Episode 37: Winter Herp Survival Transcript


Nature Boost 
February 2023 


[Music playing.]   

>>   Hey there and welcome back to Nature Boost with the Missouri Department of Conservation.   So, I went to bed the other night and my mind always thinks about random stuff before I fall asleep.   

How come my local Fazoli's closed down?   I love those breadsticks.   Uh, would it be weird if I painted my dog's toenails?   Who has my birth certificate?   Do I need to make a dentist appointment?   

Just, you know, random stuff that goes through my head.   Then I thought of this.   It's wintertime.   Where are all the reptiles?   Are they alive?   You don't see them in the winter months.   So what are they up to?   What are they doing?   

Lucky for me, I have Missouri's herpetologist, Jeff Briggler on speed dial.   

Jeff Briggler, thank you for joining me today.   

>>   You're welcome.   

>>   You know, I was thinking about it the other night.   Watching the birds and you know you see the squirrels and everything.   And I just thought . . . what are reptiles . . . what are snakes, what are turtles, what are lizards and frogs . . . how are they surviving the winter?   I wanted to get into that with you today.   I think it is pretty interesting how these types of animals survive this cold season.   

While doing some research for this episode, I was coming across a lot of terms.   I was learning about brumation, and ectothermic and endothermic animals.   Can you kind of explain a little bit about that for us?   

>>   Well, the amphibians of our state are ectothermic.   Meaning they have to get their heat from external sources.   

>>   I see.   

>>   So like a snake basking in the sun warms up.   Or they go deeper under ground from the frost line to warm up.   Whatever the temperature is outside that they are exposed to is the temperature they will be unless they go to an object to absorb heat back in.   


So for amphibians and reptiles, they really don't hibernate.   Hibernate means they are in an inactive state, mainly they are using fat reserves and stuff.   Really, the correct term is brumation.   They are basically inactive, but they are still alert in most cases.   If it warms up outside like it has in the last few weeks, you might see a snake pop out of its den and sun for a little bit and bask to warm up.   Then it might go back down.   If it gets extremely cold outside, that same snake might crawl deeper into the crevices to get farther into the ground to get below the frost line.   So they are always active.   They are just not fast.   They are slow.   Their metabolic rates are very slow.   

The same thing with a turtle.   Who hasn't seen a turtle under the ice and they say, "Oh my gosh, it's moving!"   Well, they are not inactive.   They are still moving slightly under the water.   They are just going to be slow.   They are going to absorb their oxygen under the water.   Just low low metabolic rates.   

>>   Okay, so snakes, for instance.   Let's start with that.   So these are ectothermic cold blooded animals.   You say they go into dens in the wintertime?   

>>   Some snakes do, some are solitary.   Some may all go to the same location.   So, it depends on the species of snake.   Some species like to overwinter in crayfish burrows.   There might be a certain 2 or 3 acres where there are a lot of these crayfish burrows so that is where a lot of these snakes will go because they can get below the ground.   

Or it might be the nice south facing slope of a lot of rocky crevices.   Some of the rattlesnakes like Timber rattlesnakes might bunch up in a den site.   Massasauga rattlesnake is a rare snake in our state, will bunch up.   

But most snakes are more solitary.   They will spread out.   They might go into a log or underneath deep crevices up a steep bluff or something.   Anywhere they can get underneath out of the weather.   

>>   When they start this brumation process over the colder months.   I would assume they start finding a place to hunker down in the fall?   

>>   Yes, usually in October the animals start moving to their overwintering sites.   There will be some massive migrations at some point in time to get there.   

>>   Wow.   

>>   Then the winter will occur.   Now it differs slightly from amphibians to reptiles.   Reptiles prefer the sun.   They like to be warm.   Amphibians you don't see those very often.   They like to stay near water.   They have moist skin.   They can tolerate colder conditions.   

Coming up soon in the next month some of our salamanders will start breeding.   Even though it is cold outside, they can tolerate it in the 30s.   They can tolerate a snow melt and move over land.   They can tolerate colder temperatures and still be active.   Whereas reptiles really need to have 60-70 degree temperatures to really keep moving.   

