Showing papers in "Behaviour in 2021"

Musth and sexual selection in elephants: a review of signalling properties and potential fitness consequences

Abstract: Sexual selection mediated by multimodal signals is common among polygynous species, including seasonally breeding mammals. Indirect benefit models provide plausible explanations for how and why mate selection can occur in the absence of direct benefits. Musth — an asynchronous reproductive state in male elephants — facilitates both inter- and intrasexual selection via indirect benefits, and it is further communicated through a multimodal signal. In this review, we synthesise existing evidence that supports the hypothesis that musth is a multimodal signal subject to sexual selection and that male elephants increase their direct fitness by propagating this signal while females accrue indirect benefits. Musth is characterised by a suite of physiological and behavioural changes, serving to facilitate copulation between the sexes, and via multisensory modalities musth conveys honest information about the condition of a male. Female elephants mate preferentially with musth males, increasing their own fitness in the absence of direct benefits. In addition, musth resolves dynamic dominance hierarchies among male elephants and often eliminates the need for costly physical combat. Future work in this field should investigate potential postcopulatory selection mechanisms in elephants, including sperm competition and cryptic female choice. These topics join other fundamental questions related to sexual selection, signalling, and indirect benefits that are still unanswered in elephants.

Submission signals in animal groups

Abstract: Aggression is costly, and animals have evolved tactics to mitigate these costs. Submission signals are an underappreciated example of such adaptations. Here we review submissive behaviour, with an emphasis on non-primates. We highlight the design of submission signals and how such signals can reduce costs. Animal societies necessitate frequent social interactions, which can increase the probability of conflict. Where maintaining group proximity is essential, animals cannot avoid aggression by fleeing. Mutual interest between group members may also select for efficient conflict avoidance and resolution mechanisms. As a result, submission signals may be especially well developed among group living species, helping social animals to overcome potential costs of recurring conflict that could otherwise counter the benefits of group living. Therefore, submission signalling can be a crucial aspect of social living and is deserving of specific attention within the broader context of social evolution and communication.

Reinstating reptiles: from clueless creatures to esteemed models of cognitive biology

Abstract: Non-avian reptiles have long been neglect in cognitive science due to their reputation as slow and inflexible learners, but fortunately, this archaic view on reptile cognition is changing rapidly. The last two decades have witnessed a renewed interest in the cognitive capacities of reptiles, and more ecologically relevant protocols have been designed to measure such abilities. Now, we appreciate that reptiles possess an impressive set of cognitive skills, including problem-solving abilities, fast and flexible learning, quantity discrimination, and even social learning. This special issue highlights current research on reptiles in cognitive biology and showcases the diversity of research questions that can be answered by using reptiles as study model. Here, we briefly address (the key results of) the contributing articles and their role in the endeavour for total inclusion of reptiles in cognitive biological research, which is instrumental for our understanding of the evolution of animal cognition. We also discuss and illustrate the promising potential of reptiles as model organisms in various areas of cognitive research.

Zoo-housed female chimpanzee adopts local female-specific tradition upon immigrating into a new group

Abstract: Wild female chimpanzees typically migrate to a neighbouring community at the onset of sexual maturity, a process that can be dangerous and unpredictable. To mitigate the risk of rejection in the new community, immigrants may employ several behavioural strategies. During the integration of two chimpanzee females at Royal Burgers’ Zoo (Arnhem, The Netherlands) one of the immigrant females rapidly copied a local tradition — the crossed-arm walk — which has been present in the group for over 20 years. She copied the behaviour after meeting only one resident female, and showed the behaviour frequently throughout a 6-month observation period following the introduction. The other immigrant female never adopted the crossed-arm walk, highlighting the variation in behaviour by immigrants upon integration, as well as the potential associated consequences: in a separate observation period 2 years later, the female who copied the local tradition appeared more socially integrated than the other immigrant female.

