Karen L. Overall

Interfaces between Biophysical and Physiological Ecology and the Population Ecology of Terrestrial Vertebrate Ectotherms

Physiological and biophysical processes interact with a suite of environmental factors to produce important patterns in the population ecology of terrestrial vertebrate ectotherms. We develop a mechanistic approach to understanding the relative contributions of these interactions. Our approach requires a distinction between a life history and a life-history phenotype and allows the incorporation of system-specific trade-offs and constraints in a manner that facilitates the generation of testable predictions for specific populations or sets of populations. We define operant sources of selection and the effects of these averaged over the lifetime of individuals exposed to different environmental factors (available foraging microhabitats, mate availability, preferred egg sites), and synthesize a probabilitistic definition of a life history. We apply this approach to understanding geographic variation in several life-history characters in the saxicolous, iguanid lizard Sceloporus merriami.

Variation in locomotor performance in demographically known populations of the lizard Sceloporus merriami

We examined correlates (sex, size, age) of variation in maximal burst speed (racetrack) and in stamina (time until exhaustion at 0.5 km · h⁻¹) in two populations of the iguanid lizard Sceloporus merriami in Big Bend National Park, Texas. Because these populations were known demographically and were studied in several years, we were able to examine the effects of adult age on performance, the between-year repeatability of individual performance, and environmental correlates of yearly variation in performance. Variation in locomotor capacities was striking. Males were faster than females, and lizards from the Grapevine Hills were faster than those from Boquillas (lower elevation). However, sex and population did not affect stamina. Young adults (1-yr-olds) were slightly faster but had slightly less stamina than did older adults (2-3-yr-olds). Adult size (mass, snout-vent length, hind limb length) had little effect on performance. Average performance varied significantly among years, but stamina varied more than did speed. Stamina was highest in a summer preceded by relatively wet fall and winter. Despite the between-year variation in average performance, individual speed and stamina are both significantly repeatable over at least 1 yr. Neither tail loss nor toe loss affected sprint speed, but body temperature had a marked effect on speed.

Natural animal models of human psychiatric conditions: Assessment of mechanism and validity

1. The classic animal models for human psychiatric conditions involves rodents. As prey species, their normal behaviors of avoidance would be considered pathological in humans and dogs. Hence, such models may not be homologous for similar behaviors found in psychiatric pathology in humans. 2. Dogs exhibit pathological behavioral conditions that may be equivalent to certain human psychiatric conditions. These canine conditions appear spontaneously or endogenously in the absence of genetic or neurochemcial manipulation, and as such, may be homologous to the human condition. 3. If canine conditions approach homology with human conditions they should have excellent face, predictive, and construct validity. 4. The canine conditions of separation anxiety, obsessive-compulsive disorder, cognitive dysfunction, dominance aggression, and panic disorder have good to excellent validity at all explored levels for human generalized anxiety disorder, obsessive-compulsive disorder, Alzheimers disease, impulse control disorders, and panic disorder. 5. Natural canine models can aid our understanding of human psychiatric conditions.

Metabolism of a Desert Lizard: The Effects of Mass, Sex, Population of Origin, Temperature, Time of Day, and Feeding on Oxygen Consumption of Sceloporus merriami

Characterization of metabolic rate is critical to constructing daily and seasonal energy budgets, constructing models of individuals for use in individual based modeling, understanding patterns of resource allocation, and understanding within-and among-population variation in life-history phenotypes. We investigated the efects of mass, ambient temperature, time of day, sex, population of origin, and feeding on O₂ consumption of the canyon lizard, Sceloporus merriami. We observed strong efects of mass and ambient temperature and constructed predictive relationships for O₂ consumption on the basis of these variables for scotophase and photophase. These fundamental relationships coupled with existing field body temperature data suggest that lizards from populations exhibiting different daily body temperature profiles may significantly differ in maintenance requirement. We observed strong diel cycles in O₂ consumption that were correlated with daily activity. No main effects of sex orpopulation of origin were observed. A significant higher-order interaction involving temperature, time of day, sex, and population of origin suggests that ecologically significant variation in metabolic rate may occur between groups defined by sex and population. A plateau in O₂ consumption between 32° and 34°C was observed during scotophase. This plateau is not easily explained as a mechanism of homeostasis because scotophase body temperatures may often fall below this range. Feeding significantly increased O₂ consumption in this species; the magnitude of increase was linearly related to meal size. We estimated the total energetic cost of digestion to be between 2.9% and 4.9% of dietary metabolizable energy content.

