Integrating population- and individual-level information in a movement model of Yellowstone bison.

Throughout the world, fragmentation of landscapes by human activities has constrained the opportunity for large herbivores to migrate. Conflict between people and wildlife results when migrating animals transmit disease to livestock, damage property, and threaten human safety. Mitigating this conflict requires understanding the forces that shape migration patterns. Bison Bos bison migrating from Yellowstone National Park into the state of Montana during winter and spring concern ranchers on lands surrounding the park because bison can transmit brucellosis (Brucella abortus) to cattle. Migrations have been constrained, with bison being lethally removed or moved back into the park. We developed a state-space model to support decisions on bison management aimed at mitigating conflict with landowners outside the park. The model integrated recent GPS observations with 22 years (1990-2012) of aerial counts to forecast monthly distributions and identify factors driving migration. Wintering areas were located along decreasing elevation gradients, and bison accumulated in wintering areas prior to moving to areas progressively lower in elevation. Bison movements were affected by time since the onset of snowpack, snowpack magnitude, standing crop, and herd size. Migration pathways were increasingly used over time, suggesting that experience or learning influenced movements. To support adaptive management of Yellowstone bison, we forecast future movements to evaluate alternatives. Our approach of developing models capable of making explicit probabilistic forecasts of large herbivore movements and seasonal distributions is applicable to managing the migratory movements of large herbivores worldwide. These forecasts allow managers to develop and refine strategies in advance, and promote sound decision-making that reduces conflict as migratory animals come into contact with people.

Bovine brucellosis in wildlife: using adaptive management to improve understanding, technology and suppression.

Eradication of brucellosis from bison (Bison bison) and elk (Cervus elaphus) populations in the Greater Yellowstone Area is not possible with current technology. There are considerable uncertainties regarding the effectiveness of management techniques and unintended effects on wildlife behaviour and demography. However, adaptive management provides a framework for learning about the disease, improving suppression techniques, and lowering brucellosis transmission among wildlife and to cattle. Since it takes approximately three years after birth for female bison to become reproductively active and contribute to brucellosis transmission, there is an opportunity to implement actions such as vaccination and the selective removal of infectious bison based on age and assay results to reduce the potential for transmission. Older adult bison that have been exposed to the bacteria, but recovered from acute infection, could be retained in the population to provide some immunity (resistance) against future transmission. Through careful predictions, research, and monitoring, our understanding and technology will be improved and management actions can be adjusted to better achieve desired outcomes.

Hormonal regulation of postnatal growth in children born small for gestational age.

Children born small for gestational age (SGA) are at high risk of permanent short stature, with approximately 10% continuing to have stature below the third centile throughout childhood and adolescence and into adulthood. The mechanisms involved in catch-up growth, and those that prevent catch-up growth, are still unknown. To date, no reliable anthropometric or endocrine parameter predictive of postnatal catch-up growth has been identified. However, subtle abnormalities in the growth hormone-insulin-like growth factor axis, the hypothalamic-pituitary-adrenal axis and thyroid function have been described, and a mechanism involving intrauterine programming of hypothalamic-pituitary function has been proposed.

Insulin resistance and insulin-like growth factors in children with intrauterine growth retardation. Is catch-up growth a risk factor?

AIMS: To investigate (a) the prevalence of insulin resistance in children with intrauterine growth retardation (IUGR); (b) whether catch-up growth is associated with a higher risk of insulin resistance; (c) the insulin-like growth factor (IGF) system status. METHODS: 49 children with IUGR aged 9.1 +/- 3.3 years underwent anthropometric measurements, and assessment of insulin resistance and IGF system parameters. A fasting glucose/insulin ratio (G/I) <6 was chosen as suggestive of insulin resistance. RESULTS: 11/49 (22%) children had a G/I <6. Postnatal growth closely correlated with birth size and actual body mass index (BMI). None of the insulin resistance parameters was related to linear growth and BMI. Liver function markers were significantly related to insulin sensitivity status. The IGF system status was normal and did not correlate with insulin resistance indicators. CONCLUSIONS: (a) Children with IUGR have a high prevalence of reduced insulin sensitivity; (b) postnatal catch-up growth is related to intrauterine growth and actual nutritional status; (c) insulin sensitivity status is not related to postnatal growth but to liver function; (d) IGF system is normal and not related to the insulin resistance parameters during childhood.