Animal Footprints Research Articles

Enhancing endangered species monitoring by lowering data entry requirements with imputation techniques as a preprocessing step for the footprint identification technology (FIT)

Numerous species of Earth's biota are at risk of extinction and wildlife conservation is more important than ever. Reliable baseline data are essential for wildlife management to inform on the numbers and distribution of endangered species. A promising non-invasive and cost-effective method for monitoring endangered species is the Footprint Identification Technology (FIT). It lends itself to both conservation research as well as citizen science and can be combined with other data collection methods. FIT extracts and uses morphometrics from animal footprints to create geometric profiles that are analyzed in customized classification models. These can identify species, sex and individual. The ability to identify individuals can then be used to predict various population parameters including size, distribution, and growth rate. FIT has been developed and published for several species, but it requires high quality footprints. Perfect prints are not always easy to find in the field as various factors can influence their quality. In this paper, we demonstrate that geometrical profiles derived from poor quality footprints can be seen as datasets with missing values. Missing values are a common problem in various disciplines, and well-established strategies to impute missing values are widely available. We conducted two experiments to see whether such an approach could widen the application of the FIT method. The experiments were designed to test the hypothesis that population sizes can be underestimated when incomplete footprints are discarded from the data. We artificially introduced different proportions of missing values in datasets with geometric profiles of five different species for which FIT models have been published. We also analyzed a new dataset of geometric profiles of cheetah (Acinonyx jubatus) footprints not meeting the standard FIT requirements. We demonstrated that excluding incomplete footprints led to an underestimation of the known population. As an alternative to discarding footprints, we compared different imputation techniques as data pre-processing steps by comparing the performance of resulting FIT models.When imputation was chosen instead, we could show that FIT models with imputed geometric profiles were not significantly less accurate in predicting individual ID or population size even with high rates of missing values. We believe that our findings can be generalized, and the results indicate that imperfect footprints can contribute to the robustness of the FIT method and that this approach is particularly applicable when few good-quality footprints are available. We therefore highly recommend including imputation of imperfect footprints as a data pre-processing step.

Design of an Ultrasound Sensing System for Estimation of the Porosity of Agricultural Soils.

The design of a readily useable technology for routine paddock-scale soil porosity estimation is described. The method is non-contact (proximal) and typically from "on-the-go" sensors mounted on a small farm vehicle around 1 m above the soil surface. This ultrasonic sensing method is unique in providing estimates of porosity by a non-invasive, cost-effective, and relatively simple method. Challenges arise from the need to have a compact low-power rigid structure and to allow for pasture cover and surface roughness. The high-frequency regime for acoustic reflections from a porous material is a function of the porosity ϕ, the tortuosity α∞, and the angle of incidence θ. There is no dependence on frequency, so measurements must be conducted at two or more angles of incidence θ to obtain two or more equations in the unknown soil properties ϕ and α∞. Sensing and correcting for scattering of ultrasound from a rough soil surface requires measurements at three or more angles of incidence. A system requiring a single transmitter/receiver pair to be moved from one angle to another is not viable for rapid sampling. Therefore, the design includes at least three transmitter/reflector pairs placed at identical distances from the ground so that they would respond identically to power reflected from a perfectly reflecting surface. A single 25 kHz frequency is a compromise which allows for the frequency-dependent signal loss from a natural rough agricultural soil surface. Multiple-transmitter and multiple-microphone arrays are described which give a good signal-to-noise ratio while maintaining a compact system design. The resulting arrays have a diameter of 100 mm. Pulsed ultrasound is used so that the reflected sound can be separated from sound travelling directly through the air horizontally from transmitter to receiver. The average porosity estimated for soil samples in the laboratory and in the field is found to be within around 0.04 of the porosity measured independently. This level of variation is consistent with uncertainties in setting the angle of incidence, although assumptions made in modelling the interaction of ultrasound with the rough surface no doubt also contribute. Although the method is applicable to all soil types, the current design has only been tested on dry, vegetation-free soils for which the sampled area does not contain large animal footprints or rocks.