Feline behavior guidelines from the American Association of Feline Practitioners

Z oonotic diseases are defined as being common to, shared by, or naturally transmitted between humans and other vertebrate animals (Evans 1997). Transmission of zoonotic agents from animals to people can potentially occur by direct contact with the animal, indirect contact with secretions or excretions from the animal, and contact with vehicles like water, food or fomites that were contaminated by the animal. For many agents, infection of the animal and human occurs from a shared vector or environmental exposure. Most zoonotic agents can infect anyone regardless of their immune status. However, when immunosuppressed people are infected the clinical illness is often more severe. For example, primary Toxoplasma gondii infection of an immunocompetent person is usually inapparent whereas infection in an immunosuppressed person can cause life-threatening disease. Examples of immunosuppressed individuals include those with acquired immune deficiency syndrome (AIDS), those on immune suppressive drugs for immune-mediated disease, cancer, or organ transplantation, the fetus or other young people without fully developed immune systems, and older individuals with decremental deterioration of the immune system. When immunodeficiency is detected or suspected in a family, it is often recommended that cat ownership be discontinued due to potential health risks (Burton 1989, Spencer 1992). Because there are many infectious agents that infect both cats and humans, it is sometimes assumed that zoonotic diseases are commonly acquired from cat contact. In actuality, humans are unlikely to acquire infectious diseases from healthy, adult,

Neurobehavioral Functional Deficits Following Closed Head Injury in the Neonatal Pig

Neurobehavioral deficits in higher cortical systems have not been described previously in a large animal model of diffuse brain injury. Anesthetized 3-5 day old piglets were subjected to either mild (142 rad/s) or moderate (188 rad/s) rapid non-impact axial rotations of the head. Multiple domains of cortical function were evaluated 5 times during the 12 day post-injury period using tests of neurobehavioral function devised for piglets. There were no observed differences in neurobehavioral outcomes between mild injury pigs (N=8) and instrumented shams (N=4). Moderately injured piglets (N=7) had significantly lower interest in exploring their environment and had higher failure rates in visual-based problem solving compared to instrumented shams (N=5) on days 1 and 4 after injury. Neurobehavioral functional deficits correlated with neuropathologic damage in the neonatal pigs after inertial head injury. Injured axons detected by immunohistochemistry (beta-APP) were absent in mild injury and sham piglets, but were observed in moderately injured piglet brains. In summary, we have developed a quantitative battery of neurobehavioral functional assessments for large animals that correlate with neuropathologic axonal damage and may have wide applications in the fields of cardiac resuscitation, stroke, and hypoxic-ischemic brain injury.

Medical differentials with potential behavioral manifestations.

Boundaries between behavioral conditions and medical differentials are likely to blur more rather than less as we learn more about genomic, cellular, and subcellular effects on common conditions. These changes should lead to better treatment but may also require a paradigm shift in how we view behavioral conditions and the mechanisms that contribute to them.

Pharmacologic treatments for behavior problems.

Most of the future advances in therapy with behavioral medicine probably will be pharmacologic. Newer developments in tricyclic antidepressants, specific and nonspecific anxiolytics, narcotic agonist-antagonists, and benzodiazepines will have great relevance for veterinary medicine. As the field of behavioral medicine expands, its paradigm hopefully will enlarge to include combination therapy and the implementation of neuropharmacologic intervention as a diagnostic tool. At present, the veterinary practitioner can effectively aid many common behavioral problems, with the glaring exception of most aggressions, using extant drugs.

Genetics and behavior: a guide for practitioners.

Phenotyping behavior is difficult, partly because behavior is almost always influenced by environment. Using objective terms/criteria to evaluate behaviors is best; the more objective the assessment, the more likely underlying genetic patterns will be identified. Behavioral pathologies, and highly desirable behavioral characteristics/traits, are likely complex, meaning that multiple genes are probably involved, and therefore simple genetic tests are less possible. Breeds can be improved using traditional quantitative genetic methods; unfortunately, this also creates the possibility of inadvertently selecting for covarying undesirable behaviors. Patterns of behaviors within families and breed lines are still the best guidelines for genetic counseling in dogs.

That dog is smarter than you know: advances in understanding canine learning, memory, and cognition.

Tests of canine cognition are now receiving much deserved attention. Not only are dogs excellent models for human anxiety-related conditions and those involving brain aging, but how dogs learn and problem solve are interesting stand-alone topics. A number of factors can affect learning at the molecular level including stress or distress, factors that affect olfaction, effects of breed and nutritional factors including that may affect available brain energy. This review provides an overview of how these factors may affect baseline learning and brain aging.