Conspecific scarring on wild belugas (Delphinapterus leucas) in Cunningham Inlet

Abstract: Intra-specific aggression is not frequently observed in wild cetaceans, including belugas. One proxy, identified in past research, that indicates past aggressive behaviour is the presence of rake marks (scars left on skin by the teeth of conspecifics). Behavioural observations of belugas, compared to bottlenose dolphins, suggest that belugas engage in less physically aggressive behaviour; yet, a detailed study of beluga aggressive behaviour remains to be conducted. Beluga intra-specific aggression was assessed by scoring photographs taken from July to August in 2015 at Cunningham Inlet, Canada for the presence/absence and body location of rake marks. Of the 252 belugas analysed, 44% had rake marks. The results suggest that physical aggression occurs comparatively less with only half of the observed beluga population having rake marks compared to almost all bottlenose dolphins previously surveyed. We suggest social structure, skin pigmentation, and/or species-specific behaviours as explanations for the differences in rake marks among species.

Alternate without alternative: neither preference nor learning explains behaviour of C57BL/6J mice in the T-maze

Abstract: In rodents, the T-maze is commonly used to investigate spontaneous alternating behaviour, but it can also be used to investigate preference between goods. However, for T-maze preference tests with mice there is no recommended protocol and researchers frequently report reproduction difficulties. Here, we tried to develop an efficient protocol with female C57BL/6J CrL mice for preference tests. We used two different designs, adapting habituation, cues and trial timing. However, in both experiments mice did not show any preference, although we used goods which we knew mice find rewarding. Instead, they alternated choices indicating that exploratory behaviour overruled preference. We argue that this behavioural strategy has evolved as an adaptive trait in saturated conditions where there is no need to take the reward immediately. Therefore, we deem the T-maze unsuitable for preference testing with the procedures we used here.

Lizards as models to explore the ecological and neuroanatomical correlates of miniaturization

Abstract: Extreme body size reductions bring about unorthodox anatomical arrangements and novel ways in which animals interact with the environment. Drawing from studies of vertebrates and invertebrates, we provide a theoretical framework for miniaturization to inform hypotheses using lizards as a study system. Through this approach, we demonstrate the repeated evolution of miniaturization across 11 families and a tendency for miniaturized species to occupy terrestrial microhabitats, possibly driven by physiological constraints. Differences in gross brain morphology between two gecko species demonstrate a proportionally larger telencephalon and smaller olfactory bulbs in the miniaturized species, though more data are needed to generalize this trend. Our study brings into light the potential contributions of miniaturized lizards to explain patterns of body size evolution and its impact on ecology and neuroanatomy. In addition, our findings reveal the need to study the natural history of miniaturized species, particularly in relation to their sensory and physiological ecology.

Dealing with the unexpected: the effect of environmental variability on behavioural flexibility in a Mediterranean lizard

Abstract: Harsh and variable environments have been hypothesized to both drive and constrain the evolution towards higher cognitive abilities and behavioural flexibility. In this study, we compared the cognitive abilities of island and mainland Aegean wall lizards (Podarcis erhardii), which were expected to live in respectively a more variable and a more stable habitat. We used four proxies of behavioural flexibility: a neophobia assay, a problem-solving test and a spatial + reversal learning task. Surprisingly, the two populations did not differ in neophobia or problem-solving. Insular lizards, however, outperformed mainland conspecifics in an initial spatial learning task, but were less successful during the subsequent reversal learning. Our results thus seem to indicate that the effect of environmental variability on cognition is complex, as it may favour some, but not all aspects of behavioural flexibility.

Contribution to the special issue on Reptile cognition: Chemically mediated self-recognition in sibling juvenile common gartersnakes (Thamnophis sirtalis) reared on same or different diets: evidence for a chemical mirror?

Abstract: Although self-recognition or self-awareness has been studied with the visually-based mirror test, passed by several species, primarily apes, the possibility of a chemically-based analogue is controversial. Prior studies suggested that chemical self-recognition may occur in some squamate reptiles. To evaluate this possibility, we studied 24 individually housed gartersnakes, Thamnophis sirtalis, raised from birth on either earthworm or fish diets and tested 12 male and 12 female snakes with cage liners that were either clean, their own, or from same-sex siblings fed their own or the opposite diet. Tongue flicking and activity were recorded in 30-minute video-recorded trials in a balanced design. After initial habituation to the stimuli, male, but not female, snakes discriminated between their own stimuli and those from littermates fed the same diet. Combined with other data and studies, the possibility that a chemical ‘mirror’ form of self-recognition exists in squamate reptiles is supported.

