Wildlife Cameras at Chiricahua National Monument, 2022

A bobcat (Lynx rufus). NPS photo.

The National Park Service's Sonoran Desert Network (SODN) uses remote wildlife cameras to monitor medium- and large-sized mammals in park units across the Sonoran Desert and Apache Highlands. The project began in 2016. Its goal is to detect biologically significant changes in mammal populations and communities over time, and to give park managers reliable, useful information on them. This page summarises what the cameras found at Chiricahua National Monument in 2022.

Why cameras, and what occupancy means

Remote cameras record many species at once, over wide areas, without disturbing them. SODN analyses the photographs with occupancy modelling:

• Occupancy is the share of an area a species inhabits. A species photographed at a site is present; one not photographed may be absent, or present but missed, and the models account for those misses statistically.
• Modelled over several years, occupancy, often used as a stand-in for abundance, shows whether a species is increasing, stable or decreasing.
• Covariates help explain the pattern. Following the effect of temperature and rain, for example, helps managers judge what climate change may do.

A wildlife camera at Chiricahua National Monument.

How the cameras worked in 2022

• In May 2022 field crews set up 41 cameras at unbaited, permanent monitoring sites across the monument, in the same places and with the same settings as in earlier years, on stakes or strapped to trees and other structures.
• The sites are paired with SODN's long-term vegetation and soil monitoring plots, chosen mostly by a spatially balanced random design, so that detailed data on the plants at each site, potentially important for the animals' habitat, can be added to the wildlife data.
• Triggered by motion or a sudden change in temperature, the cameras took photographs from May 16 to June 27, 2022, and were then collected.
• Technicians removed the "false triggers" (photographs with no animal), sorted the "detections" with Colorado Parks and Wildlife's Photo Warehouse database, and exported the metadata for analysis.
• One volunteer and seven interns from various parks and partner organisations helped set up and collect the cameras.

Field crews deployed 41 wildlife cameras at the monument in 2022.

Cameras have gone out at the same places every year since 2017, except in 2020, because of the COVID-19 pandemic: five years of data. The number of photographs containing an animal has ranged from 734 to 4,293 a year. Why it varies so much is not yet clear; the network hopes occupancy modelling of environmental factors will help explain it.

What the cameras saw

The cameras made 734 detections: 646 of mammals identified to 10 species, 10 identified only to genus or family, 10 of mammals that could not be identified, and the rest birds (five species and 27 unidentified birds) and 8 unidentified reptiles.

Wildlife detections from 41 cameras at Chiricahua National Monument, May 16 to June 27, 2022.

Two records stood out. Western spotted skunks are seldom seen in the monument, so two detections were intriguing. And a zone-tailed hawk, often seen flying over the monument but rarely caught on the cameras, was photographed by accident after a camera was knocked over.

An example: white-tailed deer and elevation

Trend models need several consecutive years of data, but a single season can still answer narrower questions. The network fitted a single-season, single-species occupancy model with the R package "unmarked", grouping detections into seven-day periods. It chose nine species that the cameras can reliably identify, at least 43 centimetres long, the size of a rock squirrel, which ruled out chipmunks, rats and mice, and that were detected at more than 30% of sites, which ruled out rarer species such as the western spotted skunk. Covariates were kept only if they had some explanatory power (p < 0.10).

Occupancy probability of white-tailed deer against elevation at Chiricahua National Monument, 2022: the average in green, the standard error in grey.

For white-tailed deer, elevation mattered. In the monument's lower areas their occupancy probability is high, 80–95%; above 2,100 metres it drops below 25%. The model suggests the deer prefer lower ground, likely because it gives easier access to food, water and cover than the higher areas, which are more barren, rugged and steep. The result shows managers how the deer use the monument, and how much a single season's data can tell.

Sources

• National Park Service, Sonoran Desert Network, "Wildlife Monitoring at Chiricahua National Monument." https://www.nps.gov/articles/000/sodn_wildlife-monitoring-chiricahua-2022.htm