>>   Okay so the amphibians are a little more tolerable of that cold weather.   Interesting.   Okay.   Another term that I was coming across a lot while doing research for this episode was this term for snakes called a hibernaculum.   Tell us what that is.   


>>   Well, the big term is a lot of animals are going to one place to overwinter.   Typically in the amphibians and reptiles, we use "overwintering" because hibernation you think of a bear hibernating or a groundhog hibernating or some other animal.   Amphibians and reptiles are not totally knocked out.   They are active.   If it warms up, they will warm up.   If it gets colder, they are going to get colder.   They are really going to a defined overwintering site.   

>>   So these snakes, do they, whenever they go in these dens if they are not solitary can they overwinter with other species of snakes?   Do you typically find different species of snakes in one?   

>>   Yes, it can happen.   A lot of times it is dominated by one.   But not always.   Some of our intrstf features is old rock lined wells that have been left and abandoned.   An old well where you used to drop a bucket in and pull water out, there are rocks all along the sides.   

>>   Right.   

>>   Usually they are covered.   If you get down into those, sometimes there can be 50 or 60 snakes and 5 to 6 species, like black rat snakes, racers, Garter snakes all within this well chamber.   Because it is an ideal place.   They can drop lower if they need to warm up or they can come back up in the rocks around there.   Old cisterns that used to be in houses that have rock areas that are abandoned.   Snakes are probably using those in some places.   

>>    The rock holds warmth?   

>>   Yes, the rock is a place to seek shelter.   This concept that like in Missouri, we have a lot of caves.   The concept is you go into these caves in the winter and here are all these snakes in there.   I will just tell you, if you can get in that cave and there is a bunch of snakes, they're dead because every predator will come in there and eat them.   They're inactive.   So racoons would eat them, skunks would eat them.   They have to get in tight confined spots protected by things that cannot get to them because they won't be fast enough to get away from you or to be able to even strike you.   So they have a lot of these adaptations to help them find these very tight secure locations.   

>>   Is that just because they are trying to conserve energy because they are in this low power mode?   

>>   They have cold temperatures, low metabolic rate, and they are very very slow.   Best time to photograph them because they are not going to move.   

>>   [Laughing.]   Oh, good point!   

>>   They are not fast at all.   Now if you put a heat lamp on them for about 30-40 minutes, yeah, they are going to start coming out of it and start getting more active.   The snake may rattle then.   But it's not going to be when it is really cold.   

>>   Sure.   So you brought up something interesting.   We live in Missouri, we are one of those states where, "Oh, if you don't like the weather just wait five minutes."   We are recording this in January right now and we have experienced some spring-like days.   They are aware enough to, "Oh, it's warm enough, I could come out" and then obviously it is getting back to cold, rainy and wet weather and they know just to go back in their den?   


>>   Yes, they will stay close to their den site and then go back in.   Now every winter is different.   The worst winters for amphibians and reptiles are extremely cold dry winters without snow.   The snow provides insulation on the ground and it provides moisture.   The biggest threat for a lot of these animals is dehydration, not the temperature because they can get deeper under the ground.   

A good snowy cold winter will be fine.   A very dry cold winter with no moisture, more will probably die.   Then you have this kind of back and forth.   The back and forth is okay as long as it doesn't go too far.   The snakes are coming out but if they get heated up too much they will start getting hungry.   We need their metabolic rates to get lower.   If they are getting hungry, well, is there any food out?   

There is a balance there.   That tradeoff varies back and forth.   Then if you get a cold snap after they come out, very quickly they are fast enough to get back under ground.   Like a box turtle digging back into the ground.   So you kind of like to see the temperatures being more winter-like but not get in the 70s too much.   But animals will come out.   There will be Garter snakes that will pop out on top of snow sometimes when it gets into the 60s and 70s.   

>>   Interesting!   

See it is crazy to me that they are able to go back and forth like that.   So talking with the snakes, about when do we start to see them become more active in the spring?   When do you think they have all finally left their overwintering sites?   

>>   Well, it typically depends on the state.   If you are in north Missouri or south Missouri.   But typically mid to late March into mid April things will start emerging.   Time frame as a biologist, we look at the time frame a lot but we really based it on soil temperature.   That tells us.   Usually when that soil temperature is getting to about 50-55 degrees, we know animals are going to start coming out of their den sites.   

