Investigating Metrics of Discrete-Individual Repeatability of the Stress Response.

There is currently no consensus on the most biologically meaningful way to calculate discrete-individual repeatability of stress response curves. In the current study, we compared three metrics of discrete-individual repeatability that incorporate the whole stress response curve: profile repeatability, Kullback-Leibler (KL) divergence, and hypothalamic-pituitary-adrenal (HPA) flexibility. As part of this work, we present a new R package for computing profile repeatability, "profrep.

House sparrows do not show a diel rhythm in double-strand DNA damage in erythrocytes.

DNA damage can be caused by a number of intrinsic and extrinsic factors. A recent study showed that free-living house sparrows have higher DNA damage in the summer than the winter across five different tissues. This result was consistent when house sparrows were brought into captivity and exposed to comparable light cycles, with all other variables held constant.

Investigating the effects of acute and chronic stress on DNA damage.

A hallmark of the vertebrate stress response is a rapid increase in glucocorticoids and catecholamines; however, this does not mean that these mediators are the best, or should be the only, metric measured when studying stress. Instead, it is becoming increasingly clear that assaying a suite of downstream metrics is necessary in stress physiology. One component of this suite could be assessing double-stranded DNA damage (dsDNA damage), which has recently been shown to increase in blood with both acute and chronic stress in house sparrows (Passer domesticus).

Neophobia, but not perch hopping, is sensitive to long-term chronic stress intensity.

To further elucidate the role that wear-and-tear plays in the transition from acute to chronic stress, we manipulated the intensity and duration of applied chronic stress to determine if behavior would respond proportionately. We brought wild house sparrows into captivity and subjected them to high-stress, medium-stress, low-stress, or captivity-only. We varied the number of stressors per day and the duration of stress periods to vary wear-and-tear, and thus the potential to exhibit chronic stress symptoms.

A mathematical representation of the reactive scope model.

Researchers have long sought to understand and predict an animal's response to stressful stimuli. Since the introduction of the concept of homeostasis, a variety of model frameworks have been proposed to describe what is necessary for an animal to remain within this stable physiological state and the ramifications of leaving it. Romero et al.