Semi-natural Setting Research Articles

Sex reversal of pejerrey (Odontesthes bonariensis), a species with temperature-dependent sex determination, in a seminatural environment.

This study examined the changes in sex ratios and sex reversal rates in pejerrey Odontesthes bonariensis that occur with the progression of the spawning season in a seminatural setting. Four groups of hatchery-produced pejerrey larvae were stocked in floating cages in La Salada de Monasterio lake (Pampas region), a natural habitat of this species, and reared from hatching beyond gonadal sex determination with minimum human interference. Cage 1 was stocked at the beginning of the spring spawning season and the other cages were stocked with monthly delays until cage 4 in early summer. The genotypic (amhy+, XY/YY; amhy-, XX) and phenotypic (testis, male; ovary, female) sex ratios and proportions of genotype/phenotype mismatched individuals were estimated and their relation to water temperature and daylength during the experiment was analysed by generalized linear modelling. Water temperature varied between 11 and 30.5°C, and daylength duration between 11 h 22 min and 14 h 35 min. Sex genotyping revealed nearly balanced sex ratios of XY/YY (46%-49.1%) and XX (50.9%-54%) fish in cages 2-4 whereas the genotypic sex ratio in cage 1 was clearly biased towards XY/YY fish (60.6%). Phenotypic males ranged from 42% to 54.4% in cages 1-3. Cage 4, in turn, had significantly more phenotypic males (66%). The percentage of XX males (phenotypic male/genotypic female) was 23.1% in cage 1, decreased to a minimum of 5.4% in cage 2 and gradually increased in cages 3 and 4 to a maximum of 40.7% in the latter. The percentages of XY/YY females (phenotypic female/genotypic male) were highest in cage 1 (30%) and decreased progressively in the other cages to a significantly lower value (4.3%) in cage 4. These results generally support the findings of laboratory studies on the effect of temperature on the sex determination of this species and also provide novel evidence of a XX genotype-specific masculinizing effect of short daylength.

Tokorhabditis Tauri n. Sp. and T. Atripennis n. Sp. (Rhabditida: Rhabditidae), Isolated from Onthophagus Dung Beetles (Coleoptera: Scarabaeidae) from the Eastern USA and Japan.

Two new species of Tokorhabditis, T. tauri n. sp. and T. atripennis n. sp., which were isolated from multiple Onthophagus species in North America and from O. atripennis in Japan, respectively, are described. The new species are each diagnosed by characters of the male tail and genitalia, in addition to molecular barcode differences that were previously reported. The description of T. tauri n. sp. expands the suite of known nematode associates of O. taurus, promoting ecological studies using a beetle that is an experimental model for insect–nematode–microbiota interactions in a semi-natural setting. Furthermore, our description of a third Tokorhabditis species, T. atripennis n. sp., sets up a comparative model for such ecological interactions, as well as other phenomena as previously described for T. tufae, including maternal care through obligate vivipary, the evolution of reproductive mode, and extremophilic living.

Epichloë Endophyte-Promoted Seed Pathogen Increases Host Grass Resistance Against Insect Herbivory.

Plants host taxonomically and functionally complex communities of microbes. However, ecological studies on plant–microbe interactions rarely address the role of multiple co-occurring plant-associated microbes. Here, we contend that plant-associated microbes interact with each other and can have joint consequences for higher trophic levels. In this study we recorded the occurrence of the plant seed pathogenic fungus Claviceps purpurea and aphids (Sitobion sp.) on an established field experiment with red fescue (Festuca rubra) plants symbiotic to a seed transmitted endophytic fungus Epichloë festucae (E+) or non-symbiotic (E–). Both fungi are known to produce animal-toxic alkaloids. The study was conducted in a semi-natural setting, where E+ and E– plants from different origins (Spain and Northern Finland) were planted in a randomized design in a fenced common garden at Kevo Subarctic Research Station in Northern Finland. The results reveal that 45% of E+ plants were infected with Claviceps compared to 31% of E– plants. Uninfected plants had 4.5 times more aphids than Claviceps infected plants. By contrast, aphid infestation was unaffected by Epichloë symbiosis. Claviceps alkaloid concentrations correlated with a decrease in aphid numbers, which indicates their insect deterring features. These results show that plant mutualistic fungi can increase the infection probability of a pathogenic fungus, which then becomes beneficial to the plant by controlling herbivorous insects. Our study highlights the complexity and context dependency of species–species and multi-trophic interactions, thus challenging the labeling of species as plant mutualists or pathogens.

