Maria Thaker

Indian Institute of Science | IISC · Centre for Ecological Sciences

For large herbivores living in highly dynamic environments, maintaining range fidelity has the potential to facilitate the exploitation of predictable resources while minimising energy expenditure. We evaluate this expectation by examining how the seasonal range fidelity of African elephants (Loxodonta africana) in the Kruger National Park, South A...

The field of animal movement ecology has advanced by leaps and bounds in the past few decades with the advent of sophisticated technology, advanced analytical tools, and multiple frameworks and paradigms to address key ecological problems. Unlike the longer history and faster growth of the field in North America, Europe, and Africa, movement ecolog...

A long-term monitoring programme to understand the impact of climate change on terrestrial herpetofauna of India. Hamadryad, in press. ABSTRACT. Anthropogenic climate change is likely to have wide ranging impacts on all aspects of life on earth. Among the many challenges posed by climate change, of particular importance to biologists is its impact...

Rapid physiological colour change offers dynamic signalling opportunities that can reveal distinct information to receivers in different contexts. Information content in dynamic colours, however, is largely unexplored. In males of the Indian rock agama (Psammophilus dorsalis), stressful events, including male-male agonistic interactions, induce a c...

Urbanization results in complex and variable changes to environmental conditions, which translate to shifts in selection pressures for organisms. Size of a city as well as the intensity and extent of urbanization can synergistically influence how organisms are impacted. However, less is known about how landscape heterogeneity, rate of land-use chan...

Chemical signals, such as those used in social communication, are often present as complex blends of compounds, suggesting that complexity is important in signal perception. Very few studies, however, have examined the interactions between different components of complex signals in social signalling. In the Mysore day gecko, Cnemaspis mysoriensis,...

Parental care is widespread and has fitness benefits. But caregiving parents incur costs including higher predation, and this may lead to selection for body colours or patterns that help mitigate the risks of caring. The evolution of colouration, including sexual dichromatism, however, can be driven by other factors, such as sexual selection. There...

Global change processes such as urbanization are likely to affect sleep behavior, by altering abiotic (e.g., thermal and illumination) and biotic conditions (e.g., predation pressure) that influence sleep. However, little is known of how sleep behavior responds to urbanization and whether this response is flexible or conserved across populations. W...

Urbanisation changes the structure of natural habitats and alters trophic interactions, pressuring urban species to adjust and adapt. Unlike behavioural shifts that tend to be more flexible, morphological characteristics in vertebrates are less plastic and changes may come at a greater cost. We explored the hypothesis that morphological characteris...

Fire and elephant herbivory are major drivers of large tree mortality in savanna ecosystems. Although the spatial variation of these agents is well studied, less attention has been paid to how disturbance history influences tree mortality over time. In a long‐term cohort study, we examined how the sequence of fire‐ and elephant‐induced damage influ...

Sleep is ubiquitous in the animal kingdom and yet displays considerable variation in its extent and form in the wild. Ecological factors, such as predation, competition, and microclimate, therefore are likely to play a strong role in shaping characteristics of sleep. Despite the potential for ecological factors to influence various aspects of sleep...

Aim Latitudinal gradients in life-history traits are apparent in many taxa and are expected to be strong for ectotherms that have temperature-driven constraints on performance and fitness. The strength of these gradients, however, should also be affected by diet. Because diet type (carnivory, omnivory, herbivory) influences accessibility to nutriti...

Space‐use patterns of animals are a fundamental measure of resource requirements and constraints. In some human‐modified landscapes, especially agroecosystems that depend on both rainfall and irrigation, drivers that influence animal space use can show unexpected spatial and temporal patterns due to anthropogenic activities. Animals living in such...

Young adults entering college experience immense shifts in personal and professional environments. Such a potentially stressful event may trigger multiple psychological and physiological effects. In a repeated-measures longitudinal survey (N = 6 time-points) of first year cohort of residential undergraduate students in India, this study evaluates m...

Parental care is remarkably and widespread among vertebrates because of its clear fitness benefits. Caring however incurs energetic and ecological costs including increasing predation risk. Anurans have diverse forms of parental care, and we test whether the evolution of care is associated with morphology that minimizes predation risk. Specifically...

