Social behavior in animals

Tactical multimodal signalling in birds: facultative variation in signal modality reveals sensitivity to social costs

by K-lynn Smith

Songs, scents, and senses: Sexual selection in the greater sac-winged bat, Saccopteryx bilineata.

by Mirjam Knörnschild

Voigt C, Behr O, Caspers B, von Helversen O, Knörnschild M, Mayer F, Nagy M (2008) Songs, scents, and senses: Sexual selection in the greater sac-winged bat, Saccopteryx bilineata. Journal of Mammalogy 89: 1401-1410.

Like many other mammals, Saccopteryx bilineata exhibits a polygynous mating system, in which each male defends a group... more Like many other mammals, Saccopteryx bilineata exhibits a polygynous mating system, in which each male defends a group of females called a harem. Colonies consist of several harems, and nonharem males roost adjacent to harems. Unlike most other mammals, females disperse from their natal colony and most juvenile males remain in it. Thus, colonies consist of patrilines, which promotes intense local mate competition. Females are in estrus during a few weeks at the end of the rainy season. Mating is most likely initiated by females and preceded by intense courtship displays of males. Forty percent of colony males do not sire any offspring during their tenure in the colony, whereas a few males can sire up to 6 offspring in a single year. Males use olfactory, visual, and acoustic signals for courtship, and they demonstrate territory ownership by scent marks, low frequency calls, and visual displays. Harem males sire on average more offspring than do nonharem males but produce only 30% of the offspring within their own harem territory, with 70% being sired by other harem males or nonharem males. Reproductive success of males increases with decreasing size, fluctuating asymmetry, and fundamental frequency of territorial calls. In addition, females that are closely related to the harem holder are more likely to mate with other males than with the harem holder. Sexual selection in S. bilineata is most likely influenced by intense local mate competition caused by scarce roosts and the patrilineal organization of colonies.

Remaining cryptic during motion – behavioral synchrony in the proboscis bat, Rhynchonycteris naso.

by Mirjam Knörnschild

Knörnschild M, Harview C, Moseley R, von Helversen O (2009) Remaining cryptic during motion – behavioral synchrony in the proboscis bat, Rhynchonycteris naso. Acta Chiropterologica 11: 208-211.

Duration of courtship displays corresponds to social status in male sac-winged bats, Saccopteryx bilineata.

by Mirjam Knörnschild

Knörnschild M, Fulmer A, von Helversen O (2010) Duration of courtship displays corresponds to social status in male sac-winged bats, Saccopteryx bilineata. Canadian Journal of Zoology 88: 589-594.

In species with complex courtship displays, male courtship performance is often used by females to assess male... more In species with complex courtship displays, male courtship performance is often used by females to assess male quality. The greater sac-winged bat, Saccopteryx bilineata (Temminck, 1883), lives in a harem-based resource-defence polygyny. Courting males perform complex hover displays in front of roosting females. Males differ in their social status by having females permanently or sporadically in their dayroost territory (harem males vs. non-harem males). We compared the frequency and duration of hover displays from harem and non-harem males in free-living colonies. Male social status was correlated with male age and the number of females being courted; thus these two effects were removed in order to compare the frequency and duration of hover displays for harem and non-harem males. The frequency of hover displays per hour did not differ between harem and non-harem males whereas the mean duration of hover displays was linked to male social status, with harem males exhibiting significantly longer hover displays than non-harem males. When analysing each social status separately, the hover display duration of both harem and non-harem males was neither influenced by the number of competing males nor by the number of females being courted. Mage age did not influence the hover display duration of non-harem males; however, it had a significant effect on the hover display duration of harem males, with older harem males hovering significantly longer than younger harem males. Since females are free to choose in which male territory to roost, they might use the duration of hover displays to evaluate the quality of courting males.

The ontogeny of courtship behaviors in bat pups (Saccopteryx bilineata).

by Mirjam Knörnschild

Strauss M, von Helversen O, Knörnschild M (2010) The ontogeny of courtship behaviors in bat pups (Saccopteryx bilineata). Behaviour 147: 661-676.

