments. We derive the equations of motion for the higher moments using equations (7), and (8). Specifically, for instance, to get the evolution of ⟨ δI 2 ⟩ , we multiply equation (8) by 2δI followed by statistical averaging. ...
Theoretical analysis of epidemic dynamics has attracted significant attention in the aftermath of the COVID–19 pandemic. In this article, we study dynamic instabilities in a spatiotemporal compartmental epidemic model represented by a stochastic system of coupled partial differential equations (SPDE). Saturation effects in infection spread–anchored in physical considerations–lead to strong nonlinearities in the SPDE. Our goal is to study the onset of dynamic, Turing–type instabilities, and the concomitant emergence of steady–state patterns under the interplay between three critical model parameters–the saturation parameter, the noise intensity, and the transmission rate. Employing a second–order perturbation analysis to investigate stability, we uncover both diffusion–driven and noise–induced instabilities and corresponding self–organized distinct patterns of infection spread in the steady state. We also analyze the effects of the saturation parameter and the transmission rate on the instabilities and the pattern formation. In summary, our results indicate that the nuanced interplay between the three parameters considered has a profound effect on the emergence of dynamical instabilities and therefore on pattern formation in the steady state. Moreover, due to the central role played by the Turing phenomenon in pattern formation in a variety of biological dynamic systems, the results are expected to have broader significance beyond epidemic dynamics.
... Previously, it was believed that zebras' stripes helped them to camouflage from predators. However, recent scientific findings suggest that these stripes may primarily serve as protection against biting flies such as the tsetse fly [5,26]. These flies are carriers of diseases such as anthrax and trypanosomiasis, which can be fatal to zebras. ...
... The patterns of stripes in different species of zebras evolve with distinct numbers and sizes over time [2]. Among them, the shadow stripe that emerges on some Equus burchelli zebra skin [4,5] is an interesting topic of research in the fields of mammalian and mathematical biology. The formation of shadow stripe patterns in Equus burchelli zebra skin is manifested by rapid growth effects when growing from an embryonic state to adulthood [11]. ...
We perform an in silico investigation of the formation of multiple intense zebra stripes by extending the domain with an appropriate extending speed. The common zebra has alternating dark and light stripes, creating a two phase pattern. However, some Equus burchelli zebras have an intermediate gray color stripe situated between the dark and light stripes. To numerically investigate the formation of multiple intense zebra stripes, we first find the equilibrium state of the governing system in the one-dimensional (1D) static domains using various frequency modes. After finding the equilibrium state for the governing system in the 1D static domains, we stack a numerical data. Then, we load the stacked numerical data to use as an initial state for finding the growth rate that forms the multiple intense zebra stripe formation in the 1D extended domains. Next, convergence experiments are conducted to verify the convergence of the numerical method for the governing system. Finally, numerical simulations are performed to confirm the formation of multiple intense zebra stripes in two-dimensional extending domains and on evolving curved surfaces.
... Zebras move to forage when a pioneer zebra leads the way. Thus, this pioneer zebra leads the other zebras in the herd as they go across the plains [39]. ...
... It is considered a pioneer grazer. It feeds on the higher, less nutritional grass canopy, creating an environment favorable for other species that require the shorter, more nutritious grasses to be below [39]. Regarding ZOA, the best individual within the population is called the pioneer zebra, guiding the rest of the population toward its location in the search space. ...
Cyber Threat Detection (CTD) is subject to complicated and rapidly accelerating developments. Poor accuracy, high learning complexity, limited scalability, and a high false positive rate are problems that CTD encounters. Deep Learning defense mechanisms aim to build effective models for threat detection and protection allowing them to adapt to the complex and ever-accelerating changes in the field of CTD. Furthermore, swarm intelligence algorithms have been developed to tackle the optimization challenges. In this paper, a Chaotic Zebra Optimization Long-Short Term Memory (CZOLSTM) algorithm is proposed. The proposed algorithm is a hybrid between Chaotic Zebra Optimization Algorithm (CZOA) for feature selection and LSTM for cyber threat classification in the CSE-CIC-IDS2018 dataset. Invoking the chaotic map in CZOLSTM can improve the diversity of the search and avoid trapping in a local minimum. In evaluating the effectiveness of the newly proposed CZOLSTM, binary and multi-class classifications are considered. The acquired outcomes demonstrate the efficiency of implemented improvements across many other algorithms. When comparing the performance of the proposed CZOLSTM for cyber threat detection, it outperforms six innovative deep learning algorithms for binary classification and five of them for multi-class classification. Other evaluation criteria such as accuracy, recall, F1 score, and precision have been also used for comparison. The results showed that the best accuracy was achieved using the proposed algorithm for binary is 99.83%, with F1-score of 99.82%, precision of 99.83%, and recall of 99.82%. The proposed CZOLSTM algorithm also achieved the best performance for multi-class classification among other compared algorithms.
... In the second part of this section, we will give two examples to show that there are actual contextual dysfunctions. According to Caro et al. (2014), the function of zebra stripes is to deter biting flies that carry a parasite responsible for African trypanosomiasis (sleeping sickness). Plausibly, zebra stripes that cannot deter biting flies with this parasite are dysfunctional. ...
... The same reasoning applies to the case of the zebra stripes. If Caro et al. (2014) are correct, zebra stripes have the function of distracting tsetse flies. According to our theory, this means that they have been selected for the disposition to do so. ...
Justin Garson has recently argued that proper functions are proximal activities of traits selected by phylogenetic or ontogenetic selection processes, and that traits are dysfunctional only if they cannot perform their proper functions for constitutional reasons. We partially agree with Garson, but reject the view that functions are proximal activities, as well as his account of dysfunctions. Instead, we propose our own theory that biological functions are selected dispositions and that a trait is dysfunctional in virtue of not having the dispositions for which it was selected. This account can explain both defects (or dysfunctions in Garson’s sense) and dysfunctions due to environmental factors. Moreover, it offers a neat way to explain the graduality of dysfunction.
... The zebras' first line of defense against predators is to run away in a zigzag pattern. However, occasionally, they attempt to mislead or terrify the predator by assembling [32]. This section presents mathematical models of zebras' typical behaviors to mode ZOA. ...
... When smaller predators like hyenas and dogs attack by banding together, they confuse and terrify the hunter. Therefore, zebras are more aggressive [32]. Zebras that approach water are also preyed upon by crocodiles [34]. ...
A Brain Tumor (BT), further known as an intracranial tumor, is a mass of abnormal tissue whose cells multiply and procreate uncontrolled and appear unaffected by those mechanisms that control normal cells, and it causes many people's deaths each year. BT is frequently detected using Magnetic Resonance Imaging (MRI) procedures. One of the greatest common techniques for segmenting medical images is Multilevel Thresholding (MT). MT received the researchers ' attention because of its simplicity, ease of use, and accuracy. Consequently, this paper uses the most recent Zebra Optimization Algorithm (ZOA) to deal with the MT problems of MRI images. The ZOA's performance has been evaluated on 10 MRI images with threshold levels up to 10 and evaluated against five different algorithms: Sine Cosine Algorithm (SCA), Arithmetic Optimization Algorithm (AOA), Flower Pollination Algorithm (FPA), Reptile Search Algorithm (RSA), and Marine Predators Algorithm (MPA). The experimental results, which included numerous performance metrics such as Mean Square Error (MSE), Peak Signal-To-Noise Ratio (PSNR), Feature Similarity Index Metric (FSIM), Normalized Correlation Coefficient (NCC), and fitness values, totally show that the ZOA outperforms all other algorithms based on Kapur's entropy for all the applied measures.
... For ungulates, biting flies can have an important bearing on their behaviour (Downes et al. 1986;Morschel and Klein 1997;Witter et al. 2012), habitat selection (Downes et al. 1986;Toupin et al. 1996), body condition (Helle and Tarvainen 1984), and even morphology (Caro et al. 2014). The responses of potential hosts are manifold, even within a species (Benedict and Barboza 2022). ...
... Biting insects are gaining appreciation among zoologists for their role in the evolution and ecology of large mammals. For ungulates, tabanids represent both a selective force (Caro et al. 2014) and a key component of habitat (Raponi et al. 2018). We believe that our experimental study adds to understanding the response of potential hosts to these important micropredators. ...
Biting flies can strongly influence the behaviour of their hosts, for example, there is evidence that some species may avoid harassment by reducing their locomotory activity. We tested the hypothesis that potential hosts can reduce their attraction to deer flies by remaining stationary—that reducing locomotory movement reduces exposure to new deer flies compared to remaining still. During early summer in central Ontario, Canada, we conducted 20-min trials where a human host either walked or sat quietly; tabanids were captured and counted each minute using a hat outfitted with a sticky trap. During 10 trials in each treatment, we captured a total of 868 deer flies, all in the genus Chrysops; the total capture while walking was nearly five-fold greater than while sitting. During trials, the change in catch rate also differed with host activity. While the host was sitting, the mean rate of capture declined rapidly (−16% per min) to nearly zero by 20 min. In contrast, while the host was walking, this decline was much more gradual (−5% per min); after 20 min, the catch rate remained nearly constant, at roughly half the initial rate. These results are consistent with the hypothesis.
... Due to some behavior mechanisms of individuals, species present heterogeneous but regular spatial distribution structures in both space and time, which is called as "pattern." These pattern structures exist widely in nature such as the clouds in the sky [1], the patterns on zebra [2], and the ripples on the water [3]. Except for these, Getzin et al. found the gap vegetation pattern-fairy circles in Western Australia [4], the regular stripes vegetation distribution on the hillside of Niger studied by Klausmeier et al. [5], and mussel beds in the intertidal zone show different scales of distribution, namely, large-scale banded distribution at the ecological level and small-scale reticular distribution at individual mussels level [6,7]. ...
... Biological significance and value of all parameters in the model(2). ...
Pattern structures are usually used to describe the spatial and temporal distribution characteristics of individuals. However, the corresponding relationship between the pattern structure and system robustness is not well understood. In this work, we use geostatistical method–semivariogram to study system robustness for different pattern structures based on three dynamical models in different fields. The results show that the structural ratio of different pattern structures including the mixed state of spot and stripe, cold spot, stripe only, and hot spot are more than 75 % , which indicated those patterns all have strong spatial dependence and heterogeneity. It was revealed that the systems corresponding to the mixed state of spot and stripe or cold spot are more robust. This article proposed a method to characterize the robustness of the system corresponding to the pattern structure and also provided a feasible approach for the study of “how structures determine their functions.”
... Originating in East and South Africa, zebras are distinguished by their fur that is striped in black and white [35]. These stripes both hide zebras from predators and provide a protective effect against biting flies [48]. These animals, which can run fast thanks to their long and thin legs, single-toed feet, and structures suitable for feeding on grasses close to the ground, exhibit two basic behaviors in their social lives in terms of feeding and defense strategies [33]. ...