Следы животных на строительной керамике золотоордынского Солхата

The archaeological researches of the Crimean ulus of the Golden Horde discovered a multitude of finds in the cultural layers from the late fourteenth and early fifteenth centuries, particularly building ceramic ware with footprints of animals. Such finds not only reflect the level of development of building technique, but also allow the one to determine the species composition of the fauna in the mediaeval Crimea, to amend the information on the economic and industrial activities of the population of Solkhat in the Golden Horde period. Among the footprints on bricks there are traces of canines (domestic dog and wolf), felines (cat), and artiodactyls (goat). Most of the footprints, 14 specimens, belong to canine animals, cat footprints are documented on four bricks, and only one artefact shows a footprint of goat’s hoof. This statistic is indirectly confirmed by the analysis of osteological materials, with a significant percentage of dogs’ remains and a little less of cats’. Goat’s bones are also rare; small cattle is mostly represented by sheep’s bones, the breeding area of which probably does not coincide with the place where Solkhat building ceramics were produced. The building ceramics with footprints of animals’ paws and hoofs originating from the excavations of the mediaeval settlement of Solkhat is published for the first time.

Effects of isoenergetic supplementation as water use mitigation strategy on water footprint and health of nursing bull calves.

Sustainable livestock systems focus on mitigating natural resource use such as water. Dietary management strategies can significantly reduce the water footprint of livestock animals; however, animal health is of concern when animals reduce water intake due to subacute dehydration. To evaluate potential consequences of this nutritional management intervention, a total of 23, 60 ± 3 days old nursing Holstein bull calves, weighing 94.7 ± 12.07 kg, were distributed in a completely randomized design and received one of three diets. Control was a basal diet composed of a non-medicated milk replacer (milk replacer; n = 7), and the additional two diets, were composed of the same non-medicated milk replacer in addition to either lipid [n = 8; milk replacer + menhaden fish oil (3 %)] or soluble carbohydrate [n = 8; milk replacer + corn starch (7%) isoenergetic to fat group] supplements. Animals were offered ad libitum mineral mix and water, as well as 120 g/day of a composite mix of dried microbrewery's spent grains. Data were analyzed as linear and generalized linear mixed models with diet as a fixed effect and animal as random utilizing R studio (R Core Team, 2021, Vienna, Austria; SAS Inst., Cary, NC). Within supplementation groups, lipid supplemented calves had the highest lymphocyte (63.24 vs 57.69 counts/100 lymphocytes; P < 0.033), and lowest neutrophil counts (29.3 vs 35.3 counts/100 lymphocytes; P < 0.047). Supplementation significantly increased total serum protein (P = 0.001) and skin moisture (P < 0.011), with carbohydrate group having the highest skin moisture (5.30 vs 3.99; P < 0.047). Supplementation also decreased fecal fluidity scores (P < 0.001) with no significant change in serum electrolytes (P > 0.256). No significant differences were found amongst treatments for the ingestive behavior (P > 0.338). The carbohydrate-supplemented calves significantly decreased all daily water footprints compared to the control and fat-supplemented groups: blue a 47.55 L decrease, (P < 0.001), green a 265.62 L decrease (P = 0.005), and gray a 55.87 L decrease (P = 0.009) water footprint, as well as total water footprint (369.04 L, P = 0.004). Our results indicate the potential to maintain animal performance while increasing water use efficiency through diet supplementation tailored to mitigate water use, without adverse effects on animal health.

Footprint beds record Holocene decline in large mammal diversity on the Irish Sea coast of Britain.

Long-term monitoring along the Irish Sea coast of Britain at Formby has identified hundreds of animal and human footprints in 31 discrete sediment beds. A new programme of radiocarbon dating shows that the Formby footprints span at least 8,000 years of the Holocene Epoch from the Mesolithic period to Medieval times. In a landscape largely devoid of conventional archaeology and faunal records, we show how species data from the footprint stratigraphy document long-term change in both large mammal diversity and human behaviour. The footprint beds record shifting community structure in the native fauna through an era of profound global change. As sea levels rose rapidly in the Early Holocene, men, women and children formed part of rich Mesolithic intertidal ecosystems from ~9,000 to 6,000 cal BP, with aurochs, red deer, roe deer, wild boar, beaver, wolf and lynx. Doggerland was reclaimed by the sea in this period. In the agriculture-based societies that followed, after 5,500 cal BP human footprints dominate the Neolithic period and later beds, alongside a striking fall in large mammal species richness. Stacked footprint beds can form multimillennial records of ecosystem change with precise geographical context that cannot be retrieved from site-based fossil bone assemblages.