The Effect of Visitor Number on the Behavior of Zoo-Housed Macropods

ABSTRACT Free-range exhibits are used by zoos to allow visitors to experience or interact with animals in a semi-natural setting; close interactions with animals have been shown to increase empathy and contribute to conservation outcomes, and as such zoos are increasingly implementing free-range style exhibits to facilitate this goal. We aimed to investigate whether this close proximity to zoo visitors impacted upon four species of macropod (red kangaroo Macropus rufus, red-necked wallaby Macropus rufogriseus, swamp wallaby Wallabia bicolor, and quokka Setonix brachyurus) in a free-range exhibit in an Australian zoo. Specifically, we used instantaneous scan sampling to assess animal behavior and examined whether visitor number affected the proportion of individuals that exhibited four target behaviors; visitor-directed vigilance, retreat, resting, and foraging behavior. We found that the proportion of individuals exhibiting visitor-directed vigilance significantly increased as pedestrian visitor number increased for three of the four species, and the proportion of individuals that were resting was significantly negatively related to visitor number for both wallaby species. The proportion of individuals of each species foraging or retreating was unrelated to visitor number. These data suggest that a visitor effect exists in a walk-through exhibit of macropods, and once visitor numbers go beyond a threshold, the behavior of more animals is impacted, likely compromising welfare. Interestingly, quokka do not appear to be affected by zoo visitors; which may be due to visitor pressure being perceived differently due to evolutionary differences, or that housing and husbandry ameliorate the visitor effect for this species but not others. Like many studies before, taking a species-specific approach to understanding zoo visitor–animal interactions has determined how the visitor effect likely impacts macropods differently.

A Comparative Study of the Innate Humoral Immune Response to Avian Influenza Virus in Wild and Domestic Mallards.

Domestic mallards (Anas platyrhynchos domesticus) are traditionally used as a model to investigate infection dynamics and immune responses to low pathogenic avian influenza viruses (LPAIVs) in free-living mallards. However, it is unclear whether the immune response of domestic birds reflects the response of their free-living counterparts naturally exposed to these viruses. We investigated the extent to which the innate humoral immune response was similar among (i) wild-type domestic mallards in primary and secondary infection with LPAIV H4N6 in a laboratory setting (laboratory mallards), (ii) wild-type domestic mallards naturally exposed to LPAIVs in a semi-natural setting (sentinel mallards), and (iii) free-living mallards naturally exposed to LPAIVs. We quantified innate humoral immune function by measuring non-specific natural antibodies (agglutination), complement activity (lysis), and the acute phase protein haptoglobin. We demonstrate that complement activity in the first 3 days after LPAIV exposure was higher in primary-exposed laboratory mallards than in sentinel and free-living mallards. LPAIV H4N6 likely activated the complement system and the acute phase response in primary-exposed laboratory mallards, as lysis was higher and haptoglobin lower at day 3 and 7 post-exposure compared to baseline immune function measured prior to exposure. There were no differences observed in natural antibody and haptoglobin concentrations among laboratory, sentinel, and free-living mallards in the first 3 days after LPAIV exposure. Our study demonstrates that, based on the three innate humoral immune parameters measured, domestic mallards seem an appropriate model to investigate innate immunology of their free-living counterparts, albeit the innate immune response of secondary-LPAIV exposed mallards is a better proxy for the innate immune response in pre-exposed free-living mallards than that of immunologically naïve mallards.

Investigating the toxicity of naphthenic acid fraction components from oil sands process-affected water to developing fathead minnow (Pimephales promelas)