The Zebra Optimization Algorithm (ZOA) is a newly proposed biology-based metaheuristic method drawn from zebras in nature, designed to tackle optimization problems. As with other metaheuristic algorithms, ZOA has limitations, including a decrease in population diversity, an imbalance between exploration and exploitation, restricted exploration abilities, and the inclination to get stuck in local optima. To tackle them, this paper proposes an enhanced version of ZOA with multiple strategies called CLESQ-ZOA, which combines three strategies: chaotic mapping, Logarithmic Spiral Strategy (LSS), and Enhanced Search Quality (ESQ). In CLESQ-ZOA, the initial population is produced utilizing chaotic mapping to increase population diversity and provide a more uniform and diverse spread of the initial solutions. The integration of LSS with CLESQ-ZOA allows for greater search capabilities and more efficient exploration of the search space by each individual. Moreover, the ESQ is integrated into the algorithm to minimize the likelihood of getting trapped in local optima by maintaining an equilibrium between exploration and exploitation. These multiple strategies are implemented to enhance population diversity, boost the search capability of CLESQ-ZOA, and strike a delicate balance between exploration and exploitation. The effectiveness of CLESQ-ZOA has been evaluated using standard benchmark functions. Additionally, a binary version of CLESQ-ZOA is also proposed in this paper. The binary version of CLESQ-ZOA is applied to twelve feature selection benchmark datasets to demonstrate its effectiveness in real-world applications. Besides, CLESQ-ZOA has been applied to Hepatocellular Carcinoma to further evaluate its effectiveness. The findings obtained from the CLESQ-ZOA are compared with various metaheuristic methods and the performance is analyzed with Wilcoxon rank-sum and Friedman tests. Experimental and statistical results confirm the effectiveness and reliability of CLESQ-ZOA. Evaluations of feature selection datasets show that CLESQ-ZOA exhibits effective performance in determining the optimal feature subset.
... One line of evidence of the anti-fly function is the close geographical overlap between stripes in equids and climates suitable for tabanid reproduction, and also with areas formerly inhabited by glossinids (Caro, et al., 2014;Larison, et al., 2015;Caro, et al., 2022). Caro, et al. (2022) also point to a close overlap in microhabitats, while Larison, et al. (2015) showed temperature to be an explanatory factor of stripes in equids, an analysis consistent with the trypanosomiasis hypothesis as the development of Trypanosoma is temperature dependent. ...
The function of zebra stripes has long puzzled biologists: contrasted and conspicuous colours are unusual in mammals. The puzzle appears solved: two lines of evidence indicate that they evolved as a protection against biting flies, the geographical coincidence of stripes and exposure to trypanosomiasis in Africa and field experiments showing flies struggling to navigate near zebras. A logical mechanistic explanation would be that stripes interfere with flies' analysis of the optic flow; however, both spatio-temporal aliasing and the aperture effect seem ruled out following recent experiments showing that randomly checked patterns also interfere with flies' capacity to navigate near zebras. No clear mechanistic hypothesis remains.
Here, I model from first principles how flies assess their motion relative to stripes, from image forming to motion analysis. I show that, at short distances, flies would consistently misjudge the motion of a striped object and frequently and saliently misjudge the direction of movement of a randomised check pattern. The range of distances at which stripes the model predicts flies should be impaired is consistent with observations. The model shows that image formation is subject to spatial aliasing, preventing any form of motion analysis against a striped pattern at medium distances, while the motion computation of flies is subject to a second form of aliasing, which, although independent of the temporal resolution of flies, bears conceptual similarities to spatio-temporal aliasing.
The findings highlight the necessity of accounting not only for processing and psychology but also for the optics of image formation when taking a perceptual perspective of animal colours and contrasts.
... For discussion of this last point, see Graham (2023). 81 I borrow this example from Garson (2019), who is drawing on the work of Caro et al. (2014). performing their function. ...
This essay defends an account of what things are assessable for reasonableness and why. On this account, something is assessable for reasonableness if and only if and because it is the functional effect of critical reasoning.
... Coloration patterns in mammals perform important roles in adaptive processes, from sexual selection, intra and interspecific communication, disease, protection, hunting, success to defense and camouflage against predators (Caro,2005;Caro et al. 2014;Caro & Mallarino, 2020;Howell et al. 2021). In rare cases, individuals may present abnormal coloration patterns, such as albinism (Abreu et al. 2013). ...
Coloration is crucial for mammalian adaptation, influencing predator defense and social behavior. In recent decades, chromatic anomalies have been documented in Neotropical mammals, including albinism, leucism, and piebaldism, affecting several species. Pie-baldism is a rare autosomal disorder characterized by asymmetric depigmented patches on the body. This study presents the first record of piebaldism in the collared peccary (Dicotyles tajacu Linnaeus, 1758) throughout its distribution. The record was obtained using camera traps at the Estação Ecológica (ESEC) da Terra do Meio in 2023. Observations showed that the affected peccary coexisted normally with other peccaries and engaged in typical feeding and social behaviors, suggesting that piebaldism does not affect individual social interactions. This finding is consistent with the literature indicating that chemical signals are more important than visual signals in Tayassuidae. This finding highlights the need to understand the frequency and distribution of chromatic anomalies to assess their implications for conservation plans over time.
... Female horseflies are typically facultative and may opportunistically consume blood, nectar and pollen to fulfill their energy requirements for flight, reproduction and oviposition (Leprince et al. 1983;Karolyi et al. 2014;Mullens 2019). Some of their host, including mammals, reptiles and birds, exhibit evasion and defense behaviors to avoid horsefly bites (Limeira de Oliveira et al. 2002;Barros and Foil 2007;Caro et al. 2014;Altunsoy 2015). This suggest that the foraging behavior of female horseflies can be energetically demanding, therefore, the blood intake provides them with advantages such as increased escape speed (Horváth et al. 2020a, b). ...
Male horseflies have low capture rates in Malaise traps, a widely documented pattern observed in numerous ecological studies. We present findings from a specific locality in Ecuador where a departure from this established pattern is observed. In this locality, males accounted for 59.14% of Tabanidae captures. The disruption in capture patterns observed using Malaise traps represents an uncommon feature in the scientific literature and during collections conducted over eight years in Ecuador. Despite the inherent limitations of Malaise traps in capturing male horseflies, it is possible that under specific conditions, such as the presence of optimal aggregation areas for horseflies, Malaise traps may enhance the capture efficiency of males. Additionally, we provide a detailed discussion on the disruption and disparity in capture sex proportions in Tabanidae, commonly reported in the scientific literature.
... The zebra is a social animal where for foraging, a pioneer zebra leads the group to the location rich with grass (Pastor et al., 2006). In the presence of predators in the region, the first instinct of the group is to escape in a zigzag motion pattern, however, in case of attack by a small size predator, the group of zebras gather in one place to frighten the predator (Caro et al., 2014). Mathematical modeling of these two behaviors are the fundamental inspiration of the ZOA. ...
Objectives: The main objective of the research was to build a ceramic filter bed, using red clay and diatomite, for the removal of arsenic in aqueous media and to propose an environmentally friendly and low-cost technique for rural communities in Peru that consume water contaminated with arsenic. Theoretical framework: Arsenic is a common contaminant in the drinking water of many rural communities in Peru, exceeding the limits allowed by the WHO. Prolonged exposure to arsenic can cause serious health problems. The use of low-cost non-metallic materials, such as thermally activated clay and diatomite, is proposed for its adsorption. Method: A filter bed composed of 5 cm layers of red clay and diatomite with particle sizes of 0.81, 0.31 and 0.20 mm was used. Both materials were thermally activated at 900°C and placed on a stainless steel support. The arsenic removal process was evaluated by passing a synthetic solution with 13.99 ppm of arsenic through the bed. Material characterization analyses were performed before and after the adsorption process, using techniques such as ICP-OES, SEM, FTIR, among others. Results and discussion: The filter bed composed of diatomite (83.31% SiO2) and red clay (8.23% Fe2O3) achieved an arsenic removal of up to 99.99%, highlighting the efficiency of particles with a size of 0.20 mm. This shows that the combination of these materials can be highly effective in removing arsenic in water, which is promising for its implementation in rural areas. Research implications: This research has important implications for water treatment in rural communities facing arsenic contamination problems. The technique developed is low-cost and uses abundant resources, which facilitates its application at the local level and promotes sustainable solutions for access to safe drinking water. Originality/Value: The research provides a novel approach through the use of red clay and diatomite, accessible resources, thermally activated for the removal of arsenic in water. In addition, the high removal effectiveness achieved provides a potentially scalable and replicable solution in other rural communities with similar problems.
... Higher taxonomic levels with greater numbers of species allow more statistical power and enable general conclusions to be formulated; lower taxonomic levels generate specific conclusions for certain groups, but species numbers can be so low for some groups that statistical tests are questionable. In our recent paper (Howell & Caro, 2024), we opted for the higher-level analyses; in others we have used Family-level analyses (Caro et al., 2014;Ortolani & Caro, 1996). Despite our higher-level attempt, we, like Penteriani, value examining lower-level associations: mice are unlike bears, and duikers are unlike equids, both ecologically and morphologically. ...
... Camouflage is another potential antipredatory mechanism; colours, colour gradients, and patterns allow for crypsis and masquerade to keep the animal from being detected by predators (Caro, 2011;Stevens & Merilaita, 2011) or parasites (Caro et al., 2014;Côte et al., 2018). Pigments can have a role in crypsis achieved by background matching, disruption or distraction (Caro, 2011;Stevens & Merilaita, 2011). ...
Animal coloration serves a variety of visually related functions in nature (e.g. mate choice, aposematism and camouflage) but the pigments in integumentary tissues such as skin, scales and feathers may also serve functions unrelated to the visual environment (e.g. temperature regulation, detoxification and pollutant protection). Our understanding of the significance of the non‐visual functions of animal integumentary pigments, as well as how they interact with the visually related functions to shape animal visual systems, remains limited.
Furthermore, due to their important roles in shaping species interactions and mediating interactions in the environment, animal colour traits are likely to be impacted by global change (e.g. increased temperatures, altered habitat quality and quantity, increased environmental stochasticity, pollutants and novel species assemblages).
Considering the effects of global change on both visual and non‐visual functions is important for understanding whether the selection is acting directly on the pigment or on coloration. Since changing the trait distributions can then lead to changes in visual systems, we advocate for studies to consider all potential functions of integumentary pigments, both visual and non‐visual functions and their interaction.
Towards this goal, we first highlight common functions of pigments with a focus on non‐visual functions across animal systems. Then we synthesize our current understanding of how global change can impact pigmentation and discuss factors that can modify the interactions between climate change and pigment function. Lastly, we discuss how changes in colour traits can impact visual systems and provide an example using amphibians and their responses to climate change as a model.
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... The zebra uses zigzag escape routes and haphazard sideways turning motions as a defense against lion assaults. When Dogs and hyenas, which are smaller predators attack, zebras become more combative in order to confound and terrify the hunter by congregating [36]. According to the ZOA design, there is an equal chance of one of the following two scenarios happening: ...
A wireless sensor network (WSN) is made up of one or more sink nodes, also known as base stations, and spatially dispersed sensors. Real-time monitoring of physical parameters like temperature, vibration, and motion is done using sensors, which also provide sensory data. A sensor node may act as a data router in addition to an originator of data. However, there are a number of issues with these sensors, including a high rate of energy consumption and a short network lifetime. One of the greatest ways to handle this problem is to use the clustering technique. In the WSN, selecting the optimal Cluster Heads (CHs) helps save energy consumption. Algorithms for Swarm Intelligence (SI) can assist in resolving challenging issues. We present a novel algorithm in this research to choose the top CHs in the WSN. A Chaotic Zebra Optimization Algorithm (CZOA) is the name of the new algorithm. We integrate the chaotic map and the zebra optimization algorithm (ZOA) in the CZOA. By doing so, the suggested algorithm’s processes of diversification can help to prevent the possibility of being trapped in local minima. Different SI algorithms are compared with the CZOA. The suggested algorithm’s results demonstrate that it can use less energy than the other algorithms and that more nodes are still alive for it than for the other algorithms combined. As a result, the CZOA demonstrated its superiority in lowering energy consumption and lengthening network lifetime.
... Many animals facing less sophisticated visual predators or less diverse visual surroundings have evolved simple yet effective heuristic solutions for camouflage. Examples include the stripes of zebras, which are effective at deceiving the visual system of tse-tse flies (3) or the white fur of artic hares (4), which enables a visual blending into its monotone artic surroundings. That the camouflage system of the cuttlefish is much more sophisticated can be readily appreciated by an examination of its physical structure (1). ...
