Ethology最新文献

Many animals build structures that are used for shelter, reproduction or to capture prey. The type of material used to build these structures is likely to influence their solidity, thermoregulation capacity and, in some species, may influence the attractiveness of the builders. In the case of animal nests, evidence for preference of nesting material has been documented in several species but, to date, few field experiments have been conducted, and it was seldom investigated whether individuals' attributes affected those preferences. We investigated these preferences in relation to individual attributes on sociable weavers (Philetairus socius) that build communally one of the largest known nest structures, using dry grass. We conducted an experiment where we presented two piles of straws, long and short, to wild individuals. We recorded 900 h of video and used a deep learning method to automatically detect images where birds were present (266 colour-ringed individuals). Our results showed that males picked more straws than females and showed a preference for longer straws, while no preference was found for females. In addition, older males showed a preference for long straws compared to younger males. Finally, males displayed higher repeatability than females in their preference for longer straws. In conclusion, we show that choice of nesting material is not random, and that preferences are associated with individual attributes. Future studies should assess how building is associated with social status, mating and reproductive success of the individuals building, to investigate which of these factors could have shaped the evolution of these preferences.

The role of hybridization as a formative process in evolution has received much attention in the past few decades. A particularly fascinating outcome of hybrid speciation is the formation of asexual hybrid species. The Amazon molly (Poecilia formosa) is such a hybrid and originated from a P. mexicana mother and a P. latipinna father. Consequently, a heterospecific mating must have occurred leading to the Amazon molly, indicating a breakdown of any potential prezygotic isolation between parental species. Here we studied the female mate preferences of extant P. mexicana and P. latipinna from several populations using standard binary choice tests with males of both sexual species that were matched for size. Poecilia mexicana and P. latipinna can be crossed in the lab, however, the offspring are not asexual, but sexual F₁s. In our study, we generated F₁s and tested their mating preferences with sexual males of both P. mexicana and P. latipinna against F₁ males. Overall, our results show that in extant P. mexicana and P. latipinna no female preference for conspecific males was detectable. Consequently, heterospecific matings are possible and not hindered by any apparent behavioral prezygotic isolation. If female preferences in these species were comparable around the time the Amazon molly originated as a hybrid species ca. 100,000 years ago, matings leading to hybrids would be very likely. F₁ females also have no discernable mating preferences for either sexual males or F₁ males. Such lack of prezygotic behavioral isolation could potentially lead to F₂ individuals, backcrosses, and introgression.

The behaviour shown by an animal at any one time is the consolidated output of its behavioural control mechanism. Moreover, what animals “want” is viewed as (the most) important component for individual welfare. Accordingly, studying the motivation of animals helps understanding basic mechanisms and welfare related needs. However, studying wants of animals is notoriously difficult and many previous studies on the preferences of animals have been restricted in the sense that only two choice options were presented in an artificial test environment. Here, an extended approach, the “Small World” is presented, in which the choices of animals between eight ecologically relevant resources can be observed in a long-term test to reach conclusions with respect to everyday moment-to-moment decisions. In this sense, the system offers a quasi-natural environment. The approach was tested in three experiments with observations of individual female rats, small groups of female rats (Long Evans, Rattus norvegicus) and small groups of female chickens (Lohmann Brown, Gallus gallus domesticus). The animals oriented themselves quickly in the system and it was possible to collect multifaceted data on the use of the resources. These data included the faecal and urinary markings in the Small World cages, the daily frequency and duration of visits to these cages, the sequential analyses of the choices for and decisions among the resources, and the synchrony of the animals in the groups. Given the richness of these data and the lack of a stress response in the tested animals, the use of the Small World approach seems to be highly promising as an extension to previously used procedures. To further improve the approach and more directly reflect the subjective value of the different resources from the animals' point of view, the distances between the resources in a quasi-natural landscape shall be manipulated in future studies.