The extraction of bitumen from Alberta’s oil sands region generates large volumes of oil sands process-affected water (OSPW) that is stored in tailings ponds. Toxic constituents present in OSPW such as naphthenic acid fraction components (NAFCs) can cause adverse effects to aquatic life. Recent research has focused on the toxicity of NAFCs to highly vulnerable early life stages of fish. Here we examined the embryotoxicity of NAFCs (0-54 mg/L) extracted from OSPW to native fathead minnow (Pimephales promelas) from 1-day post-fertilization to hatch in a semi-natural setting at Queen’s University’s Biological Station. Embryo heart rate, mortality, prevalence and severity of malformations at hatch, post-hatch mass, and basal activity at hatch was examined. Embryo heart rates declined with increasing NAFC concentration, preceding pronounced exposure-response patterns of mortality and non-viable hatches. Visible malformations included cardiovascular (pericardial edema; present in 81.51% of non-viable hatches), craniofacial (reduced jaw and head size; 68.96%), myoskeletal (spinal curvatures; 60.90%), and peritoneal (yolk sac edema; 26.44%) malformations, that significantly increased in severity with increasing NAFC concentration. Fish that survived lethal concentrations displayed evidence of nervous system impairment including elevated patterns of erratic twitching. Post-hatch mass generally increased with increasing NAFC exposure, potentially as a compensatory-like response. Results of this work are the first to be reported in a semi-natural exposure setting and provide important toxicological information that will aid future policy directives for the management of OSPW in Alberta, Canada.

Social information affects Canada goose alert and escape responses to vehicle approach: implications for animal-vehicle collisions.

BackgroundAnimal–vehicle collisions represent substantial sources of mortality for a variety of taxa and can pose hazards to property and human health. But there is comparatively little information available on escape responses by free-ranging animals to vehicle approach versus predators/humans.MethodsWe examined responses (alert distance and flight-initiation distance) of focal Canada geese (Branta canadensis maxima) to vehicle approach (15.6 m·s−1) in a semi-natural setting and given full opportunity to escape. We manipulated the direction of the vehicle approach (direct versus tangential) and availability of social information about the vehicle approach (companion group visually exposed or not to the vehicle).ResultsWe found that both categorical factors interacted to affect alert and escape behaviors. Focal geese used mostly personal information to become alert to the vehicle under high risk scenarios (direct approach), but they combined personal and social information to become alert in low risk scenarios (tangential approach). Additionally, when social information was not available from the companion group, focal birds escaped at greater distances under direct compared to tangential approaches. However, when the companion group could see the vehicle approaching, focal birds escaped at similar distances irrespective of vehicle direction. Finally, geese showed a greater tendency to take flight when the vehicle approached directly, as opposed to a side step or walking away from the vehicle.ConclusionsWe suggest that the perception of risk to vehicle approach (likely versus unlikely collision) is weighted by the availability of social information in the group; a phenomenon not described before in the context of animal–vehicle interactions. Notably, when social information is available, the effects of heightened risk associated with a direct approach might be reduced, leading to the animal delaying the escape, which could ultimately increase the chances of a collision. Also, information on a priori escape distances required for surviving a vehicle approach (based on species behavior and vehicle approach speeds) can inform planning, such as location of designated cover or safe areas. Future studies should assess how information from vehicle approach flows within a flock, including aspects of vehicle speed and size, metrics that affect escape decision-making.

Immigrant and extrinsic hybrid inviability contribute to reproductive isolation between lake and river cichlid ecotypes.

Understanding how reproductive barriers evolve and which barriers contribute to speciation requires the examination of organismal lineages that are still in the process of diversification and the study of the full range of reproductive barriers acting at different life stages. Lake and river ecotypes of the East African cichlid fish Astatotilapia burtoni show habitat-specific adaptations, despite different levels of genetic differentiation, and thus represent an ideal model to study the evolution of reproductive barriers. To evaluate the degree of reproductive isolation between genetically divergent lake and river populations, we performed a mesocosm mating experiment in a semi-natural setting at Lake Tanganyika. We assessed reproductive isolation in the presence of male-male competition by analyzing survival and growth rates of introduced adults and their reproductive success from genetic parentage of surviving offspring. The genetically divergent river population showed reduced fitness in terms of survival, growth rate, and mating success in a lake-like environment. Hybrid offspring between different populations showed intermediate survival consistent with extrinsic postzygotic reproductive barriers. Our results suggest that both prezygotic (immigrant inviability) and postzygotic reproductive barriers contribute to divergence, and highlight the value of assessing multiple reproductive barriers acting at different stages and in natural contexts to understand speciation mechanisms.

Development of Pointing Gestures in Children With Typical and Delayed Language Acquisition.

