What the Health Lab Counts
1Last July, after a hike in Hollow Creek Forest, seventh grader Mateus Oliveira found a tiny tick on his leg. His doctor, Dr. Seo-yeon Park, removed it, cleaned the spot and told him what signs to watch for. She explained that black-legged ticks can carry the bacteria that cause Lyme disease, and that the county health lab counts ticks in the forest every summer. In the fall, Mateus's class visited the lab, and a lab biologist, Ms. Adaeze Nwosu, shared the lab's records with them.
2A black-legged tick usually lives about two years and takes one blood meal at each of three stages: larva, nymph and adult. Larvae hatch in midsummer and feed in late summer, most often on a small mammal such as a white-footed mouse. After that meal, they drop into the leaf litter, wait through the winter and become nymphs. Nymphs look for their meal the following June and July. They are the stage most likely to bite people, because they are about the size of a poppy seed and easy to miss. Adults feed mostly on deer in the fall.
3White-footed mice eat many foods, but acorns are one of their favorites, and mice store them to eat through the winter. Oak trees in a forest tend to make a huge acorn crop in some years and very few acorns in others. Each fall, the lab counts acorns that fall into baskets on the forest floor. Each July, it traps mice, counts them and lets them go. Also each July, workers drag a white cloth along 100 m of trail and count the nymphs that cling to it (Table 1).
4In spring 2024, a windstorm blew down most of the trees on a 20-hectare patch at the edge of the forest. With the trees gone, sunlight now reaches the ground there. Ticks lose water quickly in dry air and spend most of their time in the leaf litter. In July 2025, the lab compared the blowdown patch with the closed forest nearby (Table 2). It also kept groups of nymphs in jars of air at three humidities for 10 days (Table 3).