In mammals, adult behaviour patterns are often expressed by juveniles throughout ontogeny. In bats, many social... more In mammals, adult behaviour patterns are often expressed by juveniles throughout ontogeny. In bats, many social behaviours develop before pups are weaned, but the ontogeny of social
behaviours in juvenile bats is largely unexplored. We studied bat pups’ social behaviour, specifically the solicitations for maternal care in the greater sac-winged bat, Saccopteryx bilineata. Solicitation periods were prolonged (up to 25 min) and consisted of conspicuous behavioural interactions between pups and their mothers. Since solicitation periods could be initiated by pups or mothers, their duration is probably not caused by a conflict over nursing alone. Solicitation periods were the second most prevalent use of activity time in pups. Some pup behaviours resembled the courtship behaviours of adult males and these incipient courtship behaviours occurred most often within solicitation periods. Both length and complexity of solicitation periods increased significantly during ontogeny but there was no significant difference between male and female pups. Also, the activity outside of solicitation periods was not significantly different between pups of both sexes, even though their activity differs remarkably as adults. Prolonged solicitation periods of S. bilineata pups might be comparable to mammalian play and potentially function as practice for adult courtship behaviours.

Intracolonial social distance, signalling modality and association choice in the greater sac-winged bat (Saccopteryx bilineata).

by Mirjam Knörnschild

Fulmer A, Knörnschild M (2011) Intracolonial social distance, signalling modality and association choice in the greater sac-winged bat (Saccopteryx bilineata). Journal of Ethology 30: 117-124.

Understanding patterns and motivations for social spacing greatly illuminates the structure and internal dynamics of... more Understanding patterns and motivations for social spacing greatly illuminates the structure and internal dynamics of given groups or social systems. The highly social, polygynous greater sac-winged bat, Saccopteryx bilineata, represents an excellent model for social spacing analysis, since the choice of individual roost-sites within a day-roost constitutes an enduring, often repeated decision about relative proximity to conspecifics. Day-roost colonies consist of one or multiple harem groups, each with several females and a single male. Additionally, non-harem males without females may be present. A social-distance-time-budget metric revealed that harem males, females, and non-harem males differed significantly in their respective spatial associations while roosting. Harem males and females were most closely associated, with harem males located at the center of harems instead of at the borders. Non-harem males associated significantly closer with one another than with harem females that they were trying to access. The signaling modality mediating social interactions depended on the respective social distances between communicating bats. Our results suggest a concentric social organization based around harem males, which may select roost sites in closest possible proximity to females to enhance courtship signal strength. This constitutes an interesting deviation from the normative form of harem maintenance, patrolling borders, in mammals.

Sexually selected infanticide in a polygynous bat

by Mirjam Knörnschild

Knörnschild M, Ueberschaer K, Helbig M, Kalko EKV (2011) Sexually selected infanticide in a polygynous bat. PLoS One 6: e25001.

Adult individuals of many species kill unrelated conspecific infants for several adaptive reasons ranging from... more Adult individuals of many species kill unrelated conspecific infants for several adaptive reasons ranging from predation or resource competition to the prevention of misdirected parental care. Moreover, infanticide can increase the reproductive success of the aggressor by killing the offspring of competitors and thereafter mating with the victimized females. This sexually selected infanticide predominantly occurs in polygynous species, with convincing evidence for primates, carnivores, equids, and rodents. Evidence for bats was predicted but lacking. Here we report the first case, to our knowledge, of sexually selected infanticide in a bat, the polygynous white-throated round-eared bat, Lophostoma silvicolum. Behavioral studies in a free-living population revealed that an adult male repeatedly attacked and injured the pups of two females belonging to his harem, ultimately causing the death of one pup. The infanticidal male subsequently mated with the mother of the victimized pup and this copulation occurred earlier than any other in his harem. Our findings indicate that sexually selected infanticide is more widespread than previously thought, adding bats as a new taxon performing this strategy. Future work on other bats, especially polygynous species in the tropics, has great potential to investigate the selective pressures influencing the evolution of sexually selected infanticide and to study how infanticide impacts reproductive strategies and social structures of different species.