It's always funny in the research I do. I go up to north central and northwest Missouri to look for snakes and somebody is always like, "Why are you going up north to look for snakes?"   Well, it's prairies.   The sun is beating down and heating the soil faster than it is under the forest canopy.   

>>   Oh, right.   

>>   So I go north to work on snakes earlier in the year, and then I will go into the Ozarks about a month later because it's going to take that soil temperature longer to heat up because it is under a canopy.   

>>    Right.   That makes total sense!   


With this term brumation, this is something that all reptiles and amphibians go through.   This process of brumation.   

>>   They all brumate, but there are some exceptions to the rules.   Some animals can adapt differently to certain situations.   So, like in general, amphibians and reptiles have to get out of the freezing temperatures.   They have a couple mechanisms to do that.   One you can get beneath the ground underneath rocks, logs, in crevices, in crayfish burrows, under objects below the frost line.   And have enough room that you can go deeper if you need to and come back to the surface depending on the temperature.   

Or you can do like a lot of aquatic turtles and even some of our frogs, like bullfrogs that overwinter in the bottom of lakes and ponds.   They just go to the bottom of the pond because it's not going to freeze there and they live at the base of the pond underneath rocks and logs just sitting on the bottom.   

>>   And they are able to get enough oxygen down there?   

>>   Yes.   It's extremely cold and highly saturated with oxygen.   Colder water holds more oxygen.   Their metabolic rates are very low.   They can absorb enough oxygen through their skin at that low rate to survive.   That is why you sometimes see a snapping turtle walking very slowly under the ice.   Now if that pond or wetland froze solid, they would be in trouble.   

>>   They'd have to find a new place to   . . . if they can get out.   Right.     

>>    If they can get out.   That's how that works.   What is intriguing.   A lot of these animals have to have a means to get out of it, but not all of them do.   There are some species in our state that are more northern distribution species that can be up into Canada farther.   They only overwinter underneath the leaf litter.   That's not good in the winter, especially if you are way up north and it is getting to -10 or -20.   


These frogs that are here are two species of gray treefrogs, the spring peeper, the boreal chorus frog, and the wood frog.   What is cool about these animals is that they have the ability to freeze.   

>>   They can freeze their body?   

>>   They're like an ice cube.   Since they only overwinter underneath leaf litter, they have to have some adaptation because they are not getting below the ground.   What's unique about these animals and how can they do that?   

Well, it is a very interesting process.   Don't think the government would love to learn how to do this and people.   We don't produce the right things in our blood sometimes.   What happens to a frog . . . let's say it is a wood frog underneath the leaf litter and we are getting very cold.   What is going to happen is it is going to start freezing its skin.   Kind of like how we can get frostbite very easily.   Frostbite when we get it, it sucks out all your moisture and it is deadly.   It will cause limb loss or finger loss, too.   In these animals, what they do, when they start freezing they will start being hard.   Their eyes will turn white. 

In the process, there is a special protein in their blood.   What that protein does is it starts freezing the water in their blood system first.   It starts sucking out the water out of the cells around it.   But then the most important thing they produce we call it a prior protectant or it could be an antifreeze.   Their liver produces massive amounts of glucose, a sugar.   That sugar pumps into all the cells and fills them.   They shrink down.   What that sugar is doing is it kps those cells from collapsing.   If they collapse and freeze, that frog is dead just like we would be if frozen.   It maintains the cell structure on that.   Then after that happens, the whole frog will freeze.   It will not be breathing, its heartbeat will not work.   It will not have brain functions whatsoever.   If you picked it up, it would be like an ice cube.   

>>   Like hard as a rock.   

>>   Yeah.   So they just sit there like that in that state.


  Now if you are in Canada, they may be in that state for a long time.   The research has shown they can go through freeze/thaw cycles.   If it warms back up, they can come back out.   How many times we don't really know.   

>>    Within a year like within a season?   

>>   It can happen multiple times.   Now it takes about an hour for them to come out of it.   They have to thaw back out.   

