This study investigated the effect of captivity on the chemical profiles of the female sexual attractiveness pheromone of the red-sided garter snake (Thamnophis sirtalis parietalis). Dorsal skin lipids were extracted from female garter snakes collected from the Interlake region of Manitoba, Canada. A comparison of captive and wild snakes was...
Vertebrates communicate with one another and coordinate intraspecific reproduction by using a variety of sexually dimorphic signals, such as plumage, ornaments, sounds, and/or scents. These sexual dimorphisms are maintained by physiological factors, typically sex-specific hormones (though see Chapter 3 for an exception). The purpose of the research in this dissertation...
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Robert T. Mason
Vertebrates communicate with one another and coordinate intraspecific
Pheromones are chemical cues produced by organisms that affect the behavior and/or physiology of conspecifics. The orchestration of reproductive behaviors in many animals depends on the expression of sex pheromones. In insects, intraspecific variation in sex pheromone expression is commonly observed and often influences social interactions between individuals. To what...
The benefits of reproduction are clear, but there are also costs. Much is known about the costs of reproduction in females, but only recently have male costs been investigated in any depth. These costs of reproduction may be minimized by appropriately modifying behavior, but there has been little research on...
In animals, reproductive behaviors serve to attract individuals together during the
breeding season and to coordinate the behavioral and physiological states of individuals
so that mating can successfully occur. In snakes, the various reproductive behaviors
including courtship, mating, courtship inhibition, male combat and trailing are mediated
primarily by pheromones. Pheromones...
Parasitic infections and immune challenges can affect host reproductive fitness and, ultimately, the evolution of host populations in a myriad of ways. The fitness implications of parasitic infections range from increased host mortality to subtle changes in reproductive investment. From alterations of behaviors, sexual signaling, and competitive ability to changes...
In this study, pheromone and skin lipid samples collected from red-sided garter snakes (Thamnophis sirtalis parietalis) were exposed directly to either full-spectrum light or full-spectrum plus UVB light. In addition, female and male snakes were exposed to daily doses of either full-spectrum or full-spectrum and UVB light, after which the...
Variability in the depth and duration of anesthesia in individuals within a species is
frequently observed, yet few studies have investigated its causes in reptiles. To evaluate
the potential causes of variability in reptile anesthesia, I conducted experiments to test for
effects of body temperature, body composition and time post-feeding...
Postcopulatory sexual selection—sperm competition and cryptic female choice—has become a major area of research over the past 40 years. Within this field there are many outstanding questions at every level of analysis, from proximate to ultimate. The fitness consequences for both sexes in the period after copulation and before fertilization...
Most vertebrates exhibit seasonality in many life history traits. Such seasonal rhythms are temporally organized via the transduction of environmental cues (e.g., photoperiod, temperature) into appropriate endocrine signals. However, among ectothermic vertebrates that undergo continuous winter dormancy, temperature is the only environmental cue available for synchronizing seasonal rhythms. Most intriguing...
Animals respond to stressful situations with increases in plasma levels of
glucocorticoid stress hormones. These hormones originate from the adrenal cortex
in response to stimulation of the hypothalamic-pituitary-adrenal axis.
Glucocorticoids (corticosterone in reptiles) function to mobilize energy and
suppress unnecessary functions until the stress passes. Among these immediately
unnecessary functions...
The red-sided garter snakes (Thamnophis sirtalis parietalis) of Manitoba, Canada, have been extensively studied for decades with little investigation into their immune system. These animals live very close to the arctic circle and spend over half of the year underground brumating. The annual cycle of the red-sided garter snakes make...
The Harderian gland is a large cephalic gland present in most groups of terrestrial vertebrates. Although the Harderian gland has been the focus of numerous studies for more than 300 years, its physiological function has remained largely unresolved. Harderian gland secretions are diverse among different taxa, and many putative functions...
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Robert T. Mason
The Harderian gland is a large cephalic gland present in most groups of
Sperm competition is the post-copulatory analog of male-male combat, wherein sperm
from more than one male coincide in a female’s reproductive tract and compete with one
another for fertilization of a limited number of ova. Post-copulatory sexual selection,
such as sperm competition, can be a powerful driving force for the...
A wide range of environmental and physiological factors influence the type and extent of sexual dimorphism found in animals. Influential factors include variable climate, competition for resources and mates, mate choice, and parental investment. In addition, some investigators attribute differences in body size to physiological factors influenced by genetic and...
At a time when environmental conditions are rapidly changing, understanding how thermal extremes impact wildlife is imperative to fully understanding the consequences of climate change in natural ecosystems. While many organisms are currently impacted by rapidly warming and more erratic environmental conditions, identifying and investigating model species whose life histories...
The Northern Rubber Boa (Charina bottae) is a small, secretive boa native to the Pacific Northwest. Despite this being possibly the highest latitude boas and one of only two boas native to the continental U.S., it has received surprisingly little attention. Most of the research on the natural history of...
Galápagos marine iguana population sizes have been declining since first contact with humans.This decline has historically been attributed mainly to predation by invasive species, but additional human-caused threats exist today. My thesis conducts an analysis of the present threats to the species and determines which are the most severe.Modern threats...
"Red-sided garter snakes, Thamnophis sirtalis parietalis, from Manitoba, Canada are known to be hosts to trematodes, Alaria sp., in their population. Alaria sp. have been located in the tail tissue of the snakes. The non-reproductive stage of these obligate endoparasites, known as a mesocercaria, is trophically acquired by garter snakes....
There has been a rapid increase in technological advances in the biological sciences that has contributed to an increase in societal issues that require attention from both scientists and citizens. Consequently, there is a need for the development of biologically literate citizens who have the ability to use their knowledge...