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Compared to trial-and-error learning, learning from others is often a viable means of adding new adaptive behaviours to an individual's repertoire. This is especially true in long-lived, group-living species that encounter moderate levels of environmental heterogeneity. Here we review the social learning literature that uses bats as models under the framework of Galef (2009) and Laland (2009) to examine when, where, and from whom bats are most likely to learn socially about food and other foraging behaviour. We conclude that evidence exists for bats learning about novel foods from other bats, learning how to handle such food from other bats, and that bats often learn these ways when uncertain about the quality of different foods available. There is also evidence that young bats learn about new foods from their mothers, and that adult bats learn from other adult bats, even other bat species. However, whether bats more likely to learn from familiar individuals or learn about specific foraging areas from others is less established and warrants further research. We also conclude that phyllostomid bats present the best evidence of social learning about food and suggest future research, including investigating the possibility of nonhuman culture, focus on this diverse group. Key words: bats, social learning, information use, food, echolocation, Introduction Dr. Brock Fenton is one of the most influential bat researchers, renowned for his work investigating myriad facets of bat biology, ecology, and conservation, as well as his extensive [...]

This paper reports results of the first range-wide study of the behaviors of free-living wolves in the High Arctic in response to human presence and discusses these behaviors from a conservation perspective. The study focused on wolves believed to have had little, if any, contact with humans and excluded data from areas where wolves have become habituated to people. Data consisted of incidental sightings of wolves on the Canadian Arctic Archipelago and in Greenland from 1819 to 2019. A total of 325 behavioral observations were identified: 163 from Greenland and 162 from Canada. The most commonly reported behaviors (71.4%) involved wolves seeking out humans: coming to campsites, following traveling dog teams, closely approaching a person, and following people. These behaviors are not typical of canids in lower latitudes and have the potential to create conflicts with people who might feel threatened owing to the centuries-old belief that wolves are dangerous. Some Arctic wolves have been shot in perceived self-defense, when in all likelihood the animals were only curious. In addition, aggression directed towards domestic dogs was the most common form of wolf-dog interaction and produced another source of conflict. The findings are important from a conservation perspective because of the small wolf population and the fact that vanishing sea ice is increasing human access to the Arctic wolf range. Appropriate and humanely used hazing techniques and outreach to stakeholders on what constitutes normal Arctic wolf behavior can mitigate the risk of conflict and contribute to the conservation of Arctic wolves on the Canadian Arctic Archipelago and in Greenland, while minimizing the risk that the natural behavior of this subspecies is altered by increased human activity. Key words: Arctic wolf; behavior; conservation; Greenland; Canadian Arctic Archipelago; conflict; hazing; dogs Dans cet article, nous presentons les resultats de la premiere etude a grande echelle sur les comportements des loups en liberte de l'Extreme-Arctique en reponse a la presence humaine et nous discutons de ces comportements du point de vue de la conservation. L'etude portait sur les loups qui semblaient avoir peu, voire pas du tout, de contacts avec les humains et excluait les donnees en provenance d'endroits ou les loups etaient devenus habitues aux gens. Les donnees consistaient en des observations indirectes de loups dans l'archipel Arctique canadien et au Groenland de 1819 a 2019. En tout, 325 observations de comportements ont ete relevees, soit 163 au Groenland et 162 au Canada. Les comportements les plus courants a avoir ete signales (71,4%) concernaient des loups a la recherche d'humains, allant aux campements, suivant des attelages de chiens en deplacement, s'approchant d'une personne de pres et suivant des gens. Ces comportements ne sont pas typiques des canides en plus basses altitudes et ont la possibilite de creer des conflits avec les personnes susceptibles de se sentir menacees en raison de croyances de tres longue date voulant que les loups soient dangereux. Certains loups arctiques ont ete tires en situation d'autodefense perdue quand en realite, ces betes etaient vraisemblablement seulement curieuses. Par ailleurs, les agressions visant les chiens domestiques representaient la forme la plus courante d'interaction loup-chien et produisaient une autre source de conflit. Ces constatations revetent de l'importance du point de vue de la conservation en raison de la petite population de loups et du fait que la disparition de la glace de mer accentue l'acces de l'humain a l'aire de repartition du loup arctique. Des techniques d'effarouchement adequates employees de maniere humaine et la sensibilisation des parties prenantes quant a ce qui constitue des comportements normaux pour le loup arctique peuvent avoir pour effet d'attenuer le risque de conflits et de favoriser la conservation des loups arctiques dans l'archipel Arctique canadien et au Groenland tout en minimisant le risque que le comportement naturel de cette sous-espece soit modifie par l'activite humaine accrue. Mots cles : loup arctique; comportement; conservation; Groenland; archipel arctique canadien; conflit; effarouchement; chiens, Traduit pour la revue Arctic par Nicole Giguere. INTRODUCTION For centuries, sea ice has impeded ship access to large parts of the Arctic. But this formidable barrier to vessels is [...]

