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...
While there are many more species of reptiles in the tropics than in temperate
latitudes, relatively little is known about the natural history of tropical species of
snakes. Even basic information, such as reproductive ecology and behavior, is lacking. Patterns of reproduction in tropical species differ from patterns in temperate...
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...
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...
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...
The major objectives of this study were: (1) to determine the extent to which southwest Oregon populations of Douglas-fir [Pseudotsuga menziesii var menziesii (Mirb.) Franco) differ in quantitative genetic structure (QGS); (2) to determine whether differences in QGS are associated with the environments from which populations originate; and (3) to...
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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RobertT. Mason
Vertebrates communicate with one another and coordinate intraspecific
In spite of considerable efforts to restore natural runs of anadromous salmonids in the Pacific Northwest, they remain at risk of extirpation. Along with many other factors influencing the decline, stocking from hatcheries over the past hundred years is often suggested to be a major cause. The listing of over...
Many contemporary fisheries and wildlife issues are complex, messy, and divisive. Most share a set of common characteristics including a lack of comprehensive scientific information, a limited understanding of biological processes, a scarcity of agency staff, time, money, and a tendency for differences over policy preferences to end up as...
Increasing the abundance of salmon in coastal Oregon rivers and streams is a high priority public policy objective. Salmon runs have been reduced from pre-development conditions (typically defined as the 1 850s), but it is unclear by how much. Considerable resources have been allocated to restoring salmon runs, but it...