This longitudinal study compared the development of hand and index-finger pointing in children with typical language development (TD) and children with language delay (LD). First, we examined whether the number and the form of pointing gestures during the second year of life are potential indicators of later LD. Second, we analyzed the influence of caregivers' gestural and verbal input on children's communicative development. Thirty children with TD and 10 children with LD were observed together with their primary caregivers in a seminatural setting in 5 sessions between the ages of 12 and 21 months. Language skills were assessed at 24 months. Compared with children with TD, children with LD used fewer index-finger points at 12 and 14 months but more pointing gestures in total at 21 months. There were no significant differences in verbal or gestural input between caregivers of children with or without LD. Using more index-finger points at the beginning of the second year of life is associated with TD, whereas using more pointing gestures at the end of the second year of life is associated with delayed acquisition. Neither the verbal nor gestural input of caregivers accounted for differences in children's skills.

Bad neighbors: hunger and dominance drive spacing and position in an orb-weaving spider colony

The costs and benefits of group living can vary among group members depending on their physical location within the group. If individuals can anticipate poor positions and leave the group, the society may dissolve. Therefore, understanding the geometry of social groups is critical to understanding their stability. We examined social geometry in the colonial spider, Cyrtophora citricola (Araneidae), which builds long-lasting individual webs within a shared colony framework. Group foraging benefits are thought to be an ultimate cause for the evolution of colonial living in spiders, but conflict often arises over food and territory. To understand how foraging benefits of grouping interact with inter-individual conflict to shape group geometry, we examined the effects of feeding history and body size on inter-individual spacing in the laboratory. We also examined the effect of spider density and body size on individual position within colonies in a semi-natural setting. We found that spiders with prior food stress increased their inter-individual spacing, suggesting that competition for prey may override group foraging benefits. Larger spiders built their webs first, relegating smaller spiders to the margins of the space and sometimes preventing them from completing web construction. In a semi-natural setting, spiders did not maintain close spacing, but rather spread themselves out over the substrate, and larger spiders occupied the preferred side of the substrate to the exclusion of smaller spiders. Contrary to the hypothesis that foraging advantages to group living promote greater cohesion under food stress, food competition appeared to promote group instability, and exclusion of small spiders by larger and more dominant individuals seemed to determine position in the colony. In colonial spiders, foraging benefits are thought to be the primary driver of group living, yet there is often conflict over food and territory within the group. We tested the hypothesis that foraging benefits should promote group cohesion under food stress in the colonial spider Cyrtophora citricola. By manipulating prey abundance prior to trials, but minimizing prey cues during trials, we eliminated the influence of prey position on spiders, leaving interactions among individuals to determine spider location. Prior food deprivation caused spiders to space themselves farther apart, refuting the group cohesion hypothesis. Larger spiders prevented smaller spiders from constructing webs and relegated them to less preferred positions in the group, suggesting that aggressive interactions determined spacing and placement within the colony, but that these interactions are modulated by feeding history.

Variation in native crayfish agonistic response to the invasion of the rusty crayfish Orconectes rusticus (Girard, 1852)

The consequences of biological invasions warrant continued research on the mechanisms underlying the spread of exotic species, yet interspecific behavioral interactions are largely overlooked as a contributing factor or consequence of introductions of exotic species. Our study evaluates how native crayfish species, Cambarus bartonii (Fabricius, 1798) and Orconectes propinquus (Girard, 1852), respond behaviorally to the invasion of the rusty crayfish, Orconectes rusticus (Girard, 1852) in the Upper Susquehanna River Basin, NY, USA using experiments in a semi-natural setting. We found significant effects of species, sex, year, novelty to invasion, and abiotic environment on the proportion of time native crayfish species exhibited agonistic behavior toward invading rusty crayfish. Cambarus bartonii females were generally more aggressive than males, particularly in year two, but the opposite was true for O. propinquus as males were more aggressive than females. Behavioral variation in recipient crayfish communities is a potential mechanism influencing the spread of introduced crayfishes although future study is necessary to assess the relative extent of such influence. The mechanisms driving the spread of invasive species are clearly complex and interactive, but the development of effective management plans is limited by the completeness of our understanding, which thus far has been lacking a substantial ethological component.

