2,470 research outputs found
The influence of refuge sharing on social behaviour in the lizard Tiliqua rugosa
No full textRefuge sharing by otherwise solitary individuals during periods of inactivity is an integral part of social behaviour and has been suggested to be the precursor to more complex social behaviour. We compared social association patterns of active versus inactive sheltering individuals in the social Australian sleepy lizard, Tiliqua rugosa, to empirically test the hypothesis that refuge sharing facilitates social associations while individuals are active. We fitted 18 neighbouring lizards with Global Positioning System (GPS) recorders to continuously monitor social associations among all individuals, based on location records taken every 10 min for 3 months. Based on these spatial data, we constructed three weighted, undirected social networks. Two networks were based on empirical association data (one for active and one for inactive lizards in their refuges), and a third null model network was based on hypothetical random refuge sharing. We found patterns opposite to the predictions of our hypothesis. Most importantly, association strength was higher in active than in inactive sheltering lizards. That is, individual lizards were more likely to associate with other lizards while active than while inactive and in shelters. Thus, refuge sharing did not lead to increased frequencies of social associations while lizards were active, and we did not find any evidence that refuge sharing was a precursor to sleepy lizard social behaviour. Our study of an unusually social reptile provides both quantitative data on the relationship between refuge sharing and social associations during periods of activity and further insights into the evolution of social behaviour in vertebrates
Pair-living in the Absence of Obligate Biparental Care in a Lizard: Trading-off Sex and Food?
No full textA pair-living social organisation can typically be explained by obligate biparental care. We investigated pair-living in the absence of biparental care in the Australian sleepy lizard, Tiliqua rugosa, which forms exceptionally strong pair bonds. We fitted 10 lizards, five male–female pairs, with Global Positioning System (GPS) recorders and continuously monitored social associations and separations between active pair partners, based on location records taken every 10 min over 3 mo. Males temporarily separated and reunited the pair more frequently than females, but females also contributed to the maintenance of the pair bond. These behavioural data were consistent with the hypothesis that females successfully coerce males into associations with one female. Lower frequencies of social association between pair partners once mating had finished support this interpretation. Males that are coerced into pair associations appear to experience higher costs of pair-living than females, because males initiated temporary separations of the pair more frequently than females. Males showed higher movement activity and remained active later each day. This sex bias in activity may be an important mechanism to mitigate the higher costs of pair-living for males. Costs for males might include within-pair competition for food as females appear more competitive. Our study provides detailed empirical data on a lizard pair bond and provides important insights into pair-living in the absence of biparental care
Transmission network predicts ectoparasite load in a lizard
No full textLiving in social groups facilitates cross-infection by parasites. However, empirical studies on indirect transmission within wildlife populations are scarce. We investigated whether asynchronous overnight refuge sharing among neighboring sleepy lizards, Tiliqua rugosa, facilitates indirect transmission of its ectoparasitic tick, Amblyomma limbatum. We fitted 18 neighboring lizards with GPS recorders, observed their overnight refuge use each night over 3 months, and counted their ticks every fortnight. We constructed a transmission network to estimate the cross-infection risk based on asynchronous refuge sharing frequencies among all lizards and the life history traits of the tick. Although self-infection was possible, the network provided a powerful predictor of measured tick loads. Highly connected lizards that frequently used their neighbors' refuges were characterized by higher tick loads. Thus, indirect contact had a major influence on transmission pathways and parasite loads. Furthermore, lizards that used many different refuges had lower cross- and self-infection risks and lower tick loads than individuals that used relatively fewer refuges. Increasing the number of refuges used by a lizard may be an important defense mechanism against ectoparasite transmission in this species. Our study provides important empirical data to further understand how indirectly transmitted parasites move through host populations and influence individual parasite loads
Association networks reveal social organisation in the sleepy lizard
No full textWe investigated the social organization of the Australian sleepy lizard, Tiliqua rugosa, by describing the social network of a local population. We attached activity meters and GPS recorders to 21 neighbouring lizards in a semiarid site in South Australia, and monitored their location every 10 min over 3 months (September–December 2007). From over 5000 sets of synchronized location records we calculated distances between all possible dyads of active lizards, and constructed binary social networks based on close associations between individuals. We compared empirical networks with a null model network for spatially structured populations that assumed random movement within lizard home ranges. We showed significantly lower network degree (i.e. fewer cases of individuals associating) in the observed network than in the null model, and deduced avoidance between some individuals. We found the predominant form of social organization was pair living, and, contrary to previous reports, we found pair associations persisted after mating had finished. Thus, the network analysis revealed a cryptic social organization, which cannot be explained by either biparental care or mate guarding, but may instead relate to refuge site distributions, enhanced vigilance or efficient location of mates in subsequent seasons
Lizards, ticks and contributions to Australian parasitology: C. Michael Bull (1947–2016)