Seasonal changes in home ranges of Abert's squirrels: impact of mating season

by Andrew Edelman

Edelman, A.J., and J.L. Koprowski. 2006. Seasonal changes in home ranges of Abert’s squirrels: impact of mating season. Canadian Journal of Zoology 84:404-411.

Communal nesting in asocial Abert’s squirrels: the role of social thermoregulation and breeding strategy.

by Andrew Edelman

Edelman, A.J., and J.L. Koprowski. 2007. Communal nesting in asocial Abert’s squirrels: the role of social thermoregulation and breeding strategy. Ethology 113:147-154.

Behavioural response of sicklefin lemon sharks Negaprion acutidens to underwater feeding for ecotourism purposes

by Johann Mourier

The feeding of marine predators is a popular means by which tourists and tour operators can facilitate close... more The feeding of marine predators is a popular means by which tourists and tour operators can facilitate close observation and interaction with wildlife. Shark-feeding has become the most
developed provisioning activity around the world, despite its controversial nature. Amongst other detrimental effects, the long-term aggregation of sharks can modify the natural behaviour of the animals, potentially increase their aggression toward humans, and favour inbreeding. During 949 diving surveys conducted over 44 mo, we investigated the ecology and residence patterns of 36 photoidentified adult sicklefin lemon sharks Negaprion acutidens. The group contained 20 females and 16 males. From this long-term survey, we identified 5 different behavioural groups that we described as ‘new sharks’ (7), ‘missing sharks’ (4), ‘resident sharks’ (13), ‘unpredictable sharks’ (5) and ‘ghost sharks’ (7). In spite of movements in and out of the area by some males and females, which were probably related to mating, the general trend was that residency significantly increased during the study, particularly in males, showing a risk of inbreeding due to the reduction of shark mobility. Intraand interspecific aggression was also witnessed, leading to an increased risk of potentially severe bites to humans. Our findings suggest the need for a revision of the legal framework of the provisioning activity in French Polynesia, which could include a yearly closure period to decrease shark
behavioural modifications due to long-term shark-feeding activities.

Murid stress odours: a review and a 'low tech' method of collection

by Jamie Ahloy Dallaire

Mason G, Dallaire J, and Ware N. 2009. Animal Welfare 18(3):301-310.

Stress cues can affect the welfare of animals in close proximity and are possibly useful non-invasive indicators of... more Stress cues can affect the welfare of animals in close proximity and are possibly useful non-invasive indicators of the emitters' welfare. To facilitate their study in murids, we tested whether rats' stress odours could be collected and stored using an enfleurage-type technique. 'Donor' rats were individually exposed to a compound stressor (carried circa 75 m inside a novel container, then euthanised with rising carbon dioxide) while on blotting paper dotted with melted vegetable lard. These sheets were sealed, left at room temperature for 2-5 h, and then 'bioassayed' by a blind observer for their effects on conspecifics. Compared with control sheets (exposed to unstressed rats, to CO₂ alone, or untreated), stress-exposed sheets significantly affected the unconditioned behaviour of 16 pairs of detector rats trained to enter an arena from their home cage to obtain sucrose. When used to line this arena, the stress-exposed sheets significantly increased: i) rats' latencies to eat, to place front feet into, and to completely step into the arena and ii) shuttling movements between arena and home cage. These pilot data thus suggest that odours produced by stressed rats can be simply and successfully collected and stored for several hours, though certain potential confounds (eg urine volume) may conceivably be alternative explanations for the observed effects. Future work should control for urine volume, and assess whether fat is needed for optimal odour absorption by paper and for how long sheets can be stored at various temperatures. Much fundamental work is also still needed on the nature, functions, and sources of stress odours.

