acta ethologica最新文献

The present study reports a decrease in activity and sudden immobile state, known as thanatosis, in the New Zealand endemic wrasse, Notolabrus celidotus. We observed tonic immobility immediately after wrasse collection in field studies. Escape is the primary defence of juvenile N. celidotus and our observation suggests that thanatosis can be a secondary strategy when the first has failed. The response occurred after N. celidotus was manipulated by being removed from a fishnet and placed into buckets, allowing for the conclusion that N. celidotus may use thanatosis as a secondary defence strategy following physical restraint events.

During predator–prey coexistence, prey species have developed anti-predator behavior to reduce predation risk. In terrestrial ecosystems, humans are the major predators of wild cervids (Cervidae, Cetartiodactyla, Mammalia) in regions where large carnivores have gone extinct due to anthropogenic persecution. Typical anti-predator behavior exhibited by wild cervids includes increasing nocturnality and vigilance. We investigated diel activity and vigilance in sika deer (Cervus nippon) in nonhunting areas using camera-trapping techniques, to determine whether human visitation (i.e., nonlethal effects) increases their nocturnality and vigilance. We established two study sites––inside (low risk) and outside (high risk) of a wildlife reserve at University of Tokyo Chichibu Forest, Saitama, Japan. We hypothesized that in sika deer, nocturnality and vigilance would increase at high-risk site (outside of the reserve), due to the high rate of human visitation. However, vigilance level and diel activity between the two study sites were not different. In female deer, vigilance increased in winter regardless of the site studied. Our findings suggest that hunting activities (e.g., drive hunting with dogs) outside of the studied areas triggered anti-predator behaviors, such as increased vigilance, in sika deer, although our studied sites were not designated as hunting area. Further studies need to elucidate what types of human activities and intensity levels trigger anti-predator behaviors by wild ungulates.

The embracing behavior of Japanese macaques (Macaca fuscata) is a limited number of non-technological and non-subsistence behavior with cultural variations. Existing data were obtained from only two populations. This study first reports the behavior of a provisioned Japanese macaque group on Shodoshima Island, Kagawa Prefecture. Embracing behavior of three adult males and 14 adult females were recorded using focal animal sampling over three months. Behaviors immediately before and after embracing were analyzed. A total of 39 embracing behaviors were observed. Only five females exhibited embracing and there was no evidence of social transmission of this behavior, indicating that embracing is not ingrained as a “culture” in this population. Four of the five females were young adults, suggesting that females, specifically young individuals, were more prone to the behavior. Behaviors immediately before and after embracing tended to be grooming or huddling, suggesting that embracing reduces the tension triggered by physical contact and spatial proximity. This study contributes to the knowledge of cultural variations in non-technological or non-subsistence behaviors.

Understanding the morphotypical masculinization gradient and its impact on social behavior in a natural animal model is essential for unraveling sexual differentiation dynamics and their ecological implications. In this study, we examined the presence of a morphotypical masculinization gradient in female wild cavies (Cavia aperea) and its association with social behavior. Experimental colonies in four enclosures with different initial population densities were established. Between October 2017 and June 2018, we collected two datasets. The first dataset included body mass and anogenital distance (AGD) from 48 females, collected every 15–30 days. Simultaneously, focal behavioral observations were carried out during the intervals between recaptures. The behavioral dataset encompassed 65 marked cavies (males and females); 50 in high-density and 15 low-density conditions. Behavioral data were utilized to construct a focal association index matrix. Social centrality by spatial proximity measures were calculated using eigenvector analysis. Using the AGDI as a proxy for masculinization, we categorized females into three groups based on their AGDI values: low, middle, and high. The AGDI demonstrated high repeatability, underscoring its stability as a metric. Morphotype analysis revealed distinct distributions of AGDI values across varying initial density conditions. No significant associations were found between AGDI values and social centrality. These findings enhance our understanding of social dynamics in C. aperea and emphasize the significance of accounting for morphotypical variability in ecological research.