>>   They are pretty small, too.   

>>   Yes, I mean some of them.   The wood frog is about two to two and a half inches, the peepers are about an inch.   This is their adaptation to living underneath the leaf litter.   It's a very cool mechanism for these animals to survive.   Now I have never found one.   

>>   I was just going to ask you if you had seen one.   

>>   People have always asked me.   I have seen pictures.   And "do they do it here in Missouri?" since we are on the southern edge of some of these species' range.   I am sure they do.   The odds of us finding it would be very very difficult to say the least.   

>>   Right, right.   Oh my gosh!   So they basically evolve to have that glucose kind of acting as an antifreeze in their system.   

>>   It packs into those cells and keeps that structure and keeps them from getting further dehydrated.   Whereas in us, all of our moisture sucks out.   Once that happens, your cells are going to collapse and there is nothing you can do.

We don't produce that special protein and our livers don't produce a ton of glucose to do this functioning to go into this cryopreservation state.   

>>   It is like something out of a Sci-fi movie isn't it?   If they did figure that out, would you do it?   

>>   I don't know.   Somebody else has to go first.   

>>   We need a guinea pig for that.   So it is only frogs that can do that?   

>>   Frogs, that we are aware of.   

>>   Okay.   Which ones?   

>>   In Missouri, I am sure there are other ones.   The spring peeper, the two species of gray tree frog, the boreal chorus frog and the wood frog.   Those are the ones.   Now some turtles, even our box turtles kind of have a freeze resistance.   They can tolerate a few days, several days, being really cold, almost frozen and still come out of it.   


Now what they do is, the box turtles, they will dig into the leaf litter a couple inches.   If it gets colder, they will dig a little deeper and do that.   Some hatchling turtles, especially painted turtles that have a very northern distribution.   We are learning more about this everyday.   They do some supercooling.   They can lower the temperature in their bodies below the freezing point basically.   Kind of like how air conditioners kind of work and stuff, too.   

Hatchlings, sometimes, since they are in their nest still.   If it gets extremely cold they can tolerate it for a certain amount of time due to super cooling.   It is not freezing in their body.   They have that ability to do it.   Outside of that, we don't know of any other stuff.   But I wouldn't be surprised one day.   There is always something we learn that we don't see.   It is usually all these types of adaptations that are really for these species that are more northern driven.   

>>   Okay.   

>>   That need these types of adaptations to survive.   

>>   Right, right.   Understood.   So turtles basically just kind of burrow into the soil to survive?   Most of them?   

>>   Most of our turtles overwinter, actually, in the water.   

>>   Oh, really?! 

>>   In the bottom of lakes and ponds, ditches, deep ditches and stuff.   Not all, though.   We have some species like the box turtles, the chicken turtle, the yellow mud turtle.   Those species overwinter on land.   So they dig in loose soils and dig deeper if they need to.   The brunt of them are actually in the water.   

If I go scuba diving in a river in the Ozarks in February, I might find 20 or 30 map turtles on the bottom of the river all crammed underneath a log or root wad on the bottom.   They are just sitting there.   

>>   Just trying to conserve energy.   

>>   Right.   


The water is pretty cold.   I mean, and stuff.   If it gets up to 70 degrees and the sun starts coming out, they might come up and bask for a couple days.   

>>   Well, and I would think that would be a good thing for them to have kind of just periodic warmer time.   

>>   A little bit would be as long as it is not too long so they need food.   But short term it's great.   Sunlight is great for us.   Especially in the winter!   People need to get more sunlight in the winter.   The animals are telling you that.   They need that for vitamin D production and growth.   Getting that basking helps their growth, their metabolism, it helps to clear off parasites on their body somewhat.   There is a lot of positive benefits.   

I always encourage people, even my kids and stuff, in the winter, to get out!   Get outside!   If you get a warm day, wear a t-shirt.   We all get doom and gloom in the winter because of all the cloudy days but a lot of that has to do with the fact that we need sunlight.   

>>   Absolutely.   

>>   It is one of the best things to do to get out in it and expose your skin to it when you can and take advantage of it.   These animals are doing the same thing.   