Effects of diet restriction on life history in a sexually cannibalistic spider

Diet restriction increases longevity while reducing fecundity in a broad range of organisms. However, there are exceptions to this rule, and the causes of these exceptions remain unclear. One hypothesis is that short-lived, semelparous organisms gain no benefit from increased longevity regardless of nutritional resources. Another hypothesis is that organisms may alter their behaviour to compensate for nutrient deficiencies. We examined these hypotheses in the colonial orb-weaving spider Cyrtophora citricola. Sexual cannibalism is frequent in this species so that females are long lived and interoparous while males are semelparous. Because of these differing sexual strategies, we predicted that the common pattern of increased longevity under diet restriction would hold for females but not for males. We also investigated in a semi-natural setting whether spiders could compensate for diet restriction by altering their feeding behaviour. Diet-restricted females produced fewer offspring but lived longer than well-fed females, while diet had no effect on male longevity. Despite being semelparous, virgin males were quite long-lived, suggesting that potential lifespan is relatively unimportant in determining the effects of diet restriction. Contrary to our predictions, females were unable to compensate for their restricted diet by altering their foraging behaviour. Instead, semi-natural conditions increased the differences between spiders on high and low diets, suggesting that the effects of diet restriction can be pervasive under natural conditions.

Thermal biology of the toad Rhinella schneideri in a seminatural environment in southeastern Brazil

The toad, Rhinella schneideri, is a large-bodied anuran amphibian with a broad distribution over South America. R. schneideri is known to be active at night during the warm/rainy months and goes into estivation during the dry/cold months; however, there is no data on the range of body temperatures (Tb) experienced by this toad in the field, and how environmental factors, thermoregulatory behaviors or activity influence them. By using implantable temperature dataloggers, we provide an examination of Tb variation during an entire year under a seminatural setting (emulating its natural habitat) monitored with thermosensors. We also used data on preferred Tb, allowing us to express the effectiveness of thermoregulation quantitatively. Paralleling its cycle of activity, R. schneideri exhibited differences in its daily and seasonal profile of Tb variation. During the active season, toads spent daytime hours in shelters and, therefore, did not explore microhabitats with higher thermal quality, such as open areas in the sun. At nighttime, the thermal suitability of microhabitats shifted as exposed microhabitats experienced greater temperature drops than the more insulated shelter. As toads became active at night, they were driven to the more exposed areas and, as a result, thermoregulatory effectiveness decreased. Our results, therefore, indicate that, during the active season, a compromise between thermoregulation and nocturnal activity may be at play. During the estivation period, R. schneideri spent the entire day cycle inside the shelter. As toads did not engage in nocturnal activity in those areas with low thermal quality, the overall effectiveness of thermoregulation was, indeed, elevated. In conclusion, we showed that daily and seasonal variation in Tb of an anuran species is highly associated with their respective pattern of activity and may involve important physiological and ecological compromises.

Antibiotics in ingested human blood affect the mosquito microbiota and capacity to transmit malaria.

Malaria reduction is most efficiently achieved by vector control whereby human populations at high risk of contracting and transmitting the disease are protected from mosquito bites. Here, we identify the presence of antibiotics in the blood of malaria-infected people as a new risk of increasing disease transmission. We show that antibiotics in ingested blood enhance the susceptibility of Anopheles gambiae mosquitoes to malaria infection by disturbing their gut microbiota. This effect is confirmed in a semi-natural setting by feeding mosquitoes with blood of children naturally infected with Plasmodium falciparum. Antibiotic exposure additionally increases mosquito survival and fecundity, which are known to augment vectorial capacity. These findings suggest that malaria transmission may be exacerbated in areas of high antibiotic usage, and that regions targeted by mass drug administration programs against communicable diseases may necessitate increased vector control.

The Resident-intruder Paradigm: A Standardized Test for Aggression, Violence and Social Stress

This video publication explains in detail the experimental protocol of the resident-intruder paradigm in rats. This test is a standardized method to measure offensive aggression and defensive behavior in a semi natural setting. The most important behavioral elements performed by the resident and the intruder are demonstrated in the video and illustrated using artistic drawings. The use of the resident intruder paradigm for acute and chronic social stress experiments is explained as well. Finally, some brief tests and criteria are presented to distinguish aggression from its more violent and pathological forms.

The Resident-intruder Paradigm: A Standardized Test for Aggression, Violence and Social Stress

This video publication explains in detail the experimental protocol of the resident-intruder paradigm in rats. This test is a standardized method to measure offensive aggression and defensive behavior in a semi natural setting. The most important behavioral elements performed by the resident and the intruder are demonstrated in the video and illustrated using artistic drawings. The use of the resident intruder paradigm for acute and chronic social stress experiments is explained as well. Finally, some brief tests and criteria are presented to distinguish aggression from its more violent and pathological forms.