Social interactions among animals mediate essential behaviours, including mating, nurturing, and defence.sup.1,2. The gut microbiota contribute to social activity in mice.sup.3,4, but the gut-brain connections that regulate this complex behaviour and its underlying neural basis are unclear.sup.5,6. Here we show that the microbiome modulates neuronal activity in specific brain regions of male mice to regulate canonical stress responses and social behaviours. Social deviation in germ-free and antibiotic-treated mice is associated with elevated levels of the stress hormone corticosterone, which is primarily produced by activation of the hypothalamus-pituitary-adrenal (HPA) axis. Adrenalectomy, antagonism of glucocorticoid receptors, or pharmacological inhibition of corticosterone synthesis effectively corrects social deficits following microbiome depletion. Genetic ablation of glucocorticoid receptors in specific brain regions or chemogenetic inactivation of neurons in the paraventricular nucleus of the hypothalamus that produce corticotrophin-releasing hormone (CRH) reverse social impairments in antibiotic-treated mice. Conversely, specific activation of CRH-expressing neurons in the paraventricular nucleus induces social deficits in mice with a normal microbiome. Via microbiome profiling and in vivo selection, we identify a bacterial species, Enterococcus faecalis, that promotes social activity and reduces corticosterone levels in mice following social stress. These studies suggest that specific gut bacteria can restrain the activation of the HPA axis, and show that the microbiome can affect social behaviours through discrete neuronal circuits that mediate stress responses in the brain. The gut microbiota in mice can modulate social behaviour by influencing activity in stress-related brain areas., Author(s): Wei-Li Wu [sup.1] [sup.2] [sup.3] , Mark D. Adame [sup.1] , Chia-Wei Liou [sup.2] [sup.3] , Jacob T. Barlow [sup.1] , Tzu-Ting Lai [sup.2] , Gil Sharon [sup.1] , [...]

The maintenance of species boundaries when opportunities for admixture are abundant, is a poorly understood phenomenon for many taxa. While many mechanisms for maintaining species boundaries have been described their relative importance depends largely on the particulars of the system in question. Aggregating social behavior can be a means to keep sympatric sister species distinct if it leads to segregation during reproduction. The widespread Caribbean reef gobies Coryphopterus personatus and C. hyalinus are sympatric sister species with nearly identical morphology that spend their entire adult lives in shoals in which reproduction occurs. To date no studies have investigated whether shoals are species-specific, which would be expected if aggregating behavior helps to maintain species boundaries. To address this, the species of individual fishes collected from 16 shoals were identified using morphology, mitochondrial sequence data, and microsatellite allele frequencies. Levels of admixture between the species were also assessed. Shoals were generally composed of both species in similar proportions to their relative abundances on the reef, where the shoals were found, indicating that the species are not behaviorally segregating. For most specimens, morphological, mitochondrial, and nuclear data were congruent with a single species, but 18 individuals showed disagreements with microsatellite genotypes of 16 suggesting some level of historic/contemporary admixture. Of these, two were identified as likely first- or second-generation hybrids or backcrosses. Despite co-occurrence and evidence of some gene flow, the two species show little admixture overall suggesting that microscale differences in breeding site selection, allochrony, and/or cryptic mate choice may play an important role in the maintenance of species boundaries despite cooccurrence well within the range typically thought of as sympatry., Author(s): Jason D. Selwyn [sup.1] , Elizabeth P. Hunt [sup.1] , David S. Portnoy [sup.1] , J. Derek Hogan [sup.1] Author Affiliations: (1) grid.264759.b, 0000 0000 9880 7531, Department of [...]