Prospective evolutionary drivers of allocare in wild belugas

Abstract: Allocare, investment in offspring from non-parents, poses an evolutionary enigma. While the fitness trade-offs driving parental care are universal, alloparents may be driven by kin selection, reciprocation, the need to acquire parenting skills (‘learning-to-parent’), an indiscriminate attraction towards infants (‘natal attraction’), or a combination of multiple drivers. Among belugas (Delphinapterus leucas), allocare has been reported in wild and captive populations, but its underlying mechanisms remain untested. Using over 1800 focal observations, we quantified alloparental associations in St. Lawrence Estuary (SLE) belugas to determine whether the learning-to-parent and natal attraction hypotheses are consistent with patterns of allocare in this population. We found that subadults showed little interest in providing allocare and that alloparental investment remained constant across offspring age classes. As the observed patterns of allocare are inconsistent with both the learning-to-parent and natal attraction hypotheses, allocare in SLE belugas is likely driven by kin selection, reciprocation, or a combination thereof.

Sociosexual behaviour in wild chimpanzees occurs in variable contexts and is frequent between same-sex partners

Abstract: Many animals engage in sociosexual behaviour, including that between same-sex pairs. Bonobos (Pan paniscus) are famous for their sociosexual behaviour, but chimpanzees (Pan troglodytes) apparently do not engage in sociosexual behaviour frequently. However, sociosexual behaviour in chimpanzees may have been overlooked. We observed 584 instances of sociosexual behaviour in chimpanzees at Ngogo, Kibale National Park, Uganda during three years of study. All ages and sexes engaged in sociosexual behaviour, which included mounting, touching of genitals, and pressing genitals together. Most sociosexual behaviour was between adult males. Sociosexual behaviour was often during tense contexts, such as subgroup reunions and during territorial behaviour. Among males, grooming and dominance rank relationships do not explain patterns of sociosexual behaviour. Although sociosexual behaviour may be less frequent in chimpanzees than in bonobos, and bonobos remain distinct in their genito-genital rubbing, our findings suggest that sociosexual behaviour is a regular part of chimpanzee behaviour.

The role of touch in captive and semi-captive Antillean manatees (Trichechus manatus manatus)

Abstract: Tactile signals have been neglected in aquatic animal studies despite being a major communication modality. We investigated Antillean manatees’ tactile behavioural repertoire and budget in captivity (7-females and 4-males) and semi-captivity (4-males) in Brazil. We detected 17 tactile behaviours (14.03% of the activity budget) with social, self-maintenance, or environmental exploration functions. The observation method influenced the detection of self-maintenance behaviours — focal animal and ad libitum detected more of these behaviours than scan sampling. Age, sex, housing, and centre routines influenced the tactile repertoire. The captive females and semi-captive males tactile patterns differed, suggesting that sex and animal-pool density play a role in tactile patterns. We recommend carefully choosing the observation method when investigating functional categories of manatee tactile behaviours. The monitoring and stimulation of manatee tactile behaviours should integrate rehabilitation and reintroduction practices. Environmental enrichment may stimulate tactile behaviours related to habitat exploration, key behaviours in aiding manatee navigation.

Sex differences in response to environmental and social breeding cues in an amphibian

Abstract: The relative influence of climatic and social factors on sex-specific variation in reproductive behaviour remains poorly understood. Here, we examine the influence of multiple climatic cues in combination with a social cue on the reproductive behaviours of males and females in a terrestrial breeding toadlet (Pseudophryne coriacea). Over a 115-day breeding season, arrival patterns of each sex, and male calling activity, were recorded daily, while climatic variables were logged continuously. Multivariate analysis showed that arrival of males at the breeding site, as well as male nightly calling activity, were most strongly influenced by a climatic variable (rainfall). By contrast, female arrival was strongly correlated with a social variable (male calling activity), with abiotic conditions having no influence, other than a moderate influence of lunar phase (lunar illumination). These results suggest that cues used for breeding are sex specific and provide new evidence that combinations of climatic and social cues can be integrated into breeding decisions.

