acta ethologica最新文献

The degree of prey sociality reflects trade-offs between predation risk, and competition for mates and resources. Consequently, the degree of sociality is predicted to differ spatiotemporally. Variations in nychthemeral sociality are, however, understudied. We assessed the activity of solitary, territorial black wildebeest bulls (Connochaetes gnou) over rutting and non-rutting seasons. We predicted that solitary bulls would reduce their nocturnal use of territorial stands and join herds to reduce predation risk from nocturnally hunting lions (Panthera leo), but that these responses would differ across rutting and non-rutting seasons. We used camera trap data and modelled solitary bull and herd activity over 24-hour daily cycles, across rutting and non-rutting seasons. We calculated the proportion of images with solitary bulls and herds across nocturnal and diurnal periods, across both seasons. We show that solitary bulls are predominantly diurnal across both seasons, but the probability of nocturnal detection is higher in the rutting than in the non-rutting season. Furthermore, we recorded a lower proportion of solitary bulls to herds at night in the non-rutting relative to the rutting season. Thus, wildebeest bulls may trade-off predation risk for mate acquisition during the rutting season but reduce risky solitary behaviour during the non-rutting season.

The blue-winged parrot Forpus xanthopterygius is widely distributed in South America, where it lives in groups in different types of environments and feeds on fruits, seeds, flowers and nectar. In 2023 we observed a group of these birds moving from a forested area to an area of aquatic vegetation on the bank of a water reservoir in Southeast Brazil. The birds landed among the leaves of a cluster of Polygonum ferrugineum, approximately 45 cm above the water surface, and consumed flower buds and flowers — a plant species not yet reported for their diet. This behavior occurred during the driest period of the year (April), and may represent an alternative diet due to the scarcity of the preferred resources of this bird species during this period. The species is known to use habitats associated with water and to feed at low heights or even on the ground. However, this behavior of searching for resources on aquatic vegetation at the water surface in the middle of an urban reservoir has not been described and shows the adaptability of these birds to human environments and their high capacity to find food in the most varied types of habitats.

The ladybird beetles Cheilomenes sexmaculata and Propylea dissecta serve as effective bio-control agents, preying upon aphid populations and thereby mitigating plant damage. These beetles coexist together and show different reproductive strategies. Previous studies have found prevalent heterospecific mating between C. sexmaculata male and P. dissecta female, documenting the effects of heterospecific male C. sexmaculata on the reproductive output of P. dissecta female. In light of these observations, we conducted an experiment examining the influence of heterospecific male age on the reproductive output of P. dissecta. This study involved three age groups of male: (a) young (10–20 days), (b) middle (30–40 days), and (c) old (50–60 days). These males were introduced into Petri dishes with conspecific mates of P. dissecta. Across all experimental treatments, we examined the impact of three different age cohorts of C. sexmaculata males on the mating and reproductive attributes of P. dissecta. Our findings unveiled that older heterospecific males, which displayed reduced choosiness and heightened activity, engaged in reproductive interference to a greater degree than younger C. sexmaculata males during conspecific P. dissecta mating. Further, post-mating encounters with young heterospecific males led to a reduction in the reproductive output of female P. dissecta. The insights gained from this study hold significant implications for comprehending the feasibility of releasing multiple species of ladybird beetles within the same agricultural field. Such understanding of interspecies interactions and their consequences is vital for optimizing integrated pest management strategies.

The decision to escalate aggression in a contest is based on the assessment of oneself and the opponent's capabilities, previous experiences and the asymmetries between contenders. Interestingly, there is increasing evidence that color polymorphism may also influence the result in a contest during agonistic encounters. Therefore, this research aimed to analyze, for the first time, the intra-sexual competition of adult males of the Mexican Rivulus Millerichthys robustus, testing the influence of color polymorphic variations during agonistic contests. The results of this study suggest that the aggressiveness between morphotypes is of orange and red over yellow. The orange morph was related to winning the greatest number of encounters, whereas yellow lost the most. The red morpho registered the greatest number of ties. Interestingly, in contests between more aggressive morphs (orange and red), fish tended to modulate and lower aggressiveness levels, possibly to avoid injuries. In contrast, the least aggressive morphotype (yellow) tended to raise its aggressiveness against the most successful morphotype and lower it in matches against its own color, changing to a scheme between contenders with symmetrical aggression levels. These results suggest that differential aggression between morphotypes can influence the evolution of color polymorphism in M. robustus, differentially influencing the fitness of the individuals.

Parental age plays a major role in determining the life history attributes of an organism. Variation in parental age can have a big impact on offspring development, body mass and structure of population. To test the hypothesis that the increase in parental age has negative effects on offspring development of next generation, we observed the effect of parental age on the selected population of developmental variants (slow and fast developers) in a ladybird beetle, Propylea dissecta Mulsant (Coleoptera: Coccinellidae). The newly emerged adults were divided into two lines: Slow and Fast developers on the basis of their total developmental durations. Adult body mass, slow-fast emergence, sex-ratio, percentage of immature survival of newly emerged adults was recorded. Total developmental duration increased with the increase in age across generation and more fast developers were found in the offspring of young age groups; however, only slow developers were produced by old age groups. Offspring of older age showed higher immature mortality which supports slow-growth-higher mortality hypothesis. Thus, it can be concluded that young age beetles show better performance in terms of growth and developmental duration in P. dissecta in comparison to middle age and old age groups.

The preference for colours has profound impacts on the fitness of visually oriented species, influencing the search for food resources and mates of better quality while also modulating various physiological and behavioural features. Such processes may be more important to sexually dimorphic species, especially coloured ones since visual signals play an important role in intra- and intersexual communication. Amazon small streams vary widely regarding the amount of dissolved organic carbon resulting in black (red-biased) and clear (mostly transparent) water types. The sailfin tetra Crenuchus spilurus is a small sexually dimorphic species composed of two main genetic lineages that live in black and clear water types. Recently, we have shown that the female sexual preference for male ornaments colouration differs between individuals inhabiting black and clear water types. Females from black waters do not choose males primarily based on colouration under strongly red-biased lighting, but females from clear waters do, which suggests that the importance of red colours for sexual behaviour differs between lineages of the sailfin tetra. Here, we evaluated the sailfin tetra female environmental colour preference through the choice between a red and a full spectrum illuminated environments. Females from black waters and clear waters preferred red-lightened environments. Such results suggest that the females are attracted to the red colouration outside the context of mating, irrespective of the prevailing lighting condition of their native environment. This preference for red illuminated environments may be important for several processes, including physiological and behavioural features.