Ecological segregation has been documented between males and females in different populations of seabirds. Moreover, foraging behaviour and diet have been associated with markers of oxidative status, and have been suggested to be a driver of sex-biased oxidative costs of reproduction in wild marine vertebrates. Nevertheless, the ecological role of sex driving such associations has been little studied. We, therefore, examined whether foraging habitat ([delta].sup.13C), trophic level ([delta].sup.15N), dietary antioxidants (retinol and [alpha]-tocopherol) and oxidative status (antioxidant capacity and oxidative damage, ROM) were ecologically segregated by sex in Magellanic penguins (Spheniscus magellanicus) breeding in Peninsula Valdés (Argentina) visualizing the isotopic, dietary antioxidant, and oxidative status Bayesian spaces as proxies for ecological niches. Our results suggest that specific sexual segregation by ecological niche partially drives the relation between foraging, dietary antioxidants, and oxidative status. The dietary antioxidant niche showed females with extremely low [alpha]-tocopherol levels relative to males, although retinol values seemed to be similar between sexes. Higher trophic levels preys (high [delta].sup.15N) were positively associated with [alpha]-tocopherol in males suggesting that their greater dependence on the Argentinian hake (a benthopelagic fish rich in [alpha]-tocopherol) led to a higher absorption of specific dietary antioxidants than females. In addition, a positive relation between [alpha]-tocopherol and ROMs in males suggested that their benthic foraging was associated with greater oxidative damage, and that higher levels of alpha-tocopherol in benthopelagic fish were not sufficient to prevent higher levels of oxidative damage associated with the consumption of such fish. Overall, sex-biased dietary antioxidant niche linked with sex-specific ecological segregation., Author(s): Roger Colominas-Ciuró [sup.1] [sup.7] , Marcelo Bertellotti [sup.2] [sup.3] , Verónica L. D'Amico [sup.2] , Eliana Carabajal [sup.4] , Jesús Benzal [sup.5] , Virginia Vidal [sup.1] , Miguel Motas [...]

Wild birds are sometimes brought into captivity in order to conduct more controlled experiments, then released. Follow up work investigating how successful these birds are at reintegrating into their original habitats are rare. Here, I investigate the reintegration success of 13 New Caledonian Crows (Corvus moneduloides) who spent from 4-210 days in a large outdoor aviary in 2012 and 2014, then were released at their capture site. Five of the crows were monitored by telemetry for 2 weeks after their release in November 2014. In March and April 2015, 12 of the 13 crows were recorded at feeding sites where they were captured. The released crows showed a high degree of site fidelity and appeared to rapidly reintegrate with resident crows in the area. There were two cases of released crows successfully breeding. Long-term stay in captivity appears to have minimal impact on the ability of sub-adult and adult crows to re-establish their wild lifestyles, but juvenile crows Key words: aviary confinement, Con'us moneduloides, New Caledonian Crow, radio tracking, reintegration success, re-establishment, site fidelity., Temporarily placing wild birds in captivity is an important option for researchers wishing to conduct more controlled experimental work. Surprisingly, reports about the ability of such captive birds to successfully [...]

Among social species, iterative interactions may lead to social preferences among group-mates and often are associated with increased mating opportunities or improved indirect fitness benefits. Although preferential associations have been documented in multiple species, this phenomenon has never been empirically studied in bats--the second largest order of mammals, where many of the 1200+ species live in groups of tens to hundreds of individuals. Given the current understanding of the social behaviour exhibited in this species, we explored the possibility that adult female big brown bats (Eptesicus fuscus (Beauvois, 1796)) show preferential association between group-mates using a pairwise choice design with individuals from a captive colony. Focal individuals were placed in a Y-maze and were given free choice of two familiar conspecifics. We measured the time focal individuals spent in close proximity to each conspecific. Our results indicate that some bats exhibit preferential association between group-mates, as multiple individuals spent significantly more time in close proximity to one conspecific versus another, despite randomizing the position of stimulus bats between trials. Given the frequent and long-term associations between group members of this species, social preferences could play a significant role in the outcomes of their long- term fitness. Key words: social associations, Eptesicus fuscus, social bias, Y-maze. Chez les especes sociales, les interactions iteratives peuvent mener a des preferences sociales entre membres d'un meme groupe et sont souvent associees a une augmentation du nombre de possibilites d'accouplement ou a de meilleurs avantages indirects sur le plan de l'aptitude. Si des associations preferentielles ont ete documentees chez de nombreuses especes, ce phenomene n'a jamais ete etudie de maniere empirique chez les chauves-souris, le deuxieme ordre de mammiferes en importance, dont bon nombre des plus de 1200 especes vivent en groupes de dizaines de milliers d'individus. Etant donne la comprehension actuelle du comportement social de cette espece, nous avons explore la possibilite que les femelles adultes de la serotine brune (Eptesicus fuscus (Beauvois, 1796)) fassent preuve d'association preferentielle au sein de leur groupe, en appliquant a des individus d'une colonie captive un schema de choix par paire. Les individus vises etaient places dans un labyrinthe en Yet avaient le choix entre deux congeneres qui leur etaient familiers. Nous avons mesure le temps que les individus vises passaient en etroite proximite avec chaque congenere. Nos resultats indiquent que certaines chauves-souris font preuve d'association preferentielle avec des membres de leur groupe, puisque de multiples individus passaient significativement plus de temps en etroite proximite avec un congenere plutot qu'un autre, malgre le fait que, entre les essais, les chauves-souris stimuli etaient reparties aleatoirement. Etant donne les associations frequentes et a long terme de membres du meme groupe chez cette espece, les preferences sociales pourraient jouer un important role dans la determination de leur aptitude a long terme. [Traduit par la Redaction] Mots-cles: associations sociales, Eptesicus fuscus, bais social, labyrinthe en Y., Introduction As an adapted response to counter the costs of predation, mate finding, and resource limitation, many animals congregate in groups ranging in size from tens to hundreds to millions [...]

