Journal of Ethology最新文献

Division of roles was observed during group hunting by the false cleanerfish, Aspidontus taeniatus (Blenniidae), when they raid the nests of the damselfish (Pomacentridae) and eat their guarded eggs. In this paper, we provide the first description of the collaborative group egg-eating behavior by the false cleanerfish. When raiding the nests of the three-spot dascyllus, Dascyllus trimaculatus, whose eggs are guarded by parents, the false cleanerfish divided roles as follows: “decoy” or “watcher” to draw attention and attract attacks from the parents, and “hider” or “intruder” to avoid detection by the parents and invade the nest. The potential differential costs associated with each role are unique among examples of group hunting strategies in fishes. However, once any individual in the group successfully invaded the nest, all individuals quickly achieved successful predation of the eggs and gained immediate shared benefit. We propose that the group egg-eating behavior of the false cleanerfish not only reinforces the evidence that fish can collaborate with other individuals but also suggests the hypothesis that collaborative hunting can evolve through mutualism even in fishes. Digital video images related to the article are available at http://www.momo-p.com/showdetail-e.php?movieid=momo240411at01a, and http://www.momo-p.com/showdetail-e.php?movieid=momo240411at02a.

It has been argued that a preexisting sensory bias for food color influences female mate preference for male ornament color. However, the effect of diet color over a short period on female preference for color-polymorphic male ornaments has not yet been investigated. In this study, we examined the effect of diet color on female preference for mate color in the guppy Poecilia reticulata, with color-polymorphic ornaments such as orange and black spots. From an early age, females were reared on a diet with orange and black color, respectively. A dichotomous mate choice experiment using females was conducted between males with large orange spots and males with large black spots. Females fed on an orange-colored diet preferred males with large orange spots, whereas those fed on a black-colored diet preferred males with large black spots. Afterward, the diet color treatment for the females was reversed for seven days. This dietary color alteration resulted in the reversal of female preference for male color. These results suggest that diet color has a great influence on female preference for mate color, even within a short period, and environmental gradients may function to maintain color-polymorphic male ornaments in this species.

We describe the details of the mating behavior of the Japanese badger, Meles anakuma, using camera trapping. Similar to other mustelid species, the females copulated with multiple males (mean = 3.0). Repeated mounting with the same male was observed, occurring 3.4 times on average. The average duration of the mounting bout was approximately 70 min, which was much longer than that observed for the congener M. meles. Following the initial mounting bout, males constructed a rest site by gathering fallen leaves and branches close to the female sett. Males rested at these sites between mounting bouts, likely to guard their mates from rival males. The mating pairs displayed a preference for returning to the same location for copulatory activities, which resulted in the dispersal of fallen leaves and surface soil disturbance. We found that some males restored the copulation site by covering it with leaves, soil, and branches after all mating behaviors were completed. This action prevented rival males from locating females, especially if they relied on olfactory cues from the copulation sites. Our study reveals interspecific differences in mating behavior within Meles and the relationship between social systems and mating behavior. Digital video images related to this article are available at http://www.momo-p.com/showdetail-e.php?movieid=momo240213ma01a, http://www.momo-p.com/showdetail-e.php?movieid=momo240213ma02a, http://www.momo-p.com/showdetail-e.php?movieid=momo240213ma04a, http://www.momo-p.com/showdetail-e.php?movieid=momo240213ma05a, and http://www.momo-p.com/showdetail-e.php?movieid=momo240213ma06a.

We recorded intra-sexual behaviour of adult male sub-Antarctic fur seals Arctocephalus tropicalis at Gough Island, Southern Ocean, during the 1975/76 summer breeding season. Our re-analysed data address male ‘contest competition’, which relates to the costs of intra-sexual disputes, including fights. We considered the risks/benefits of fighting through investigation of injuries (n = 353) sustained by adult males (n = 124) in fights. Injuries were predominantly on the forequarters, especially around the insertion areas of the front flippers (41%) with its sparse pelage, compared to the neck and chest areas combined (29%), an area which is well protected by thick pelage. The infliction of serious, sometimes debilitating, injuries to competitors increases a male’s access to females. Injuries predominate in injured, defeated males that gather at non-breeding sites, suggesting that injuries inflicted by dominant males were successful in excluding competing males from breeding sites.

We reported the social parasitism behavior between Vespula structor and Vl. flaviceps for the first time. These two Vespula species are both popular edible wasps in southwest China. Such a nest with these two mixed Vespula species in their natural state was found in the field, and observations both in situ and in doors were performed. Workers of the two Vespula species have distinct different looking but possess similar antennal sensilla. Mitochondrial DNA analysis proved these two Vespula were indeed two different species, with genetic difference of 14%. The queen observed in the nest belongs to Vl. structor which was supported both from morphology and DNA. The larvae collected during nest dissecting could not be distinguished which species they belong to, but DNA analysis proved that they were all Vl. structor individuals. Combined the behavior observation with the DNA data, we concluded that it was the queen of Vl. structor encroached on the nest of Vl. flaviceps, killed the queen of Vl. flaviceps, enslaved the workers in the nest, laid its own eggs, and gradually established the population of Vl. structor. Phylogenetic analysis based on complete mitochondrial genomes showed that they are close, and the Vl. structors was the more ancient species in evolution. In this case of wasp parasitism, the relatively ancient species Vl. structors parasitized the younger species Vl. flaviceps, suggesting that the social parasites (Vl. structor) were not evolved from their host (Vl. flaviceps), which rejected the Emery’s rule in its strict sense.

