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Our objective was to determine the effect of lead (Pb) on the behavior of the Mexican mojarra, which is native to the Balsas River basin, and the convict cichlid, which is an exotic invasive there. Both fish species were exposed to Pb, followed by Pb depuration, to evaluate its impacts on behavior. We evaluated swimming activity, predation attempts, prey consumed, foraging efficiency, and aggressive behaviors. The behavioral effects of Pb differed between the two species. While swimming activity decreased in both species during Pb exposure, swimming activity recovered during the Pb depuration period in the convict cichlid, but not in the Mexican mojarra. In both species, the total predation attempts and prey consumed increased during exposure to Pb and remained elevated during Pb depuration. Pb did not affect the foraging efficiency or number of aggressive behaviors of the convict cichlid. In contrast, the foraging efficiency of the Mexican mojarra decreased with Pb exposure and remained low during Pb depuration, and the number of aggressive behaviors increased under Pb exposure and remained elevated during Pb depuration. Pb exposure affected Mexican mojarra more strongly than the convict cichlid, which could induce changes in the ecological relationships between these species.

Yamato et al present the first documentation of conspecific aggression in dugongs (Dugong dugon) in Thailand. Conspecific aggression, which involves attempts to injure or monopolize resources, has been observed in various marine mammal species. Agonistic behavior is also present in sirenians, such as dugongs and manatees. Male-male aggression in dugongs is driven by competition for resources and mates. They used drones to observe and analyze the aggressive behavior of dugongs in two events. The events included approaching, pursuing, agonistic collision, rushing, mounting, and separating behaviors. The initiators of the aggression were presumed to be males, based on their behavior. The events were distinguishable from mating behavior and were characterized by brief and violent contacts. The study provides insights into the behavioral categories and indicators of dugong aggression and highlights the advantages of using drones for aerial observations. Further research is needed to understand the benefits and functions of aggression in dugongs.

A 30 portable emission measurement system (PEMS) test was conducted in this study to examine the effect of driving modes (aggressive and normal) and road type (urban and rural) on tailpipe emissions. Driving modes were assessed using relative positive acceleration and velocity × positive acceleration factors. The findings revealed that aggressive and normal driving modes differed significantly on urban and rural roads, as evident from paired sample t-test ( p < 0.05). Furthermore, aggressive driving exhibited more prominent speed and acceleration on rural roads, while normal driving modes showed consistent acceleration or speed patterns regardless of road conditions as observed from kernel density estimation and box plot analysis. Emission rates (CO, CO 2 , HC, and NO x ) significantly varied between aggressive and normal driving modes on urban and rural roads, as indicated by paired sample t-test analysis ( p < 0.05). Aggressive driving increased CO 2 , CO, and HC emission rates for acceleration and deceleration modes by 18% to 40% compared to normal driving. Aggressive driving modes increased the emission factors (CO, HC, and CO 2 ) by 5% to 25% compared to the normal driving mode on both urban and rural roads. Moreover, the NO x emission factors were also found significant during normal driving conditions on urban roads. This study provides real-world emission factors of diesel cars considering the impact of route, vehicle familiarity, and driving behavior induced by varying traffic conditions, which will contribute to improve the current emissions inventory on both a local and global level.

Mass coral bleaching causes population declines and mortality of coral reef species1 yet its impacts on behaviour are largely unknown. Here, we unite behavioural theory with community ecology to test whether bleaching-induced mass mortality of corals can cause consistent changes in the behaviour of coral-feeding fishes. We documented 5,259 encounters between individuals of 38 Chaetodon (butterflyfish) species on 17 reefs within the central Indo-Pacific, of which 3,828 were repeated on 10 reefs both before and after the global coral bleaching event in 2016. Aggression between butterflyfishes decreased by two-thirds following large-scale coral mortality, despite no significant change in fish abundance or community composition. Pairwise encounters were most likely to be aggressive between obligate corallivores and on reefs with high coral cover. After bleaching, the proportion of preferred Acropora corals in the diet decreased significantly (up to 85% fewer bites), with no increase in overall bite rate to compensate for the loss of these nutritionally rich corals. The observed reduced aggression at low resource levels due to nutritional deficit follows the predictions of the economic theory of aggressive behaviour2,3. Our results reveal synchronous changes in behaviour in response to coral mortality. Such changes could potentially disrupt territories4, leading to reorganization of ecological communities.

After observing a fight between two snowflake eels in southern Taiwan, we had difficulties locating scientific information on eel–eel aggressive behaviour and looked further afield. We collected and scored 34 videos posted on social media, to provide more insight into antagonistic behaviours in eels. The videos showed 12 different species of moray eels involved in aggressive interactions, with the genus Gymnothorax contributing to ~ 71% and Echidna contributing to 24% of the observed occurrences. 82% of the videos documented antagonistic interactions between conspecifics. The fights involved “knotting”, when opponents curl around each other and shove with their bodies, and some biting. Overall, the incidence of injury and death of losers, as well as injury of winners, was higher in smaller-bodied opponents. Conspecific encounters elicited the greatest intensity of aggressive behaviour, which we interpreted as rivalry due to dominance hierarchies and territoriality. This normally included a visible resource the opponents fought over (a den, a food item, a mate). Same-species fights started after gaping mouths at each other, with individuals being roughly equal in size. Conspecific opponents were often injured, but never killed. Available videos with fights between different species included predatory attacks and defensive reactions. Except for one case, interspecific encounters often ended with one eel being killed and eaten, with the winner being a fish-eating Gymnothorax species. Pre-fight, the killer was observed displaying food searching behaviour by checking holes. Both conspecific and interspecific fights frequently incurred deep, V-shaped wounds that were not apparently life threatening. Old V-shaped scars occurred on the bodies of some eels. Such scars could be used in research further investigating aggressive behaviour in moray eels.

