05/23/2026
A biologist tracking a female bobcat through a wildfire burn scar in the Simi Hills could not find the den. The GPS collar said the cat was right there. The ground-level brush where bobcats normally hide their kittens was gone, burned to nothing two and a half years earlier. Then the biologist looked up.
Joanne Moriarty had been studying bobcats in the Santa Monica Mountains for seventeen years. She knew where dens were supposed to be. In thick chaparral. In coastal sage scrub. In the large stick-and-leaf nests that woodrats build and bobcats commandeer. Those were the standard locations confirmed across decades of fieldwork by the National Park Service research team at Santa Monica Mountains National Recreation Area.
None of those options existed anymore. The Woolsey Fire had burned through the Simi Hills and Santa Monica Mountains in November 2018, consuming nearly 97,000 acres and destroying roughly two-thirds of the natural habitat in the Simi Hills. Two and a half years later, very little vegetation had grown back. The dense ground cover that bobcats depend on for denning was simply not there.
B-370 was a female bobcat first captured in the Simi Hills more than a year after the fire. When biologists trapped her, they noted she appeared to have nursed previously. They fitted her with a radio collar and released her. In April 2021, her GPS data showed a pattern that Moriarty recognized immediately. The cat was returning to the same spot repeatedly, a strong indicator that she had given birth and was nursing a litter in a den somewhere nearby.
Moriarty hiked to the coordinates and searched. Nothing on the ground. No den entrance in the brush, because there was no brush. She later described the moment simply. "I swear she's in this tree, but I can't find her. Then I look up into this little tiny hole in the tree, and her face is just poking out at me. Of course, she's been staring at me the whole time."
B-370 had denned inside the hollow cavity of a large oak tree, high off the burned ground. Moriarty used a remote camera mounted on an extension pole to look inside the cavity without disturbing the cat. Three kittens. One female and two males, designated B-379, B-380, and B-381. They weighed between 500 and 600 grams each and were approximately thirty days old.
Tree denning in bobcats is rare. Moriarty, with seventeen years of field data, called the location unusual. The standard denning architecture for the species is ground-level. Thick vegetation or a woodrat mound provides concealment from coyotes, mountain lions, and raptors that will kill exposed kittens. A tree cavity provides the same concealment but requires the mother to climb every time she enters or leaves the den, which is energetically expensive and exposes her to detection during the ascent and descent.
B-370 chose the tree because the fire had eliminated every ground-level alternative. The chaparral was gone. The sage scrub was gone. The woodrat nests, which are built from accumulated material over generations, had burned. The landscape she was denning in looked nothing like the habitat her species had evolved to use. She adapted to what was available, found a cavity in a surviving oak, and raised three healthy kittens in it.
The kittens would stay in the natal den for four to five weeks before the family moved to secondary den sites. The mother would care for them until nine to eleven months of age, at which point they would begin following her on hunts and gradually become independent. The NPS bobcat study, running continuously since 1996, would continue tracking them.
Source: National Park Service / Santa Monica Mountains National Recreation Area Wildlife Tracking