For efficient background matching it is essential that animals closely match a set of salient visual statistics of their visual surroundings. The mean intensity of a background is a key statistic, because it can be estimated across a large range of viewing distances by a simple computation. We investigated how the dynamic neuromuscular camouflage system of the cuttlefish Sepia offcinalis responds to changes in the mean background intensity of uniform backgrounds. We find that cuttlefish adapt their body intensity in response to variations in the mean background intensity, yet show biases in their body intensity beyond what can be predicted from the limited dynamic range of their camouflage system. On sandy backgrounds of various reflectance values their uniform body patterns maintain a constant yellow hue. This color constancy may represent an example of a color prior in a colorblind animal because a yellow body color would be the optimal hue for camouflage on sands typically encountered in their natural environment. Cuttlefish adapt their appearance to the background via a dynamic process composed of a complex mixture of intensity transients spanning timescales from the subsecond to the minute range. In very young animals camouflaging on dark sands the masquerade strategy is preferred over background matching. Masquerade is implemented by combining partial background matching with frequent expression of disruptive components. We furthermore provide an objective definition of disruptive components using hierarchical clustering and automated image analysis thus highlighting the role of chromatophore activity correlations in structuring the motor output of S.officinalis .
... Therefore, the mode S1 in Eq. (50) can be used to mathematically represent this strategy. In the second technique, when other predators attack one of the zebras, the other zebras in the herd move toward the attacked zebra in an attempt to confuse and intimidate the predator by forming a protective structure (Caro et al., 2014). Mode S2 in Eq. (50) is used to formally represent the zebra behaviors. ...
The performance of the robotic manipulator is negatively impacted by outside disturbances and uncertain parameters. The system’s variables are also highly coupled, complex, and nonlinear, indicating that it is a multi-input, multi-output system. Therefore, it is necessary to develop a controller that can control the variables in the system in order to handle these complications. This work proposes six control structures based on neural networks (NNs) with proportional integral derivative (PID) and fractional-order PID (FOPID) controllers to operate a 2-link rigid robot manipulator (2-LRRM) for trajectory tracking. These are named as set-point-weighted PID (W-PID), set-point weighted FOPID (W-FOPID), recurrent neural network (RNN)-like PID (RNNPID), RNN-like FOPID (RNN-FOPID), NN+PID, and NN+FOPID controllers. The zebra optimization algorithm (ZOA) was used to adjust the parameters of the proposed controllers while reducing the integral-time-square error (ITSE). A new objective function was proposed for tuning to generate controllers with minimal chattering in the control signal. After implementing the proposed controller designs, a comparative robustness study was conducted among these controllers by altering the initial conditions, disturbances, and model uncertainties. The simulation results demonstrate that the NN+FOPID controller has the best trajectory tracking performance with the minimum ITSE and best robustness against changes in the initial states, external disturbances, and parameter uncertainties compared to the other controllers.
... Accordingly, geometric morphometrics has become a powerful and widely adopted tool in recent years for obtaining body shape data that can be used to detect phylogenetic signal associated with phenotypic variation (Adams et al. 2004;Rodríguez-González et al. 2017). In particular, finding a correlation between a phenotypic trait (such as body shape) and a function in an evolutionary context can provide interesting insights into natural history, sometimes offering answers to long-standing questions in biology (Caro et al. 2014;Kelley et al. 2015). ...
Insects are suitable model organisms for functional morphology research, especially in the context of exaptation, when the same morphological trait represents an advantage in disparate niches. Phylogenetically distant groups of pygmy grasshoppers (Orthoptera: Tetrigidae) have various pronotal projections, defining their general appearance, i.e., body shape. However, pronotum shape has never been related to niche occupation in these insects, thus the aim of this study is to investigate the relationship between body shape and macrohabitat adaptation in Scelimeninae, a group of Asian and Papuan tetrigids encompassing amphibious and corticolous (bark-dwelling) representatives. With the use of geometric morphometrics and phylogenetic comparative methods, two morphological and functional groups were distinguished, with the body shape exhibiting a significant phylogenetic signal. The first group consists of elongated amphibious taxa (Scelimenini tribe) with highly uniform pronotum morphology, likely due to strong selection for streamlined body shape. Stouter corticolous taxa (Discotettigini tribe) exhibit more conspicuous body shape variability, possibly increasing camouflage efficiency in tree bark habitats. Ecological divergence associated with macrohabitat adaptation may thus have been the primary driver of speciation in this insect group, but the evolutionary constraints leading to this divergence are still to be identified.
... together, however, they could try to confuse or frighten the predator [44]. One kind of optimizer is the zebra optimization algorithm (ZOA), which uses zebras as part of its population. ...
This research article presents the optimization of the hot wire gas-tungsten arc welding (HW-GTAW) process parameters for joining AISI super 304 H (SS304H) plates with experiments designed using historic data design methodology. HW-GTAW can overcome the low deposition efficiency of the conventional GTAW process. The current of hot wire, welding current, and wire feed rate are the input factors, and the weight of weld deposition (WWD) and bead width (BW) are the outputs measured for analysis. Micrographs of weldment show defect-free joints; a higher wire feed rate leads to the disturbance of the main arc, whereas a lower wire feed rate results in droplet transfer, interrupting the welding. The weld interface exhibits the presence of finer grains and partially deformed grains in the partially mixed zone (PMZ) and coarser grains in a heat-affected zone (HAZ). The presence of columnar dendrites leads to superior tensile properties compared to the base metal. Optimization shows that the joint fabricated with a welding current of 150 A, hot wire current of 40 A, and a wire feed rate of 1500 mm/min exhibits a higher WWD and BW of 23.97 g and 13 mm, respectively. Wire feed rate revealed a higher influence on WWD, and welding current has a higher effect on the BW of SS304H joints. The optimized SS304 H joint exhibits a maximum strength in tension (598 MPa) and a mean hardness of 188 HV at the fusion zone (FZ) and HAZ. Nature-inspired metaheuristic zebra optimization algorithm also produces identical results from desirability analysis of historical data.
... Zebras are herbivorous animals native to the African continent and belong to the equidae family. They are famous for their unique black and white striped pattern [46], which makes them highly visible in the grasslands. Zebras often live in small herds, they can protect each other, work together to find food, and respond collectively to threats from predators. ...
The Zebra Optimization Algorithm (ZOA) is a newly proposed heuristic algorithm, which simulates the foraging behavior and defense strategy of zebras in nature. Like other optimization algorithms, ZOA also has some limitations. In this paper, an improved Zebra Optimization Algorithm (IZOA) was proposed. An adaptive oscillation weight is used to replace the random operator of ZOA , enabling the algorithm to adaptively adjust the search space and avoid falling into local optima. Additionally, this paper designs an improved golden sine operator added to ZOA. By using the search characteristics of the sine function and the golden ratio in GoldSA, the algorithm's convergence and optimization accuracy are further improved. The last replacement strategy was formulated to mimic the survival status of zebras in nature, improving the algorithm's search capabilities in complex scenarios. Finally, to assess the optimization performance of IZOA, this paper utilized the 30 benchmark functions in CEC-2017 and three common engineering problems for experiments, and the results clearly demonstrated the significant advantages of IZOA.
... If we were interested in how stripe spacing affects a biting fly's ability to gauge its distance to zebra skin when landing (Caro et al., 2019), we would have to model zebra colour patterns as biting flies would see them. If we were interested in how zebra stripes scale with body growth over development or whether stripes are more prevalent in regions with more biting flies (Caro et al., 2014), we could answer this question with uncalibrated images. ...
Colour pattern variation provides biological information in fields ranging from disease ecology to speciation dynamics. Comparing colour pattern geometries across images requires colour segmentation, where pixels in an image are assigned to one of a set of colour classes shared by all images. Manual methods for colour segmentation are slow and subjective, while automated methods can struggle with high technical variation in aggregate image sets. We present recolorize, an R package toolbox for human‐subjective colour segmentation with functions for batch‐processing low‐variation image sets and additional tools for handling images from diverse (high‐variation) sources. The package also includes export options for a variety of formats and colour analysis packages. This paper illustrates recolorize for three example datasets, including high variation, batch processing and combining with reflectance spectra, and demonstrates the downstream use of methods that rely on this output.
... Zebras are members of the horse family and are mostly found in the regions of the east and south sides of the African continent. Zebras are most recognized for their unique black and white striped skin, which serves as an optical illusion by protecting themselves from predators and helps to prevent insect bites [25]. The zebra is a muscular mammal characterized by its long and slim limbs, which allow the animal to run fast when required. ...
New progress in machine learning (ML) have paved the way for solving various existing complex problems, including in the medical field. In the proposed paper, we have investigated methods to detect Parkinson’s Disease (PD) with Nature Inspired Feature Selection (NIFS) using the Zebra Optimization Algorithm and Recursive Feature Elimination Cross Validation (RFECV). A vocal feature-based dataset has been used for PD Detection as it contains data relating to the vocal features of PD patients. It has been proven from research that vocal disorders are observed in the majority of individuals in the preliminary phases of this disease. The number of features has been reduced from 754, in the original dataset, to 40 using feature selection, and the classification results have been obtained for two cases, one being a 70:30 train test split and the other being tenfold cross-validation. We have implemented the proposed technique on 11 different classifiers. Out of these, the Gaussian Process classifier showed the best accuracy for both cases. The accuracy values obtained for cases one and two are 96% and 97.07%, respectively, one of the highest accuracy values obtained for similar research done by other researchers. Additionally, the generalization capability of the model obtained may be enhanced by including more data points in the dataset.
... In contrast, over the past decade research has shown that Diptera are averse to landing on stripes. In brief, stripes reduce landings of tabanid horseflies based on experimental studies with striped artificial targets (Waage, 1981;Brady & Shereni, 1988;Gibson, 1992;Sasaki et al., 2020), horse models (Egri et al., 2012), human models (Horvath et al., 2019), painted cows (Kojima et al., 2019) and comparisons of live plains zebras (Equus burchelli) with domestic horses How et al., 2020), and there is a co-occurrence of tabanid annoyance and striping in wild equids (Caro et al., 2014). Of two candidate explanations for stripes thwarting controlled landings on zebras, the barber pole and wagon wheel illusion (How & Zanker, 2014), experimental work shows that neither is likely to be operating (How et al., 2020;Caro et al., 2023). ...
‘Dazzle coloration’ describes a wide variety of high-contrast patterns allegedly providing protection against attack during motion. Previous research falls into three broad groups. First, studies using humans demonstrate that certain surface patterns can cause significant misperceptions in controlled laboratory conditions, although the effects are inconsistent in both direction and magnitude. Second, experiments on target capture or tracking also show effects that are strongly dependent upon the test paradigm. It has not been established that these laboratory findings generalize to other species, or to the real world. Third, mainly comparative studies build a case for longitudinal striping being involved in escape strategies in some squamate reptiles. We suggest that: (1) the concept of dazzle conflates a description of appearance with presumed function; (2) some effects attributed to dazzle have not been distinguished clearly from other mechanisms of protective coloration; and (3) confusion persists over the evidence necessary to attribute a dazzle function to markings. We refine the definition of dazzle to exclude appearance: dazzle is coloration that interferes with target interception, as a result of misperception of its speed, trajectory and/or range. Our review clarifies discussion of dazzle, and sets out a coherent and practical framework for future research.
... those caused by differences in the ambient light), and thus it is not clear if the gloss is sufficient to induce such an effect. Alternatively, when the glossy object passes in front of the eye, the fast changes of bright and dark patterns may distract an observing insect, in a similar way to how the black and white stripes of zebras reduce attractiveness to tabanid biting flies 8,9 . In such a case, it would be difficult for the brain to reliably extract information on brightness/colour contrasts or shape of the object, which may inhibit a behavioural response. ...
