Innovative technology helps Washington track black-tailed deer in dense forests
This blog was originally published by the Blacktail Deer Foundation and includes contributions from the Washington Department of Fish and Wildlife (WDFW).
Columbian black-tailed deer have long proven difficult to count in their densely vegetated habitats. The challenge is significant and critical for the future of black-tailed deer conservation and management. Deep in the forested Cascade Range of southwest Washington, research is underway that could transform how biologists and wildlife managers monitor one of our most elusive big game animals.
The Washington Department of Fish and Wildlife (WDFW) launched an innovative study earlier this year that is testing a combination of technologies to develop a way to monitor the state’s black-tailed deer. The Blacktail Deer Foundation (BDF) jumped on the opportunity to support this multi-year study in its first year. BDF raised funds through its volunteer member chapters that were used to support the purchase of research-grade trail cameras, proximity sensors, and GPS collars to help provide a detailed picture of local black-tailed deer populations.
Columbian black-tailed deer populations likely peaked in the 1960s, and these deer now exist at lower densities than in the past. Understanding current population dynamics that can more accurately determine the ratio of bucks to does is essential for setting appropriate hunting seasons and ensuring long-term sustainability of the subspecies. The innovative monitoring methods being tested in Washington could benefit deer management across its entire range and help identify locations in which habitat restoration will be the most effective for black-tailed deer populations.
Trail cameras as a monitoring tool
In 2015, WDFW adopted an updated game management plan for black-tailed deer, with population management objectives that depend on knowing the numbers of bucks-per-100 does. The core barrier to getting this information is habitat. Black-tailed deer live in densely vegetated forests where you simply can’t see and count individual animals over large areas like you might with mule deer or white-tailed deer in open prairie or agricultural landscapes.
Standard population surveys have proven unreliable in thick forests and annual pre- and post-hunt herd composition data cannot provide the precision needed for accurate estimates. To address this shortfall, WDFW staff from different divisions are developing black-tailed deer field and statistical methods that they and other state agencies can potentially use to produce defensible estimates for buck-to-doe and juvenile-to-doe ratios.
In recent years, there has been a surging interest in using camera traps as a passive tool for monitoring. This project will ultimately deploy 120 trail cameras across the landscape, strategically positioned in different habitat types. Most deer home ranges will contain two trail cameras, one in clearcut habitat and one in forested areas. These cameras capture both motion-triggered photos and five-minute time-lapse images, to providing the detections of deer needed to estimate deer encounters with camera stations.
WDFW’s study combines the use of trail cameras with GPS collars to estimate home range extent, size, and movement rates relative to season. Additionally, proximity sensors are mounted on the tree of the camera trap, passively monitoring for collared deer that might approach the camera station, which is logged as an encounter. From those encounters, the probability of detection is calculated from checking the camera trap photos to see if the collared deer was seen in one of the images. Together, this data will help WDFW determine how to best place camera traps to monitor black-tailed deer populations in different areas throughout western Washington.
Technologies working together
The study’s innovation lies in how multiple technologies work together. The GPS collars take four-hour GPS fixes throughout the year, and those locations are used to estimate the extent of the seasonal home range. The collars also take 15-minute locations for 24-hour periods for six to eight days spread throughout each season. These high-frequency GPS locations are used to calculate a movement rate relative to season. On the same tree as the camera trap is a proximity sensor that communicates with the GPS collar if it comes within 100 meters of the tree.
When a collared deer passes within 100 meters, the interaction is logged on the GPS collar worn by the deer. Whether the deer is detected by the camera images at that specific camera station helps researchers calculate the probability that deer will be detected at camera stations, an important model parameter used to estimate uncertainty in population estimates. Across all 120 cameras, the probability of detection becomes a model parameter that informs estimates for determining ratios of bucks-to-does and fawns-to-does.
In January and June of this year, WDFW biologists installed 40 GPS collars on black-tailed deer (26 adult females and 14 bucks), and over 90 cameras were placed on collared deer home ranges. Ryan Krapp, BDF Regional Conservation Coordinator for Oregon and Washington, joined WDFW Ungulate Specialist Brendan Oates in the field over the spring and summer to help deploy and maintain trail cameras. Maintenance included refreshing memory cards and batteries, measuring camera viewsheds for visible distance, and resetting some camera viewsheds after curious black bears shifted the camera angles.
This winter, the first batch of images collected from camera stations will be classified to species, sex, and age class of detected deer and other animals. Additional GPS collaring of deer is planned for January 2026, with new camera stations added within the home ranges of those deer in March 2026. Cameras installed in 2025 will be serviced with new batteries and memory cards. GPS collars from the deer captured in January 2025 will also remotely drop from the neck of the deer in early March 2026, then collected from the field. A full year’s dataset of locations and interactions with camera stations can be downloaded and analyzed. Camera station refreshes and ongoing analysis of image and collar data will continue through summer 2027.
Producing a monitoring framework
WDFW biologists hope results from this study will help them create a monitoring framework for black-tailed deer across Western Washington, with camera grids rotating among management zones each year.
“We are excited to be developing this novel monitoring framework for black-tailed deer — it’s something we’ve been wanting to do for years,” said Oates. “As we fine-tune the field and analytical methods of this study, we’re hopeful that we can start rotating a camera grid throughout the different black-tailed deer management zones in Western Washington to provide better information on demographic rates, which will help us manage these populations more effectively.”
The Blacktail Deer Foundation wanted to get on-the-ground of this new effort and support this emerging science with the hope that these innovative monitoring methods could benefit deer management across other parts of the U.S. and Canada.
“The combination of camera traps, GPS technology, and proximity sensors represents an advancement in wildlife research, one that could finally give us the tools we need to effectively monitor and manage black tailed deer populations in even the densest forest habitats,” said Krapp.
For hunters, wildlife managers, and conservationists alike, better population data means better ecological understanding and sustainable deer hunting opportunities for all.
