Track D Social Science, Human Rights and Political Science

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/138414/1/jia218442.pd

Testing the robustness of transmission network models to predict ectoparasite loads. One lizard, two ticks and four years

We investigated transmission pathways for two tick species, Bothriocroton hydrosauri and Amblyomma limbatum, among their sleepy lizard (Tiliqua rugosa) hosts in a natural population in South Australia. Our aim was to determine whether a transmission network model continued to predict parasite load patterns effectively under varying ecological conditions. Using GPS loggers we identified the refuge sites used by each lizard on each day. We estimated infectious time windows for ticks that detached from a lizard in a refuge. Time windows were from the time when a detached tick molted and become infective, until the time it died from desiccation while waiting for a new host. Previous research has shown that A. limbatum molts earlier and survives longer than B. hydrosauri. We developed two transmission network models based on these differences in infective time windows for the two tick species. Directed edges were generated in the network if one lizard used a refuge that had previously been used by another lizard within the infectious time window. We used those models to generate values of network node in-strength for each lizard, a measure of how strongly connected an individual is to other lizards in the transmission network, and a prediction of infection risk for each host. The consistent correlations over time between B. hydrosauri infection intensity and network derived infection risk suggest that network models can be robust to environmental variation among years. However, the contrasting lack of consistent correlation in A. limbatum suggests that the utility of the same network models may depend on the specific biology of a parasite species

Resource leveling in construction by genetic algorithm-based optimization and its decision support system application

Traditional analytical and heuristic approaches are inefficient and inflexible when solving construction resource leveling problems. A computational optimization technique, genetic algorithms (GAs), was employed in this study to overcome drawbacks of traditional construction resource leveling algorithms. The proposed algorithm can effectively provide the optimal or near-optimal combination of multiple construction resources, as well as starting and finishing dates of activities subjected to the objective of resource leveling. Furthermore, a prototype of a decision support system (DSS) for construction resource leveling was also developed. Construction planners can interact with the system to carry out ad hoc analysis through “what-if” queries.

Data mining for tunnel support stability: neural network approach

This paper presents a data mining approach to the prediction of tunnel support stability using artificial neural networks (ANN). The case data of a railway tunnel recently finished in Taiwan were used to establish the model. The main rock type was sedimentary rock. Rock mechanical and construction-related parameters with significant influences on support stability were filtered to train and test the ANN. Validation was also performed to show that the ANN outperformed the discriminant analysis and the multiple non-linear regression method in predicting tunnel support stability status.

When the going gets tough: behavioural type-dependent space use in the sleepy lizard changes as the season dries

Understanding space use remains a major challenge for animal ecology, with implications for species interactions, disease spread, and conservation. Behavioural type (BT) may shape the space use of individuals within animal populations. Bolder or more aggressive individuals tend to be more exploratory and disperse further. Yet, to date we have limited knowledge on how space use other than dispersal depends on BT. To address this question we studied BT-dependent space-use patterns of sleepy lizards (Tiliqua rugosa) in southern Australia. We combined high-resolution global positioning system (GPS) tracking of 72 free-ranging lizards with repeated behavioural assays, and with a survey of the spatial distributions of their food and refuge resources. Bayesian generalized linear mixed models (GLMM) showed that lizards responded to the spatial distribution of resources at the neighbourhood scale and to the intensity of space use by other conspecifics (showing apparent conspecific avoidance). BT (especially aggressiveness) affected space use by lizards and their response to ecological and social factors, in a seasonally dependent manner. Many of these effects and interactions were stronger later in the season when food became scarce and environmental conditions got tougher. For example, refuge and food availability became more important later in the season and unaggressive lizards were more responsive to these predictors. These findings highlight a commonly overlooked source of heterogeneity in animal space use and improve our mechanistic understanding of processes leading to behaviourally driven disease dynamics and social structure

Spatial proximity and asynchronous refuge sharing networks both explain patterns of tick genetic relatedness among lizards, but in different years

A major question for understanding the ecology of parasite infections and diseases in wildlife populations concerns the transmission pathways among hosts. Network models are increasingly used to model the transmission of infections among hosts – however, few studies have integrated host behaviour and genetic relatedness of the parasites transmitted between hosts. In a study of the Australian sleepy lizard Tiliqua rugosa and its three‐host ixodid tick (Bothriocroton hydrosauri ), we asked if patterns of genetic relatedness among ticks were best explained by spatial proximity or the host transmission network. Using synchronous GPS locations of over 50 adult lizards at 10 min intervals across the three‐month activity period, over 2 years, we developed two alternative parasite transmission networks. One alternative was based on the spatial proximity of lizards (at the centre of their home ranges), and the other was based on the frequency of asynchronous shared refuge use between pairs of lizards. In each year, adult ticks were removed from lizards and their genotypes were determined at four polymorphic microsatellite loci. Adult ticks collected from the same host were more related to each other than ticks from different hosts. Similarly, adult ticks collected from different lizards had a higher relatedness if those lizards had a shorter path length connecting them on each of the two networks we explored. The predictors of tick relatedness differed between years. In the first year, the asynchronous shared refuges network was the stronger predictor of tick relatedness, whereas in year two, the spatial proximity‐based network was the stronger predictor of tick relatedness. We speculate on how changing environmental conditions might change the relative importance of alternative processes driving the transmission of parasites.Caroline K. Wohlfeil, Stephanie S. Godfrey, Stephan T. Leu, Jessica Clayton and Michael G. Gardne

