Here’s how California’s heat wave is affecting wild animals

While larger mammals like bears, coyotes and mountain lions are most adaptable to heat, smaller ones that can’t regulate their temperature and are more reliant on water, such as fish, amphibians and birds, are the most vulnerable. But even the more hardy animals can become more stressed under extreme heat and may venture into human territory in search of water and prey, biologists say.

“In general, animals are much more adaptable than we give them credit for, and the species that can easily move will often fare better than those that can’t,” said Jordan Traverso, spokeswoman for the California Department of Fish and Wildlife, in an email.

There have not yet been reports of massive die-offs of animals because of soaring temperatures this week. The toxic algae bloom that has killed tens of thousands of fish in the San Francisco Bay and Lake Merritt started in July, before the heat wave, and already shows signs of slowing down. Yet ecologists say that the state’s most vulnerable wildlife, such as endangered tiger salamanders and chinook salmon, along with delicate hummingbirds and even desert raptors, are dealing with too many catastrophes at once.

A newt counted and removed from the road by a volunteer group along Chileno Valley Road at Laguna Lake in Marin County.  During heat waves, smaller animals that can't regulate their temperature and are more reliant on water, such as fish, amphibians and birds, are the most vulnerable.

A newt counted and removed from the road by a volunteer group along Chileno Valley Road at Laguna Lake in Marin County. During heat waves, smaller animals that can’t regulate their temperature and are more reliant on water, such as fish, amphibians and birds, are the most vulnerable.

Santiago Mejia/The Chronicle

“These extreme heat waves are really hitting many of California’s wildlife species really hard, and at a time when they are facing so many other stressors like drought and habitat loss,” said Shaye Wolf, climate science director of the nonprofit organization Center for Biological Diversity .

For example, last year, when water temperatures in the Sacramento River stayed above the threshold of 53.5 degrees for too long because there was less water flowing from Shasta Dam during the drought, dozens of endangered winter-run chinook salmon and countless numbers of their eggs died. Wolf is worried that it could happen again this year.

When even the coast, which normally stays cool, is under a heat advisory like it was Tuesday, Wolf said intertidal animals like mussels and barnacles can die at low tide. That happened last summer in the Pacific Northwest, when temperatures over 100 degrees killed one billion sea creatures along the Vancouver coast alone, scientists said.

“Intertidal creatures are vulnerable to heat during low tide, because they’re already living so close to their temperature limits,” said Wolf. Because many of them can’t move, she said, “They can essentially get cooked to death.”

A black bear captured in a wildlife camera in Shasta-Trinity National Forest in July 4. Larger mammals like bears, coyotes and mountain lions are most adaptable to extreme heat waves, while smaller wildlife that can't regulate their temperature and are more reliant on water, such as fish, amphibians and birds, are the most vulnerable.

A black bear captured in a wildlife camera in Shasta-Trinity National Forest in July 4. Larger mammals like bears, coyotes and mountain lions are most adaptable to extreme heat waves, while smaller wildlife that can’t regulate their temperature and are more reliant on water, such as fish, amphibians and birds, are the most vulnerable.

Provided by Julia Hartman/Shasta-Trinity National Forest

The Allen’s hummingbird is another animal that relies on coastal temperatures staying cool. A smaller species of hummingbird, it is native to coastal southern California and is currently migrating from Northern California, where it breeds, to the Los Angeles area. The bird has died off in droves in previous heat waves, said Lisa Tell, professor of avian medicine at the UC Davis School of Veterinary Medicine.

The birds need lots of shade, water for bathing and extra food when it’s hot.

“They spend a lot of their time perching and resting,” Tell said. “If there’s good shady areas they’ll probably spend more time doing that.”

In the forest, most animals just adjust their behavior in response to the heat, said Todd Johnson, a wildlife biologist at the Shasta-Trinity National Forest, where high temperatures are common in summer.

An elk captured in a wildlife camera at Shasta-Trinity National Forest in 2021. Larger mammals are most adaptable to extreme heat waves, while smaller wildlife that can't regulate their temperature and are more reliant on water, such as fish, amphibians and birds , are the most vulnerable.

An elk captured in a wildlife camera at Shasta-Trinity National Forest in 2021. Larger mammals are most adaptable to extreme heat waves, while smaller wildlife that can’t regulate their temperature and are more reliant on water, such as fish, amphibians and birds , are the most vulnerable.

Provided by Julia Hartman/Shasta-Trinity National Forest

“They’re going to be active during the coolest parts of the day or night,” he said. “During heat of the day, they’re going to seek out the coolest places they can find to wait it out.”

That includes north-facing slopes and areas near water, with good vegetative cover and where they can catch afternoon breezes.

Amphibians and reptiles, which are more vulnerable to outside temperatures because they can’t self-regulate, go into hiding. Some snakes can be killed if they’re out in the sun too long, and Johnson has seen salamanders, which breathe through their skin, hide in cool limestone formations or burrow below ground where it’s cool and damp.

Other animals adapt by spending more time in the water.

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