Most colours in nature are matte, but across the tree of life glossiness has evolved numerous times, suggesting that glossiness can be beneficial. Recent research finds that glossiness may confuse observers and protect against predators.
... Much work remains to be done on the mechanism that produces this phenomenon, but corroborating evidence in the form of reduced fly harassment and the rarity of zebra blood in captured flies indicate that the stripes do indeed deter biting flies. It has been argued that hair depth in equids is shallower than in other savanna herbivores and within the range of the length of a tabanid, Stomoxys, and glossinid fly proboscis, explaining why sympatric bovids have not developed similarly striking coat patterns (Caro et al., 2014). However, why other equids have not evolved stripes remains poorly understood given the widespread distribution of biting flies and the many serious diseases they carry across the global range of equid populations. ...
In this chapter, we review exposure risk dynamics and coping mechanisms that equids employ against macroparasites, with a focus on gastrointestinal nematodes. As bulk-feeding grazers, equids are particularly exposed to nematodes—faecal-orally transmitted parasites that quest for hosts on low-lying vegetation. In contrast, ticks and biting flies seem to parasitize herbivores of all feeding guilds relatively equally. Mounting evidence suggests that equids have developed relatively tolerant immune systems to nematodes, investing in tissue repair and maintaining body condition in the face of chronic infection. In fact, several equid populations show signs of being hypertolerant to—or even commensal with—their nematode parasites. Grevy’s zebras (Equus grevyi) and plains zebras (Equus burchellii) in Kenya, for example, seasonally exhibit a positive relationship between nematode egg counts in faeces and body condition, rather than the negative relationship expected for a costly parasite. Faecal egg counts in equids (grazing perissodactyls) are more similar to those in black rhinoceroses (Diceros bicornis, browsing perissodactyls) than to those in African buffalo (Syncerus caffer, grazing ruminants), suggesting that gut morphology may be more important than feeding guild in establishing the patterns of chronic nematode infection, and potentially of immune tolerance. Exposure to ticks is unavoidable for equids, as it is for many other herbivores, and equids have developed both deterrence and resistance mechanisms that seem to be especially strong in donkeys. In contrast, equids deal with biting flies largely through avoiding exposure, including seeking out habitat refuges, gathering in groups to dilute fly exposure and to enable mutual tail switching, and potentially even by evolving fly-evasive coat patterns.
... However, the distribution of some tsetse fly species closely follows the drought corridor, that bridges dry East-African and dry Southern African savannas. On this drought corridor, the stripe pattern is strongest (Caro et al., 2014). Stripes have been shown to deter flies effectively (Caro et al., 2019). ...
Presently, the equid lineage occurs completely outside tropical rainforest environments, which is thought of as the cradle of Perissodactyls and early equid ancestors. The ancestral food of those early equids was based on seeds, fruits, foliage and C3-grasses. The CO2-content of the atmosphere was very high, and C4-grasses had not evolved yet. Zebras and horses are considered to be typical grazers often on C4-grasses, even though Asian equids (and the mountain zebra) have a high proportion of browse in their diet. In comparison to more open environments, present-day tropical forests represent marginal habitats for large ungulates in comparison to more open environments. The suite of traits of large ungulates is not very well adapted to this environment, but equids should not be considered the pinnacle of adaptation to open environments; they retain basal tropical forest traits and lack certain derived open environment traits. Also, equids should not be considered some “non-ruminating ruminant”: their physiology is very different from that of the artiodactyls with which they are often compared; in particular, they are much better at digesting starch and other soluble carbohydrates. We present four storylines on why extant equids may be absent from tropical rainforests: one centred on carbon dioxide, one on chemical plant defence, one on metabolism, and finally a parasitism storyline. Storylines are helpful to envisage how things could have evolved but, of course, do not provide proof.
... In tigers, spatial frequencies in all bands are present to the same extent as in the background, whereas amplitudes of spatial frequencies of zebra stripes diverge from the background in higher frequency bands, rendering zebras more conspicuous. These results are consistent with the literature showing that tiger stripes evolved for camouflage (Ortolani 1999), whereas zebras evolved stripes to confuse and disorientate biting flies, which means they need to be visible (Caro et al. 2014(Caro et al. , 2019. How being conspicuous relates to aposematism has been extensively studied in arthropods with regards to color and luminance (e.g., Prudic et al. 2007;Arenas et al. 2014;Briolat et al. 2018), but a potential relationship with the spectral slope of a pattern has yet to be investigated. ...
The origins of preferences that drive the evolution of arbitrary sexual signals have been hotly debated for more than 150 years. An emerging but little-tested theory, efficient coding theory, proposes that male visual courtship displays are adapted to pre-existing processing biases shaped by the statistical properties of the natural environment. Natural scenes show strong spatial correlations with average amplitudes of spatial frequencies falling with an average spectral slope of –1 and humans have been shown to prefer random amplitude spectrum images that possess similar slopes. It has been proposed that other animals may also prefer the statistics of their natural environment and that this preference drives the evolution of sexual signaling displays. Here, we measure the spectral slope of the male display pattern of the Australian peacock jumping spider Maratus spicatus and test for a general preference toward that slope. We present spiders (male, female and juvenile) with random images of the male slope of –1.7 compared with: (a) a shallower slope of –1.0 and (b) a steeper slope of –2.3. Spiders spent more time oriented toward the shallower slope than toward the male slope and spent the same amount of time oriented toward the male slope and the steeper slope. Our results indicate that spiders, like humans, prefer the average natural slope of –1, suggesting that this is likely the slope typically found in their natural habitat. Rather than exploiting a potential processing bias it seems that males have evolved slopes that contrast with the visual background to enhance conspicuousness.
... Predation represents one of the strongest forms of selection in nature (1)(2)(3)(4)(5)(6). As a result, animals have evolved sophisticated adaptations to modify the sensory information they emit (4,(7)(8)(9)(10) and alter their chances of capturing prey (11,12) or avoiding being caught (13)(14)(15)(16). Camouflage has been widely studied as an antipredator defense, with mechanisms including background matching, disruption, and self-shadow concealment facilitating predator avoidance (15). ...
Predator-prey arms races have led to the evolution of remarkable disguise strategies. While the theoretical benefits of predator camouflage are well established, no study has yet been able to quantify its consequences for hunting success. High-resolution movement data therefore allowed us to study how barn owls (Tyto alba) conceal their approach when using a sit-and-wait strategy, as well as the power exerted during strikes. We hypothesized that hunting owls would reduce their landing force, and therefore noise, on perches located close to a hunting event. Analyzing 87,957 landings from 163 individuals equipped with GPS and accelerometer tags, we show that landing force predicts hunting success. Landing force also varied with the substrate, being lowest on man-made poles in field boundaries, most likely due to the opportunities for enhanced flight control in open landscapes. The physical environment therefore affects the capacity for sound camouflage, providing an unexpected link between predator-prey interactions and land-use. Finally, hunting strike forces were the highest recorded in any bird, relative to body mass, revealing the remarkable capacity of these predators to modulate their landing force and the range of selective pressures that act on landings. Overall, our results provide the first measurements of landing force in a wild setting revealing a new form of motion-induced sound camouflage, its link to hunting success and hence to fitness.
Understanding the evolutionary mechanisms behind lizard scale patterns is crucial for deciphering their role in thermoregulation, a vital survival trait. Traditional methods struggle with the complexity and high dimensionality of biological pattern data, limiting predictive accuracy. This study introduces a novel bioinformatics-driven framework integrating generative adversarial networks (GANs), convolutional neural networks (CNNs), and reaction-diffusion (RD) dynamics to address these challenges. By correlating melanocyte density distributions with scale patterns across developmental stages, we generated a training dataset expanded from 200 to 1,000 samples using deep convolutional GANs (DCGANs) (Sliced Wasserstein Distance (SWD) = 0.0588 ± 0.0020). The trained CNN achieved 99% accuracy in identifying RD coefficients from biological samples, enabling precise pattern evolution predictions. Experimentally, artificial scale arrays demonstrated that IV patterns exhibited the highest heat absorption, with localized temperature increases up to 9.0°C (73.1% higher than patterns frequently used in thermal regulation) under simulated solar radiation.
Our framework identified optimal RD coefficients (e.g., F = 0.081, K = 0.059) for thermoregulatory patterns, outperforming traditional fitting approaches. This approach advances the mechanistic understanding of biological textures and provides a programmable tool for designing biomimetic materials with tailored thermal regulation properties. The method’s generalizability was validated across multiple squamate species, offering insights for evolutionary biology and bio-inspired engineering.
Bottom‐up self‐organization of unordered molecules into ordered, spatiotemporal patterns of complex structures through non‐equilibrium reaction–diffusion (RD) processes is ubiquitous in nature across all scales. Unlike many RD processes that typically lead to transient patterns, periodic precipitation reactions governed by the Liesegang phenomenon are distinguished by the formation of stable, permanent structures. This unique characteristic makes them valuable tools in the development of hierarchical multifunctional materials, an area that has seen significant progress in recent decades. This review summarizes the fundamental aspects of the Liesegang phenomenon, focusing on the key characteristics, compositional features, inherent properties, and formation mechanisms of Liesegang patterns in chemical systems, while also highlighting their occurrence in biological and geological settings. We discuss recent advancements in applying periodic precipitation to address global challenges in microelectronics and environmental monitoring, concluding with a forward‐looking perspective on the promising future applications of the Liesegang periodic precipitation in materials science, nanotechnology, medicine, and environmental engineering.
Bottom‐up self‐organization of unordered molecules into ordered, spatiotemporal patterns of complex structures through non‐equilibrium reaction–diffusion (RD) processes is ubiquitous in nature across all scales. Unlike most RD processes that typically lead to transient patterns, periodic precipitation reactions governed by the Liesegang phenomenon are distinguished by the formation of stable, permanent structures. This unique characteristic makes them valuable tools in the development of hierarchical multifunctional materials, an area that has seen significant progress in recent decades. This review summarizes the fundamental aspects of the Liesegang precipitation phenomenon, focusing on the key characteristics, compositional features, inherent properties, and formation mechanisms of Liesegang patterns in chemical systems, while also highlighting their occurrence in biological and geological settings. We discuss recent advancements in applying periodic precipitation to address global challenges in microelectronics and environmental monitoring, concluding with a forward‐looking perspective on the promising future applications of the Liesegang phenomenon in materials science, nanotechnology, medicine, and environmental engineering.