Animal signals in multiple modalities expands the opportunity for effective communication. Among diurnal geckos of the genus Cnemaspis, chemical signalling traits preceded the evolution of visual traits. Males of all species possess chemical secreting ventral glands, but only in some species, males also express yellow gular patches. This difference...

Sleep is ubiquitous in the animal kingdom and yet displays considerable variation in its extent and form in the wild. Ecological factors, such as predation, competition, and microclimate, therefore, are likely to play a strong role in shaping characteristics of sleep. Despite the potential for ecological factors to influence various aspects of slee...

Interspecific competition can occur when species are unable to distinguish between conspecific and heterospecific mates or competitors when they occur in sympatry. Selection in response to interspecific competition can lead to shifts in signalling traits-a process called agonistic character displacement. In two fan-throated lizard species-Sitana la...

Predation risk is a strong driver of prey distribution and movement. However, fitness-influencing behaviours, such as mating, can alter risk and influence predator-prey space-use dynamics. In tree crickets, Oecanthus henryi, mate searching involves acoustic signalling by immobile males and phonotactic movement by females. Space-use patterns in tree...

To be effective, animal signals need to be detectable in the environment, but their development and expression require resources. For multimodal communication, investment in elaborating traits in one modality could reduce the elaboration of traits in other modalities. In Cnemaspis geckos, chemical signals for conspecific communication pre-dated the...

Accurately quantifying species’ area requirements is a prerequisite for effective area‐based conservation. This typically involves collecting tracking data on species of interest and then conducting home‐range analyses. Problematically, autocorrelation in tracking data can result in space needs being severely underestimated. Based on previous work,...

There is a large and growing interest in non‐consumptive effects of predators. Diverse and extensive evidence shows that predation risk directly influences prey traits, such as behaviour, morphology, and physiology, which in‐turn, may cause a reduction in prey fitness components (i.e., growth rate, survival, and reproduction). An intuitive expectat...

Young adults entering into college experience immense shifts in both personal and professional environments and this may result in some of them experiencing a lot of stress and difficulty in coping with their new surroundings. Such potentially stressful events may trigger multiple psychological as well as physiological effects. The current study in...

The forces of sexual and natural selection are typically invoked to explain variation in colour patterns of animals. Although the benefits of conspicuous colours for social signalling are well documented, evidence for their ecological cost, especially for dynamic colours, remains limited. We examined the riskiness of colour patterns of Psammophilus...

Satellite telemetry is an increasingly utilized technology in wildlife research, and current devices can track individual animal movements at unprecedented spatial and temporal resolutions. However, as we enter the golden age of satellite telemetry, we need an in-depth understanding of the main technological, species-specific and environmental fact...

R-code for boosted beta regression (Fix acquisition rate). (R)

Covariate partial effects on the variability of the fix acquisition rate. (PDF)

Tagged individuals per species. (PDF)

Covariate partial effects on the variability of the Overall fix success rate. (PDF)

Trends in observed data. (PDF)

Global dataset for boosted beta regressions. (CSV)

Description of data fields in S1 Data. (CSV)

Satellite telemetry articles published. (PDF)

Distribution of response variables and covariates. (PDF)

Unit purchase and operation costs. (PDF)

R-code for boosted beta regression (Overall fix success rate). (R)

Standardized data collection questionnaire. (PDF)

Satellite telemetry evaluations. (PDF)

Enhanced cognitive ability is beneficial in unpredictable and harsh environments, as it enables animals to respond with flexibility. For animals living in urbanized areas, local environments not only are altered but can rapidly change during their lifetime. Urban residents are therefore challenged with identifying novel dangers and safe refuges in...

Movement strategies of animals have been well studied as a function of ecological drivers (e.g., forage selection and avoiding predation) rather than physiological requirements (e.g., thermoregulation). Thermal stress is a major concern for large mammals, especially for savanna elephants (Loxodonta africana), which have amongst the greatest challen...