Spacing behaviour of male pheasants, Phasianus colchicus, in relation to dominance and mate acquisition

by Mats Grahn

Cross-modal individual recognition in domestic horses (Equus caballus)

by Leanne Proops

Antics of ants: Ants as agents of bioturbation in a midden deposit in southeastern Queensland (PROOF)

by Andrew Robins

Robins, R. & Robins, A. "The antics of ants: ants as agents of bioturbation in a midden deposit in Southeast Queensland". Environmental Archaeology, 16(2),pp. 151-161 http://www.ingentaconnect.com/content/maney/env/2011/00000016/00000002/art00007?crawler=true

During salvage excavations of an Aboriginal shell midden at Hollywell, on the Gold Coast of Queensland, ant activity... more During salvage excavations of an Aboriginal shell midden at Hollywell, on the Gold Coast of Queensland, ant activity was noted as a contributor to both bioturbation, and to the introduction of modern material, including metal fragments, plastic, nylon fishing line and cotton thread into the deposit. This material was found at depths of up to 400 mm and adjacent to excavation units with shells with a calibrated age of 1050–900 BP. These observations prompted the development of a small experiment to illustrate the impact that one species of common Australian ant observed on site, the green-head ant (Rhytidoponera metallica), can have on cultural material in sandy deposits.

Friendship affects gaze following in a tolerant species of macaque, Macaca nigra

by Jerome Micheletta

Animal Behaviour, Volume 83, Issue 2, February 2012, Pages 459–467, DOI: 10.1016/j.anbehav.2011.11.018

Gaze following, the ability to follow the direction in which others are looking, is thought to allow individuals to... more Gaze following, the ability to follow the direction in which others are looking, is thought to allow individuals to acquire valuable information from their physical and social environment. Recent studies, using artificial stimuli, showed that gaze following can be modulated by social factors such as dominance or social context, suggesting the importance of integrating these factors in future cognitive studies to understand better the evolution and function of gaze following. Whether this finding still holds true when animals are tested with conspecifics is unknown. Moreover, additional social factors remain to be tested. Testing live conspecifics, we show that friendship (i.e. strong positive bonds between individuals) improved gaze-following responses in a tolerant primate: the crested macaque. Subjects did not follow the gaze of friends more often, but in dyads characterized by a high friendship index, subjects were quicker to react to gaze cues. The increased social tolerance characteristic of crested macaques’ social relationships may lessen the constraints imposed by dominance and kinship, thus allowing sociocognitive abilities to be better used among friends. Together with previous findings, our results suggest the importance of relationship quality and species’ social style in shaping primate cognition.

Conventional tagging and acoustic telemetry of a small surgeonfish, Zebrasoma flavescens, in a structurally complex coral reef environment

by Jeremy T. Claisse

Claisse, J.T., T.B. Clark, B.D. Schumacher, S.A. McTee, M.E. Bushnell, C.K. Callan, C.W.  Laidley and J.D. Parrish (2011) Conventional tagging and acoustic telemetry of a small surgeonfish, Zebrasoma flavescens, in a structurally complex coral reef environment. Environmental Biology of Fishes. 91:185-201

Baeza, J.A. and C. Piantoni. 2010. Sexual system, sex ratio and group living in the shrimp Thor amboinensis (De Man): relevance to resource-monopolization and sex-allocation theories. Biological Bulletin 219: 151–165.

by Antonio Baeza

Do singing rock hyraxes exploit conspecific calls to gain attention?

by Amiyaal Ilany

Signal detection theory predicts that signals directed at distant or busy receivers in noisy backgrounds will begin... more Signal detection theory predicts that signals directed at distant or busy receivers in noisy backgrounds will begin with an alert component, in order to draw attention. Instead of an alert component, however, animals could get the same effect by using an external stimulus. Here we combined observations of free-living rock hyraxes (Procavia capensis) with playback experiments to elucidate the circumstances under which males begin singing. We show that males sing following hyrax pup screams, which elicit a strong response from hyraxes within hearing distance, which are potential receivers. We hypothesize that singers enhance their singing display by exploiting the rarely emitted pup screams. To our knowledge, our findings are the first indication that animals may enhance signal reception by exploiting conspecifics' signals and the differential attention to these signals. We suggest that the utilization of external stimuli by signalers may be widespread, as an adaptive strategy for communication in complex environments.

Group structure in a restricted entry system is mediated by both resident and joiner preferences

by Lyndon Alexander Jordan

The effects of familiarity and social hierarchy on group membership decisions in a social fish

by Lyndon Alexander Jordan