İkhnoarkeolojik Bir Bakış: Andriake'de Bulunan Roma Kiremitlerindeki Hayvan Ayak İzleri

Archeology is a science that tries to interpret the thoughts and behaviours of the society living in the past by documenting, researching, and analysing the physical residuals left behind by human behaviour. By doing this, it is benefitting from many branches of science. One of the branches of science that archeology benefits from is “ichnology”, which is derived from the Greek words “ἴχνος (ikhnos)=track” and “λόγος (logos)=science”, which studies fossil traces and residuals. From the joint work of ichnology and archeology, a new discipline, ichnoarcheolgy, has emerged. In this study, the animal footprints on the terracotta tiles found in the port settlement of Myra of Andriake were tried to be interpreted from an ichnoarcheological point of view. From the interpretation made, conclusions were reached regarding the formation processes of the traces, to whom and/or what they belong, and the environmental conditions of the production workshop. The results have revealed that the tile-producing workshop was located in a rural area close to the forest area and the workshop was visited by savage and wild animals.

The genome and diet of a 35,000-year-old Canis lupus specimen from the Paleolithic painted cave, Chauvet-Pont d'Arc, France.

The Chauvet-Pont-d'Arc Cave (Ardèche, France) contains some of the oldest Paleolithic paintings recorded to date, as well as thousands of bones of the extinct cave bear, and some remains and footprints of other animals. As part of the interdisciplinary research project devoted to this reference cave site, we analyzed a coprolite collected within the deep cave. AMS radiocarbon dating of bone fragments from the coprolite yielded an age of 30,450 ± 550 RC yr. BP (AAR-19656; 36,150-34,000 cal BP), similar to ages assigned to Paleolithic artwork and cave bear remains from the same cave sector. Using high-throughput shotgun DNA sequencing, we demonstrated a high abundance of canid DNA and lesser amounts of DNA from the extinct cave bear. We interpret the sample as feces from a canid that had consumed cave bear tissue. The high amount of canid DNA allowed us to reconstruct a complete canid mitochondrial genome sequence (average coverage: 83×) belonging to a deeply divergent clade of extinct mitochondrial wolf lineages that are most closely related to coeval (~35 ka) Belgian wolves. Analysis of the nuclear genome yielded a similar coverage for the X chromosome (2.4×) and the autosomes (range: 2.3-3.2×), indicating that the Chauvet canid was a female. Comparing the relationship of the nuclear genome of this specimen with that of a variety of canids, we found it more closely related to gray wolves' genomes than to other wild canid or dog genomes, especially wolf genomes from Europe and the Middle East. We conclude that the coprolite is feces from an animal within an extinct wolf lineage. The consumption of cave bear by this wolf likely explains its intrusion into the dark cave sectors and sheds new light on the paleoecology of a major cave site.

Playing with invisible animals: An interactive system of floor-projected footprints to encourage children’s imagination

Playing is essential for a child’s development, and it has various positive effects. In particular, playing with toys enhances children’s imagination. In recent years, children have been tending to play with smart toys equipped with built-in computers, which present various advantages that leverage their digital characteristics. For example, smart toys can provide augmented reality functionalities through which digital information can be added to physical reality. These characteristics offer an important benefit of stimulating the interest and presence of children. However, wearable devices may be required to realize this. Wearable devices are ineffective when people do not own or cannot wear them. Therefore, we developed a system that stimulates the imagination and interest of children in playing without any wearable devices. Our system projects animal footprints onto the floor, encouraging children to play with invisible animals based on their imagination from the footprints. The footprints respond to the children’s movements. To evaluate the developed system, we conducted several experiments with children. First, we investigated the fundamental effects of the system on elementary school students. Then, we investigated the different effects of various interactions. Our experimental results showed that the developed system encourages the imagination of children while playing.

HETEROPODY INDEX: A SQUARE PEG IN A ROUND HOLE?

ABSTRACT Heteropody Index (HI) is a tool used to calculate area differences between the manus and pes of fossil trackways. HI uses a simple length × width calculation to estimate area. However, since most foot impressions are rarely close to square in shape, HI using a different area calculation could potentially more accurately reflect differences in manus and pes foot area. In this study, accuracy of length × width (L×W) as an area estimate for basic shapes and animal footprints, was tested against two other area calculations, the area of a circle: πr2, and length × carpal width (L×CW) (the width at the most proximal point of the foot in contact with the ground). In addition, accuracy of HI calculations using these methods was tested against HI calculations using actual area of the corresponding shape or underfoot area. It was discovered that in general L×W is a better estimate for area than πr2, in most animals except ungulates. However, for those animals where L×W was a better estimate than πr2, L×CW was more accurate. This paper additionally proposes that by combining the findings of these tests with those of Strickson et al. (2019), foot area estimates for dinosaurs can be estimated more accurately using L×CW, to return an area close to estimates for soft tissue. Previous HI measurements may have overestimated extreme heteropody in sauropod dinosaurs.