Evolutionary explanations of mental disorders are a longstanding aim of evolutionary psychiatry, but have suffered from complexities including within‐disorder heterogeneity and environmental effects of contemporary societies obscuring possible ancestral functions. Studying the relevant processes of human evolution directly is not possible, so hypotheses have remained speculative, exaggerating “just‐so storytelling” critiques. This is despite significant evidence existing in genetics, neuroscience and epidemiology, all of which bears some inferential relevance to evolutionary hypotheses, but which is often not marshalled in a systematic way. To utilise this evidence best to investigate evolutionary explanations of psychiatric (or other) traits we present a novel framework of evidence synthesis and analysis and exemplify it by systematically reviewing evidence related to autism. In the five stages of this “DCIDE framework” analysis, Description identifies a trait to explain and Categorisation initially excludes verifiably non‐adaptive cases by utilising evidence from genetics, neuroscience, and environmental factors. Integration then hones a target for adaptive explanation by considering evidence of age of onset, environmental effects, duration, prevalence and sex differences, incorporating relevant correlated traits visible to selection. Evolutionary hypotheses are then Depicted and Evaluated for their ability to explain all the evidence at hand, using standardised areas of evidence and theoretically motivated principles (e.g. traits arising at birth and lasting for life have different plausible explanations than traits arising in adolescence and receding in adulthood). Competing evolutionary hypotheses can thus be systematically compared for their sufficiency in explaining a wide range of available evidence. In the DCIDE review of autism, when Described with current diagnostic criteria, up to 20% of cases Categorise as non‐adaptive, primarily caused by de novo mutations and environmental trauma. The remaining cases are eligible for adaptive explanation. For Integrating genetically correlated phenotypes, evidence of high prevalence of subclinical familial traits and camouflaged female cases is necessary. Competing Depictions contrast a high intelligence by‐product hypothesis with social niche specialisation for high “systemising” cognition. In Evaluation, broad evidence supports the social niche hypothesis while the intelligence by‐product hypothesis fails to predict various lines of evidence. This provides not only the most robust synthesis of autism research relevant to evolutionary explanation to date, but is a first example of how the structure of the DCIDE framework can allow improved systematic evolutionary analysis across psychiatric conditions, and may also be adopted to strengthen evolutionary psychology more generally, countering just‐so storytelling and cherry‐picking critiques.
The selected effects theory is supposed to provide a fully naturalistic basis for statements about what biological traits or processes are for without appeal to final causes or intelligent design. On the selected effects theory, biologists are allowed to say, for instance, that hindwing eyespots on butterfly wings serve to deflect predators’ attacks away from vital organs because a similar fitness-enhancing effect explains why eyespots themselves were favoured by natural selection and persisted in the population. This is known as the explanatory dimension of the selected effects theory. According to it, appealing to the fitness-enhancing effect of a certain trait or process is sufficient to explain its current presence in a population, namely, why it persisted and still exists in that population. In this paper, however, I will call such a claim into question, and I will do so by discussing a mathematical Hawk-Dove example and a real case scenario taken from evolutionary biology, that of Perissodus microlepis. These are scenarios in which the selective filter does not allow variants with the highest fitness at a certain moment to prevail over their available alternatives. In similar cases, I will argue, citing fitness-enhancing effects does not represent an adequate explanation of what happens in the population, undermining the explanatory dimension of the selected effects theory.
In this chapter, we deal with the following aspects of the polarotaxis in horseflies (Tabanidae): Seasonality and weather-dependent flight activity of polarotactic male and female horseflies monitored by polarization and canopy traps. Why do horseflies need polarization sensitivity for host detection? Striped bodypaintings protect against horseflies. Horsefly reactions to black tilted polarizing surfaces. Water collection by flying polarotactic horseflies. Horseflies attracted to vertical grey and black-grey striped surfaces—stripes repel tabanids independently of their width and darkness. Critique of some erroneous measurements and interpretations of reflection polarization of striped patterns with implications for polarotactic reactions of horseflies to zebra stripes.
The emergence of instabilities and steady-state pattern formation in epidemic spread are studied using a stochastic Partial Differential Equation compartmental epidemic model. Strongly nonlinear infection transmission forces and random environmental effects are taken into account in the study. Environmental uncertainties are modeled using the Ornstein-Uhlenbeck process and instabilities are studied by computing the maximal Lyapunov exponent obtained using higher-order perturbation analysis. Steady-state pattern formation is studied using stationary solutions obtained by numerically solving the PDE model equations. A range of values of the diffusion coefficient and correlation time in parameter space that support the onset of instabilities are obtained. It is shown that the stability and pattern formation results depend critically on the correlation time of the Ornstein-Uhlenbeck stochastic process; specifically, lower values of steady-state infection density are obtained for higher correlation times. For an Ornstein-Uhlenbeck process with a lower correlation time, the results are shown to approach those obtained for the case of white noise. The correlation time of the Ornstein-Uhlenbeck plays a significant role in the onset of Turing-type and noise-induced instabilities, as well as self-organized pattern formation in a stochastic epidemic model with strongly nonlinear infection forces.
Griffiths and Matthewson (2018) employ the selected effects theory to contend that disease involves the impairment of the normal functioning of biological items. Since the selected effects theory focuses on the past effects of those items, I refer to their proposal as “aetiological naturalism”. In this paper, I argue that aetiological naturalism cannot constitute an adequate theory of disease. This is due to the fact that the selected effects theory, which lies at the heart of aetiological naturalism, is flawed. One promise of the selected effects theory is indeed that it is able to account for our normative intuitions about dysfunctional biological items by grounding them on the concept of natural selection incorporated in the selected effects theory itself, where this promise rests upon its claim that appealing to the fitness-enhancing effect of biological items can always explain why they persisted in a population. However, I contend that the naturalisation of normativity cannot be cashed out in terms of biological items’ past effects by discussing two biological phenomena: phenotypic plasticity and negative frequency-dependent selection. I illustrate that in both cases the selected effects theory cannot recognise adaptive items as having a selected effects function, therefore preventing the possibility to assign them any dysfunction. The normative force of the selected effects theory is consequently much diminished, leading in turn to a weakening of aetiological naturalism, given that such project actually relies on the assumed normative force of the selected effects theory itself.
Predator-prey arms races have led to the evolution of finely tuned disguise strategies. While the theoretical benefits of predator camouflage are well established, no study has yet been able to quantify its consequences for hunting success in natural conditions. We used high-resolution movement data to quantify how barn owls (Tyto alba) conceal their approach when using a sit-and-wait strategy. We hypothesized that hunting barn owls would modulate their landing force, potentially reducing noise levels in the vicinity of prey. Analysing 87,957 landings by 163 individuals equipped with GPS tags and accelerometers, we show that barn owls reduce their landing force as they approach their prey, and that landing force predicts the success of the following hunting attempt. Landing force also varied with the substrate, being lowest on man-made poles in field boundaries. The physical environment, therefore, affects the capacity for sound camouflage, providing an unexpected link between predator-prey interactions and land use. Finally, hunting strike forces in barn owls were the highest recorded in any bird, relative to body mass, highlighting the range of selective pressures that act on landings and the capacity of these predators to modulate their landing force. Overall, our results provide the first measurements of landing force in a wild setting, revealing a new form of motion-induced sound camouflage and its link to hunting success.
Predator-prey arms races have led to the evolution of finely-tuned disguise strategies. While the theoretical benefits of predator camouflage are well established, no study has yet been able to quantify its consequences for hunting success in natural conditions. We used high-resolution movement data to quantify how barn owls ( Tyto alba ) conceal their approach when using a sit-and-wait strategy. We hypothesized that hunting barn owls would modulate their landing force, potentially reducing noise levels in the vicinity of prey. Analysing 87,957 landings by 163 individuals equipped with GPS tags and accelerometers, we show that barn owls reduce their landing force as they approach their prey, and that landing force predicts the success of the following hunting attempt. Landing force also varied with the substrate, being lowest on man-made poles in field boundaries. The physical environment therefore affects the capacity for sound camouflage, providing an unexpected link between predator-prey interactions and land-use. Finally, hunting strike forces in barn owls were the highest recorded in any bird, relative to body mass, highlighting the range of selective pressures that act on landings and the capacity of these predators to modulate their landing force. Overall, our results provide the first measurements of landing force in a wild setting, revealing a new form of motion-induced sound camouflage and its link to hunting success.
Male horseflies have low capture rates in Malaise traps, a widely documented pattern observed in numerous ecological studies. We present findings from a specific locality in Ecuador where a departure from this established pattern is observed. In this locality, males accounted for 59.14% of Tabanidae captures. The disruption in capture patterns observed using Malaise traps represents an uncommon feature in the scientific literature and during collections conducted over eight years in Ecuador. Despite the inherent limitations of Malaise traps in capturing male horseflies, it is possible that under specific conditions, such as the presence of optimal aggregation areas for horseflies, Malaise traps may enhance the capture efficiency of males. Additionally, we provide a detailed discussion on the disruption and disparity in capture sex proportions in Tabanidae, commonly reported in the scientific literature. Understanding these aspects of tabanid behavior is essential due to the outbreaks and deaths associated with trypanosomiasis infections in Ecuador.
The generalized selected effects theory of function (GSE) holds that a trait’s proper function is an activity that historically caused its differential persistence or differential reproduction within a population, construed as a collection of individuals that impact each other’s persistence or reproduction chances. Several critics have taken aim at GSE on the grounds that its appeal to populations is either unfit for purpose or arbitrary. Here I revise GSE by articulating a notion of population that is fit to purpose and showing that its selection is not arbitrary but flows from the realist commitments of the selected effects theory itself.
Predator-prey arms races have led to the evolution of remarkable disguise strategies. While the theoretical benefits of predator camouflage are well established, no study has yet been able to quantify its consequences for hunting success. High-resolution movement data therefore allowed us to study how barn owls (Tyto alba) conceal their approach when using a sit-and-wait strategy, as well as the power exerted during strikes. We hypothesized that hunting owls would reduce their landing force, and therefore noise, on perches located close to a hunting event. Analyzing 87,957 landings from 163 individuals equipped with GPS and accelerometer tags, we show that landing force predicts hunting success. Landing force also varied with the substrate, being lowest on man-made poles in field boundaries, most likely due to the opportunities for enhanced flight control in open landscapes. The physical environment therefore affects the capacity for sound camouflage, providing an unexpected link between predator-prey interactions and land-use. Finally, hunting strike forces were the highest recorded in any bird, relative to body mass, revealing the remarkable capacity of these predators to modulate their landing force and the range of selective pressures that act on landings. Overall, our results provide the first measurements of landing force in a wild setting revealing a new form of motion-induced sound camouflage, its link to hunting success and hence to fitness.
Predator-prey arms races have led to the evolution of remarkable disguise strategies. While the theoretical benefits of predator camouflage are well established, no study has yet been able to quantify its consequences for hunting success. High-resolution movement data therefore allowed us to study how barn owls (Tyto alba) conceal their approach when using a sit-and-wait strategy, as well as the power exerted during strikes. We hypothesized that hunting owls would reduce their landing force, and therefore noise, on perches located close to a hunting event. Analyzing 87,957 landings from 163 individuals equipped with GPS and accelerometer tags, we show that landing force predicts hunting success. Landing force also varied with the substrate, being lowest on man-made poles in field boundaries, most likely due to the opportunities for enhanced flight control in open landscapes. The physical environment therefore affects the capacity for sound camouflage, providing an unexpected link between predator-prey interactions and land-use. Finally, hunting strike forces were the highest recorded in any bird, relative to body mass, revealing the remarkable capacity of these predators to modulate their landing force and the range of selective pressures that act on landings. Overall, our results provide the first measurements of landing force in a wild setting revealing a new form of motion-induced sound camouflage, its link to hunting success and hence to fitness.
Wild and domesticated members of the Equidae display considerable phenotypic variation, and an elegant adaptation to the areas in which they live. Although once extremely widespread, the family survives today in the form of wild zebras and asses living in either Africa or Asia, together with a global distribution of domesticated horses and donkeys. Major climatic change, and the presence of humans, undoubtedly played a role in the equine evolutionary narrative. But the question we address here is whether disease agents too have been significant in determining the present-day distribution of the extant wild equids? We identify and discuss several viral, bacterial, and protozoal disease challenges affecting both wild and domesticated equines and evaluate the extent to which they might have played, and continue to play, a defining role in equine evolutionary ecology. We briefly consider the social and historical impact resulting from disease-constrained equine distributions and emphasise the risk of exotic animal movement by humans, which may facilitate the introduction and establishment of diseases in hitherto unaffected countries.
