Extreme population fluctuation in the Northern Pygmy Mouse (Baiomys taylori) in southeastern Texas

The Northern Pygmy Mouse (Baiomys taylori) occurs throughout much of Mexico and into the southwestern United States, with its range currently expanding northward in the U.S. Despite documentation of species range expansion, there have been very few studies that have monitored population growth patterns in this species. During a 16-month mark-recapture study in coastal southeastern Texas, a striking fluctuation in densities of Pygmy Mouse populations was observed. The extreme population increase and decline was evaluated with respect to several biotic and abiotic variables postulated to affect rodent population levels. Highest population levels were preceded by high fruit and seed availability, and variation in 6-month cumulative precipitation totals explained 73.8% - 77.1% of the population variation in the study.