Ethology最新文献

The ability of anuran larvae to efficiently locate food is essential for their growth and development, but little is known about the sensory modalities they use to find food. We experimentally assessed the role of visual and chemical cues in finding food in tadpoles of the invasive species Lithobates catesbeianus. In the two-choice experiment, using rectangular containers that offer visual and/or chemical food cues on opposite ends, tadpoles chose the side where the chemical cues of the food were present consistently. The visual cues alone showed an initial transient attraction of tadpoles, which disappeared after a few minutes, suggesting that tadpoles are potentially capable of seeing contrasting objects, at least, at a close range and in clear waters and daylight conditions. We also evaluated the foraging behaviour and the capability of tadpoles to find food in an open field experiment under two different lighting conditions: natural daylight and darkness. Results showed that tadpoles find food faster in dark conditions, confirming that chemical cues alone are sufficient for tadpoles of this species to find food. Moreover, the time spent feeding and the number of tadpoles simultaneously exploiting the food patch were greater in darkness suggesting that environments with low visibility conditions could favour the establishment of L. catesbeianus. Understanding the sensory modalities used by tadpoles of this invasive species to find food could help to understand the potential abilities to expand and establish in novel environments.

Oviposition site selection by parents is an important factor that affects offspring survival and parental fitness. The relative importance of sexes in oviposition site selection in anurans is rarely evaluated, especially in species with resource-defense mating systems, where males defend territory containing eventual oviposition sites before advertising for females. Using a phytotelm-breeding frog (Kurixalus eiffingeri) with male territoriality, we examined 310 bamboo stumps (potential for oviposition sites) to determine whether male and female choice of oviposition site based on physical characteristics (stump height, inner diameter, stump depth, water depth, and water volume). We found that males preferred a site with higher stumps that were deeper and contained more water, while females showed no preference for sites based on the characteristics observed. Although we do not exclude the possibility that K. eiffingeri female oviposition site selection can be relied on and/or correlates to male advertisement calls, this study is one of few studies to examine the role of both sexes in oviposition site selection simultaneously, and provides empirical evidence that oviposition site selection is primarily determined by males in an amphibian with a resource-defense mating system.

In animal fights, there are often size asymmetries between opponents. Although larger individuals typically dominate smaller ones, size is not the sole determining factor, as the competitors' motivation, aggressiveness, resource value, physiological characteristics, and strength also play crucial roles in fighting outcomes. In this study, we evaluated the influence of body size on dominance hierarchy and contest success during intra- and inter-specific contests in two fish species: the native mojarra of the Balsas basin Amphilophus istlanus and the invasive convict cichlid Amatitlania nigrofasciata. We used size-asymmetric males to carry out experimental contests. The number and type of aggressive behaviors, time to contest outcome, and dominant individual at the end of the contest were determined. In contests between two native mojarra, the smaller individual always lost. In contests between convict cichlids, the smaller contestants lost in all contests where size asymmetry was greater than 20%. In interspecific contests, the native mojarra performed more aggressive behaviors than the invasive convict cichlid and dominated convict cichlids despite a size disadvantage. This suggests that in terms of competition via interference, the native mojarra can counter the arrival of the invasive convict cichlid.

Resistance to mating by females has been hypothesized as a tactic to assess potential mates and avoid undesirable ones. Previous studies show infection with the pathogenic bacteria, Pseudomonas aeruginosa, triggers a costly immune response and negatively impacts fitness in the wolf spider Schizocosa ocreata (Hentz 1844). Studies also show that infection can be transmitted during copulation, suggesting that there are potential fitness costs associated with mating with an infected individual. We examined impacts of infection on mating interactions of male and female S. ocreata. As studies show infection can be detected through chemical cues, we tested whether males or females avoid mating with infected individuals when given the opportunity. We paired infected and uninfected (control) males and females and recorded their behavior. We found that mating outcome was independent of infection for males and females. While higher male courtship rates and more frequent female receptivity displays were associated with successful mating, we saw no direct effect of infection status on mating outcome. However, among spider pairs that did not mate, females were found to be significantly more resistant and aggressive toward infected males than control males. Male aggression, on the other hand, was greater in pairs that did result in mating. These results suggest that sexual conflict in mating can be related to infection status, and that females can recognize infected males and alter their behavior in response.

For decades, texts on methods in animal behavior research have stressed the need for observers of behavior to work to minimize potential unconscious biases in their coding of data. Two major ways of minimizing these biases are to carry out data coding blind to the key comparisons being made in the study and to have high inter-observer reliability. Over 10 years ago, Burghardt et al. (2012, Ethology, 118, 511) reviewed five major journals in the field of animal behavior and coded randomly selected articles from five decadal volumes (1970 to 2010). That earlier article found poor rates of reporting these two common methods for minimizing potential biases. Here, we carried out similar coding for the 2020 volumes from those same five journals. We found that rates of reporting have increased in all five journals – some substantially. However, rates of reporting still lag behind the journal Infancy, which publishes research on human infant development and relies on many of the same behavioral observation and coding methods used by animal behavior researchers. Given increased calls for transparency and reproducibility in many different fields of scientific study, we argue that we – researchers, reviewers, and editors – can and need to do better at making sure we are actively conducting research in ways to minimize potential observer biases.

