Recently, the Contra Costa UC Master Gardener Help Desk received the following concern about the deer population in Walnut Creek. “I think the deer population has changed due to the climate crisis. I’ve lived here in Walnut Creek next to John Muir Medical Center for 35 years,” a local gardener wrote in.

“They’re usually aggressive starting in August. But I’ve seen them walking the streets early in the morning in early May. That’s never happened before.

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“And my neighbors have complained that deer are chopping away at their gardens, eating things they’ve never attacked before. Like a Jasmine vine that is almost 30 years old,” they added.

“Have you heard if there is something changing in the deer population? If so, please let me know, and I will share with my neighbors. We’re all very puzzled.”
The Help Desk volunteer replied, “Thank you for contacting the UC Master Gardener Program Help Desk with a question about the deer population and whether it’s changed due to the climate crisis.

“Deer are common in many residential areas in Contra Costa. Deer can display aggressive behavior when protecting their young in the spring or during rutting season in the fall. Deer can also become aggressive toward people when they are intentionally being fed and lose their fear of people. If you have aggressive deer due to this habituation, contact the California Department of Fish and Wildlife. (707) 428-2002.”

The volunteer added, “If you mean they are more aggressively feeding on things they didn’t normally eat before, this happens when surrounding areas begin to dry up, and our landscaped yards continue to be watered. Deer are opportunistic and will try a wide variety of plants, especially when hungry. And I’m sure they have individual tastes, too.

“Another factor may be that something has changed in their territory that you don’t know about. Deer can travel at least several miles in a day. Studies in other parts of California indicate that the deer population is declining due to habitat loss. I couldn’t find similar studies for the Bay Area, though.”

The volunteer also provided this link for more information about managing deer:
https://ipm.ucanr.edu/home-and-landscape/deer/pest-notes/#gsc.tab=0

Finally, this document has a long list of supposedly deer-resistant plants: 
https://nrm.dfg.ca.gov/FileHandler.ashx?DocumentID=83544&inline
 

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