Abstract

Male–male combat occurs in many snake species and is often thought to result from competition for mates. We argue a more thorough assessment of the contexts in which combat occurs is warranted for snakes. We made field video observations of Agkistrodon conanti in central Florida, A. piscivorus in eastern North Carolina, and A. contortrix in eastern Kentucky. These observations were made in frequently used foraging sites; near drying ephemeral ponds in Florida and North Carolina and in a forested area with abundant emerging cicadas in Kentucky. In all three populations, males engaged in ritualized combat. In four instances, a variety of lines of evidence including season, local food resource abundance, local female abundance, and postcombat behaviors all indicated that access to food resources, rather than mating opportunities, was the catalyst for agonistic behavior. Behaviorally, food-induced combat appears nearly identical to mating-induced combat. Simplistic assumptions about the environmental contexts that induce combat may lead researchers to make inaccurate conclusions concerning the duration of the breeding season and the frequency of intraspecific competition for food in snake species. We outline a rigorous set of criteria that should be used to determine the context of male–male combat bouts. Videos showing the examples of combat discussed are available at http://www.momo-p.com/showdetail-e.php?movieid=momo231230ac01a, http://www.momo-p.com/showdetail-e.php?movieid=momo231230ac02a, http://www.momo-p.com/showdetail-e.php?movieid=momo231228ap01a, and http://www.momo-p.com/showdetail-e.php?movieid=momo231230ap01a.

Behavioural interactions between alien invasive fishes and native fishes is considered one of the drivers of native fish decline. However, there are few experimental studies on their behavioural interactions at the individual level. In this study, we investigated the behavioural interactions between the threatened native killifish Valencia letourneuxi, and the alien invasive Eastern mosquitofish Gambusia holbrooki, thought to induce the killifish’s rapid population decline. The aim was to assess aggressive behaviours, disruption in activity, stress levels, boldness, forging efficiency and shelter use by the native fish in the presence of the mosquitofish. Interspecies interactions were assessed in a three-tiered experimental setup, i.e. in an empty arena, in the presence of an artificial cover, and during feeding, using two opponents at each trial. The behaviours recorded and assessed were nips, following, approach, moving/immobile, top/bottom, erratic movement, cover use, feeding and latency to exit. The results showed that the mosquitofish was bolder, followed the native species, spent significantly less time under the cover and consumed food, as opposed to no following by the native species, significantly higher cover use and time immobile, as avoidance behaviours, and zero feeding in the presence of the mosquitofish. More significantly, the native species received direct aggression by the mosquitofish, as opposed to no aggression at all exhibited by it. Future research needs, as well as the conservation implications of our findings are briefly discussed.

Several species of birds deliberately drop hard food items, such as walnuts and molluscs, from high places to break the shell and eat the content. Although the carrion crow Corvus corone preys on the introduced apple snail Pomacea canaliculata by directly breaking the shells with their beaks in paddy fields in Japan, snails living in ponds are too large and hard for crows to directly break the shells. We found that carrion crows dropped apple snails in and around dried ponds in winter in Marugame, Kagawa, Japan, and conducted detailed observations on their predation behaviour. The crows dropped the snails onto various substrates in and around Hachijo Pond, and the release point was higher when the substrate was wet mud than when it was concrete, rock, or grass. As carrion crows rarely prey on other freshwater snails in Japan, this foraging behaviour has likely developed since the introduction of apple snails in the 1980s. The intense predation by the crows likely reduced the snail density in this reservoir pond.

Western sand lance Ammodytes japonicus exhibits dormancy in summer known as estivation, a distinctive ecology among teleosts. Estivation starts in early summer and continues until winter even water temperature lowered than the initiation threshold. In this study, we examined the onset of estivation in western sand lance reared under two experimental conditions of 14–25 °C-shift or 12 °C-constant. Our observations revealed that estivation in this species can be induced by intrinsic circannual rhythms other than either high or fluctuating water temperatures.

Abstract

Mucus-mediated communication plays a significant role in shaping community dynamics, particularly in marine organisms found in intertidal zones with complex topography. In this study, we investigated the host preference of a flatworm Stylochoplana pusilla, which lives symbiotically with intertidal gastropods, and its responses to the host and conspecific mucus. Our line transect surveys revealed differences in flatworm prevalence among sympatric gastropods, with multiple flatworms found in a single host individual, indicating host preference. The body mucus of gastropods and flatworms was applied to one side of a Petri dish to experimentally determine whether flatworms prefer the mucus-coated side under light and dark conditions. However, contrary to our expectations, the experiments in both light and dark conditions showed that the mucus of none of the host gastropods effectively attracted flatworms, suggesting that mucus-mediated communication may not be the primary factor in establishing host preference, and other ecological factors may play a role. Nonetheless, under dark conditions, flatworms were attracted to conspecific mucus, indicating that they may engage in collective homing behaviour or conspecific aggregation to find a suitable position in the mantle cavity. Overall, our results highlight the complex ecological interactions involved in shaping symbiosis between flatworms and gastropods.