Structure in sociality is known to relate to intrinsic and extrinsic factors. Less understood are the mechanics of sociality expressed as fine-scale behaviours that maintain hierarchies, mediate competition, or transmit pathogens. A recent novel approach to quantifying fine-scale social behaviour has been to use proximity-logging biotelemetry collars. This technology continuously records data whenever collars are within a predefined distance of each other, at times of day, and in habitats where traditional ethological approaches to focal-individual sampling of behaviours are unfeasible. We tested a series of expectations on fine-scale ([less than or equal to] 1.4 m) interaction rates and durations consistent with competing hypotheses of seasonal and sexual segregation for elk (Cervus canadensis Erxleben, 1777). Female-female dyads interacted 4 times more frequently than male-male dyads (mean interaction rate per year: female-female = 62 vs. male-male = 14; P < 0.001), and male-male interactions were 1.5 times longer in duration than female-female interactions (mean interaction length: female-female = 30 s vs. male- male = 45 s; P < 0.001). We propose that fine-scale interactions among members of a population can be modeled as a trade-off between the frequency (quantity) and the duration (quality) of interactions. Our results have implications for understanding sex- based differences in sociality in gregarious herbivores and for disease transmission, which may follow from social intercourse. Key words: behaviour, Cervus canadensis, disease, elk, sexual segregation, sociality. Il est etabli que la structure dans la socialite est associee a des facteurs intrinseques et extrinseques. La mecanique de la socialite exprimee par l'entremise de comportements a petite echelle qui maintiennent les hierarchies, modulent la concurrence ou transmettent des pathogenes est toutefois moins bien comprise. Une nouvelle approche de quantification des comportements sociaux a petite echelle consiste a utiliser des colliers de biotelemetrie qui enregistrent la presence d'autres individus situes a proximite. Cette technologie enregistre des donnees en continu quand des colliers se trouvent en dec; a d'une distance donnee les uns des autres, a des heures du jour et dans des habitats ou les approches ethologiques traditionnelles d'echantillonnage des comportements a l'echelle individuelle ne peuvent etre utilisees. Nous avons verifie un ensemble de predictions concernant la frequence et la duree d'interactions a petite echelle ( Mots-cles: comportement, Cervus canadensis, maladie, wapiti, segregation sexuelle, socialite., Introduction Sociality, broadly defined as group living, has implications for several ecological phenomena (Krause and Ruxton 2002; Silk 2007). It may arise as an adaptive response to a number of [...]

Social behavior abnormalities in Fragile X syndrome (FXS) are characterized by social withdrawal, anxiety, and deficits in social cognition. To assess these deficits, a model of FXS, the Fmr1 knockout mouse (Fmr1 KO), has been utilized. This mouse model has a null mutation in the fragile X mental retardation 1 gene (Fmr1) and displays physical and behavioral characteristics similar to humans with FXS. Several studies have investigated the social behavior of this model, but the results on the behavioral phenotype have not been consistent. In order to further characterize the social behavior in the knockout, isolation-reared Fmr1 KO were evaluated to determine if they differ in their social behavior compared to wild-type littermate controls. Differences by genotype were not observed in social approach behavior; however, the knockout mice showed a significantly reduced preference for social novelty and decreased sniff time in the sociability phase. These findings add to the growing body of knowledge on the subtle differences in social behavior shown by the Fmr1 knockout mice, and that differences occur when the subjects are isolation-reared. Validity of the model and possible changes to methodology are discussed. Keywords Fragile X syndrome * fmrl knockout mouse * Social behavior, Introduction Fragile X syndrome (FXS) is the most common inherited cause of intellectual disability and autism (Cohen et al. 2005; Hagerman and Hagerman 2002). The disorder is caused by a [...]