Pattern biases, but not positional cues, influence learning in the little brown skink, Scincella lateralis

Abstract: Studies of many lizard species have established they are capable of learning to escape to one specific retreat out of several available retreats and will escape to it when subjected to a simulated predator attack. Recently, researchers have focused on the processes involved in learning, including what cues lizards use to learn to escape to a retreat. Previous work on the little brown skink lizard, Scincella lateralis, has shown that it is capable of learning to escape to a specific retreat when it has gained prior experience with its environment and that its performance is better when a retreat is associated with a vertical stripe local cue than when the retreat was associated with a horizontal stripe one. Here I report the results of two additional experiments undertaken to gain a better understanding of how little brown skinks react to cues in their environment. In Experiment 1, the positional cue test, I tested if little brown skinks could be trained to escape to a specific retreat when the only cue available was a positional cue that lizards could use to orient themselves by conducting a series of trials in which little brown skinks were trained to escape to the retreat to the left or the right of a vertical cylinder. Only 2 of the 16 (12.5%) little brown skinks met the learning criterion. This was not significantly different from what is expected if lizards chose their retreats at random suggesting little brown skinks are poor at learning when only a positional cue is available. In Experiment 2, the pattern bias test, I tested if the little brown skink’s superior performance learning to escape to a retreat with a vertical stripe cue in previous experiments was due to a bias for vertical stripes (or against horizontal stripes) through a series of trials in which little brown skinks had to choose between two escape retreats: one with a vertical stripe local cue and the other with a horizontal stripe local cue. A significant bias for the vertical stripe local cue retreat was found among 24 adults, but not among 12 neonates. These results suggest pattern bias among adult little brown skinks impacted the results of previous studies. The possibility that lizards may have biases for colours or shapes and that these biases may have an impact on learning studies is discussed.

Does anthropogenic noise promotes advertisement call adjustments in the rubí poison frog Andinobates bombetes

Abstract: Anthropogenic noise, characterized by higher intensities at low frequencies, can restrict acoustic communication between conspecifics and eventually reduce the fitness of populations. We analysed changes in the call features of 52 males of the poison frog A. bombetes subjected to anthropogenic noise through playback experiments. Thirty-one males did not call during playbacks, but the remaining 21 males did. Fourteen of those 21 males increased their dominant call frequency on average 130.76 Hz when exposed to noise. Males did not increase or diminish the emission rate, number of pulses, and duration of their calls. It is possible that males by increasing the frequency of their calls are showing a behavioural strategy that maintain signal-to-noise ratio, which allows them to communicate acoustically in noisy habitats. Further studies are necessary to corroborate this hypothesis given that the magnitude of the increase in call frequency was small (<100 Hz) for most males.

Body size, habitat quality, and territory defense in Bachman’s sparrow

Abstract: Many wild populations of animals conform to the ideal despotic distribution (IDD) in which more competitive individuals exclude less competitive individuals from high quality resources. Body size and aggressiveness are two important traits for resource defense, and they positively covary so that larger individuals are usually more aggressive. Using Bachman’s sparrows, we tested the hypothesis that larger birds are more aggressive and are thus able to compete for the best quality territories. We found that larger males were more aggressive, and more aggressive birds fledged at least one young. However, we did not find consistent relationships between aggressiveness and habitat characteristics. Our results suggest that Bachman’s sparrows meet most of the predictions of the IDD. Frequent ecological disturbances, such as fires, might disrupt the IDD or make it difficult to detect. Additional studies are needed to test for relationships between ecological disturbances and territorial behaviour.

Parasites differentially impact crayfish personality in different contexts

Abstract: The expression of an individual animal’s behaviour can be placed along many different personality spectra. Parasite load can alter animal behaviour and, thus, fitness. The personality traits of rusty crayfish, Faxonius rusticus, were analysed in three different behavioural contexts: foraging, exploration, and threatened. Each crayfish was tested in each context 3 times, giving a total of 9 assays per crayfish. After assays were completed, crayfish were dissected, and the hepatopancreas of each crayfish was photo analysed to determine the parasite load of the trematode, Microphallus spp. A composite personality score for each assay and parasite load was loaded into a PCA. The PCA model showed that as parasite load increased, crayfish became bolder in threatening contexts and less exploratory in novel environments, whether or not a food stimulus was present. Thus, parasite load alters the placement of crayfish on different personality spectra, but this change is context specific.