Automated long-term tracking and social behavioural phenotyping of animal colonies within a semi-natural environment

Social behaviour has a key role in animal survival across species, ranging from insects to primates and humans. However, the biological mechanisms driving natural interactions between multiple animals, over long-term periods, are poorly studied and remain elusive. Rigorous and objective quantification of behavioural parameters within a group poses a major challenge as it requires simultaneous monitoring of the positions of several individuals and comprehensive consideration of many complex factors. Automatic tracking and phenotyping of interacting animals could thus overcome the limitations of manual tracking methods. Here we report a broadly applicable system that automatically tracks the locations of multiple, uniquely identified animals, such as mice, within a semi-natural setting. The system combines video and radio frequency identified tracking data to obtain detailed behavioural profiles of both individuals and groups. We demonstrate the usefulness of these data in characterizing individual phenotypes, interactions between pairs and the collective social organization of groups.

Clay Caterpillar Whodunit: A Customizable Method for Studying Predator–Prey Interactions in the Field

Predator–prey dynamics are an important concept in ecology, often serving as an introduction to the field of community ecology. However, these dynamics are difficult for students to observe directly. We describe a methodology that employs model caterpillars made of clay to estimate rates of predator attack on a prey species. This approach can be implemented as a field laboratory in almost any natural or seminatural setting, and is designed to allow educators to pursue any number of student-generated hypotheses representing varying degrees of scientific sophistication ranging from middle school to college level.

Influence of fungal isolates infecting tall fescue on multitrophic interactions

Abstract The epichloae are ascomycetous fungi in the genera Epichloe and Neotyphodium that live within grasses. Some of these fungi produce alkaloids that can help protect the host from herbivores. The alkaloids may also travel up the food web and affect members of the third trophic level. In this way they can produce trophic cascades which are rippling effects when a trophic level impacts those above or below it. We briefly summarize the general patterns of multitrophic effects of endophytes and highlight the most recent studies on this topic. Further, we report on our study in which we tested if different fungal strains in tall fescue (cultivar Jesup) affect multitrophic interactions involving aphids and their parasitoid natural enemies. Using both the common strain of N. coenophialum and a novel isolate (AR577), we allowed potted plants to be colonized by aphids and parasitoids in a semi-natural setting. We found that endophyte infection of tall fescue resulted in greater vegetative growth of the plant. We also found that N. coenophialum modified bottom-up cascades by depressing both aphid and parasitoid densities. Finally, we found that multitrophic effects were modified by fungal isolate: the common strain had stronger negative impacts on aphid and parasitoid densities than did the novel isolate.

Toe function and dynamic pressure distribution in ostrich locomotion

The ostrich is highly specialized in terrestrial locomotion and is the only extant bird that is both didactyl and exhibits a permanently elevated metatarsophalangeal joint. This extreme degree of digitigrady provides an excellent opportunity for the study of phalangeal adaptation towards fast, sustained bipedal locomotion. Data were gathered in a semi-natural setting with hand-raised, cooperative specimens. Dynamic pressure distribution, centre of pressure (CoP) trajectory and the positional inter-relationship of the toes during stance phase were investigated using pedobarography. Walking and running trials shared a J-shaped CoP trajectory with greater localization of CoP origin as speed increased. Slight variations of 4th toe position in walking affect CoP origin and modulation of 4th toe pressure on the substrate allows correction of balance, primarily at the beginning of stance phase at lower speeds. Load distribution patterns differed significantly between slow and fast trials. In walking, the 3rd and particularly the 4th toe exhibited notable variation in load distribution with minor claw participation only at push-off. Running trials yielded a distinctly triangular load distribution pattern defined by the 4th toe tip, the proximal part of the 3rd toe and the claw tip, with the sharp point of the claw providing an essential traction element at push-off. Consistency of CoP trajectory and load distribution at higher speeds arises from dynamic stability effects and may also reflect stringent limitations to degrees of freedom in hindlimb joint articulation that contribute to locomotor efficiency. This novel research could aid in the reconstruction of theropod locomotor modes and offers a systemic approach for future avian pedobarographic investigations.