For many mammalian and avian species, it has been proposed that cognitive enrichment, such as puzzle feeders, can improve welfare in captive conditions. A well-established method to evaluate the need for cognitive enrichment is to observe the preference of the animal between freely available food and a puzzle feeder. We investigated this preference in a teleost fish, the guppy. In most of our experimental trials, guppies first chose the feeder with freely available food over the puzzle feeder, in contrast with what was observed in most other species. Nevertheless, the guppies' number of choices for the puzzle feeder was significantly greater than zero. Moreover, after consuming the freely available food, most of the guppies tackled the puzzle feeder. This pattern of results suggests that guppies displayed a certain interest in the puzzle feeder that was overshadowed by their strong attraction towards the free food. Interestingly, several measures of performance indicated that female guppies responded more positively towards the puzzle feeder as compared to the males, suggesting sex differences in the preference for cognitive enrichment. In conclusion, our study highlights the potential significance of cognitive enrichment for captive fish. Considering that the number of individual fish maintained in captivity exceeds by far that of any other vertebrate group, it is paramount to investigate cognitive enrichment in other teleost species.

Parental investment is any expenditure of time or energy by parents that increases their offspring survival at the cost of future reproduction. The costs associated with parental investment can be reflected in a deterioration of their physiological condition. In insects, juvenile hormone has been identified as having a role in the control of parental care. However, its effects on parental investment remain unclear for many taxa, especially in species with exclusive paternal care. We evaluated whether juvenile hormone influences postzygotic parental investment in Abedus ovatus, a waterbug with exclusive paternal care. Males provide parental care by carrying eggs on their backs and ventilating them by generating water currents through push-ups called brood pumping. In an experiment, we applied methoprene (an analog of juvenile hormone) to males at early and late parental care stages and quantified the frequency of brood pumping and the contents of energy reserves (lipids, carbohydrates, and glycogen) at the end of parental care as a measure of physiological condition. We found that methoprene increases the frequency of brood pumping only when the water temperature increases. However, there was no correlation between the parent's energy reserves and methoprene treatments. We found that males who cared for large egg pads had lower amounts of lipids and carbohydrates at the end of parental care, and both effects are greater as the water temperature increases. These results suggest that energy expenditure during parental care is high due to intense muscular activity during brood pumping, which depletes male energy reserves and could affect future reproduction.

Interactions between predator and prey are fundamental drivers of ecological and evolutionary dynamics. Behavioral responses are one of the most common strategies that prey species use to deter predation, especially through highly stereotyped defensive displays. However, these displays are also predicted to show strong context-dependence, in which individuals can dynamically employ different display elements as a function of their own characteristics (e.g., age and sex) or those of the predator (e.g., type of predator). In this study, we experimentally tested for the effects of four simulated predator cues on defensive displays in two species of South American calico snakes (genus Oxyrhopus). We found that juvenile snakes were both more likely to respond and to respond more strongly than adults and that displays were most common in response to tactile stimuli than to other treatments. However, we also found broad similarity across both simulated predator treatments and species in the components used in each snake's defensive display, suggesting a high degree of stereotyping. This research suggests an important role for both ontogeny and intensity of predation risk in structuring variation in defensive behavior in Neotropical snakes and emphasizes the foundational importance of context dependence in conceptual frameworks for understanding predator–prey interactions.

Reciprocally patterned behavior is widespread in animals in the wild, but experimental evidence has been frustratingly inconsistent. Contrary to earlier contentions that this inconsistency is because reciprocity in non-human species is a rare or fragile effect, recent authors have argued that the evidence suggests that reciprocity is widespread, that it often relies on cognitive mechanisms that are common across species, and is potentially an important factor in animals' daily lives. Another possible explanation for its apparent rarity, then, is that due to experimental studies' (intentionally) structured environment, they can lack the appropriate context to promote and support reciprocity. Focusing on outcomes from experimental reciprocal tasks in non-human primates, I consider several factors that may be important, including the identity of the interactors and their relationship to one another, whether there is free choice of partners, whether the individuals are interacting directly, the timing of the interaction, the commodity involved, whether individuals have a reason to reciprocate, and the equity of the interaction. Clarifying the role of each of these factors will help improve experimental tasks and the social and ecological contexts that promote reciprocity.

Reproductive interference between species is vital to understand interspecific interactions along with their ecological and evolutionary patterns in nature. We studied potential reproductive interference between two sympatric species of ladybird beetles Propylea dissecta and Cheilomenes sexmaculata (Coleoptera: Coccinellidae). Our aim was to determine whether heterospecific matings occur between these two species, and if so, how they affect the reproductive output of females of both species. We found that heterospecific mating occurs, with P. dissecta females mating with C. sexmaculata males, but not vice versa. To compare the effect of conspecific and heterospecific males on the reproductive output of P. dissecta females, we used two mixed mating treatments: conspecific mixed (an additional P. dissecta male with conspecific pair of P. dissecta), and heterospecific mixed (a C. sexmaculata male with conspecific pair of P. dissecta). We found that conspecific interference did not affect reproductive parameters. However, the presence of a heterospecific C. sexmaculata male interfered with conspecific matings in P. dissecta through multiple mating attempts, resulting in reduced fitness and reproductive success of P. dissecta. Our results indicate that the presence of heterospecific males significantly affected the reproductive output of P. dissecta, apparently as a result of the greater attempted mating activity of C. sexmaculata males. Our findings may be relevant for effective biocontrol strategies involving these insect species.