Measuring trail use with remote detectors

Posted 01/7/16

People walking on trails through forest may negatively affect birds nesting nearby without even knowing it. Birds may perceive people as predators, and change their behavior at the nest when people are nearby. For example, if a person or pet gets close, a bird may flush from the nest, leaving the nest exposed to harm. Max developed a technique to measure the number of people hiking on a trail.

Max made a technological contribution to both the fields of wildlife ecology, and parks & recreation by developing a device to measure how heavily trails are used. His goal was to quantify both group size and frequency of groups (groups/hour) along a given trail, but the available solutions were more than his research budget could manage. Having someone count hikers all day along several trails required more personnel than was practical. Meanwhile, he worried that sampling use in small time periods would provide representative data, because trail use varies throughout the day. The idea to use an automatic sensor was desirable, but the options on the market were too expensive. So he collaborated with someone with technical expertise to invent a tool that met his needs.

Components of the Trail Monitor inside a protective weather-proof box

The solution was found in open source software and DIY hardware. First, he acquired a passive infrared (PIR) sensor that can detect warm-bodied objects that passed by (these are the same types of sensors that control automatic light switches by detecting when someone walks into a room). Then, he connected this sensor to an Arduino Uno board ( that supports open source software. The board receives input from the sensor, and can be controlled by a user-written script. This is connected to a data logging shield ( which contains a clock and an SD card to store data. Then, the data can be imported Excel sheet. Max used pivot tables to translate the sensor’s detections into his variables of interest. For example, the duration of time the sensor is activated can be used as an index of  the number of people in a group passing by.

Installing a trail monitor along a trail

Max’s invention is a great alternative to what’s commercially available, in part due to the price point: one of Max’s units costs less than $250, in contrast to commercially available counters that cost about $1000/unit. Also, Max’s device can be left out in the woods for about a week between battery replacement. Its relatively small size means it can be easily hidden, which makes it relatively safe from tampering. Thus, Max continues to produce technology that will likely be used by many researchers in the future! “

Story by Jessica Gorzo