It’s Cold. Can Monarch’s Survive?

It’s getting cold here in Houston.  According to the latest weather reports I’ve seen, the temperature might get down to 22 degrees tonight.

Although we’ve been keeping a few Monarch Caterpillars indoors, we’ve kept several outside, we just covered them up to provide some insulation.

As we were covering our plants and pipes tonight, Leecy and I also decided it might be a little chilly for the Monarch Caterpillars that have been in our outdoor enclosure.

Little did we know we had 15 Caterpillars!  Fortunately, we’ve been protecting much of our Milkweed so we should have plenty enough for them to eat.

Monarch Caterpillars Brought Indoors Before 20 Degree Freeze

Monarch Caterpillars Brought Indoors Before 20 Degree Freeze

That got me to thinking.  How cold can it be for Monarch Caterpillars to survive?  I was able to find out that Monarch Butterflies can crawl at temperatures of 41 degrees, and need a temperature of 55 degrees to be able to fly (see here for reference).  In terms of mortality, Monarch Butterflies can survive temperatures of around 17 degrees, but not for very long, and around 50% of Monarch Butterflies will die at this temperature.

But what about Monarch Caterpillars (not Butterflies), how low can the temperature be before they begin to die?  Unfortunately, I couldn’t find the answer to this question.

Can anyone help answer the question above?  I’m really curious.

Valerie Evanson - I’ve been wondering that myself, but haven’t come across anything on it. Since they overwinter as adults, I’m guessing they aren’t as hardy as swallowtails. Looking at my pupas that are overwintering, the swallowtail and moth shells are very tough in comparison to the monarchs. In respect to species that overwinter as pupas, my one insect book quotes Dale Schweitzer, “A good general rule is that underground pupae should not be exposed to temperatures below 20-25 degrees F. Unless your climate frequently has nights below about 10 degrees F the easiest approach might be keeping above-ground pupae outside in a shaded sheltered place.” So . . . a monarch would need it to be warmer than that. I’ll see if I can find a more definitive answer, but first I need to get out the snow blower and clear the driveway. 🙂January 12, 2011 – 10:14 am

Valerie Evanson - I contacted Karen Oberhauser at MLMP (U of Minn) and she said there is no good data on the subject and that one of her students is starting a study on it.January 13, 2011 – 10:30 am

Tonya - Do you know where i could get butterflies to release on feb 6 for a meorial ceremony ?January 13, 2011 – 7:42 pm

texdr - Yea that’s what I found out as well. I emailed Dr. Bill Calvert and he essentially said the same thing. They really don’t know.January 13, 2011 – 8:24 pm

texdr - No I’m sorry I don’t. Are you located in Texas? It might be tough to get Butterflies right now (I’m guessing) because they need pretty warm temperatures to be able to fly.January 13, 2011 – 8:27 pm

leecytx - Well we kinda found out a little on this post. Today the temperature was 60F so we were looking at the milkweed we had outside and sure enough, we found 3 little cats. They were 1st instar stage. We did not see them on the day we brought all the others inside & the temps outside got down to 22F (we know that because our pool automatically comes on 27F that temp to keep the pipes from freezing). We have left them outside for now and maybe we can test this whole question on these guys -especially since we are almost out of milkweed! Stay tuned …January 15, 2011 – 7:32 pm

Sandi Barr - Hi, I live in So.Cal (North Tustin). It was 41 deg. last night and the grass has frost. I know that isn’t cold for some of you BUT I must have at least 50+ Monarch cats munching in my yard. The weather has been so unpredictable. It will get in the 60’s today with lots of sun BUT it is supposed to rain by Sun. Should I just bring inside as many of the cats that I can? I have 2 big cages. I will do anything to rescue them. Directions please 🙂 SandiDecember 20, 2012 – 12:27 pm

E - hi i live in canada. my mom and i found a monarch butterfly on our front step. we thought he was dead. when we took him inside and warmed him up he started to fly around. we put him under a big strainer with banana and apple slices. there is still snow on the ground here and it is cold. we don’t want him to die. should we keep him with us or should we let him go? is it ok to let him go when there is snow on the ground? how warm does it need to be outside for him to live>April 24, 2013 – 9:30 pm

texdr - That’s amazing that you already have a Monarch in Canada! I would really recommend you report your sighting to Journey North ( I’ve never heard of a Monarch making it that for North this early in the year.

To fly, Monarch’s need the temperature to be at least 50 degrees Fahrenheit. They can survive temperatures below freezing for short periods of time, but the bigger issue is it will need a source of food and if there is snow on the ground, you probably don’t have any nectar plants for it to feed. I don’t think they will use Apples or bananas. However, I do have a solution, and if you do a search on my blog, I’m pretty sure I have some posts and a video or two about how to do what I’m going to suggest.

You can feed it gatorade, or this juice product we have in the States (not sure if it’s in Canada) called Juicy-Juice. Soak a cotton ball in the juice. You can then try placing the monarch on the cotton ball. If it’s really hungry (and/or smart) it will start feeding. Sometimes they need a little encouragement, so you can hold it by the top of it’s wings, and have someone every so lightly unfurl it’s proboscis into the cotton ball with juice. After a couple of attempts, it should start drinking.

As far as letting it go, if there are any flowering plants, and if the temps are above 50, you can probably let it go, although it may really have to hunt for food. Depending on if it’s male or female, if it’s the latter, she’s probably going to be hunting for milkweed to lay her eggs on.

