It's common knowledge that animals such as lizards and get their heat from the environment. But what happens when a large lizard lives in a cold environment? How does it warm up and where does it get the heat needed to incubate its' eggs through winter? These are problems faced by Rosenberg's Goanna, a large monitor lizard that lives on Kangaroo Island off South Australia. And researcher Peggy Rismiller has uncovered a surprising array of techniques used by these goannas to stay warm when it gets cold - including getting some heating help from the local termites!

TRANSCRIPT

Narration
I've always wanted to come to Kangaroo Island. But you need to be prepared for the weather. There's nothing much between here and the Antarctic so even in summer you can get big swings in temperature. Not a problem if your car has a good heater.

But what about so-called "cold-blooded" reptiles that rely on the sun for heat?

Shouldn't they just shut down when the sun doesn't shine and it gets too cold?

Dr. Peggy Rismiller
Paul, good to see you.

Paul Willis, reporter
Nice to meet you.

Narration
Peggy Rismiller first asked herself the same question when she was just a young girl.

Dr. Peggy Rismiller
I grew up in an area in the United States in Ohio and one year we had a late snow around March and I saw these snakes out basking in the snow and I thought that's probably one of the strangest things I've ever seen many years later when I was at university I started sort of looking at reptiles and their body temperature and how the environment actually effects body temperature regulation.

Narration
Penny has become an expert on thermo regulation in reptiles and she's now investigating how Kangaroo Island's most impressive lizard survives in extreme conditions.

Dr. Peggy Rismiller
Rosenberg's' goanna is of specific interest to me because they are one of the largest monitor lizards that lives the furthest away from the Equator so that means its had to adapt to living in a cool climate.

Narration
So how many goannas are you tracking through this reserve?

Dr. Peggy Rismiller
Currently we have transmitters in 38 different goannas. Both males, females and very few juveniles.

Narration
We've picked up the signal of a goanna called Gimp - a male that Peggy's been studying for over 10 years.

Dr. Peggy Rismiller
Okay what I generally do is check his condition you can see that he's shedding so probably after eating.

Paul Willis, reporter
Shall I make a note of that?

Dr. Peggy Rismiller
He's just eaten a full wallaby, so we should find something.

Paul Willis, reporter
That little fellow took out a wallaby?

Dr. Peggy Rismiller
He did, he did, a person saw this animal dragging a baby wallaby last week.

Paul Willis, reporter
Phoooooooh!

Dr. Peggy Rismiller
Eating the whole thing too.

Narration
Eating such a large item of prey is all part of Gimp's energy budget. So recording some basic measurements at this time helps Peggy piece together the energy puzzle posed by these amazing reptiles.

Dr. Peggy Rismiller
Okay ready to release him.

Paul Willis, reporter
Better let him go.

Dr. Peggy Rismiller
This is where you let your hand go really quick

Narration
I'm visiting Kangaroo Island in Summer when average temperatures are in the twenties and thirties, so there's plenty of solar energy to keep goannas on the move.

But what happens in mid-winter when the ground temperature drops to zero? To answer this question, Peggy's been monitoring the temperature of a goanna called Charlie. This goanna has been doing things with her body temperature that for a lizard should just not be possible.

Dr. Peggy Rismiller
You can see the red is the body temperature of Charlie...So what you are seeing is a very very slow um lowering of body temperature in the evening and in the morning all of a sudden the body temperature shoots up from in this case seventeen to about thirty seven degrees in a matter of minutes.

Paul Willis, reporter
But that means that she's actually hotter than the surrounding environment so where's she getting that heat from ?

Dr. Peggy Rismiller
Now that is a very good question and if we could answer that then we would be a lot closer to understanding body temperature regulation in reptiles.

Paul Willis, reporter
Do you have any ideas of how she could be doing that?

Dr. Peggy Rismiller
Well a lot of people say that reptiles can't increase their metabolism like humans do to keep a stable body temperature but one possibility is in some reptiles in the northern hemisphere they actually just put their head out with the sun first comes out they are able to heat up their brain basically shunt the blood between the heart and the head and when the heart is warm enough then they shunt the blood to the rest of the body.

Paul Willis, reporter
So sort of accelerated heating?

Dr. Peggy Rismiller
That's right.

Narration
Another a big problem for the goannas of Kangaroo Island is how to keep their eggs warm in winter.

It's a problem their tropical cousins don't have to deal with.

Dr. Peggy Rismiller
Living closer to the equator they would choose a warm place to lay their eggs and their eggs would be incubated by the sun and hatch. But here on Kangaroo Island it can get very cold in the winter time in fact in some areas of the island the temperatures will go below freezing so somewhere along the line Rosenbergs' goannas learned to lay their eggs in a termite mound.

OK there's the mound, and you can see the hole in it, it's already quite large.

Paul Willis, reporter
So that's where the young have actually dug their way out of the nest.

Dr. Peggy Rismiller
Yeah that's right that's the same place where the female dug in to lay her eggs, about seven to eight months later the young actually dig out.

So I want to try to measure the temperature inside the mound.

Dr. Peggy Rismiller
So it looks like I'm down as far as it will go, this will take just a minute

Let's have a look how high it is now, it's up to 31.2

Paul Willis, reporter
Wow, so it's warm and humid, that must be the perfect conditions for an egg and young goannas.

Narration
Peggy has been trying to find out just what the conditions are inside the mounds, but the termites keep destroying her monitoring equipment!

She's been more successful seeing how the hatchlings live inside the mound: and it looks like the perfect spot for a young goanna with a free breakfast of termites laid on every morning.

But when they venture outside, it's a different story.

Dr. Peggy Rismiller
We know that most of the young do not survive from a mound with twelve eggs if one survives the first twelve months that's probably good. But how many actually survive to adulthood and at what age is adulthood? These are things that we need to look more carefully into especially for the conservation of the species.

Narration
Peggy has come along way since she first saw those garter snakes in the snow back in the USA.

She's finally figuring out how big reptiles cope with the cold.

Dr. Peggy Rismiller
Things can't be answered in a year or two...

We have no illusions that we're going to be able to answer all the questions with goannas in our lifetime because I think that the young that are hatching now are probably going to outlive me!

Story Contacts

Dr. Peggy Rismiller
Anatomical Sciences
University of Adelaide

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