Although much attention has been focused on explaining and describing the diversity of social grouping patterns among primates (1-3), less effort has been devoted to understanding the evolutionary history of social living (4). This is partly because social behaviours do not fossilize, making it difficult to infer changes over evolutionary time. However, primate social behaviour shows strong evidence for phylogenetic inertia, permitting the use of Bayesian comparative methods to infer changes in social behaviour through time, thereby allowing us to evaluate alternative models of social evolution. Here we present a model of primate social evolution, whereby sociality progresses from solitary foraging individuals directly to large multi-male/multi-female aggregations (approximately 52 million years (Myr) ago), with pair-living (approximately 16Myr ago) or single-male harem systems (approximately 16 Myr ago) derivative from this second stage. This model fits the data significantly better than the two widely accepted alternatives (an unstructured model implied by the socioecological hypothesis or a model that allows linear stepwise changes in social complexity through time). We also find strong support for the co-evolution of social living with a change from nocturnal to diurnal activity patterns, but not with sex-biased dispersal. This supports suggestions that social living may arise because of increased predation risk associated with diurnal activity. Sociality based on loose aggregation is followed by a second shift to stable or bonded groups. This structuring facilitates the evolution of cooperative behaviours (5) and may provide the scaffold for other distinctive anthropoid traits including coalition formation, cooperative resource defence and large brains., Anthropoids differ from other social vertebrates in the prevalence of stable groups and bonded relationships between individuals (6). Explaining how primate social systems evolved is central to understanding the evolution [...]

Common marmosets (Callithrix jacchus) show either a left- or right-hand preference for reaching to pick up food and they retain the same preference throughout adult life. We compared the behavior of 10 right-handed and 10 left-handed marmosets, matched for age and sex. They were presented with live crickets both when alone and when in their social group. The marmosets captured more crickets and the latency to capture the first cricket was shorter when they were in a group than when they were alone. This effect of social facilitation was significantly greater for right- than left-handed individuals. The number of vocalizations (tsik, crackle, very brief whistle, cough, and phee) produced by the left- and right-handed marmosets differed significantly: right-handed marmosets produced an increased number of all of these calls when the crickets were presented, whereas left-handed marmosets did not show a change from pretesting levels. The right-handed marmosets also produced more tsik (mobbing) calls than left-handed marmosets when they were presented with a fear-inducing stimulus and performed more head cocking and parallax movements than the left-handed marmosets. Hence, hand preference is associated with differences in exploratory and social behavior, the latter including vocal communication. Keywords: hand preference, common marmosets, vocalizations, social facilitation, mobbing responses DOI: 10.1037/a0019736

Social animals, such as primates, must behave appropriately in complex social situations such as dominance interactions. Learning dominance information through trial and error would be dangerous; therefore, cognitive mechanisms for rapid learning of dominance information by observation would be adaptive. We used a set of digitally edited artificial social interactions to examine whether rhesus monkeys (Macaca mulatta) can learn dominance relationships between unfamiliar conspecifics through observation. Our method allowed random assignment of stimulus monkeys to ranks in an artificial hierarchy, controlling for nonbehavioral cues that could indicate dominance. Subject monkeys watched videos depicting 1 stimulus monkey behaving dominantly toward another and were rewarded for selecting the dominant individual. Monkeys rapidly learned this discrimination across 5 behavior types in Experiment 1 and transferred performance to novel videos of new individuals in Experiment 2. In addition, subjects selected the dominant individual more often than expected by chance in probe videos containing no behavioral dominance information, indicating some retention of the relative dominance status of stimulus monkeys from training. Together, our results suggest that monkeys can learn dominance hierarchies through observation of third-party social interactions. Keywords: social cognition, observation, social behavior, hierarchy, computerized testing Supplemental materials: http://dx.doi.org/10.1037/a0019751.supp DOI: 10.1037/a0019751

