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Our Border Wildlife Study seeks to understand which species live and move across the border. The study focuses on mammals readily documented by passive infrared cameras. But birds, reptiles, invertebrates, cattle, and humans are also recorded across the 58-camera array.
Two years into the study, we now have a detailed view of how the wildlife community is distributed across the 30-mile stretch of border spanning the Patagonia Mountains, San Rafael Valley, and Huachuca Mountains. As the cameras continue taking photographs 24/7, the number of species we document grows. We’re also seeing trends for when and where wildlife show up across the seasons. The results below cover our first two years and will be updated moving forward.
This count includes all animals identified to the species level and animals identified to unique taxonomic groups such as genus or family. Small wildlife are often difficult to identify to species from photos alone, so they’re identified to the extent possible. For example, we can identify woodrats (Neotoma spp.) to genus but not species level from photos. So we classify all woodrat detections as Neotoma spp.
This count includes all animals identified to the species level and animals identified to unique taxonomic groups such as genus or family. Small wildlife are often difficult to identify to species from photos alone, so they’re identified to the extent possible. For example, we can identify woodrats (Neotoma spp.) to genus but not species level from photos. So we classify all woodrat detections as Neotoma spp.
Figure 1 — We’ve observed 114 species or unique taxa on our Border Wildlife Study cameras from March 2020 to March 2022.
This count includes all animals identified to the species level and animals identified to unique taxonomic groups such as genus or family. Small wildlife are often difficult to identify to species from photos alone, so they’re identified to the extent possible. For example, we can identify woodrats (Neotoma spp.) to genus but not species level from photos. So we classify all woodrat detections as Neotoma spp. and consider this one unique taxa in our tally, even though the number of woodrat species may be greater.
Our results: 48% of species seen were birds (55 taxa). 29% of species seen were mammals (33 taxa). And 23% of species seen were either invertebrates or reptiles (26 taxa).
On our radar moving forward will be ways to capture rare species and those not easily photographed or identifiable on camera. This will help us see the region’s true biodiversity. In summer 2022, for instance, we’ll start using acoustic sensors to identify nocturnal wildlife like bats.
Figure 2 — Along the 30-mile stretch of border from the western Patagonia Mountains to the eastern Huachuca Mountains, we observed a variation in total species. Each bar in the figure represents a different block of cameras. The greatest number of species was seen in the western Patagonia Mountains.
Figure 3 — This figure shows total photographs taken by Border Wildlife Study cameras that identified mammals, birds, reptiles, invertebrates, cattle, other domestic animals (housecats, dogs, horses), humans and vehicles.
The most common group was cattle (41%), followed closely by wildlife mammals (40%), birds (10%), invertebrates (5%), humans (3%), reptiles (1%), and other domesticated animals (<0.01%). While we’ve detected more bird species than wildlife mammal species in the study so far (see Figure 1), the total number of wildlife mammal detections is significantly higher. Another finding: while cattle are incredibly common at the border, observations of humans on foot or in vehicles are not.
Figure 4 — This figure shows how our results varied over time within each of our eight blocks of cameras. The unit shown is number of independent wildlife detections per camera-trap day.*
The highest rates were observed on either side of the San Rafael Valley, in the eastern Patagonia Mountains and westernmost foothills of the Huachuca Mountains. Interestingly detections decreased over time in the eastern Patagonia Mountains, while detections increased in the westernmost Huachuca Mountains. No data is available at Coronado National Memorial for 2020, and data for Rancho Los Fresnos in 2022 is still being analyzed.
*Detections are standardized by the number of days the cameras were active during the year to prevent any recording gaps from affecting our data. Further, independent detections were calculated using a 30-minute interval between observations of the same species on the same cameras. In other words, if a camera collected multiple images of white-tailed deer within 30 minutes of each other, only the first image would be counted as an independent record and count toward the detection rate shown here. Such temporal thresholds are common in wildlife camera studies to avoid overestimating counts of animals.
Figure 5 —This figure shows how often cattle were seen from 2020-2022 within each of our eight blocks of cameras. The unit shown is independent cattle seen per camera trap-day.*
The highest rate of cattle detection occurred in Sonora at Rancho Los Fresnos. While cattle aren’t permitted at the San Rafael State Natural Area or Coronado National Memorial, some trespass is apparent in the San Rafael Valley. Livestock presence affects vegetation and may influence wildlife diversity at the border, so we’ll continue to evaluate the influence of cattle on wildlife going forward.
*Detections are standardized by the number of days the cameras were active during the year to prevent any recording gaps from affecting our data. Further, independent detections were calculated using a 30-minute interval between observations of cattle on the same cameras. In other words, if a camera collected multiple images of cattle within 30 minutes of each other, only the first image would be counted as an independent record and count toward the detection rate shown here. Such temporal thresholds are common in wildlife camera studies to avoid overestimating counts of animals.