Teleology is the study of purposes and goals. While humans and other intelligent creatures can act on purposes, are there purposes in nature, too? Biologists often explain the development of organisms, the behavior of plants and animals, and the working of body parts and processes, in terms of their ‘purposes’, ‘goals’, or ‘functions’. This gives rise to a philosophical problem: how can we make sense of teleological language in the life sciences? Important philosophical definitions of ‘biological function’ include the selected effects theory, the goal‐contribution theory, and the causal role theory, among others. A related problem is understanding the concept of ‘goal directedness’.
Key Concepts
Teleology is the study of goals and purposes.
Teleological language such as ‘function,’ ‘goal’, and ‘purpose’ is prevalent in the life sciences.
Philosophers and scientists disagree about whether teleological language is consistent with modern science and its avoidance of supernatural explanations.
Philosophers debate the correct definition of ‘biological function.’
The ‘selected effects theory’ holds that the function of a trait depends on what it was selected for, by natural selection.
The ‘goal‐contribution theory’ holds that a function of a trait depends on its contribution to survival or reproduction.
The ‘causal role theory’ holds that a trait's function depends on its contribution to some interesting system capacity.
It's possible that biologists use ‘function’ in multiple senses.
There are philosophical problems surrounding the concept of goal directedness as well.
The paper addresses the topic of architectural intelligence whose sole purpose is to create affordances and make experience ‘stand on its own’, apart from architecture and distinct from the architect. The principles of sensation constitute the principles of composition of an existential niche whose structure reveals the genetic conditions of real experience. The argument is unpacked across three sections by reference to the Simondonian concept of allagmatics defined as the theory of operations. The first section ‘Ticks and Cats’ argues in favour of inserting an interval between the input and output, with the aim of debunking the mechanicist allegiance to linearity and promoting the concept of quasi-causality. In the second section ‘Ducks and Rabbits’ the affordance theory meets contemporary neurosciences to revamp the concept of metastability and plasticity. Its goal is to reframe the subject as the effect of (architectural) affect. The concluding radical empiricist section ‘Zebras and Flies’ revisits the lesson of the Leibnizian Monadology to tie sense to sensibility and matter to manner. The overall ambition of the paper is to contest the philosophy of representation through the concept of difference and multiplicity.
The old primary classification of the Tabanidae, based on the presence or absence of hind tibia1 spurs, has been replaced by one based primarily on the genitalia of both sexes, but supported by a significant, though not complete, correlation with external characters. The early stages, so far as known, support the new arrangement. The following subfamilies and tribes are recognized: Pangoniinae Scepsidinae Chrysopinae Tabaninue Pangoniini Bouvieromyiini Diachlorini Scionini Chrysopini Haematopotini Philolichini Rhinomyzini Tabanini Distribution of the family is world-wide, but can be divided into three main sections. More primitive groups are predominantly southern, occurring in some or all of South America, southern Africa, Australia, and New Zealand, with occasional northern extensions, and, in one case (Pangoniini), an extensive Holarctic arc. More specialized groups show two patterns. Southern regional radiations have occurred in South America and Africa, with extensions respectively into the Nearctic and Oriental-Australasian regions. Northern radiation of Chrysopini,Haematopotini, and Tabanini has resulted in a radial distribution like that of the eutherian mammals.
Preferred associate (nearest neighbour) and mutual grooming relationships among mares, in an isolated family band of free-ranging horses (Equus caballus), were studied, and the structural and functional differences between these two relationships were examined. The frequent partners accompanying the mare were not the same in both these relationships (p < 0.05) and mares changed their partners during the study period between 1988-1990. Individual horses of similar rank tended to remain closer together in both winter and summer. Aggressive-submissive behaviour was so infrequent during spring that rank determinations could not be made; however, in fall, although rank could be determined, rank was not correlated with nearest neighbour. Three subgroups, based on preferred associate relationships in summer, fall and winter, directly reflected the age and social rank of the mares in the group. Individual horses of higher rank tended to have many partners in winter, while individuals of lower rank had fewer. There was no significant correlation between the frequency of mutual grooming and individual rank. The mutual grooming relationship was strongly influenced by seasonal changes as the relative amount of grazing time per day increased. Thus, the frequency of mutual grooming was lowest in winter and highest in summer. The mutual grooming relationship was based on the bonds between individual horses, which were little influenced by social rank. Lower ranking individuals tended to have a greater variety of grooming partners in summer.
The horses of Shackelford Banks, North Carolina, USA, are heavily parasitized by intestinal worms and harassed by dipterans, and although both types influence behavior only internal parasites affect bodily condition and the structuring of horse society. Thirteen species of internal parasites were identified, but only 4 of 13 groups contain them all and even within groups differences among individuals are large. Among individuals ova emissions vary ranging from 50 to 76,875 eggs per gram. The most important environmental factors influencing egg production are season and a group's location on the island, presumably because of salinity and soil differences and their effects on ova survival. Of the social and life history factors, age, and group size, but neither reproductive state nor dominance status are important. The fitness consequences of internal parasitism may be large since the number emitted is negatively correlated with next year's bodily condition. Biting fly burdens are also affected by a variety of environmental factors. In general, horses are covered with more flies on sunny days, when winds are moderately brisk, when occupying dunes, and around mid-day. In contrast to endoparasites, fly burden is affected by reproductive condition and dominance status and tends to decrease as groups increase in size. Since groups do not grow very large, nor do females attempt to bring groups together, the negative effects of endoparasites appear to overide those associated with ectoparasites. Consequently, endoparasites appear to exert a stronger influence on social structure, even though ectoparasites seem to play a stronger role in shaping details of behavior.
1. Gridded climatologies have become an indispensable component of bioclimatic modelling, with a range of applications spanning conservation and pest management. Such globally conformal data sets of historical and future scenario climate surfaces are required to model species potential ranges under current and future climate scenarios.
2. We developed a set of interpolated climate surfaces at 10′ and 30′ resolution for global land areas excluding Antarctica. Input data for the baseline climatology were gathered from the WorldClim and CRU CL1·0 and CL2·0 data sets. A set of future climate scenarios were generated at 10′ resolution. For each of the historical and future scenario data sets, the full set of 35 Bioclim variables was generated. Climate variables (including relative humidity at 0900 and 1500 hours) were also generated in CLIMEX format. The Köppen–Geiger climate classification scheme was applied to the 10′ hybrid climatology as a tool for visualizing climatic patterns and as an aid for specifying absence or background data for correlative modelling applications.
3. We tested the data set using a correlative model (MaxEnt) addressing conservation biology concerns for a rare Australian shrub, and a mechanistic niche model (CLIMEX) to map climate suitability for two invasive species. In all cases, the underlying climatology appeared to behave in a robust manner.
4. This global climate data set has the advantage over the WorldClim data set of including humidity data and an additional 16 Bioclim variables. Compared with the CRU CL2·0 data set, the hybrid 10′ data set includes improved precipitation estimates as well as projected climate for two global climate models running relevant greenhouse gas emission scenarios.
5. For many bioclimatic modelling purposes, there is an operational attraction to having a globally conformal historical climatology and future climate scenarios for the assessments of potential climate change impacts. Our data set is known as ‘CliMond’ and is available for free download from http://www.climond.org.
2007: Zebra stripes as an amplifier of individ-ual quality? — Ann. Zool. Fennici 44: 368–376. Amplifiers belong to a class of signals that alone do not indicate an individual's qual-ity, but through design they improve the receiver's ability to assess pre-existing cues and signals. Amplifiers are cost free to produce and maintain, but may yield disadvan-tages to the individuals that are compelled to reveal their inferior quality. We suggest that zebra stripes, combined with the movement and proximity of other individuals with the same pattern, might function as an amplifier of the individual's escape poten-tial. As a zebra flock is set in motion by predators, stripes may facilitate ascertainment of the quality of the moving individuals (i.e., their escape potential) relative to other individuals in the flock. We tested whether the suggested relationship between stripes such as that of the zebra and quality ascertainment might occur by constructing anima-tions involving 5 moving objects, with one object moving differently from the others. A test panel was asked to identify the deviant object in 4 animations, each of the 4 ani-mations having objects with a different color pattern (striped, black, gradient and spot-ted). This study lends support to the hypothesis as behaviorally deviant objects were easiest observed in "flocks" of zebra striped objects. Thus, zebra stripes may make odd individuals more visible rather than making them less distinguishable.
Resting time in red deer (Cervus elaphus) was shown to be more than twice as long on days when harassment by head flies (Hydrotaea irritans) was considered severe compared with days when fly harassment was estimated as low. Avoidance reactions in the deer decreased as soon as the deer reclined and became stabilized at a level corresponding to approximately 50% of the initial response frequency. The present observations do not give any clear indications as to whether it is the head flies per se or climatic factors that are the primary cause of reduced locomotory behaviour in the deer. It is concluded, however, that due to a causal relationship between the appearance of flies and certain types of weather, and because lying down has a relieving effect, inactivity may be an important part of the strategy used by red deer to cope with head fly harassment.
The characteristic striped appearance of zebras has provoked much speculation about its function and why the pattern has evolved, but experimental evidence is scarce. Here, we demonstrate that a zebra-striped horse model attracts far fewer horseflies (tabanids) than either homogeneous black, brown, grey or white equivalents. Such biting flies are prevalent across Africa and have considerable fitness impact on potential mammalian hosts. Besides brightness, one of the likely mechanisms underlying this protection is the polarization of reflected light from the host animal. We show that the attractiveness of striped patterns to tabanids is also reduced if only polarization modulations (parallel stripes with alternating orthogonal directions of polarization) occur in horizontal or vertical homogeneous grey surfaces. Tabanids have been shown to respond strongly to linearly polarized light, and we demonstrate here that the light and dark stripes of a zebra's coat reflect very different polarizations of light in a way that disrupts the attractiveness to tabanids. We show that the attractiveness to tabanids decreases with decreasing stripe width, and that stripes below a certain size are effective in not attracting tabanids. Further, we demonstrate that the stripe widths of zebra coats fall in a range where the striped pattern is most disruptive to tabanids. The striped coat patterns of several other large mammals may also function in reducing exposure to tabanids by similar mechanisms of differential brightness and polarization of reflected light. This work provides an experimentally supported explanation for the underlying mechanism leading to the selective advantage of a black-and-white striped coat pattern.
Stable flies, Stomoxys calcitrans (L.), are among the most damaging arthropod pests of cattle worldwide. The last estimate of their economic impact on United States cattle production was published 20 yr ago and placed losses at 254, 132, 1,279, or 360 million for dairy cattle, 1,268 million for pastured cattle, and 2,211 million per year. Excluded from these estimates are effects of stable flies on feed conversion efficiency, animal breeding success, and effects of infested cattle on pasture and water quality. Additional research on the effects of stable flies on high-production dairy cows and nursing beef calves is needed to increase the reliability of the estimates.
Camouflage patterns that hinder detection and/or recognition by antagonists are widely studied in both human and animal contexts. Patterns of contrasting stripes that purportedly degrade an observer's ability to judge the speed and direction of moving prey ('motion dazzle') are, however, rarely investigated. This is despite motion dazzle having been fundamental to the appearance of warships in both world wars and often postulated as the selective agent leading to repeated patterns on many animals (such as zebra and many fish, snake, and invertebrate species). Such patterns often appear conspicuous, suggesting that protection while moving by motion dazzle might impair camouflage when stationary. However, the relationship between motion dazzle and camouflage is unclear because disruptive camouflage relies on high-contrast markings. In this study, we used a computer game with human subjects detecting and capturing either moving or stationary targets with different patterns, in order to provide the first empirical exploration of the interaction of these two protective coloration mechanisms.
Moving targets with stripes were caught significantly less often and missed more often than targets with camouflage patterns. However, when stationary, targets with camouflage markings were captured less often and caused more false detections than those with striped patterns, which were readily detected.