Animal Footprints on Roman Tiles from Perge and Aizanoi

For many years, tremendous interest has been reserved for the most beautiful, the largest, and the most spectacular of finds. This is especially true in the field of Classical archaeology. This has often resulted in an unfortunate disregard for other finds such as traces. Indeed every object from the past has valuable information to convey to us. The task of archaeologists is to examine the object at hand without prejudice. This study focuses on terracotta building materials with such traces. Examples from Perge and Aizanoi are analyzed from an ichnoarchaeological viewpoint, and interpretations regarding the environment and the economy of the relevant time period are offered on the basis of this analysis. The finds revealed that the environment surrounding the workshop area in Aizanoi was wider than the one in Perge. In this period, it is thought that Aizanoi had an open geography with little forestation and climatic conditions similar to current times.

Efficacy of l-glutamic acid, N,N-diacetic acid to improve the dietary trace mineral bioavailability in broilers.

Trace minerals are commonly supplemented in the diets of farmed animals in levels exceeding biological requirements, resulting in extensive fecal excretion and environmental losses. Chelation of trace metal supplements with ethylenediaminetetraacetic acid (EDTA) can mitigate the effects of dietary antagonists by preserving the solubility of trace minerals. Lack of EDTA biodegradability, however, is of environmental concern. l-Glutamic acid, N,N-diacetic acid (GLDA) is a readily biodegradable chelating agent that could be used as a suitable alternative to EDTA. The latter was tested in sequential dose–response experiments in broiler chickens. Study 1 compared the effect of EDTA and GLDA in broilers on supplemental zinc availability at three levels of added zinc (5, 10, and 20 ppm) fed alone or in combination with molar amounts of GLDA or EDTA equivalent to chelate the added zinc, including negative (no supplemental zinc) and positive (80 ppm added zinc) control treatments. Study 2 quantified the effect of GLDA on the availability of native trace mineral feed content in a basal diet containing no supplemental minerals and supplemented with three levels of GLDA (54, 108, and 216 ppm). In study 1, serum and tibia Zn clearly responded to the increasing doses of dietary zinc with a significant response to the presence of EDTA and GLDA (P < 0.05). These results are also indicative of the equivalent nutritional properties between GLDA and EDTA. In study 2, zinc levels in serum and tibia were also increased with the addition of GLDA to a basal diet lacking supplemental trace minerals, where serum zinc levels were 60% higher at the 216 ppm inclusion level. Similar to the reported effects of EDTA, these studies demonstrate that dietary GLDA may have enhanced zinc solubility in the gastrointestinal tract and subsequently enhanced availability for absorption, resulting in improved nutritional zinc status in zinc-deficient diets. As such, GLDA can be an effective nutritional tool to reduce supplemental zinc levels in broiler diets, thereby maintaining health and performance while reducing the environmental footprint of food-producing animals.

Early Marine Isotope Stage 5 sea levels, coastal dune palaeoenvironments, and human occupation on the southeast coast of South Africa

Quaternary-age human and animal footprints have been reported from coastal deposits along the South African coast. These footprints and their sedimentary contexts can inform on Quaternary palaeoenvironments and processes stratigraphically associated with the palaeoanthropological record of past human occupation in the coastal zone, and exploitation of its resources. This study examines the palaeoenvironmental context and sedimentology of Marine Isotope Stage 5 aeolianite at Nahoon Point, southeastern coast of South Africa, where preserved human footprints have been previously recorded. This study identifies seven sedimentary facies from 20 logged profiles through the coastal aeolianite in order to develop a landscape-scale stratigraphic framework for coastal palaeoenvironmental reconstruction during the period of the MIS 5 highstand. Two phases of aeolianite deposition are identified, which bracket a single stepped sea-level transgression phase up to +7.82 ± 0.82 m asl, evidenced by intraformational beachrock facies and marine benches. This correlates with the second known global MIS 5e highstand; no evidence for the first highstand reported from the literature was found in the study area. Aeolianite bed geometries and sedimentary structures indicate that wind regimes and rainfall seasonality were similar to present. Newly discovered faunal tracks in aeolianites of the first depositional phase suggest the presence of unidentified bovids of varying sizes. Evidence for human activity is preserved in all three recorded depositional phases, suggesting people were present throughout the early MIS 5 sequence despite changing environmental conditions. This evidence suggests that human occupation of coastal areas, and the exploitation of marine food resources was more widespread than generally thought in southern Africa during early MIS 5.