>>   When you explain it like this, how they are overwintering in these colder months.   It makes so much sense why you really start to see them crossing roads in the spring and they are trying to soak up that sunlight and look for some food and trying to look for a mate.   In the springtime, you really do see a lot of turtles crossing roads and they are more active.   

>>   They are definitely more active.   They are moving, mating, and establishing their territory.   Same thing if you are floating in an Ozark river in the springtime on a sunny day, the turtles are basking.   But then when the middle of summer comes and it gets hot, they might bask a little bit in the morning but then they are going to get too hot.   You won't see them as much.   If it is a cloudy day on an Ozark stream in the middle of the summer, they may not be out at all.   Every day varies a little bit.   

Sometimes we do counts of turtles on rivers and we have to pick the right day to float so we get the best population estimate for that river by how many turtles are basking on those sites.   

>>   Interesting.   I never really thought that they could overheat and get too much.   


>>   Oh yeah.   If you keep amphibians and reptiles, there is a preferred range for them.   Animals are different.   Collared lizards like it in the 80s and 90s but most lizards can't tolerate that.   So they become active early in the morning to heat up, forage and feed and they go back under rocks and logs in the heat of the day and come back out right before evening and do that.   It varies.   

In the spring, everybody wants to be out in the sun.   In the fall, they still want to be in the sun but they are all moving back to where they will overwinter.   

Do they typically overwinter in the same area?   Do they have the same range?   

>>   Yes.   We don't get animals enough credit.   It is just like us.   We are driving home, we drive to work.   They have their established territories.   

Let's talk about a species called the crayfish frog.   They overwinter in crayfish burrows.   Crayfish burrows can be very deep.   They can drop down really low and come back up.   In February and March, they will start migrating to a nearby fishless pond to breed in.   

Here's this one hole this crayfish frog has been living in.   He might make it to that pond the first night.   But if he doesn't he might stop and occupy another hole along the way.   But when he leaves, the odds are pretty high he will occupy that same hole but more importantly he will come back to that same hole he lived most of his year in.   He will keep returning to that same hole if its still there.   

It is the same thing with any animal.   Path of least resistance.   You know?   Where they go.   You have to sit and watch.   I know at my house where this racer always will be eery day.   I just have to look and not mess with it.   I know it's there.   Some people know where that toad is.   But if you really sit back and watch they are going to do the same thing every day.   They have their territories.   They have their homes.   

Box turtles are the same way.   They will return back to where they like to overwinter.   The thing they do is they have what we call mini apartments.   They are called forms.   What they do, in their territory they may go a long distance.   This one spot is where they will stay like a vacation for several weeks.   It may be a pile of leaves and they will sleep in there at night.   They come back and forage and feed.   Then they might move again for a couple of weeks.   But eventually they will come back for the winter back to this spot.   We don't give a lot of these animals enough credit.   Most of them are probably returning exactly where they came from.   


At my house, down by the creek, I have been monitoring this one female box turtle for almost seven years.   She comes back to the same little dimple in the woods with leaf litter to overwinter.   I check on her all winter.   I peek down and open it up and put leaves back on her she is there.   She will show up late October.   When I get a really warm sunny day I will drive past her with the four Wheeler and stop to see if she is sunning a little bit.   Sometimes she will be.   When it is super cold and the snow is there, she is dug down deeper.   She will leave come out about mid-April.   She will disappear and I won't see her again.   But come October I will find her again because she comes back to that exact same spot and this has been seven years in a row.   

>>   Do you remember when I came to your property to record our episode on snakes?   

>>   We walked right past it.   

>>   I remember!   I was going to say.   Is that the same one you were talking about?   

>>   Yes, she is in there right now in that hole.   

>>   Oh my gosh.   Creatures of habit.   

>>   I always worry, what will it be like the day she doesn't come back because probably something bad happened.   But again, pay attention to nature.   If I ever found a wood frog under leaf litter somewhere, the odds are that is the spot to go every year.   It's just very hard to find that.   

>>   Do you think a lot of that has to do with their safety and survival?   They repeat the same because they know.   