The common cuckoo Cuculus canorus is an obligate brood parasite of many Eurasian bird species that exploit the parental care of their hosts. Although only females lay eggs in nests of passerine hosts, male and female cuckoos should cooperate to have a success in nest parasitism. Many bird species mobbing cuckoos as an element of deterrence of cuckoos from the breeding territory of the host. However, mobbing behaviour is costly, although only cuckoo females pose a threat to the dangers of the host. Because only the presence of a female cuckoo is dangerous, due to laying eggs in the nests of hosts, birds should mainly attack cuckoo females. Therefore, we tested for differences in anti-parasite response using field experiments with female and male cuckoo dummies, in 92 breeding sites with prime habitats in Poland. tested for differences in cuckoo responses in anti-parasite response using field experiments and cuckoo dummies (male and female) placed at 92 breeding sites with prime habitats in Poland. The host species that behaved most aggressively towards cuckoos was the barn swallow Hirundo rustica, while the most aggressive behaviour recorded in the non-host group was the great tit Parus major. Generally, host species reacted to cuckoo female dummies with a significantly higher probability than cuckoo males dummies. We conclude that differences in reaction by hosts and non-hosts may have arisen from selection for recognition of danger (parasite female) by reduction of reproductive success.

Bats are prey for several vertebrate and invertebrate predators including spiders. We report the first case of a subadult female mastiff bat (Molossus molossus, Molossidae) trapped in a communal spider web of Parawixia bistriata (Araneidae, Araneae) with photographs and videotapes. This event occurred in the garden of a house next to a wetland in the east of Santa Fe province, Argentina (Paraná flooded savanna ecoregion). The day after the event, the bat was found dead entangled in the spider web. However, it remained in the spider web for three days until falling due to the effects of a strong storm. During this time in the spider web, the bat was daily visited during twilight by one to four spiders at a time. Over three days, the spiders strengthened the web around the bat and bit it with their chelicerae, which could indicate that they engaged in cooperative feeding on the trapped mammal.

Urban noise can potentially disturb the acoustic signals of animals inhabiting urban areas. Although a wide variety of noises from different sources is common in cities, the impact of non-engine noise on animal calls is less studied. In a natural experiment, we evaluated the effect of different urban noises on the advertisement calls of urban frogs (Eleutherodactylus nitidus) in the metropolitan area of Puebla, Mexico. We recorded and analyzed 672 advertisement calls from 28 male frogs and the corresponding environmental noises from three distinct localities. Our analysis focused on four acoustic properties of the calls: inter-call interval, call duration, dominant frequency, and call amplitude. To standardize the amplitude measurements of sound pressure levels produced by noise and frog calls, we employed a practical approach using a reference signal for calibration. We treated the longitudinal data of different noises occurring before, during, and after advertisement calls as repeated measures within the urban locations. During our samplings, frogs called amidst spontaneous urban noises, including dog barking, fireworks, and vehicle engine sounds. Our results indicate that vehicle engine sounds and dog barking do not cause significant distortions in the calls of these urban frogs. However, we observed slight variations in the dominant frequency of calls, decreasing by 11 Hz, during and after fireworks. Given the observed plasticity of E. nitidus in response to noise, urban noises may not pose a severe problem for this urban frog.

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.

We documented alloparenting and social group behavior within a leopard (Panthera pardus fusca) population in the Jhalana Reserve Forest (JRF), northwest India. Our observations revealed subadult offspring assisting their mothers in raising their newborn litters, exhibiting previously undocumented alloparenting behaviors. We propose that the familial intra-specific interactions and inter-specific competition collectively influence the social structure of the leopard population. Specifically we suggest that the inter-specific competition and predation, particularly with striped hyenas (Hyaena hyaena), may encourage alloparenting in leopards. Aditionally, we hypothesize that alloparenting, combined with natal philopatry, serves as an alternative strategy for leopards to enhance the survival chances of their progeny.