1Last week, we started looking at reptiles, including crocodiles and snakes.
2Today, I'd like us to have a look at another reptile - the lizard -
3and in particular, at some studies that have been done on a particular type of lizard
4whose Latin name is tiliqua rugosa.
5This is commonly known as the sleepy lizard,
6because it's quite slow in its movements and spends quite a lot of its time dozing under rocks or lying in the sun.
7I'll start with a general description.
8Sleepy lizards live in Western and South Australia, where they're quite common.
9Unlike European lizards, which are mostly small, green and fast-moving,
10sleepy lizards are brown,
11but what's particularly distinctive about them is the colour of their tongue, which is dark blue,
12in contrast with the lining of their mouth which is bright pink.
13And they're much bigger than most European lizards.
14They have quite a varied diet, including insects and even small animals,
15but they mostly eat plants of varying kinds.
16Even though they're quite large and powerful,
17with strong jaws that can crush beetles and snail shells,
18they still have quite a few predators.
19Large birds like cassowaries were one of the main ones in the past,
20but nowadays they're more likely to be caught and killed by snakes.
21Actually, another threat to their survival isn't a predator at all, but is man-made -
22quite a large number of sleepy lizards are killed by cars when they're trying to cross highways.
23One study carried out by Michael Freake at Flinders University
24investigated the methods of navigation of these lizards.
25Though they move slowly, they can travel quite long distances.
26And he found that even if they were taken some distance away from their home territory,
27they could usually find their way back home as long as they could see the sky -
28they didn't need any other landmarks on the ground.
29Observations of these lizards in the wild have also revealed that their mating habits are quite unusual.
30Unlike most animals, it seems that they're relatively monogamous,
31returning to the same partner year after year.
32And the male and female also stay together for a long time,
33both before and after the birth of their young.
34It's quite interesting to think about the possible reasons for this.
35It could be that it's to do with protecting their young -
36you'd expect them to have a much better chance of survival if they have both parents around.
37But in fact observers have noted that once the babies have hatched out of their eggs,
38they have hardly any contact with their parents.
39So, there's not really any evidence to support that idea.
40Another suggestion's based on the observation that male lizards in monogamous relationships
41tend to be bigger and stronger than other males.
42So maybe the male lizards stay around so they can give the female lizards protection from other males.
43But again, we're not really sure.
44Finally, I'd like to mention another study that involved collecting data by tracking the lizards.
45I was actually involved in this myself.
46So we caught some lizards in the wild
47and we developed a tiny GPS system that would allow us to track them,
48and we fixed this onto their tails.
49Then we set the lizards free again,
50and we were able to track them for twelve days and gather data,
51not just about their location, but even about how many steps they took during this period.
52One surprising thing we discovered from this
53is that there were far fewer meetings between lizards than we expected -
54it seems that they were actually trying to avoid one another.
55So why would that be?
56Well, again we have no clear evidence,
57but one hypothesis is that male lizards can cause quite serious injuries to one another,
58so maybe this avoidance is a way of preventing this - of self-preservation, if you like.
59But we need to collect a lot more data before we can be sure of any of this.