In our laboratory, we measure hormones such as testosterone, melatonin, or corticosterone to relate hormone concentrations to the behavior of animals. Sometimes, we get samples of animals whose hormone concentrations had been altered by hormone implants or injections. Usually, those are measured to test if the hormonal manipulation had worked. I typically ask the experimenter which of the samples are from manipulated animals and which ones are from control animals. As an answer, I sometimes receive a raised eye brow and a questioning face. This kind of answer makes me happy because it shows my cooperation partner is aware of observer bias. I then explain that I would actually prefer not to know, which animals had been manipulated or not. However, our method to measure the hormones, the radioimmunoassay, requires me to know about it. The method is quite sensitive, but has a narrow range of concentrations in which we can reliably tell the correct hormone concentrations. Therefore, we need to adjust the dilution of the samples to remain in the expected range of concentrations we can measure with high precision. Hormone-treated samples might easily fall out of this range, if not diluted properly.

Presumably, the radioimmunoassay as a biochemical method is unlikely to produce observer bias, but this is different with behavioral observations, where our expectations as experimenters may inadvertently bias data collection. For this reason, good textbooks such as the classic Martin and Bateson (1985) or its latest edition (Bateson & Martin, 2021) caution against observer bias and also highlight the importance of testing for inter-observer reliability. A good way to do so is blinding observers to the treatment and apply established methods to test and improve inter-observer reliability.

About 12 years ago, Gordon Burghardt and colleagues investigated how major journals in animal behavior did with regard to reporting observer bias. They demonstrated that in 2010 major journals of our field (Animal Behaviour, Behaviour, Behavioural Ecology and Sociobiology, and Ethology) had observer bias reporting rates of <10%, therefore lagging behind Infancy, a journal on human infant behavior with reporting rates of more than 75% (Burghardt et al., 2012). Journal of Comparative Psychology had reporting rates of 20%.

In this issue of Ethology, Todd Freeberg, Scott Benson, and Gordon Burghardt offer a follow-up study (2024), showing that all behavioral journals have improved on reporting. This is good news! However, with rates in the range of 50% our field still lags behind Infancy, where basically every study reports observer bias and tests for inter-observer reliability. Also, Journal of Comparative Psychology still does better with roughly 75% or articles reporting on observer bias. Admittedly, it is more difficult and sometimes impossible to condu

Birds from at least a dozen orders engage in dustbathing, including Galliformes. Dustbathing is generally considered a behavioural need for poultry. It involves a precise and orderly sequence of movements repeated over time. The most characteristic movement involves tossing the dust with the wings and undulating the body beneath the dust shower. Thus, repetitive changes in body position during dustbathing could be automatically detected through data processing of body-mounted accelerometer recordings. The approach was tested in 13 adult male Japanese quail (Coturnix japonica) fitted with a body mounted triaxial accelerometer. Behaviour was video-recorded for at least 6 h. Observations showed that when the animal lies on its left- or right-side during dustbathing, the lateral (swaying) component of the acceleration vector adopts values of +1 or −1, respectively. Analysis shows that the bird repeats these shifts in body position every 25–60 s. The wavelet analysis (i.e. complex Morlet continuous wavelet transform (CWT)) detected this oscillatory behaviour within the time series as higher power values. This characteristic was used to automate the detection of dustbathing events, for which a threshold value for the maximum power value estimated was established for the corresponding range of scales between 25 and 60 s. The overall general accuracy of this classification method for dustbathing detection was 80%, with individual variations falling within the range of 66%–100%. Finally, an example of the potential of this method in the study of temporal dynamics, such as daily rhythms of dustbathing, is provided. Our results show that combining accelerometry and wavelet analysis could be useful for the assessment of intra- and inter-individual variability in dustbathing dynamics over long-term studies, even within large complex environments, such as natural habitats or breeding facilities. Moreover, this approach could open doors for future in-depth studies exploring the relationship between dustbathing and poultry welfare.

The presence of conspecifics plays a crucial role in mitigating stress responses in social teleost species and holds potential for enhancing welfare in captive fish. While studies on social buffering effects have typically focussed on single species, marked interspecific differences can exist. Here, we conducted an analysis of social buffering of stress response in two of the most extensively farmed fish, the Nile tilapia and the koi carp. Subjects were exposed to a behavioural stress response assay (open-field test) in three conditions simulating increasing levels of social enrichment: isolation, pairs, or shoals of five fish. We obtained five stress indicators from the assay: thigmotaxis, freezing, activity, erratic movements and interindividual distance in conditions with more than one fish. In both species, erratic movements significantly decreased with increasing levels of social enrichment, suggesting a similar social buffering effect. However, other indicators revealed species differences. Koi carp, but not Nile tilapia, showed a socially-mediated reduction in thigmotaxis, whereas Nile tilapia, but not Koi carp, showed a socially-mediated reduction in freezing behaviour. Furthermore, social enrichment determined opposite effects on the activity of the two species: Nile tilapia were more active as group size increased, whereas the opposite trend was found in koi carp. Finally, Nile tilapia showed increased interindividual distance with increasing social group size, whereas no changes were observed for koi carp. Our study indicates that the buffering effects of social enrichment on the behavioural stress response do not completely overlap between different fish species, highlighting the importance of developing finely-tuned species-specific enrichments and welfare indicators.

