Summary of Southern California Monarch Season 2023

Summary of Southern California Monarch Season 2023

Based on posts from the Facebook Group I administer: “Monarch Butterfly Guardians – southern California”

April and May, 2023 – Absolutely NOTHING – NO MONARCHS, no eggs, no cats, milkweed not developing There was great concern if the monarchs were wiped out in the 12 atmospheric river storms. However April, May and June were exceptionally cool, cloudy and raining. Extremely unusual for SoCal. Usually monarchs are here early April, no predators and several eclosures by early to mid-May. NONE this year. I can verify with my own personal habitat AND the 4 parks I oversaw planting in the City of Dana Point. I did have 3 new caterpillars mid-May that eclosed in early June. But only saw 1 monarch in my garden all May.


June, 2023 – The month was also much colder and wetter than a normal June. Milkweed started to grow the minute the sun hit and monarchs started to show up with the sun – a day or two in early June, more by mid and late June. All across LA, Orange and San Diego, group members began posting lots of photos of caterpillars, newly eclosed monarchs. It’s like the spicket turned on. Milkweed, both native and tropical, began growing abundantly (keep in mind it had more rain this winter/spring than any other year I’ve known in SoCal across 50 years!).  Everyone was delighted and thrilled.

June/July 2023 – Were wonderful months with Facebook group members reporting many monarchs, egg bombing, many caterpillars, successful chrysalids and newborns. Posts every single day of July were filled with photos of healthy newly eclosed monarchs — And keep in mind, netted habitats are NOT allowed to be used by members. If they do, they cannot post any photos or mention of it, so I think many adhered to the No touching, No rearing CDFW Ruling. It was so heartwarming to hear that the monarchs were here in abundance. I finally saw them flying around all over Orange County as they usually do in June and July.

August 2023 – PREDATORS GALORE. Late July into August, temps hit hi-80’s, low-90’s along coastal SoCal. With it, predator propagation and 50 to 90% loss to T-fly reported THIS week (8/11/2023). Lizards, wasps, praying mantises all being seen LA, OC, San Diego, Riverside, San Berdu.  Also, people report seeing monarchs EVERY DAY in their gardens. I have had males soaring across my garden every single day now for 4 weeks. HOWEVER, what changes with the heat is females come, lay eggs, eggs disappear within a day. VERY few hatch. Caterpillars that do hatch disappear as well. VERY few make it to 5th instar, fewer to chrysalid – 80% loss to T-fly once in chrysalid. This has been the pattern here for the last 5 years, with T-fly increasing dramatically as of 3 years ago. Nonetheless, monarchs are here flying all about LA, Orange, San Diego, but Riverside and San Berdu get into the 100’s and see much fewer monarchs, eggs, cats.

Many people report seeing monarchs mating as of late July and August. Monarch like the temps in the 80’s and are active throughout coastal SoCal right now. Some are certainly successful at newborns even with the predators. Just today, I was at checked out the monarch habitat planted at one of the Dana Point parks (Lantern Bay Park). It was first started 2 summers ago, with subsequent maintenance and additional plants for the past 2 springs. It has the most profuse, 3′ tall milkweeds and nectar plants I have ever seen! There were 8 monarchs flitting all about. I found plants that had clearly been stripped of leaves as well as 2 dead chrysalises. But clearly, that habitat is successful right now.

September 2023 – Expectation based on past 5 years:  if the temps stay in the 80’s to 90, we will continue similarly to August – with eggs not hatching, cats dying more and more either from t-fly or viruses, predators going strong. So urban gardeners/group members will report more and more being heartbroken about the T-fly losses (up to 90%), but I remind them again and again, 2 in 1,000 eggs makes it to a butterfly. The T-fly is particularly upsetting because Ag brought it in with no research whatsoever the impact on other insects/monarchs.  I suspect that group members may use netted habitats to protect some caterpillars just to feel some joy in having monarch caterpillars in one’s garden, but no mention of photo of such is ever put on the Facebook group. If temps get into 90 to hi 90’s several days, we will stop seeing monarchs, eggs, etc.

October 2023 – same as September but less and less monarchs/eggs until we have some cool days in the 70’s to lo -80’s. Then, Monarchs show up again, predators start to decrease as the weather cools. We can have an October BUMP in the number of monarchs in SoCal. Everyone kind of looks forward to that after 2 months of devastation from T-flys, wasps, lizards.

This is how it appears to unfold in coastal California. Based on the reports of several people from several counties reporting having around 30 and 40 monarchs eclose in their gardens throughout June and July without habitat protection, we have a solid monarch presence this year.

FYI – About migration from southern California:
I rarely hear anyone say that we may have a good Thanksgiving count in central coast California based on southern California migrants. They always seem to talk about the monarchs coming south from northwest and northern Cal. Our SoCal monarchs DO migrate – they leave in November, come back usually by April (this year June). I believe coastal California monarchs are a rich source of monarch population at the migratory sites, otherwise, what explains the abundant monarch activity June thru September, and then they are gone. They have to go someplace. No one is able to tag SoCal monarchs these days in October and early November to verify that because of CDFW Ruling, but I truly suspect that SoCal contributes as much to the count at overwintering in central coast CA as the northwest, etc.