Mice will be captured with Sherman live traps and handled using standard small mammal field techniques. Approximately 50-100 traps will be set at dusk baited with oats and they will be checked that evening (3 hrs later) or in the following morning. We will carry out this trapping on UMBS Burn Plots and Colonial Point as these areas have reasonable mouse abundance. The work at these sites would not involve euthanizing animals and we will euthanize animals on areas of UMBS that are separate from long-term mouse trapping areas established and run by Phil Myers. The project will take place approximately April 1 to September 1 in each year. At each capture, we will record the species and identity of mouse, sex, reproductive condition, age and body mass, and we will collect fecal samples (from the traps) and saliva samples (using a cotton swab briefly placed into the mouth). We will also assess tick burden at each capture by counting the number of ticks (at different stages) on each individual. At the first capture, we will permanently mark each mouse with uniquely labeled metal ear tags. We will collect hair, whisker, and blood samples at the beginning and end of this summer field season. At the first and last capture, we will collect hair by shaving a dime sized piece of hair from between the shoulder blades. We will pluck two whiskers from the snout and obtain blood samples (<1% of body mass as suggested) from the tail vein. The hair and blood samples will be used to quantify reproductive and stress hormone levels and how they change seasonally. Blood samples will also be useful for screening for Hanta virus. The whisker samples will be used for stable isotope analysis to analyze dietary patterns and how they change seasonally. The saliva samples will be used to assess viral pathogen load. All of these sampling techniques other than blood sampling is minimally invasive after the animal is captured and blood sampling will only be performed by experienced personnel. At the first and last captures, we will quantify the behavior of mice using open-field trials, which is a standard way to measure the temperament of small mammals in the field. Mice will be captured in the evening and placed into a portable arena for a maximum of 20 min while their behavior is recorded with a video camera. These behavioral trials provide a quantitative way to assess the activity, aggression, and exploratory behavior of small mammals, which may be correlated in range expansion. We will aim to measure the behavior of each mouse two times with 4 weeks between each trial. All non-target animals captured (anything other than mice) will be noted and then released without handling. We will trap on different parts of the study area on each night to avoid recapturing the same mice on consecutive days. However, the same areas will be repeatedly trapped throughout the summer to estimate survival and reproductive investment of the same individual mice. As such, we will handle mice where they were captured and release them at the same spot. On some of the UMBS Burn Plots, we will capture mice and record their species identity, weight, sex, reproductive condition, and age. We will then collect saliva, hair, and whisker samples and perform the open field trial as described above. At the conclusion of this open-field trial, we will euthanize the mouse using an isoflurane overdose. We will then collect the brain and other organs for subsequent physiological measures (hormone receptor expression, oxidative stress signaling, markers of damage due to stress). The pelt and skeleton and any other unused tissues will be deposited as a specimen in the UM Museum of Zoology. These data collected at UMBS will be combined with other similar data we collect at other sites throughout the lower and upper peninsula of Michigan. This will allow us to document how the age since colonization impacts the expression of different life history, physiological, and behavioral traits. For example, we predict that at the most recent colonizations of P. leucopus in the eastern upper peninsula of Michigan, mice should be the most aggressive, active, exploratory and have faster metabolic rates with decreased stress responsiveness. Such mice may be most likely to expand their range successfully. Taken together, this project will assist in our understanding of how some species may experience range expansions due to climate change whereas others that are less able to expand their range may suffer the consequences. This project should also provide information about pathogen (Hanta virus) load of mice on UMBS property.