Alarm calls of house wrens (Troglodytes aedon bonariae) elicit responses of conspecific and heterospecific species

Abstract: Nesting house wrens (Troglodytes aedon bonariae) use two basic alarm calls (Type I and Type II) when detect a threat near the nest. We experimentally analysed if calls distract predators or serve to recruit other birds to create a mobbing flock to deter predators. The results show that individuals preferentially position themselves in front of the threat, disclosing the location of the nest. Also, using playbacks of house wren alarm calls we found that these calls recruited both conspecific and heterospecific individuals to create a mobbing response. The alarm calls of house wrens seem to fulfil multiple functions, not only conveying information about the threat to their mates and nestling as revealed in previous studies, but also as a signal that attracts the attention of other conspecific and heterospecific individuals and can trigger a mobbing response to deter the predator.

Do long-tailed macaques avoid large heterospecific carcasses?

Abstract: This anecdotal observation details the response of long-tailed macaques (Macaca fascicularis) to a heterospecific carcass. The subgroup of macaques we were following abruptly changed their direction of travel upon reaching a tree line while displaying silent vigilance behaviour. We later discovered a dog carcass in the area and concluded their behaviour may have been in response to the smell of that carcass. The carcass was not visible from the response point at the tree line due to its distance from that point (approximately 30 meters) and the uneven and densely vegetated terrain between. The macaques were therefore most likely responding to scent cues from the carcass. We suggest the observed vigilance behaviour is excessive under a strictly pathogen-avoidance explanation and may be understood as a response to a cue of potential predation risk. We review alternative explanations and suggest future research on nonhuman primate heterospecific carcass avoidance is necessary to fully assess the potential relation to perceived risk of predation.

Drop when the stakes are high : adaptive, flexible use of dropping behaviour by aphids

Abstract: RKH was funded by the Perry Foundation and the University of St Andrews. AJK is supported by the strategic research programme funded by the Scottish Government’s Rural and Environment Science and Analytical Services Division.

Swimming and diving as social play in juvenile rhesus macaques (Macaca mulatta)

Abstract: Although play is ubiquitous throughout the animal kingdom, and in primates especially, the ultimate explanations and proximate mechanisms of play are not well understood. Previous research proposes that primate play may be important for the development of cognitive skills including executive function, emotional regulation, and impulse control, and could help to build social skills and network connections needed in later life. However, many of these hypotheses have not been thoroughly tested. Here, we report observations of novel play behaviour that could provide unique opportunities to explore these hypotheses: young rhesus macaques (Macaca mulatta) engaging in aquatic social play in a naturalistic setting. Based on our observations, we propose that aquatic play has social elements that make it ideal for testing ultimate explanations of primate play and hypotheses about the cognitive mechanisms that support it.

The effects of habituation on boldness of urban and rural song sparrows (Melospiza melodia)

Abstract: As urban development continues to dominate landscapes across the United States, wildlifespecies are changing their behavior in many ways. Urban animals are often bolder, or less fearfulof new stimuli, than rural animals. While natural selection and adaptation can drive behavioralchanges in urban animals, other factors, such as learning or habituation, can also lead tobehavioral modifications. Habituation may play an important role, if urban individuals learnthrough repeated exposure that humans do not represent a threat. To determine how repeatedhuman exposure affects song sparrow (Melospiza melodia) populations in an urban and ruralhabitat, I measured boldness as flight initiation distance (FID), after repeated exposure to a nonthreatening human subject. FID measures the distance between human and bird, at which the bird flies away in fear of disturbance or predation. I collected FID data on male song sparrows in an urban and rural environment over 5 consecutive days. I found that after 5 days of successive trials, FID was individually repeatable in both urban and rural populations. Urban birds had consistently lower FID than their rural counterparts. I also found that FID went down over 5 days of repeated trials in the rural populations, but not the urban. These results suggest that habituation can occur quickly in rural birds and account for the greater boldness we typically see in urban populations.