Our study provides the clearest evidence to date that some patterns inhibit the capture of moving targets, but that camouflage and motion dazzle are not complementary strategies. Therefore, the specific coloration that evolves in animals will depend on how the life history and ontogeny of each species influence the trade-off between the costs and benefits of motion dazzle and camouflage.
Movement is the enemy of camouflage: most attempts at concealment are disrupted by motion of the target. Faced with this problem, navies in both World Wars in the twentieth century painted their warships with high contrast geometric patterns: so-called "dazzle camouflage". Rather than attempting to hide individual units, it was claimed that this patterning would disrupt the perception of their range, heading, size, shape and speed, and hence reduce losses from, in particular, torpedo attacks by submarines. Similar arguments had been advanced earlier for biological camouflage. Whilst there are good reasons to believe that most of these perceptual distortions may have occurred, there is no evidence for the last claim: changing perceived speed. Here we show that dazzle patterns can distort speed perception, and that this effect is greatest at high speeds. The effect should obtain in predators launching ballistic attacks against rapidly moving prey, or modern, low-tech battlefields where handheld weapons are fired from short ranges against moving vehicles. In the latter case, we demonstrate that in a typical situation involving an RPG7 attack on a Land Rover the reduction in perceived speed is sufficient to make the grenade miss where it was aimed by about a metre, which could be the difference between survival or not for the occupants of the vehicle.
To test the generality of adaptive explanations for coat coloration in even-toed ungulates, we examined the literature for hypotheses that have been proposed for color patterns exhibited by this taxon, and we derived a series of predictions from each hypothesis. Next, we collected information on the color, behavioral, and ecological characteristics of 200 species of even-toed ungulates and coded this in binary format. We then applied chi-square or Fisher's Exact probability tests that pitted presence of a color trait against presence of an ecological or behavioral variable for cervids, bovids, and all artiodactyls. Finally, we reanalyzed the data by using concentrated-changes tests and a composite molecular and taxonomic phylogeny. Hinging our findings on whether associations persisted after controlling for shared ancestry, we found strong support for hypotheses suggesting even-toed ungulates turn lighter in winter to aid in concealment or perhaps thermoregulation, striped coats in adults and spotted pelage in young act as camouflage, side bands and dark faces assist in communication, and dark pelage coloration is most common in species living in the tropics (Gloger's rule). Whereas white faces, dark legs, white legs, dark tails, and white tails did not appear to assist in communication alone, legs and tails that were either dark or white (i.e., conspicuous) did seem to be linked with communication. There was moderate support for hypotheses that countershading aids concealment, that white faces are a thermoregulatory device, and that white rumps are used in intraspecific communication. There was weak support for spots in adults and stripes in young providing camouflage and for dark leg markings being a form of disruptive coloration. We found little or no evidence that overall coat color serves as background matching, that side bands are disruptive coloration devices, or that white rumps help in thermoregulation. Concealment appears the principal force driving the evolution of coloration in ungulates with communication, and then thermoregulation, playing less of a role. Copyright 2003.
Genetic data from extant donkeys (Equus asinus) have revealed two distinct mitochondrial DNA haplogroups, suggestive of two separate domestication events in northeast Africa about 5000 years ago. Without distinct phylogeographic structure in domestic donkey haplogroups and with little information on the genetic makeup of the ancestral African wild ass, however, it has been difficult to identify wild ancestors and geographical origins for the domestic mitochondrial clades. Our analysis of ancient archaeological and historic museum samples provides the first genetic information on the historic Nubian wild ass (Equus africanus africanus), Somali wild ass (Equus africanus somaliensis) and ancient donkey. The results demonstrate that the Nubian wild ass was an ancestor of the first donkey haplogroup. In contrast, the Somali wild ass has considerable mitochondrial divergence from the Nubian wild ass and domestic donkeys. These findings resolve the long-standing issue of the role of the Nubian wild ass in the domestication of the donkey, but raise new questions regarding the second ancestor for the donkey. Our results illustrate the complexity of animal domestication, and have conservation implications for critically endangered Nubian and Somali wild ass.
White horses frequently suffer from malign skin cancer and visual deficiencies owing to their high sensitivity to the ultraviolet solar radiation. Furthermore, in the wild, white horses suffer a larger predation risk than dark individuals because they can more easily be detected. In spite of their greater vulnerability, white horses have been highly appreciated for centuries owing to their natural rarity. Here, we show that blood-sucking tabanid flies, known to transmit disease agents to mammals, are less attracted to white than dark horses. We also demonstrate that tabanids use reflected polarized light from the coat as a signal to find a host. The attraction of tabanids to mainly black and brown fur coats is explained by positive polarotaxis. As the host's colour determines its attractiveness to tabanids, this parameter has a strong influence on the parasite load of the host. Although we have studied only the tabanid-horse interaction, our results can probably be extrapolated to other host animals of polarotactic tabanids, as the reflection-polarization characteristics of the host's body surface are physically the same, and thus not species-dependent.
The problems of existence, uniqueness and location of maximum likelihood estimates in log linear models have received special attention in the literature (Haberman, 1974, Chapter 2; Wedderburn, 1976; Silvapulle, 1981). For multinomial logistic regression models, we prove existence theorems by considering the possible patterns of data points, which fall into three mutually exclusive and exhaustive categories: complete separation, quasicomplete separation and overlap. Our results suggest general rules for identifying infinite parameter estimates in log linear models for frequency tables.
The transformation of wild animals into domestic ones available for human nutrition was a key prerequisite for modern human societies. However, no other domestic species has had such a substantial impact on the warfare, transportation, and communication capabilities of human societies as the horse. Here, we show that the analysis of ancient DNA targeting nuclear genes responsible for coat coloration allows us to shed light on the timing and place of horse domestication. We conclude that it is unlikely that horse domestication substantially predates the occurrence of coat color variation, which was found to begin around the third millennium before the common era.
Alighting of horse flies (Diptera: Tabanidae) and non-biting muscids (Diptera: Muscidae) was studied at Khartoum, Sudan, using black cylindrical models mimicking a goat, calf and cow. Flies were intercepted by attaching electrocution grids or clear adhesive film to models. Alighting sites and defensive behaviour were also documented on hosts through observation. Female Tabanus sufis (Jennicke), T. taeniola (Palisot) and Atylotus agrestis (Wiedemann) were the main tabanids captured. Muscids landed in equal numbers on all sizes of models. They had a strong preference for the upper portions of both models and hosts. Landings of T. taeniola and A. agrestis increased with model size, but not so for T. sufis. T. taeniola and A. agrestis scarcely alighted on the legs of models whereas 60-78% of T. sufis did so. Landings of T. sufis on artificial legs did not vary with model size. Landings of all tabanids on the lower and upper portions of a model increased with model size. For both hosts and models, most tabanids (88-98%) alighted on the lower half and legs. Most muscids (63-89%) alighted on the upper half. Landing of tabanids on the cow was 34.9 and 69.3 times greater than that on the calf and goat, respectively. These results are discussed in relation to strategies for the control of blood-sucking flies associated with farm animals using either insecticide-treated live baits or their mimics.
Individual recognition is considered a complex process and, although it is believed to be widespread across animal taxa, the cognitive mechanisms underlying this ability are poorly understood. An essential feature of individual recognition in humans is that it is cross-modal, allowing the matching of current sensory cues to identity with stored information about that specific individual from other modalities. Here, we use a cross-modal expectancy violation paradigm to provide a clear and systematic demonstration of cross-modal individual recognition in a nonhuman animal: the domestic horse. Subjects watched a herd member being led past them before the individual went of view, and a call from that or a different associate was played from a loudspeaker positioned close to the point of disappearance. When horses were shown one associate and then the call of a different associate was played, they responded more quickly and looked significantly longer in the direction of the call than when the call matched the herd member just seen, an indication that the incongruent combination violated their expectations. Thus, horses appear to possess a cross-modal representation of known individuals containing unique auditory and visual/olfactory information. Our paradigm could provide a powerful way to study individual recognition across a wide range of species.
Many traits in animals reduce the rate of attack from visually hunting predators, including camouflage, warning signals and mimicry. In addition, some animal markings may reduce the likelihood that an attack ends in successful capture. These might include dazzle markings, high-contrast patterns that make the estimation of speed and trajectory difficult. However, until now, no study has experimentally tested whether some markings may achieve such an effect. We developed a computer 'game' where human 'predators' have to capture computer-generated prey moving across a background. In two experiments, we find that although uniform camouflaged targets were among the hardest to capture, so were a range of high-contrast conspicuous patterns, such as bands and zigzags. Prey were also more difficult to capture against more heterogeneous than uniform backgrounds, and at faster speeds of movement. As such, we find the first experimental evidence that conspicuous patterns, similar to those found in a wide range of real animals, make the capture of moving prey more challenging. Various anti-predator markings may work prey during motion, and some animals may combine such dazzle patterns with other functions, such as camouflage, thermoregulation, sexual and warning signals.
Tools for performing model selection and model averaging. Automated model selection through subsetting the maximum model, with optional constraints for model inclusion. Model parameter and prediction averaging based on model weights derived from information criteria (AICc and alike) or custom model weighting schemes.
[Please do not request the full text - it is an R package. The up-to-date manual is available from CRAN].
Species and subspecies of zebras are examined using traditional (pelage and craniometric) taxonomic methods, including multivariate analysis. Mountain Zebras are split into two species, Equus zebra and Equus hartmannae, because they differ absolutely (100%); Burchell's or plains zebras, however, are placed in Equus quagga because there are no absolute differences. The subspecies of Equus quagga are revised; six subspecies are recognisable. E. zebra, E. hartmannae and E. grevyi are monotypic.
Blood-sucking insects are the vectors of many of the most debilitating parasites of man and his domesticated animals. In addition they are of considerable direct cost to the agricultural industry through losses in milk and meat yields, and through damage to hides and wool, etc. So, not surprisingly, many books of medical and veterinary entomology have been written. Most of these texts are organized taxonomically giving the details of the life-cycles, bionomics, relationship to disease and economic importance of each of the insect groups in turn. I have taken a different approach. This book is topic led and aims to discuss the biological themes which are common in the lives of blood-sucking insects. To do this I have concentrated on those aspects of the biology of these fascinating insects which have been clearly modified in some way to suit the blood-sucking habit. For example, I have discussed feeding and digestion in some detail because feeding on blood presents insects with special problems, but I have not discussed respiration because it is not affected in any particular way by haematophagy. Naturally there is a subjective element in the choice of topics for discussion and the weight given to each. I hope that I have not let my enthusiasm for particular subjects get the better of me on too many occasions and that the subject material achieves an overall balance.
Horse flies (Tabanidae) on and around feral ponies in harem groups were counted at Assateague Island National Seashore, Maryland, U.S.A., between June and August 1985. Harem stallions attracted the most flies; adult mares showed intermediate fly numbers, while few flies landed on foals under any circumstances. The use of thermal and chemical cues by flies selecting a host may have helped create this disparity. When flies were abundant, ponies reduced spacing within the group. Ponies in larger groups suffered from fewer flies than ponies in smaller groups. There was, however, no evidence that ponies merged into larger groups in response to fly harassment, suggesting that biting flies play little role in structuring pony social organization.
Abstract A field study in Zimbabwe of Glossina pallidipes Austen and G. morsitans morsitans Westwood supported Waage's (1981) hypothesis that the striped pattern of zebras may protect them from being bitten by blood-sucking flies. In addition, the results suggest that the orientation of the stripes may be crucially important for the unattractiveness of zebras.
