acta ethologica最新文献

Gibbons exhibit territorial behavior, and mated pairs defend exclusive territories. However, reports on contacts with neighbors near or outside the respective range boundaries are scarce because observing unhabituated neighboring groups is difficult. Studies of encounters have yielded a wide range of observations (aggressive, neutral, communicative, or affiliative) across gibbon species and geographic regions. As it is important to understand behavioral ecology and social relationships among gibbon groups, we studied three Northern Gray gibbon groups (Hylobates funereus) in the Danum Valley Conservation Area (DVCA), Malaysia and observed their interactions with neighboring groups. From 2001 to 2020, three groups were followed for 162 days (2236.4 h), and we observed 30 instances of encounters at the range boundary or intrusions between a study group and a respective neighboring group. Neutral or communicative encounters were observed in most cases, with the exception of one instance of aggressive encounter (chasing). Gibbons interacted through particular vocalizations (termed songs) in many cases. We report details of some characteristic interactions among gibbon groups during encounters at the range boundary or intrusions. Regarding intrusions, we observed an unusual instance where a neighboring group intruded deep into the study group’s territory, and the neighboring group did not respond to the songs of the resident group. Considering that no physical fighting occurred during encounters or intrusions, gibbon groups in the DVCA seem to be non-aggressive toward each other. We briefly discuss possible explanations for such non-aggressive relationships among gibbon groups.

Animal personality is defined as behavior that is consistent across time and context. Ecological and evolutionary pressures might exert sexually dimorphic effects on personality traits. In this study, variations in docility and exploratory behaviors of male and female plateau zokor (Eospalax baileyi) in two populations from different geographical sites were quantified during their breeding season, using bag and open field test. We observed significant repeatability of behaviors in the bag and open field test, except for sniffing behavior in zokors from TZ site. We found that sex influences the personality traits of plateau zokors more than geographical variation in both the bag and open field test. Females had a higher docility than males in the bag test. The findings of this study emphasize the importance of considering plateau zokors’ sex and personality traits when assessing their fitness, behavior, or suitability for behavioral future research work.

The impact of re-introduction of a temporally separated individual to a group on social integration and hormone levels is an important topic in terms of the management and welfare of captive animals. Using two cases in which a temporally separated male re-joined an all-male group of captive chimpanzees, Pan troglodytes, we investigated how social reunion affected social interactions and salivary steroid hormone levels (C, cortisol; T, testosterone). In both cases, social reunion was conducted over three stages, separation, acclimation, and reunion. In both cases, behavioral observations revealed increased agonism and tension reduction after the reunion, suggesting that the reunion induced reformation of social relationships. In both cases, the separated male showed an increased C level at the acclimation stage, in which the separated male was moved to its original indoor room and released solely into an outdoor compound. The T level did not vary among males or stages, but increased for the re-joined male after reunion in one of the two cases. This study suggests that the relationships between hormones and behavior during a reunion could be affected by multiple factors and that special attention should be paid to the acclimation rather than characteristics of social reunion, to ensure the success of member reunion.

Abstract

Species are facing environmental challenges caused by rapidly changing environments. Globally, extreme weather events, like droughts or extreme rainfall, are increasing in frequency. Natural selection usually acts slowly, while adaptations through phenotypic plasticity are limited. Therefore, organisms may utilise other mechanisms to cope with such rapid change. Cooperative breeding is hypothesised to be one such mechanism, as helpers could increase survival probabilities of offspring, especially in harsh years. Rainfall is a cue for onset of breeding in many tropical species, to ensure young are born when food abundance is highest. Using 21 years of data, we investigate the effect of rainfall on social behaviour and life history in the insectivorous Seychelles warbler (Acrocephalus sechellensis), a facultative cooperative breeder. We found that low rainfall is associated with reduced reproductive output and possibly with decreased survival. However, there were no statistical differences in response between groups with helpers, groups with only non-helping subordinates, and breeding pairs without subordinates. With low rainfall, more sons (the sex less likely to help) were produced, and those subordinate males already present were less likely to help. Thus, in contrast to expectations, cooperative breeding does not seem to buffer against harsh environments in Seychelles warblers, indicating that group living may be costly and thus not a mechanism for coping with changing environments. Our study showed that the interaction between the environment and life histories, including social behaviour, is complex, but that this interaction is important to consider when studying the impact of changing environments on species survival.