Dusky damselfish (Stegastes fuscus) behaviour was investigated under natural and controlled conditions to evaluate how territory and familiarity affect aggressive behaviour. In the natural environment, fish occupies territories of 2.74 ± 1.3 m2 and the most frequent behaviours exhibited were monitoring swimming, feeding, shelter occupation and agonistic interactions. Larger-territory individuals spend more time in monitoring swimming than smaller-territory ones, which results in a reduction of food intake. Agonistic interactions were more frequent with heterospecifics than conspecifics. Whenever agonistic interaction occurred, confrontations were not frequent. Territorial behaviour in the lab was evaluated considering two variables: prior residence and familiarity between conspecific opponents. Resident fish invested more against intruders irrespective of the intruder’s identity (familiar or unfamiliar). When no previous territory was established, S. fuscus showed lower aggressive behaviour, and it was even lower when a familiar fish was the opponent. Data from the field and the lab suggest that S. fuscus territoriality and aggression are related to the size of the defended area and the competitor’s identity. Thus, reduced reef areas may result in increased interindividual aggression, while the intruders’ recognition may be a key trait controlling agonistic behaviour in the reef community where S. fuscus is inserted.

Cannibalism is a common phenomenon that occurs in over 30 fish families. Most of the species are valuable objects of aquaculture and cannibalism is highly undesirable. Cannibalism is an aggressive behaviour, which can be caused by stress induced by various population and environmental factors and can occur in two main forms: early larval and late juvenile (or adult). Each of these forms can lead to severe losses of stock. Losses are caused not only by fish eating each other, but also by an increase in the number of infections (the result of body surface damage). It is important to understand the phenomenon of cannibalism in order to properly prevent, diagnose and reduce it. The main aim of this study was to present and examine some of the well-examined methods of cannibalism mitigation. Most of the methods consist of creating rearing conditions similar to natural conditions and to reduce stress. Moreover, because of large interspecies differences, similar methods can result in different effects depending on the species. Additional studies are needed to better understand the biology of each cultured species with particular emphasis on the impact of domestication, as well as to improve fish rearing conditions.

Fish social behavior can be affected by artificial environments, particularly by factors that act upon species that show aggressive behavior to set social rank hierarchy. Although aggressive interactions are part of the natural behavior in fish, if constant and intense, such interactions can cause severe body injuries, increase energy expenditure, and lead the animals to suffer from social stress. The immediate consequence of these factors is a reduced welfare in social fish species. In this paper, we consider the factors that impact on the social behavior and welfare of Nile tilapia, an African cichlid fish widely used both in fish farms and in research; this species is frequently used as a model for physiology and behavior research. This is a polygynous species whose males interact aggressively, establishing a territorial based hierarchy, where a dominant male and several subordinate males arise. When social stability is shrunk, the negative effects of prolonged fighting emerge. In this paper, we summarized how some of the common practices in aquaculture, such as classifying individuals by matching their sizes, water renewal, stock density, and environment lighting affect Nile tilapia social aggressive interactions and, in turn, impact on its welfare. We also discuss some ways to decrease the effects of aggressive interactions in Nile tilapia, such as environment color and body tactile stimulation.

Recreational use of illicit methiopropamine (MPA) is a public health concern because it produces neurochemical effects comparable with those induced by methamphetamine (METH). The present study investigated the effects of MPA on the expression of an aggressive behaviour. Eighty CD-1 male mice, after receiving intraperitoneal injection of saline, MPA (0.01–10 mg/kg), METH (0.01–10 mg/kg), or AMPH (0.01–10 mg/kg), once a week over a 5-week period, underwent the resident–intruder test and spontaneous locomotor activity measurement. Results showed that all psychostimulants induce aggressive behaviour even at low doses, with a dose-dependent increase and a time-dependent sensitisation. MPA potency was similar to METH and superior to AMPH. Therefore, MPA-induced aggressive behaviour may appear even at MPA dosages free of cardiovascular or other behavioural adverse effects and could become a non-intentional side effect that users experience after increasing and repeating MPA consumption.

Population expansion of the black‐winged kite Elanus caeruleus has been a global trend in recent decades. Since first recorded in Taiwan in 2001, they rapidly occupied plains areas of this subtropical island which has led to interspecific competition with the wintering Eurasian kestrel Falco tinnunculus. In this study, we analyzed historical surveys to estimate the population trends of both species in Taiwan. We then used Pianka's index to quantify the degree of niche overlap based on diet composition and foraging peaks. Finally, we designed an experiment to test the aggressiveness of the two raptors when facing conspecific or heterospecific intruders. Airport avifauna survey (2002–2017) data from eight different airports and eBird data (2000–2019) from 21 hotspot grids both showed population turnover between the two raptors, with a decline in the wintering Eurasian kestrel and an expansion of the black‐winged kite. Rodents were the largest share of prey for both species, indicating that the two raptors have a high degree of niche overlap (an overlap index of 0.74 by prey frequency, 0.97 by prey biomass and 0.89 by foraging time). The black‐winged kite exhibited higher boldness and aggressiveness toward intruders, with its aggressiveness toward kestrel specimens (2.9 ± 2.4 strikes) significantly higher than that toward kite specimens (1.1 ± 1.8 strikes). Attacks by the black‐winged kite may have prompted the Eurasian kestrel to choose other wintering grounds. As a result, the number of wintering kestrels decreased, leading to opposing population trends of the two species.