The relative attractiveness of five different stationary targets (black, white, grey, vertically-striped and horizontally-striped; stripe width = 5 cm) were each tested on their own and in pairs of all combinations, with artificial host odour (CO2 plus acetone) always present. Electric nets were used to catch flies as they attempted to land on or circle the targets. The results were similar for the two species of tsetse. When tested on their own, grey and vertically-striped targets caught similar numbers of flies and both caught significantly fewer than black or white targets (c. 36% as many). Horizontally-striped targets caught <10% as many flies as any other single target.
Although there was no significant difference between the attractiveness of grey and vertically striped targets when they were presented together, when paired with the other targets, grey was as attractive as black or white, but the vertically-striped target was significantly less attractive than black or white (P < 0.001). In other words, a difference between grey and vertical stripes was found only in their attractiveness in relation to other targets. The horizontally-striped target, however, always caught the fewest flies, regardless of whether it was presented alone or alongside another target.
ABSTRACT The literature addressing evolutionary reasons for the striped patterns of zebra coats is reviewed here. Possible mechanisms, and the evidence for and against them, are discussed. These mechanisms span four general themes: protection from predators; social functions; thermoregulation; and protection from tsetse flies. The last is the only hypothesis that has been tested experimentally, and the results of these tests are inconclusive. Additionally or alternatively, although stripes apparently increase zebra visibility in daylight, it is at least plausible that they provide effective cryptic protection from predators in poor light, although critical testing has not been attempted. Other related evolutionary questions are raised and suggestions made for future research.
Species and subspecies of zebras are examined using traditional (pelage and craniometric) taxonomic methods, including multivariate analysis. Mountain Zebras are split into two species, Equus zebra and Equus hartmannae, because they differ absolutely (100%); Burchell's or plains zebras, however, are placed in Equus quagga because there are no absolute differences. The subspecies of Equus quagga are revised; six subspecies are recognisable. E.zebra, E.hartmannae and E.grevyi are monotypic.
Blood-sucking insects transmit many of the most debilitating diseases to man including malaria, sleeping sickness, filariasis, dengue, typhus and plague. Additionally these insects cause major economic losses in agriculture by direct damage to livestock. This new edition of The Biology of Blood-Sucking in Insects has been fully updated since it was first published in 1991. It provides a unique, topic-led commentary on the biological aspects that are common to blood-sucking insects. This account focuses on the biological adaptations that clearly suit the blood-sucking habit and further discusses host-insect interactions and the transmission of parasites by blood-sucking insects. It also outlines the medical, social and economic impact of blood-sucking insects. The final chapter is designed as a useful quick-reference section. Written in a clear, concise fashion and well illustrated throughout, the text will be of direct interest to advanced undergraduate and postgraduate students of medical and veterinary entomology and parasitology.
In the current resurgence of interest in the biological basis of animal behavior and social organization, the ideas and questions pursued by Charles Darwin remain fresh and insightful. This is especially true of The Descent of Man and Selection in Relation to Sex, Darwin's second most important work. This edition is a facsimile reprint of the first printing of the first edition (1871), not previously available in paperback. The work is divided into two parts. Part One marshals behavioral and morphological evidence to argue that humans evolved from other animals. Darwin shoes that human mental and emotional capacities, far from making human beings unique, are evidence of an animal origin and evolutionary development. Part Two is an extended discussion of the differences between the sexes of many species and how they arose as a result of selection. Here Darwin lays the foundation for much contemporary research by arguing that many characteristics of animals have evolved not in response to the selective pressures exerted by their physical and biological environment, but rather to confer an advantage in sexual competition. These two themes are drawn together in two final chapters on the role of sexual selection in humans. In their Introduction, Professors Bonner and May discuss the place of The Descent in its own time and relation to current work in biology and other disciplines.
Ten species of Tabanus, five of Chrysops, and one of Atylotus are recorded from the Churchill, Manitoba, area. Of these, Tabanus itasca Philip, Tabanus sp. (new?), and Atylotus ohioensis (Hine) represent new records. It is established that Tabanidae in this region overwinter in the larval stage and that most species have at least a three-year life cycle. Problems in taxonomy are discussed. Methods of rearing the immature stages, of collecting adults emerging in the field, of estimating larval and adult populations, and of correlating adult activity and weather conditions are described, and the results are presented. Larvae of the tipulid Prionocera dimidiata (Lw.) are reported as predators of larvae of Chrysops spp. The emergence of the chalcid parasite Diglochis occidentalis (Ashm.) from pupae of Tabanus and Chrysops spp. reared from the larval stage is recorded.
During the summer of 1957, experiments to determine the effect of biting f1y control on weight gain in beef cattle were conducted in Centre County, Pennsylvania. Insecticide-repellent formulations were applied daily to a herd of Aberdeen Angus by means of an electric-eye-controlled sprayer at the rate of approximately 75 ml. per animal. A water-base spray containing N, N-diethyl-m-toluamide and methoxychlor provided effective protection against biting flies, which included the horn fly, Siphona irritans (L.), the stable fly, Stomoxys calcitrans (L.), and a negligible number of a horse fly, Tabanus quinquevittata (Wied.). Equally satisfactory results were achieved with an oil base spray containing 2,3,4,5-bis (∆2 butylene)-tetrahydrofurfural, pyrethrins, N-octyl bicycloheptene dicarboximide and piperonyl butoxide. Both formulations were much more effective against the horn fly than against the stable fly, when data for each species were treated separately. After 8 weeks of treatment, none of the cattle was adversely affected.
The favorable effect of biting fly control was demonstrated by the greater weight gain of the treated animals as compared with that of the untreated. As a result of treatments, the mean gain in weight of the treated group was found to surpass that of the untreated group by approximately one-half to two-thirds of a pound per animal per day. Statistical analyses indicated that the difference in weight gain between the two groups was significant. The cost of spray material was, in average, one cent a day for each animal.
Adult female horse flies (Tabanus spp. L.) were collected hourly in modified Malaise traps. Regression analyses of numbers of flies collected and the values of various meteorological factors in the ranges observed indicated which factors influenced activity. From greater to lesser influence, these factors were: barometric pressure, temperature, evaporation and evaporation change per hour, total sky radiation change per hour, total sky radiation and wind velocity change per hour, and relative humidity and temperature change per hour. The influence of these factors upon activity of the 6 most abundant species was also determined. Prediction equations are presented and the traps described.
The landing preferences of fed males of Glossina morsitans morsitans Westwood and Stomoxys calcitrans (L.) were measured under constant conditions in a two-choice situation. Pairs of black-and-white landing targets were presented on the grey walls of an arena ca 60 cm in diameter. In a simple choice of blackness vs whiteness, G. m. morsitans showed a ninefold greater preference for black; S. calcitrans displayed no preference. G. m. morsitans landed twice as frequently on a 15×30-cm vertical black stripe as on a horizontal one, but S. calcitrans preferred the horizontal one. Comparisons between a vertical stripe (or a horizontal one) and similar stripes sloping at various angles indicated that at about 50° G. m. morsitans distinguished the sloping stripe from the vertical (or the horizontal), but did not well distinguish slopes closer to the vertical (or horizontal). Tests with multiple vertical stripe patterns indicated that G. m. morsitans did not significantly distinguish between a single 15-cm stripe and two- or three-striped targets of the same total black area, but landed significantly less frequently on targets of four or five stripes, implying an angular, behavioural visual ‘resolution' of roughly 17°; S. calcitrans responded similarly. Both species showed a marked preference for landing near the edge of the black on all targets, with G. m. morsitans strongly biassed to the black side of an interface.
Lions Panthera
leo are generally thought to prey on medium to large ungulates. Knowledge of which species are actually preferred and which are avoided is lacking, however, as is an understanding of why such preference or avoidance may arise. An analysis of 32 studies over 48 different spatial locations or temporal periods throughout the distribution of the lion shows that it preferentially preys upon species within a weight range of 190–550 kg. The most preferred weight of lion prey is 350 kg. The mean mass of significantly preferred prey species is 290 kg and of all preferred species is 201 kg. Gemsbok, buffalo, wildebeest, giraffe and zebra are significantly preferred. Species outside the preferred weight range are generally avoided. Species within the preferred weight range that are not significantly preferred (such as roan, sable and eland) generally have features that reduce predation either morphologically (e.g. sable horns), ecologically (e.g. roan and sable occurring at low density), or behaviourally (e.g. the large herd size and increased vigilance of eland). Warthog are below the preferred weight range yet are taken in accordance with their availability and this is probably due to their sympatry with lion, their relatively slow evasion speed and their lower level of vigilance. Plots of prey preference against prey body mass follows a bell curve with a right skew that, we argue, is caused by collective hunting by lions of larger-bodied prey. Our methods can be used on all large predators and are likely to be useful in assessing competition in sympatric communities of predators, cooperative hunting and predicting predator diets. This will allow us to move beyond descriptive dietary studies to improve our predictive understanding of the mechanisms underlying predator–prey interactions.
Some striped animals are camouflaged in their natural environment, whereas others are conspicuous. Mammals are known to have spatial frequency analysers in their visual mechanism, and it is suggested that the spatial characteristics of a striped pattern are different in camouflaged and conspicuous animals. Fourier analysis of the stripes of the zebra shows spatial frequencies in the pattern that are unlikely to be present so strongly in their natural background scene. A similar analysis of the camouflaging stripes of a tiger show that the distribution of spatial frequencies are similar to that in the background scene.
Spotted hyaenas Crocuta crocuta were once considered mere scavengers; however, detailed research revealed that they are very efficient predators. Information on what spotted hyaenas actually prefer to prey on and what they avoid is lacking, as well as the factors that influence prey selection. Data from 14 published and one unpublished study from six countries throughout the distribution of the spotted hyaena were used to determine which prey species were preferred and which were avoided using Jacobs' index. The mean of these values for each species was used as the dependent variable in multiple regression, with prey abundance and prey body mass as predictive variables. In stark contrast to the rest of Africa's large predator guild, spotted hyaenas do not preferentially prey on any species. Also surprisingly, only buffalo, giraffe and plains zebra are significantly avoided. Spotted hyaena most prefer prey within a body mass range of 56–182 kg, with a mode of 102 kg. The dietary niche breadth of the spotted hyaena is similar to that of the lion Panthera leo, and the two species have a 58.6% actual prey species overlap and a 68.8% preferred prey species overlap. These results highlight the flexible and unselective nature of spotted hyaena predation and are probably a reason for the species' success throughout its range, despite a large degree of dietary overlap with lions.
The literature published during 1970–1981 on tsetse ecology is reviewed. The geographical distribution of some species was affected during the drought of early 1970s. New maps of tsetse distribution in Africa and a few national maps have been published. The habitats of several species have been described in detail, particularly atypical habitats in peridomestic situations. Pupal ecology has not held the attention of ecologists so much; however, pupal duration and mortality have been assessed for a few species. Due to the importance of selective application of insecticides, resting sites and resting behaviour have been described in detail. Activity patterns have been correlated with climatic factors and also with sampling methods. Several works on host-seeking behaviour, flight performance and energy metabolism have been described. Host preferences of certain species have been found to be somewhat different from those previously recorded; and new host species have been discovered. Studies on fat and haematin content showed that these metabolites are useful indices of nutritional status to interpret feeding behaviour in relation to population sampling. A tsetse contact sex-pheromone has been discovered and synthetised; and attempts have been made to use it in the field. Studies on sound production by both sexes under various conditions of light and physiological state are in progress. Comparative studies on sampling techniques have received particular attention; several trap devices have been designed and tested to evaluate the reliability of samples. The determination of the age structure of populations has become more relevant to studies on population dynamics. Attempts have been made to calculate the growth rate of populations. Density-dependent factors started being taken into consideration in the assessment of populations. Several methods have been tried out to estimate population size. New pathogens, parasites and predators have been recorded.