Multimodal signals are used by many animals for intraspecific communication and can provide information about sex identity as well as quality of the signaller. In diurnal geckos of the genus Cnemaspis, chromatic colour patches in males evolved after chemical secretions, providing us with an opportunity to examine the utility of evolving multimodali...

Wind farms are a cleaner alternative to fossil fuels for mitigating the effects of climate change, but they also have complex ecological consequences. In the biodiversity hotspot of the Western Ghats in India, we find that wind farms reduce the abundance and activity of predatory birds (for example, Buteo, Butastur and Elanus species), which conseq...

Animals engage in social interactions with changes in their behaviour and physiology. Environmental challenges, however, can influence social interactions by adding additional stressors. Here, we investigated the effects of urbanisation on the behaviour and hormonal responses of a tropical lizard species, Psammophilus dorsalis, during social intera...

The rapid rate of urbanization worldwide and its consequences for affected species and ecosystems urgently warrants research and action. Whether animals are effectively coping from urbanization is hotly debated, especially since interpretations are based on different measures of animal responses. Here, we take a physiology-centric view of animal co...

Vertebrates lateralize many behaviours including social interactions. Social displays typically comprise multiple components, yet our understanding of how these are processed come from studies that typically examine responses to the dominant component or the complex signal as a whole. Here, we examine laterality in lizard responses to determine whe...

Dynamic physiological colour change allows animals to alter colours and patterns for communication, camouflage and thermoregulation. Using reflectance spectrometry and digital photography, we found that males of the Indian rock agama, Psammophilus dorsalis, can rapidly express intense colours that are different from the neutral state and specific t...

Animals are often faced with the challenge of signalling to multiple receivers that might differ in their detection abilities and preferences. Such conditions are expected to favour the evolution of complex signals. The superb fan-throated lizard, Sarada superba, possesses one of the most complex sexual trait of any lizard: an enlarged dewlap with...

Escape strategies of animals are economic decisions, expected to vary as a function of both intrinsic (e.g., performance ability) and extrinsic factors (e.g., level of threat and microhabitat). Anthropogenic disturbance, especially urbanization, changes a range of environmental factors including habitat characteristics and predation risk. As a cons...

Rapid urbanization is a growing threat to biodiversity, causing wide-scale extirpation of species from their natural habitats. Some species such as rock agamas, Psammophilus dorsalis, seem to be sufficiently tolerant and continue to persist in urban environments. Given that urbanization alters species composition at multiple trophic levels, we expe...

Elephant are considered major drivers of ecosystems, but their effects within small-scale landscape features and on other herbivores still remain unclear. Elephant impact on vegetation has been widely studied in areas where elephant have been present for many years. We therefore examined the combined effect of short-term elephant presence (< 4 year...

http://www.nature.com/nature/journal/v513/n7517/abs/nature13717.html#comment-64445

Most ecosystems have multiple predator species that not only compete for shared prey, but also pose direct threats to each other. These intraguild interactions are key drivers of carnivore community structure, with ecosystem-wide cascading effects. Yet, behavioral mechanisms for coexistence of multiple carnivore species remain poorly understood. Th...

Background/Question/Methods Spatial patterns of animals are driven primarily by the distribution of resources and the presence of predators, however these factors can differ in their magnitude of effect and predictability. Although prey may have a reliable knowledge of the current distribution of resources, their perception of the spatial and tem...

Background/Question/Methods Most ecosystems have multiple predator species that not only compete for shared prey but also pose direct threats to each other. These intraguild interactions are key drivers of carnivore community structure with ecosystem-wide cascading effects. Yet, behavioral mechanisms for coexistence of multiple carnivore species...

All animals are either predators or prey and, in most cases, they are both. The interactions involved in attempting to eat and avoid being eaten have strong and wide-reaching influences across all facets of ecology, from individual phenotypic responses and population dynamics, to community interactions, and even to how we attempt to manage and cons...

Sport hunting is often proposed as a tool to support the conservation of large carnivores. However, it is challenging to provide tangible economic benefits from this activity as an incentive for local people to conserve carnivores. We assessed economic gains from sport hunting and poaching of leopards (Panthera pardus), costs of leopard depredation...