Endure your parasites: Sleepy Lizard (Tiliqua rugosa) movement is not affected by their ectoparasites

Movement is often used to indicate host vigour, as it has various ecological and evolutionary implications, and has been shown to be affected by parasites. We investigate the relationship between tick load and movement in the Australian Sleepy Lizard (Tiliqua rugosa (Gray, 1825)) using high resolution GPS tracking. This allowed us to track individuals across the entire activity season. We hypothesized that tick load negatively affects host movement (mean distance moved per day). We used a multivariate statistical model informed by the ecology and biology of the host and parasite, their host–parasite relationship, and known host movement patterns. This allowed us to quantify the effects of ticks on lizard movement above and beyond effects of other factors such as time in the activity season, lizard body condition, and stress. We did not find any support for our hypothesis. Instead, our results provide evidence that lizard movement is strongly driven by internal state (sex and body condition independent of tick load) and by external factors (environmental conditions). We suggest that the Sleepy Lizard has largely adapted to natural levels of tick infection in this system. Our results conform to host–parasite arms race theory, which predicts varying impacts of parasites on hosts in natural systems.Patrick L. Taggart, Stephan T. Leu, Orr Spiegel, Stephanie S. Godfrey, Andrew Sih, and C. Michael Bul

Why is social behavior rare in Reptiles? Lessons From Sleepy Lizards

We report on 35. years of research into behavior and ecology of the Australian sleepy lizard, Tiliqua rugosa. We describe the unusually long monogamous pairing period in this lizard before mating takes place each spring, and the long-term persistence of mating pairs, reforming each spring for up to 27. years. We review hypotheses, observations, and experiments and conclude that females drive the pairing, becoming more receptive to males that have provided prolonged attention, because of the advantages they gain through greater awareness of approaching danger. We suggest that long-term pair fidelity has resulted from a higher reproductive efficiency between familiar partners. We then consider the broader social network structure in the sleepy lizard population, suggesting from our analyses that lizards make more contacts with their neighbors, sometimes agonistically, than if they were moving at random. There are few kin-based associations in the networks, but lizards with different personality types have different network positions. The broad social structure of the population is robust to ecological and environmental changes, although various network parameters are adjusted with different climate or habitat conditions. The overall social structure of the sleepy lizard population has an important role in transmission of parasites and pathogens. Finally we consider why this species is one of the very few reptiles for which stable social living has been reported. This may be because reptile social living is relatively under studied. Alternatively, we suggest, many reptile species may be constrained from evolving social structures, because they lack either the necessary cognitive ability or a strong defense against the high risk of pathogen transmission that comes from social living

Consistent after all: behavioural repeatability in a long-lived lizard across a 6-year field study

Despite growing attention to the ecological and evolutionary importance of consistent individual differences in behaviour (animal personality), long-term field studies quantifying factors associated with behavioural repeatability remain rare. Here, we studied animal personalities over an 8-year period, representing 6 study years, in a wild population of the long-lived sleepy lizard, Tiliqua rugosa. Using Bayesian generalized linear mixed models for 170 unique individuals and a total of 379 lizard-years, we (1) considered the effects of a suite of predictors – particularly lizard sex, mass and tick counts – on lizard aggression and boldness (2) assessed repeatability (i.e. consistent differences among individuals), of these behaviours over different timescales and between lizard sexes and (3) evaluated the correlation, or behavioural syndrome, between aggression and boldness. We found that males were marginally more aggressive and bolder than females, mass had no significant effect and tick loads exhibited a positive relationship with aggression and boldness. For repeatability, we found that even with the long timescales considered in this study, aggression and boldness were both repeatable – across the entire data set (∼0.4 and ∼0.3, respectively) using all lizards, as well as among years (∼0.4 and ∼0.4, respectively) using lizards observed in multiple years (93 for aggression, 73 for boldness). Repeatability did not differ substantially between the sexes. We found no syndrome between aggression and boldness – despite a weak positive correlation in multivariate mixed models, the 95% credible interval for this correlation included zero. Our results are notable because they demonstrate that wild animals may exhibit consistent personality differences in ecologically relevant behaviours over extended periods even in the face of substantial temporal variation in ecological and social factors, a fact that has likely ecological and evolutionary consequences.E.Payne, D.L.Sinn, O.Spiegel, S.T.Leu, M.G.Gardner, S.S.Godfrey, C. Wohlfeil, A.Sih ... et al