Urbanization is a significant driver of the global biodiversity crisis. Turtles are particularly impacted by urbanization because of the vulnerability of riparian habitats to habitat loss and road mortality. Behaviour plays a crucial role in determining the success of urban animals. Behavioural responses to urbanization, however, are rarely studied in turtles even though many turtles are at-risk and sometimes live in urban areas. Therefore, we evaluated behavioural changes in painted turtles (Chrysemys picta) living in wetlands surrounded by a gradient of urbanization. We tested the consistency of painted turtle behaviour in the laboratory and examined the behaviour of painted turtles from 24 wetland sites across an urbanization gradient in Ottawa, Ontario, Canada. We assessed: (i) aggression by measuring the number of active defensive behaviours the turtles performed in response to handling, (ii) boldness by measuring the amount of time the turtles took to emerge from their shells and move from their initial locations in a circular arena and (iii) activity by measuring the amount of time the turtles spent moving in the same circular arena. We found that all behaviours were consistent in the laboratory. We also found that as the level of urbanization increased, turtles were more aggressive and bolder. Urbanization affects painted turtle behaviour, but further research is required to understand the mechanisms responsible and the conservation implications.

Animals have myriad adaptations to help them hunt and feed in the most efficient and effective manner. One mysterious behavior related to hunting and feeding is the posterior toe tapping behavior of some frogs. Biologists and hobbyists alike have long noticed this behavior, but there is little empirical data to explain its causes and consequences. To test the hypothesis that tapping is related to feeding and modulated by environmental context, we conducted a series of related experiments in the Dyeing poison frog, Dendrobates tinctorius. We first confirmed that tap rate was higher during feeding as has been observed in other species. Interestingly, this effect was heightened in the presence of a conspecific. We next asked whether frogs tapped less under conditions when prey were visible, but inaccessible. Finally, we asked whether D. tinctorius adjusted tap rate based on substrate characteristics and whether prey capture success was higher when tapping. In addition to confirming an association between tapping and feeding, our work demonstrates modulation of toe tapping based on social context, prey accessibility, and substrate characteristics. Based on our findings, we suggest that tapping could act to induce prey movement and thereby facilitate prey detection and capture by frogs.

Steroid hormones play a pivotal role in shaping arthropod phenotypes, with 20-hydroxyecdysone (20E) serving as a key regulator of molting, a vulnerable period in an insect's lifecycle. Despite its critical role in arthropod growth and development, the influence of 20E on arthropod behavior, particularly defensive strategies, remains poorly understood. We investigated the impact of 20E on the bioacoustic characteristics of hisses in the Madagascar hissing cockroach (Gromphadorhina portentosa), a social species with multiple complex acoustic signals. With increased 20E, we predicted that hiss production would be more likely and more defensive (i.e., longer hisses with greater intensity (dB) and reduced frequency (Hz)). We injected male G. portentosa with either a low- (35 μg) or high-dose (70 μg) of 20E or a control (0 μg 20E), and we measured the presence/absence of hissing responses and their bioacoustic characteristics following a standardized tactile stimulus. Contrary to our prediction, there was no difference in the likelihood of hissing or hiss duration with 20E administration. However, administering 20E resulted in reduced hiss intensity and increased hiss frequency (as measured by peak and center frequencies), suggesting potential shifts from defensive to aggressive signaling. Our study contributes to the limited knowledge of the behavioral effects of 20E, suggesting that some arthropods may experience increased aggression or energetic limitations to defense during molting. Behavioral changes elicited by hormones have important implications for both fundamental ecology and applied pest management.