Active scent marking with urine has been described in a number of mammal species, including felids. In Eurasian lynx (Lynx lynx), scent marking plays a role in intra-sexual competition and territory defence as well as in attracting sexual partners during the mating season. Marking is most frequent during the mating season and least frequent during the period when females give birth and lactate. Males generally mark more frequently than females and resident animals mark more frequently than dispersers. Juveniles have never been recorded actively marking. Here, however, we present a well-documented case of an actively marking juvenile lynx. Lynx females Koka and Baronka were born in 2019 to mother Nela, who disappeared in December 2019. Nela’s territory stayed vacant, with her juvenile daughters being the only females recorded there. On the 30^th March 2020, during the mating season, Koka was recorded on a camera trap video actively marking with urine, rubbing her face and again marking with urine on a rock. On the following day, she again marked with urine on the same marking site. After that, Koka left the area and the former territory of Nela was taken over by Baronka. In the BBA lynx population, juvenile lynx females were documented to successfully reproduce. This poses the question of whether their adult-like marking behaviour should be explained in the context of early reproduction, or if it has other reasons. Neither Koka nor Baronka successfully reproduced with the local male during their first year of life, but that does not mean they did not try to attract him by marking. Also, juveniles’ competition over the territory left vacant by their mother is a feasible explanation. We suggest that high population turnover may result in unusual social situations, with juveniles consequently performing unusual behaviour. This does not have to be related to early reproduction.

In many animals, vocalizations are necessary for social interactions to occur; however, anthropic noise can pose a problem as it can disrupt acoustic communication. Oscine birds display a variety of strategies to presumably increase the chances of detection in noisy habitats. On the other hand, suboscines, a group of birds with arguably less vocal flexibility, have been less studied, and we have a poor understanding of the strategies that they may use to cope with noise. Anecdotal evidence suggests that vermilion flycatchers (Pyrocephalus rubinus), a suboscine that produces song bouts, interrupts its bouts in the presence of sudden urban noise (SUN, e.g., when a car passes by), avoiding peak noise. To test this idea, we conducted a playback experiment on 27 free-living males. We recorded the song bouts of each individual: before playback, during SUN playback, and after playback. Ambient noise and artificial light at night (ALAN) have been shown to influence bird singing. To evaluate if there is an association between these pollutants and birds’ response to SUN, we also measured mean ambient noise, ambient noise coefficient of variation, and ALAN in the males’ territories. We found that birds sang shorter bouts during the SUN treatment. Song bout length during the SUN treatment was not associated with mean noise levels or coefficient of variation in males’ territories; however, it was positively associated with ALAN. This result was dependent upon an influential point and should be taken cautiously. We found no association between singing recovery (latency to sing and song bout length after SUN relative to before SUN) and mean ambient noise, ambient noise coefficient of variation, and ALAN. Our results show SUN-induced temporal singing flexibility and suggest that vermilion flycatchers are well adapted to acoustically polluted environments, with males living in territories with more light pollution possibly being less affected by traffic noise peaks. A previous study showed that song bout length is an important signal during intra-sexual interactions; interrupting this acoustic component may have important consequences during social interactions.

Abstract

There is growing concern that anthropogenic noise has various deleterious effects on wildlife in urban environments. In humans, it has been suggested that anthropogenic noise exposure during childhood can have long-term effects on cognitive processes in adulthood. Here we tested if urban noise impacts avian cognitive performance by testing adult zebra finches (Taeniopygia guttata) on several cognition tasks in the presence or absence of urban noise playback. We also tested if urban noise impacts growth and cognitive development by testing adult zebra finches on cognition tasks after exposing them to urban noise, pink noise, or no noise during their first 90 days of life. We found that urban noise exposure marginally reduced cognitive performance during tests of a novel motor skill but did not reduce performance during tests of color association learning or spatial memory tasks. We found that urban noise exposure during development marginally affected cognitive performance in adulthood on a color association task. While urban noise exposure during development did not affect adult body size, treated males and females developed less bright bill coloration and redder bills, respectively, than untreated birds. Our results suggest that urban noise exposure may affect morphological traits, such as bill color, that influence social interactions and mate choice. Future studies should examine how noise exposure affects other cognitive behaviors, such as social behavior, and how social behavior in turn might exacerbate or mitigate negative effects of noise.