The vegetation dynamics of the savanna ecosystem are driven by complex interactions between biotic and abiotic factors, and thus are expected to exhibit emergent properties of biocomplexity. We explore the relative importance of static and dynamic drivers in explaining the patterns of mortality of large trees in the Kruger National Park, South Afri...

Elephant and fire are considered to be among the most important agents that can modify the African savanna ecosystem. Although the synergistic relationship between these two key ecological drivers is well documented, it has proved much more difficult to establish the relative effects they have on savanna vegetation structure at a fine-scale over ti...

Studies that focus on single predator-prey interactions can be inadequate for understanding antipredator responses in multi-predator systems. Yet there is still a general lack of information about the strategies of prey to minimize predation risk from multiple predators at the landscape level. Here we examined the distribution of seven African ungu...

Physical barriers, such as rivers and roads, constrain the movement of animals, usually by preventing access to adjacent habitats and impeding dispersal. Fences are artificial barriers that are commonly used as a conservation tool to intentionally restrict movements of animals to within protected reserves. However, the potential edge-effect of fenc...

Social interactions of conspecifics are a function of complex relationships involving resource defense, anti-predatory tactics, and mate acquisition. Consequently, individuals often associate non-randomly with conspecifics in their habitats, with spatial distributions of adults ranging from territorial spacing to aggregations. Site tenacity and coh...

Elevated plasma corticosterone during stressful events is linked to rapid changes in behavior in vertebrates and can mediate learning and memory consolidation. We tested the importance of acute corticosterone elevation in aversive learning of a novel stressor by wild male eastern fence lizards (Sceloporus undulatus). We found that inhibiting cortic...

Background: Group dynamics of gregarious ungulates in the grasslands of the African savanna have been well studied, but the trade-offs that affect grouping of these ungulates in woodland habitats or dense vegetation are less well understood. We examined the landscape-level distribution of groups of blue wildebeest, Connochaetes taurinus, and Burch...

The structure of mammalian carnivore communities is strongly influenced by both intraguild competition and predation. However, intraguild interactions involving the world’s most common carnivore, the domestic dog (Canis familiaris), have rarely been investigated. We experimentally examined the behavioural responses of a small canid, the Indian fox...

Most females exhibit preferences for certain males and females based on mating and social decisions. Unisexual females that reproduce by gynogenesis are also expected to express association preferences, which may have been inherited from parental species, or may have evolved in response to selection pressures associated with their unisexual mating...

In response to stressful events, most vertebrates rapidly elevate plasma glucocorticoid levels. Corticosterone release stimulates physiological and behavioral responses that can promote survival while suppressing behaviors that are not crucial to immediate survival. Corticosterone also has preparatory effects for subsequent stressors. Using male tr...

Most vertebrates respond to acute stressors with rapid plasma glucocorticoid elevations. Variation within species in this hormonal response should correlate with differences in physiological responses and behavioural tactics, yet this is rarely documented. We measured behavioural and hormonal responses of free-ranging male tree lizards (Urosaurus o...

Mating behavior of Tetraopes tetrophthalmus was investigated in the labo-ratory and in a field population. Mating duration varies considerably in this spe-cies and factors influencing mating duration (defined as the total time a male is mounted on a female) were elucidated. Males, rather than females, were more likely to terminate matings by diseng...

The mode and effectiveness of signals greatly depends on habitat characteristics and the activity patterns of a species. Visual cues frequently are involved in social interactions, although their effectiveness can be reduced with nocturnal species or in habitats with limited visibility. The combination of multiple signals, such as chemical and visu...

ABSTRACT Tn5-induced mutations in Agrobacterium vitis F2/5 resulted in both altered grape necrosis and tobacco leaf panel collapse phenotypes, suggesting that the underlying mechanisms of the reactions are related. The reaction on tobacco resembles the classical hypersensitive response (HR) caused by several plant pathogenic bacteria in that it is...

Vita. Thesis (M.S.)--Texas State University-San Marcos, 2004. Includes bibliographical references (leaves 9-15, 27-31, 43-46, 54-55).