>>   They know this territory.   They have done well here.   They have survived here for a long time.   But in general, they are creatures of habit.   Just like we are.   We take the same paths to work every day.   Same thing on a campus.   Think about all the sidewalks.   There will be a spot where the path of least resistance where everybody will walk where the new trail is because it is shorter.   Everybody does this.   Just naturalally you do these things as you travel and go about your merry way.   These animals do the same thing.   

It's cool.   A   turtle basking on a certain log, it will probably bask on that log eery day.   Now in the afternoon it might bask somewhere else because the Sun's angle might be better over here.   They are going to adjust.   Just think.   You put a lot of time and energy into just sitting there.   It is amazing sometimes the things we can learn by just sitting in a chair with a pair of binoculars and sitting back and observing and watching.   Sometimes that is the best approach for some of the endangered turtles.   They are more likely to bask and we know they are there and other things.   

>>   Fascinating!   Thank you for shedding some light on this.   I just randomly had this thought the other day: what are our turtle and lizard and frog friends doing this time of year?   Obviously we are not seeing them.   They are in low power mode conserving their energy, and waiting for the temperatures to warm up.   

So one thing I did want to briefly touch on as we wrap this up.   You have worked very very hard on one of MDC's publications, it is a third edition of the amphibian and reptile guide book.   That is out there now.   People can buy that on our nature shop online?   

>>   It has been out for about a year now.   We've worked on it hard for several years.   It is there revised expanded edition.   There is a lot of new information, new photos, new species accounts, and a lot of updated information.   To keep with the spirit of our book, the co=author Tom Johnson is part of the book.   We kept with his artwork and illustrations.   The new cover is more artwork by Tom and artwork throughout the book which makes it a little more special.   


>>   That's wonderful.   It's even got some new stuff in it as far as distribution maps and different information on habitats and breeding and name.   It has a guide on tadpoles, too?   

>>   On the back we have all the artwork for all the tadpoles and salamander larve completed by Tom Johnson.   The previous book did not have all of them.   We expanded upon that.   There is new species added because we find new species, or genetics change some of the species.   Where we once thought these were all the same and it winds up being two different types of animals.   They get new accounts.   We do have quite a few new accounts in the book.   It is definitely a revised expanded version.   Almost 100 pages more!   

>>   Oh wow!   

>>   A lot of updated photos.   We were able to provide some habitat photos for a large number of the species throughout the accounts, too.   Rarely are you able to do that in most amphibian and reptile books.   It was nice to show some key features of habitat that certain species really like.   

>>   Oh yeah, that is really cool.   I would think that would be a great resource for people who are interested in learning about reptiles and amphibians.   I'm sure you get questions all the time, "Hey, what is this?   I found this in my backyard!"   

>>   Yeah, it is like today.   Go in the gray tree frog section or the wood frog section.   There will be something talking about cryoprotection a little bit.   Every species, somewhere in there in the remarks I am always looking for some interesting fact that we don't know or something.   Like narrow mouthed toads just specialize on ants and termites more.   Their bodies and how they adapt to that.   

Sometimes some of the remarks and stuff will be really cool things we don't think about.   A lot of it is just from my own personal observations sitting out in my yard or paying attention to certain things.   A lot of the photos, I have favorite photos I have taken.   I took a lot of these photos.   I will remember where I took them, hoping to pose these animals in their natural condition.   They all have a story behind them.   Each photo does.   

I could probably talk to people day after day on every animal and where I photographed it, what the animal did that day.   Tips on photographing amphibians and reptiles.   Some are easy and some are really hard.   It is fun to know we did complete this book and it is available.   A lot of people will be very interested in this expanded edition.   

>>   Awesome!   Well, it's the amphibians and reptiles of Missouri guide book.   You can find it online available for purchase at MDCnatureshop.com.   You should check it out.   

Jeff, thanks so much for shedding light on this today.   You have given me some great information and told our listeners a lot of stuff they probably didn't know.   I thank you 

>>   You're welcome.   

>>   Thanks again to Missouri state herpetologist Jeff Briggler and thanks to you for tuning in to another episode of Nature Boost!   I'm Jill Pritchard with the Missouri Department of Conservation, urging you to get your daily dose of the outdoors.