No full textProfessor C. Michael Bull was a great scientist and mentor, and an Associate Editor of this journal. While his research career spanned the fields of behavioural ecology, conservation biology and herpetology, in this article, we pay tribute to his major contribution to Australian parasitology. Mike authored more than eighty articles on host-parasite ecology, and revealed major insights into the biology and ecology of ticks from his long term study of the parapatric boundary of two tick species (Amblyomma limbatum and Bothriocroton hydrosauri) on the sleepy lizard (Tiliqua rugosa). In this article, we provide an overview of how this research journey developed to become one of the longest-running studies of lizards and their ticks, totalling 35 years of continuous surveys of ticks on lizards, and the insights and knowledge that he generated along that journey. Keywords: Skink, Long-term research, Disease ecology, Acari, Wildlife parasitology, Field-based researc
Transmission mode and distribution of parasites among groups of the social lizard Egernia stokesii
No full textThe original publication is available at www.springerlink.comWe explored patterns of infection of three apicomplexan blood parasites with different transmission mechanisms in 46 social groups across seven populations of the Australian lizard, Egernia stokesii. There was higher aggregation of infections within social groups for Hemolivia, transmitted by ticks, and Schellackia, either tick-transmitted or directly transmitted from mother to offspring, than for Plasmodium, with more mobile dipteran vectors. Prevalence was not related to group size, proximity to other groups or spatial overlap with adjacent groups for any of the parasites. However, for Hemolivia, groups with higher levels of relatedness among adults had higher parasite prevalence. Living in social groups leads to higher risk of infection for parasites with low transmission mobility. An unanswered question is why so few lizard species tolerate these risks to form stable social aggregations.Stephanie S. Godfrey, C. Michael Bull, Kris Murray and Michael G. Gardne
Associations between blood parasite infection and a microsatellite DNA allele in an Australian scincid lizard (Egernia stokesii)
No full textThe original publication is available at www.springerlink.comWe used blood samples from 175 individuals of the Australian lizard Egernia stokesii to determine infection status of three apicomplexan blood parasites from the genera Hemolivia, Schellackia, and Plasmodium and to determine genotypes at 12 microsatellite DNA loci. We found one significant association between genotype and infection status. For locus Est4, individuals carrying allele 159 had lower prevalence of infection with Hemolivia (14.3% of 28 lizards) than individuals that did not carry the allele (58.4% of 89 lizards). We interpret this as a linkage to a functional gene associated with parasite resistance. We found no evidence among seven lizard populations that the frequency of allele 159 was related to the population prevalence of Hemolivia infection and discuss several explanations of that pattern.Stephanie S. Godfrey, C. Michael Bull and Michael G. Gardne
Recommended from our members
Sound moves: iPod culture and urban experience
No full textThis innovative study opens up a new area in sociological and urban studies: the aural experience of the social, mediated through mobile technologies of communication. Whilst we live in a world dominated by visual epistemologies of urban experience, Michael Bull argues that it is not surprising that the Apple iPod, a sound based technology, is the first consumer cultural icon of the twenty-first century. This book, in using the example of the Apple iPod, investigates the way in which we use sound to construct key areas of our daily lives. The author argues that the Apple iPod acts as an urban Sherpa for many of its users and in doing so joins the mobile army of technologies that many of us habitually use to accompany our daily lives. Through our use of such mobile and largely sound based devices, the book demonstrates how and why the spaces of the city are being transformed right in front of our ears
Fitness of the endangered Pygmy Blue Tongue Lizard Tiliqua adelaidensis in artificial burrows
No full textThe endangered Pygmy Blue Tongue Lizard, Tiliqua adelaidensis, occupies narrow vertical burrows, probably constructed by spiders. We assessed the fitness of female lizards in artificial burrows added to a 1-ha plot within a natural population, over a three-year period. Compared with females in natural burrows, females in artificial burrows had significantly better body condition and produced larger offspring with better body condition. We discuss possible explanations for these differences but conclude that adding artificial burrows was not detrimental to reproductive females in a population and could be used in the conservation management of this species.Tim Milne, C. Michael Bull and Mark N. Hutchinso
Use of burrows by the endangered pygmy blue-tongue lizard, Tiliqua adelaidensis (Scincidae)
No full textThe pygmy blue-tongue lizard, Tiliqua adelaidensis , had been considered extinct until its recent rediscovery near Burra in the mid-north of South Australia. The lizards apparently rely on spider burrows with a single entrance as refuge sites. In this paper we describe observations from all-day video recordings of the entrances of burrows occupied by lizards on 31 days across the spring and early summer of 1996. The lizards spent most of each day either retreated down the burrow or basking at the burrow entrance. Early in the season, when temperatures were cooler, lizards spent more of each day basking, and more of their basking time fully emerged from the burrow, than later in the season. Results are consistent with the hypothesis that the lizards thermoregulate by moving in and out of the burrow. Lizards also fed by making short excursions from the burrow, often to catch passing invertebrate prey, although they also fed on flowers early in spring. Later in the season lizards were more likely to vacate their burrows for longer times, or to move away from their burrows, and mating activity was observed when males approached burrows occupied by females. The observations suggest that pygmy blue-tongue lizards rely heavily on burrows for many activities, and that any conservation management scheme for this endangered species will rely on maintaining an adequate supply of burrows.Tim Milne, C. Michael Bull and Mark N. Hutchinso
- …
