Townsville Australia - May 5th

Townsville is on the northeast coast of Australia between Cairns to the north, gateway to the Great Barrier Reef; and Brisbane to the south, the heart of Australia’s Gold Coast. And the site of the world’s largest coral reef aquarium, which is where Joani and I went.

Thursday was predator day, with a lecture on Great Barrier Reef predators at 10:30 AM and a predator feeding at 2:30 PM. So basically we saw sharks, manta rays, and turtles (yes, sea turtles are predators who can hold their own with the sharks and the rays).

Only three out of hundreds of shark species are real threats to humans: great whites, tiger sharks, and bull sharks. 

Black Tip Shark

Black tips are commonly seen swimming lazily around reefs all over the world. They never stop swimming because that’s what moves air dissolved in the water over their gills. If they stopped they would suffocate; they even swim while they sleep. Although they can grab, hold onto tightly, and kill or tear apart smaller fish with their front row of long and sharp teeth, they are not dangerous to humans. Only three out of hundreds of species generally are: great whites, tiger sharks, and bull sharks.

Leopard Shark

Leopard sharks are often seen just lying on the bottom doing nothing, like a manta ray. In fact, they are closely related to manta rays, with similar holes on the top of their heads behind their eyes to suck in water to pass over their gills. That allows them to lie around on the bottom so much. They have lots of rows of little teeth top and bottom, allowing them to grind up crustaceans and mollusks and the like; sucking the meat into their stomachs and spitting out the pieces of shell and bones.

Nurse Shark

Like the leopard shark, nurse sharks have lots of rows of small teeth for grinding up, rather than big sharp front teeth for grabbing, ripping and tearing. And a small mouth like a manta ray. Like all sharks they prefer easy prey: the weak, the sick and slow moving; or even better already dead. 

Manta Ray

Manta rays lie on the bottom and are very skittish: when diving you’ll sometimes see them explode away from you if you get too close. They have no offensive weapons: no barbed tail like a sting ray and a small mouth without long sharp front teeth. Like leopard sharks and nurse sharks, they are vacuum cleaners that cleanse the water of the weak and the sick and of debris left over from a kill.

Sea Turtle

We don’t think of sea turtles as predators, but they are just as likely to be seen feeding on a shark carcass as vice-versa. They were much more aggressive than the manta rays, leopard sharks and nurse sharks during the feeding. One immediately grabbed a six-inch piece of chum; and when a leopard shark made a half-hearted attempt to take half, the turtle slapped it in the head.

Grouper

How does a grouper survive in the same tank with sharks? The grouper is big and healthy and the whole tank is fed regularly. Three times a week, on Tuesdays, Thursdays and Saturdays at exactly 2:30 PM. No one attacks anyone. Why expend the effort?

People think sharks have tiny brains and are dumb. But these fish can tell time and know the days of the week. On Tuesdays, Thursdays, and Saturdays they become very active and excited between 2:15 and 2:20 PM. They know it’s time for dinner. This never happens on the other days of the week or at other times of the day. After years on the same routine, they know. Go figure.

A day at sea tomorrow, and then on to Brisbane. Joani and I have booked two hours of court time at a local tennis club. As we have done in Sydney. But we have two days in Sydney and I am climbing the Harbour Bridge on the other day.