At first glance, the Australian jacky dragon lizard has little in common with people - until you see the males wave, do push ups and try to appear impressive in the hope of getting a mate.
The male lizards engage each other in territorial disputes, expressing frantic rapid visual displays that involve discrete motor patterns, including arm waving and pushups, combined with open-mouthed charges and occasionally full-blown biting and wrestling competitions.
Macquarie University PhD student Michael Watt, supervised by Associate Professor Jean Joss (Department of Biological Sciences), has studied the behavioural patterns of male jacky dragons as part of his thesis, looking at what their amusing and bizarre displays mean and how they are used for communication.
Only their mothers can tell them apart - Macquarie PhD candidate Michael Watt and his jacky dragon
He found that specific displays serve crucial and highly specific purposes in revealing how aggressive a male is likely to be when confronted with a potential rival, relating to each male's need to achieve reproductive success.
Watt explains that male jacky dragons come out fighting in early spring, when each struggles to establish a territory that overlaps the home ranges of as many ready-to-breed females as possible. Unfortunately, nearly every male is trying to do the same thing. Territories become prime pieces of real estate. To proclaim ownership of his area and a readiness to defend it, territory holders will produce a specific type of display.
First an arm is raised and returned to the ground in a backward, circular motion, which resembles a wave. The same arm is then rotated rapidly forwards. Then the male lizard will lean forward and suddenly raise himself up in a push-up like motion. This display only takes a matter of seconds, and is repeated rapidly several times. The territory holder will then wait to see what the intruder will do. If he is trying to muscle-in on the territory, the intruder will respond with the same display as a form of challenge.
If the intruding dragon does not wish to fight, or fears he has met his match, he waves his arm slowly several times. If he feels extremely threatened, he bows his head up and down as though praying. By using displays to reveal the way they feel, the males can assess each other without always having to fight, which can otherwise result in some pretty nasty injuries.
Watt also looked at the influence of hormones such as testosterone and corticosterone on such behaviour, finding that while testosterone was needed for males to display aggressively, the level of aggression depends on the levels of corticosterone their bodies produce.
So why is it important to know what jacky dragons say to each other, and what's influencing their communication?
“By studying the natural behaviour of a more primitive vertebrate like lizards, we can get insights into some of the mechanisms controlling social behaviour in other vertebrate animals,” Watt says.
“Vertebrates tend to share a lot of similarities in the way our bodies work. For example, when a lizard gets stressed, its brain gets fired up in much the same way as a person's brain. It sends a message to the adrenal glands for them to make the stress hormone corticosterone, which then travels through the blood back to the brain to induce behavioural changes like being more cautious or less aggressive in that specific situation. Such changes can keep a lizard safe - it stops him recklessly taking on other males that could easily beat him up.
Watt says the jacky dragon research also had implications in conservation.
“Jacky dragons are pretty common in the bush throughout eastern Australia. When a species like that starts disappearing, it usually means there are serious problems with the habitat. The more we know about what requirements a species has for living its life and reproducing, the better chance we have of conserving them in the future,” Watt says.
The male lizards engage each other in territorial disputes, expressing frantic rapid visual displays that involve discrete motor patterns, including arm waving and pushups, combined with open-mouthed charges and occasionally full-blown biting and wrestling competitions.
Macquarie University PhD student Michael Watt, supervised by Associate Professor Jean Joss (Department of Biological Sciences), has studied the behavioural patterns of male jacky dragons as part of his thesis, looking at what their amusing and bizarre displays mean and how they are used for communication.
Only their mothers can tell them apart - Macquarie PhD candidate Michael Watt and his jacky dragon
He found that specific displays serve crucial and highly specific purposes in revealing how aggressive a male is likely to be when confronted with a potential rival, relating to each male's need to achieve reproductive success.
Watt explains that male jacky dragons come out fighting in early spring, when each struggles to establish a territory that overlaps the home ranges of as many ready-to-breed females as possible. Unfortunately, nearly every male is trying to do the same thing. Territories become prime pieces of real estate. To proclaim ownership of his area and a readiness to defend it, territory holders will produce a specific type of display.
First an arm is raised and returned to the ground in a backward, circular motion, which resembles a wave. The same arm is then rotated rapidly forwards. Then the male lizard will lean forward and suddenly raise himself up in a push-up like motion. This display only takes a matter of seconds, and is repeated rapidly several times. The territory holder will then wait to see what the intruder will do. If he is trying to muscle-in on the territory, the intruder will respond with the same display as a form of challenge.
If the intruding dragon does not wish to fight, or fears he has met his match, he waves his arm slowly several times. If he feels extremely threatened, he bows his head up and down as though praying. By using displays to reveal the way they feel, the males can assess each other without always having to fight, which can otherwise result in some pretty nasty injuries.
Watt also looked at the influence of hormones such as testosterone and corticosterone on such behaviour, finding that while testosterone was needed for males to display aggressively, the level of aggression depends on the levels of corticosterone their bodies produce.
So why is it important to know what jacky dragons say to each other, and what's influencing their communication?
“By studying the natural behaviour of a more primitive vertebrate like lizards, we can get insights into some of the mechanisms controlling social behaviour in other vertebrate animals,” Watt says.
“Vertebrates tend to share a lot of similarities in the way our bodies work. For example, when a lizard gets stressed, its brain gets fired up in much the same way as a person's brain. It sends a message to the adrenal glands for them to make the stress hormone corticosterone, which then travels through the blood back to the brain to induce behavioural changes like being more cautious or less aggressive in that specific situation. Such changes can keep a lizard safe - it stops him recklessly taking on other males that could easily beat him up.
Watt says the jacky dragon research also had implications in conservation.
“Jacky dragons are pretty common in the bush throughout eastern Australia. When a species like that starts disappearing, it usually means there are serious problems with the habitat. The more we know about what requirements a species has for living its life and reproducing, the better chance we have of conserving them in the future,” Watt says.