Some things can only be found if you know exactly where to look. The Peebles Navajo Cactus, at less than 3 centimeters tall, doesn’t seem to want to be found. Its thorny spines mimic surrounding grit so closely, it nearly disappears into the sand.
The Museum of Northern Arizona has monitored a population of this federally endangered cactus since the 1980s.
In 2023, the team decided to experiment with Passive Integrated Transponder (PIT) tags, the same technology used in pet microchips, to track the elusive plants. Because the cactus is so small, researchers inserted the tags into the soil next to each plant. Each tag is about the size of a sharp pencil point. They’re not often used in plants, though Saguaro National Park has put them in saguaros to help deter theft, as illegal cactus poaching poses a threat to both species.
Two years ago, researchers tagged 21 cacti within a habitat known for Peebles Navajo Cactus. When they returned the following year, they found all 21 tags…but only 11 plants. The rest had either died or disappeared.
In 2025, the team again located 11 tagged cacti: eight were the same individuals seen previously, two had reappeared after being “missing,” and one was a brand-new seedling. Even with PIT tags, the cacti were tough to track down; possibly because they pulled themselves partway underground or were hidden under rocks.
The tags are a new way to track this small cactus, helping determine whether missing plants are truly dead or simply buried treasures.
This Earth Note was written by Danika Thiele and produced by KNAU and the Sustainable Communities Program at Northern Arizona University.
