Other animals on the farm can also be vulnerable to fire smoke. Horses have massive lungs – the animals are born to run and suck in lots of air in the process. “We don’t know for sure, but horses may be one of the most sensitive species to smoking of all mammals,” says Kent E. Pinkerton, director of the Center for Health and the Environment at the University of California, Davis. “The amount of air that they’re ingesting, which is basically full of particles in the air that they’re breathing in, can really be quite devastating to the horse.”
The infamous 2018 Camp Fire, which destroyed the town of Paradise, bathed the UC Davis campus in smoke, giving Pinkerton and his colleagues a unique opportunity to determine the effects on another species: the rhesus macaque. At the campus’s California National Primate Research Center, the macaques live in outdoor enclosures. So, just as Skibiel did with dairy cows, Pinkerton could monitor them as the haze rolled in.
He found one increase in abortion during the breeding season, which happened to overlap with the smoke incident: 82 percent of the smoke-exposed animals gave birth, when the average proportion of live births in a normal year is between 86 and 93 percent. “We actually had a small, but statistically significant, reduction in birth outcomes,” Pinkerton says. “We don’t know all the details of it or what the exact cause would be, other than the fact that it was associated with wildfire smoke.”
In Indonesia, which is plagued by peat fires, primatologist and ecologist Wendy Erb of the Cornell Lab of Ornithology has studied the effects of smoke on another primate, the orangutan. Peat fires have created a serious public health crisis in Indonesia, where developers are draining peatlands and setting them on fire to create farmland. This is a particularly nasty type of fire, as it smolders through carbon-rich fuel for months, bathing cities and surrounding forests in smoke for far longer than, say, a California wildfire tearing through the vegetation.
Erb monitors individual orangutans in the wild by collecting urine and stool samples (yes, that means standing under trees to catch the stuff) and following them around throughout the day to see how much they eat and how much energy they use . From the urine samples, she can determine ketosis, or whether the animal converts fat as an energy source.
After smoke events, she found, ketosis among orangutans increased significantly. “We actually saw that they ate more calories, but despite eating more calories, they also rested more and they traveled shorter distances,” says Erb. “So they show this energy-saving strategy—they move less, they slow down, and they eat more calories—but they still go into ketosis.”
One hypothesis the team has yet to test is that the orangutan’s bodies are building an immune response to the flurry of smoke, and that they need more calories to fuel this defense. But this can use up calories that the animals need for other life needs, such as growing, reproducing and feeding their offspring. (Of all primates, orangutan mothers spend the most time raising their young.) Conserving energy by moving less also means fewer opportunities to socialize, a concern for a primate that is already critically endangered because it losing its habitat to deforestation.