Ecology and social behaviour of the Mongolian gerbil: a generalised review

Abstract: The present review provides a compilation of the published data on the ecology and social behaviour of Mongolian gerbils. Behavioural observations in the wild show that the Mongolian gerbil is a diurnal social rodent living in extended family groups. Seasonal breeding is typical of Mongolian gerbils in their natural habitat. Social monogamy seems to be characteristic of the Mongolian gerbil reproductive strategy, which however does not exclude facultative polygyny and promiscuity. A typical feature of the space use system in this species is territoriality. Social relationships in family groups may be defined as a subordination hierarchy. The hierarchy order is primarily determined by the age of the animals and maintained chiefly by the subordinates’ behaviour patterns. The complex social organisation in the Mongolian gerbil is characterised by cooperation in different activities. Cooperation appears to enhance the survival of family groups of this species under the extreme climatic conditions of Central Asia.

The voices of an alleged mute: sound emissions in a Tropidurus lizard

Abstract: Although the major Squamata lineages are primarily oriented by chemical or visual sensory systems, many lizards are able to use acoustic information and several species produce sounds. However, while gekkotans are renowned by their complex vocal repertoires, sounds of other lizards are much less known. Herein we characterize the sounds emitted by individuals of Tropidurus catalanensis (Tropiduridae) from southeastern Brazil in response to threat stimuli. Our results revealed that the acoustic display was consistently emitted by adult individuals. The typical sound emission consisted of a single click, very short in duration, and without frequency modulation. This is the first report of sound emission by Tropidurus lizards, expanding the knowledge on the behavioural repertoire of the genus, and contributing to understanding the extension of sound emission in lizards.

Courtship rhythm in Nasonia vitripennis is affected by the clock gene period

Abstract: The clock gene period (per) is a regulator of circadian rhythms but may also play a role in the regulation of ultradian rhythms, such as insect courtship. Males of the parasitoid wasp Nasonia vitripennis court females by performing series of head movements (‘head-nods’) and wing vibrations within repeated cycles. The pattern of cycle duration and head-nod number is species-specific and has a genetic basis. In this study, the possible involvement of per in regulating Nasonia courtship rhythms was investigated in a southern and northern European strain that differ in number and timing of courtship components. Knockdown of per via RNA interference (RNAi) resulted in a shortening of the circadian free running period (tau) in constant darkness (DD), and increased both the cycle duration and the number of head-nods per cycle in both strains. These results point at a role of per in the regulation of ultradian rhythms and male courtship behaviour of N. vitripennis and may contribute to resolving the controversy about the role of per in insect courtship behaviour.

Birds using artificial plants as nesting material

Abstract: Here we present the first cases of birds using artificial plants as nest material. We report our findings for the common coot (Fulica atra) from Leiden, the Netherlands, in 2019. This is the first population of freshwater birds studied for its use of anthropogenic nest materials, and together with another report from the same year, the earliest case of an entire bird population with plastic in all nests. We also report the first artificial plants used as nesting material by birds, and discuss the implications of their usage as such.

Do male Boana goiana (Lutz, 1968) (Anura: Hylidae) discriminate between the calls of neighbours and strangers?

Abstract: Neighbour-stranger discrimination is an important mechanism in social behaviour, as it allows the individual to avoid the high energetic costs of repeated agonistic interactions with neighbours. In some anuran species, the owners of territories respond more aggressively towards strangers than neighbours. Here, we investigated whether gladiator frog, Boana goiana, males discriminate between neighbours and strangers. This is a lek-breeding species; therefore, it does not defend fixed territories which are associated with a specific resource. We conducted a playback field experiment with a repeated-measures design, based on three treatments: (i) neighbour’s call in initial position, (ii) stranger’s call in initial position, and (iii) neighbour’s call in new position. We did not observe any systematic modification in the acoustic properties (call duration, dominant frequency, repetition rate) of the advertisement and short aggressive calls of B. goiana males given in response to our playback treatments. Our results indicate that B. goiana males do not exhibit vocally mediated ‘dear enemy’ relationships. We discuss the possible ecological and social factors that may have impeded the evolution of ‘dear enemy’ relationships in this species.