This study examined whether daily periods of maternal separation during the first two weeks of life would decrease attraction to familiar nest odors in CD-1 mice 10 and 14 days old. We also investigated whether placing a group of mice (Mus musculus) in nest shavings during the 180-min separation period would mitigate possible separation-induced deficits. The maternal separation procedure has been widely used as a rodent model for the effects of inconsistent or inadequate early caretaking on human development. From postnatal day (PND) 1 to 14, litters were separated from the dam, but not littermates for either 15 or 180 min, or were facility-reared controls. Control, facility-reared mice preferred home-cage nest to clean familiar shaving odors on PND 10, but not PND 14. In contrast, home-cage nest odors attracted maternally separated mice on both test days. Our results suggest that maternal separation maintains the olfactory tether to the nest in a period when the attraction normally begins to weaken. Keywords: maternal separation, odor preference, nest odor, social behavior, infant development, mice DOI: 10.1037/a0018896

Southern flying squirrels (Glaucomys volans) face a dilemma: winter aggregation is beneficial for thermoregulation but costly due to nest mates pilfering stored food in the home area and the tendency for groups to attract predators. Living with kin in winter aggregations may mitigate these deleterious effects because if an individual dies, its stored food can be beneficial to relatives, thereby increasing inclusive fitness. Southern flying squirrels from 7 populations and a captive colony were genotyped at 6 microsatellite loci. We calculated group mean relatedness and dyad relatedness within groups. In the wild, winter populations were found to be more highly related than expected by chance. Fifty-seven percent of animals were associated with a highly related individual in their winter aggregation. We show that southern flying squirrels have a preference for relatives as winter nest mates. DOI: 10.1644/09-MAMM-A-238.1. Key words: Glaucomys volans, group nesting, kinship, microsatellite DNA, southern flying squin-el, winter aggregation

Although mouse lemurs are solitary foragers, they are known to form sleeping associations. I examined several factors that could influence the choice to sleep communally and the composition of sleeping associations in Microcebus griseorufus, an inhabitant of the subarid spiny forest of southern Madagascar. These include the quantity and quality of available sleeping sites, socio-territoriality, predation risk, and thermoregulation. I radiotracked 26 individuals (12 males and 14 females) and recorded 222 uses of 151 sleeping sites. Mouse lemurs slept most often in tree forks and tangles of vegetation and preferred sleeping sites in Alluaudia spp. (36%) and Euphorbia spp. (30%), 2 very common tree genera in the spiny forest. Sleeping associations allowed the animals to use larger and more extensively overlapping home ranges and to have access to more food. Predation risk was much higher during nocturnal activity than during diurnal rest. Sleeping groups were small, usually pairs. Animals showed no signs of vigilance in sleeping sites and did not huddle consistently. Sleeping sites were chosen for their inaccessibility to predators and were well buffered against high and low ambient temperatures. Therefore, sleeping association was better explained by social territoriality than by predation pressure or thermoregulation. DOI: 10.1644/09-MAMM-A-239.1. Key words: foraging, predation, social territoriality, socio-ecological model, thermoregulation

We monitored populations of 2 species of desert rodents, the sandy inland mouse (Pseudomys hermannsburgensis) and spinifex hopping-mouse (Notomys alexis), over 18 years in the Simpson Desert, central Australia. Populations fluctuated synchronously from very low numbers, or 'busts,' during prolonged dry periods to high numbers, or 'booms,' after heavy rainfall 3 times over the study period. On the basis of observations that food resources expand after rainfall, we predicted that rodents would show increased rates of recapture, fidelity to burrows, and burrow sharing during population increase (boom) phases compared with decline or bust phases, and also reduce their movements and foraging activity in open habitats during population booms. The behavior of both species was similar but not as we had anticipated. Burrow fidelity and numbers of animals per burrow were roughly 2-fold higher during both the population increase and decrease phases as compared with the population-low phase, whereas rates of movement were reduced by about half. As revealed by giving-up density trials, animals foraged less at experimental food patches during population increase and decrease phases than during busts, and also foraged less in open than in covered habitats. Recaptures of N. alexis were similar across all population phases, whereas P. hermannsburgensis was recaptured more often when populations were decreasing than at other times. The results suggest that both species are dispersed and highly mobile during bust periods but sedentary and more social during population increases and collapses. These changes in movements and social organization appear to be unusual in desert rodents, and we propose that future studies seek to identify the roles of food and other factors in driving them. DOI: 10.1644/09-MAMM-S-205.1. Key words: Australia, burrows, desert rodents, long-term study, movements, Notomys, population dynamics, Pseudomys, social organization