Hope that helps somewhat. Let me know how it turns outApril 24, 2013 – 9:55 pm

Elizabeth - I found this on a website about temps and monarch’s cat

cold weather (below about -5F) does kill monarchs, at any stage, and definitely slows down their development.December 20, 2013 – 10:21 am

texdr - Thank you Elizabeth, that’s good information!December 20, 2013 – 8:45 pm

Tess - I have been bringing my Monarch caterpillers in when the temp fall below 40°. I phoned the Butterfly Encounter Group and they said the caterpillers will die at 32°. They are the only ones I’ve found that knew the answer.January 17, 2014 – 12:45 pm

texdr - That’s good information! Thank you for sharingJanuary 18, 2014 – 10:29 pm

David - We’ve had multiple nights of 35 to 40 degree temps in NE L.A. The caterpillars on the milkweed along my driveway were motionless, no response when I poked the leaves they were clinging to, even in the middle of the day. I thought maybe they’d expired. But this morning, in full sun, one them had revived and was busy feeding. Do they kind of shut down when it gets too cold, go into hibernation until conditions improve?January 2, 2015 – 11:52 am

texdr - As long as it’s not below freezing, I have found the caterpillars doing just fine. Of course, they don’t move hardly at all, just secure themselves to the leaves and wait until warmer temps. Now if it will get below freezing, what I have done is just bring them inside and cut off a few stems of milkweed. I use those plastic containers that you put hermit crabs in. Put a paper towel in the bottom so they can grip betterJanuary 2, 2015 – 4:17 pm

Joshua - Well I Am Rasing Baby Monarchs Right Now And They Will Not Eat I Have Been Feeding Fresh Milkweed Too Them I Checked Them And They Were Alive

ThanksAugust 12, 2015 – 9:04 am

Toy - I live in Houston it’s about 60 to 80 degrees and have only two milkweed plants. Yesterday I was so happy to see 5 caterpillars just eating away so in my ignorance I cover them with Tull thinking birds were the predators I was wrong only one survived and I brought it inside (I read how to do it inside a glass container with a nice juicy branch he’s eating. The stem in a small bottle with water and small neck. Wish me luck!!October 14, 2015 – 6:10 pm

nelda broom - What do I do if I run out of milkweed for Monarch butterflies?January 8, 2016 – 12:32 pm

Nelda Broom - Where do I house the Monarch caterpillars that have stopped crawling? Inside or outside?January 14, 2016 – 9:02 am

Dave - Can you use a lamp to keep them warm outside? We have a screened habitat on our back porch.Will that light effect them any?January 18, 2016 – 5:34 pm

texdr - Butterflies or caterpillars? If it’s caterpillars that’s the only thing they eat. If it’s butterflies they use the milkweed for nectar and to lay their eggsJanuary 18, 2016 – 7:15 pm

texdr - Stopped crawling because it’s cold outside or ….? They tend to eat for a while, then just sit there, then eat some more. If it’s cold out they move slower. If you bring them inside I would provide them milkweed until they turn into chrysalisJanuary 18, 2016 – 7:17 pm

texdr - I don’t think the light will have any effect on them other than perhaps making them a bit more activeJanuary 18, 2016 – 7:17 pm

Rene - I live a little NW of New Orleans and after a summer of no monarchs or caterpillars, I counted as many as 15 caterpillars on my milkweed plants during December. ( I think this large lady bug looking bug, who kinda appeared last year has been the reason for no monarch caterpillars during these last 2 summers). I would cover the plants during a frost hoping to hold onto my milkweed. After Christmas I decided to bring them inside and put them in this athletic chair tent and made an awesome butterfly habitat out of it. By some miracle, Lowes had some milkweed plants (I told them it was a mistake that they had them at this time of the year.) I bought 6 with each having 3 plants in each one. My caterpillars were in heaven. Now, I have 7 in the crystilist state all hanging from the top-funny looking, 3 in the “J” shape and 4 munching away. My delimma which I’m sharing with my Monarch loving neighbor, is what to do with the Monarchs once they emerge from their cocoons. I feel like if I release them, they will die with our weird weather, hot today, freezing and rainy tomorrow. I’m wondering if I can keep the Monarchs in my 5 ft tall habitat with a supply of milkweed plants and maybe halved oranges on a stick. And then release them when all chances of a frost are gone…maybe around late March early April. Any suggestions????January 31, 2016 – 4:32 pm

texdr - As long as it’s about 50 degrees they can fly. They can survive colder temperatures than that. This generation of Monarchs is likely not the long living 8 month generation, more like the 2-3 week generation. Thus, they wouldn’t live that long to last until March or April. I’ve never ever seen a Monarch get nectar from any fruit, like oranges and such. Only from nectar oriented plants. I can’t quite visualize what kind of habitat you built for them, but if you wanted to slow their progression from chrysalis to Butterfly, cooler temperatures will help with that. If it’s above freezing, maybe about 40 degrees or say, if you can take that habitat outside then do that. Let me correct one thing. I’ve never seen a monarch get nectar from fruit, but I have manually fed them grape juicy-juice (which is basically sugar water). Even if you release them and are unsure they can fly, you’ll know as soon as you let them go. If they go straight to the ground, then it’s too cold or they need to warm up a bit. Hope that helps somewhat.January 31, 2016 – 5:32 pm

Rene - Your comments made sense. I forgot about the life scan of the Monarchs . I just worry they will not be able to find any food when I release them. All my milkweed outside has died due to several freezes we’ve had. Could not believe I found a Monarch caterpillar eating on a dead seed pod outside today. I put him in my habitat. ( I used one of these…. ….. with 6 pots with 3 plants each of milkweed plants inside). It is awesome. Someone mentioned the fruit; probably wrong. I still have lots of flowers on the Milkweeds I bought at Lowes. May go check tomorrow to see if they have any more. Maybe I can keep them for a few days to build up their strength and release them as long as the weather looks half decent for a week or so. Wish I could send you pictures of what I have.January 31, 2016 – 6:27 pm

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