DISTRIBUTION PATTERNS AND HABITAT OF MAMMALS IN MANDALAWANGI RESORT OF MOUNT GEDE PANGRANGO NATIONAL PARK

Distribution pattern and habitat quality of mammals is essential to keep the existing of mammals which depends on interactions between its intrinsic evolutionary and ecological system. Mandalawangi Resort aside from being a conservation area, it is also a tourist area. Tourism activities carried out in the region, will directly and indirectly affect the sustainability of mammal diversity. The benefits of mammals are to stabilize the food chain, the spread of plant seeds, as an object of research and education. The study aims to determine the distribution patterns and habitat of mammals in Mandalawangi Resort . Research on mammal diversity was carried out using 4 methods: rapid assessment, line transect, animal footprint. Habitat data obtained using vegetation analysis and field observation methods. The diversity of mammals in the Mandawalangi Resort consists of 7 types of mammals from 6 families, namely kekes squirrel (Tupaia javanica), langur (Trachypithecus auratus), wild cats (Felis domesticus), wild boar (Sus scrofa), leopard (Panthera pardus melas) , civet mongoose (Paradoxurus hermaphroditus) and house gutters (Suncus murinus). Species wealth index is low (0.50). The diversity index of mammals is included in the low diversity category (0.25). The highest level of mammal species meeting is kekes squirrel (Tupaia javanica) with a value of 29.4%. Evenness index is included in the unstable community category (0.15). Mammalian habitat is divided into tropical rain forests and open land with dominating trees namely Damar (Agathis damara) and Rasamala (Altingia excelsa).

Особливості формування та поширення зоогенного рельєфу в заплаві річки Остер

During 2015–2020, we carried out a series of field studies of zoogenic relief in the Oster River floodplain. In the process, the method of field route observations, polls, photography, morphological and morphometric analyses were actively used. Mathematical methods and computer technologies were used to process and summarize the obtained data. Based on the field research data, it was established that the natural conditions of the Oster River floodplain are favourable for the emergence of zoogenic relief forms. Zoogenic landforms are common here, and their size and location depend on the animal species which live in the area or constantly migrate through it. The influence of individual representatives of the animal world on the formation of the surface of the studied area is presented. It was shown that some of them simultaneously create both accumulative and negative forms of biogenic relief. Accumulative zoogenic landforms are represented in the Oster floodplain by individual small dams and beaver huts; muskrat huts; earthen anthills and anthills formed from dry grass and twigs; molehills; mice’s soil nano-strands; hamster mounds; pico-humps formed by worms and beetles. Among the negative landforms of zoogenic origin there are burrows and burrow nests; underground galleries of animals and insects; nano-basins of forest and field mice; livestock trails and wildlife migration trails; burrowing of wild pigs; footprints of various animals. Beavers, moles, wild boars and ants are found to cover the highest proportion of landform creation activity within the Oster River floodplain. It was also found that the size of most zoogenic landforms in the studied area have the rank of pico- and nano-relief. Relief microforms are much less common. The lifespan of zoogenic landforms can range from tens or even hundreds of years to several hours. It is discovered that fires significantly affect the landforms of zoogenic origin. As a result of the flames, many of the forms change their shape and size, and some even cease to exist.

Reassessing Hominin Skills at an Early Middle Pleistocene Hippo Butchery Site: Gombore II-2 (Melka Kunture, Upper Awash valley, Ethiopia)

Single-carcass sites of Lower and Middle Pleistocene age have attracted much attention since they were first recorded. They have been the focus both of science and of museum displays, with reconstructions of “hominins-feasting-on-a-carcass” purposefully illustrating a major step in human evolution. Here we report the Acheulean site Gombore II-2 in the upper Awash Valley of Ethiopia, dating to 0.7 Myr. In the 1970s, due to the presence of hippo remains, the site was published as a single-carcass butchering site. New excavations revealed an ichnosurface displaying animal and human footprints associated with bones and lithics. Subsequent studies of lithic and faunal remains of recent and past excavations as well as archive studies show that Gombore II-2 represents one of the earliest sites with hominin-hippo interaction. The hippo remains belong to a minimum of three carcasses, at least one of them butchered by hominins and subsequently ravaged by hyenas. However, instead of single carcasses exploited on the spot, evidence suggests the existence of a living floor where butchering episodes were performed through time, possibly transporting portions from scavenging sites at a distance. Gombore II-2 thus provides unique insight into planning capacities and control over the environment probably by early representatives of Homo heidelbergensis.

The Elephant's Footprint: An Ancient Indian Logic Diagram

A seminal article by Margaret Baron, published in 1969, explored the history of set diagrams (Venn diagrams). However, Baron did not look beyond the evidence of European sources. This article presents evidence of a literary simile from ancient India that exemplifies the idea of a larger circle including within it many smaller circles, each circle standing for an ethical concept. The simile – an elephant's footprint enclosing the footprints of smaller animals – first appears in the Buddhist Canon, and it was used occasionally in South Asian literature through the following millennia until the eighteenth century. I argue that the Elephant's Foot simile can be added to Baron’s catalogue of historical cases where ancient authors were using language that implied a simple concept of logical sets.

Late Ediacaran trackways produced by bilaterian animals with paired appendages.

Ediacaran trace fossils provide key paleontological evidence for the evolution of early animals and their behaviors. Thus far, however, this fossil record has been limited to simple surface trails and relatively shallow burrows. We report possible trackways, preserved in association with burrows, from the terminal Ediacaran Shibantan Member (ca. 551 to ca. 541 million years ago) in the Yangtze Gorges area of South China. These trace fossils represent the earliest known trackways. They consist of two rows of imprints arranged in poorly organized series or repeated groups. These trackways may have been produced by bilaterian animals with paired appendages, although the phylum-level phylogenetic affinity of the trace makers remains unknown. It is possible that the trackways and associated burrows were produced by the same trace maker, indicating a complex behavior involving both walking and burrowing. Together, these trackways and burrows mark the arrival of a new era characterized by an increasing geobiological footprint of bilaterian animals.

Making the Animals on the Plate Visible: Anglophone Celebrity Chef Cookbooks Ranked by Sentient Animal Deaths

Recent decades have witnessed the rise of chefs to a position of cultural prominence. This rise has coincided with increased consciousness of ethical issues pertaining to food, particularly as they concern animals. We rank cookbooks by celebrity chefs according to the minimum number of sentient animals that must be killed to make their recipes. On our stipulative definition, celebrity chefs are those with their own television show on a national network in the United States, the United Kingdom, Canada or Australia. Thirty cookbooks by 26 such chefs were categorized according to the total number of cows, pigs, chicken, fish and other species they included as ingredients. The total number of animals killed was divided by the number of non-dessert recipes to generate an average number of animal deaths per recipe for each book. We outline the rationale for our project and its methodology before presenting a ranked table of 30 cookbooks by celebrity chefs. This method generates several interesting findings. The first concerns the wide variation in animal fatalities among cookbooks. The chef with the heaviest animal footprint killed 5.25 animals per recipe, while the omnivorous chef with the smallest footprints killed 0.19 per recipe. Clearly, not all approaches to meat eating are equal when it comes to their animal mortality rate. Pigs and large ruminants are all substantially bigger than poultry, which are themselves bigger than many fish. The prime determinant of a chef’s place in the index was the number of small animals his or her recipes required. Whether a chef cooked in the style of a particular cuisine (Italian, French, Mexican etc.), by contrast, had no discernible influence on his or her ranking. We analyze how different chefs present themselves—as either especially sensitive or insensitive to ethical issues involving animals and food—and note cases where these presentations do or do not match their index ranking.

Animal and human footprints on Roman tiles from Brigetio

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Footprints of a flapping wing

Birds have to flap their wings to generate the needed thrust force, which powers them through the air. But how exactly do flapping wings create such force, and at what amplitude and frequency should they operate? These questions have been asked by many researchers. It turns out that much of the secret is hidden in the wake left behind the flapping wing. Exemplified by the study of Andersenet al.(J. Fluid Mech., vol. 812, 2017, R4), close examination of the flow pattern behind a flapping wing will inform us whether the wing is towed by an external force or able to generate a net thrust force by itself. Such studies are much like looking at the footprints of terrestrial animals as we infer their size and weight, figuring out their walking and running gaits. A map that displays the collection of flow patterns after a flapping wing, using flapping frequency and amplitude as the coordinates, offers a full picture of its flying ‘gaits’.