I have had a deep fascination of sharks and rays since I was a child, and would read, collect and cut out anything I could find about elasmobranches. My favourite shark was always the leopard shark (Stegastoma fasciatum) or zebra shark as some call it after the patterning of the juveniles. From the reference books I discovered that the leopard shark was the only member of the family Stegostomatidae and was easily identifiable not only by its spots, but by the ridges that run along body, similar to a whale shark. They also have an exceptionally long tail, which is almost as long as their body. Leopard sharks reach a length of 3.5m, though 2.5m is considered average size. They are oviparous, laying leathery egg cases, up to four at a time, but very little is really known about their reproductive behaviour.
Leopard sharks are most commonly seen resting throughout the day and are thought to feed at night. They have rows of small teeth set in powerful jaws and feed on molluscs, shrimps, crabs and small fish. They are a popular aquarium shark and do very well, being easy to feed and maintain. They are found in tropical to warm temperate seas from South Africa to Japan and the northern half of Australia to Samoa, but while some books labelled them rare, others said they were locally common, I was determined to find out.
Growing up in Sydney I was a mad snorkeller, always looking out for sharks and rays. But my first chance to look for leopards was a trip to Heron Island in January 1979. An over keen 14 year old I was hardly out of the water, and even though I didn’t see a leopard shark I still had a wonderful time. I returned for two more trips to Heron Island over the next three years, but still no sign of a leopard shark.
I then advanced to scuba diving in 1983, and read an article on Lady Elliot Island stating that both manta rays and leopard sharks were commonly seen. December 1984 found me a Lady Elliot for a week of intense diving. After seeing plenty of manta rays and other amazing creatures, and not one leopard shark I was beginning to wonder how common they really were. Then on the fourth day while drifting near the Lighthouse Bommies I saw a large shape resting on the bottom in the distance. Drifting closer I was over whelmed when I saw the leopard spot pattern colouring its body, my first leopard shark. But the experience didn’t last long, the shy creature lifted off the bottom and swam off before I got within 6m of it. Over the next 3 days I encountered two more leopards, both singular, and both shy.
Over a year later I was again at Lady Elliot Island in February 1986, and observed four leopard sharks over a one week period. Three of these sharks were very shy, but I managed to get close enough to one to pat it gently. Over the next few years I did several other trips to locations throughout the Great Barrier Reef and Coral Sea, but didn’t see one leopard shark. At the time I was also reading all the dive magazines about other divers trips to reef locations, and leopard sharks were only being seen at Lady Elliot Island it appeared.
In January 1990 I moved from Sydney to Brisbane and quickly learnt from local divers that leopard sharks were seen at a few dive sites in the area. Over the next year I had many enjoyable dives, but never saw one leopard, so thought these local divers were pulling my leg. Then in February 1991 I found some leopard sharks, not off Brisbane, but 400km south at North Solitary Island. On one very exciting dive in a shallow bay at the northern end of the island I encountered three leopard sharks. They were all quite small, about 1.5m long, and were patrolling the gutter. I thought leopards slept during the day, and here were three of them swimming around close to the reef and in midwater. I photographed and observed this strange behaviour for almost half an hour before running out of film.
The next day I observed another leopard shark on the western side of the island resting on the bottom. This shark was again quite small and proved to be a great photographic subject. It didn’t seem to be disturbed by our presence and we managed to softly pat it without causing distress.
Returning to Brisbane I was to have the most amazing experience in April 1991. I received a call from Kev Russell, from the now defunct Pro Dive North Stradbroke, saying they had found a new dive site that day with half a dozen manta rays. The next day I was heading out to The Group with Kev, to a spot that is now called ‘Manta Bommie’. Within seconds of hitting the water I saw a large manta ray, I followed it for several minutes until I spotted four leopard sharks lazing on the bottom. The manta forgotten I took several photos of the closest shark before it lifted off the sand, also disturbing two of the others. The fourth shark remained in place allowing me to capture many close photos.
Over the next 45 minutes I was to encounter many more manta rays, turtles, stingrays, wobbegongs, and more importantly for me, a dozen 2 to 3m long leopard sharks. This dive site was something special, so every chance I got I returned to The Group with Kev. For the next month there were leopard sharks all around The Group, resting in gutters and out on the sand. I captured some wonderful photos, but started to ask questions. Why were the sharks congregating? Was it food? Or was it favourable local conditions? I was to be even more puzzled when diving The Group in May and not one leopard shark was too be seen. Where had they all gone? Over the next month we continued to dive The Group, and while the manta rays were still about, the leopard sharks had definitely disappeared.
Then in November 1991 I
was to discover something quite startling on a dive at Flat Rock, also off North
Stradbroke Island. Kev had mentioned to me that leopards were also seen at Flat
Rock occasionally over summer, the area being more famous for Grey Nurse Sharks
over winter. So I was quite surprised at the end of the dive when I headed into
the shallows. In about 6m of water we swam into a gutter and spotted a leopard
swimming around. Following it through the gutter we saw another leopard, then
another and another. There were around a dozen leopards swimming around in the
shallows.Not having my camera with me, due to an earlier flood, I stopped and studied what was happening. The sharks weren’t just swimming around, they appeared to be following each other. It was then that I noticed that it was the males following the females, could this be a mating congregation? All of the sharks were quite large 2.5m to 3m long and there appeared to be an even ratio of males to females.
I watched as a female slowly swam up the gutter with a male following closely behind, she then turned in a large arc and disappeared down the gutter with the male hot on her tail. I was to see this happen several times and one female was followed by three males, was she more receptive I wondered? All too soon my tank ran low.
On the same day we also had a dive at The Group, but there was only one male leopard shark resting on the sand. I had certainly learnt a lot this day. They appeared to be gathering in some sort of mating aggregation, and they seem to prefer warm water if they were only seen from November to April. But where did they go for the other six months of the year? Where they migrating into deep water or up the coast?
I didn’t get a chance to go back to Flat Rock that season due to bad weather conditions, but had a few dives at The Group in December 1991 and saw a dozen leopards on each dive. I now started to record the sexes, and found that the males out numbered the females 10 to 1 at The Group. There was also no mating behaviour taking place here. Was this a resting area? or an area for immature males with low social standing in the world of leopard sharks?
In the summers of 1992/93 and 1993/94 I again dived with the sharks as often as I could. They could always be found at The Group during the season, but not always at Flat Rock. Was the mating period confined to just a few days? or was I just unlucky to be missing it each time?
With so many leopard sharks at The Group, and being so docile and sleepy, I managed to closely photograph and study quite a few sharks. I soon discovered that they had a high number of isopods around their nose. These parasites feed off their host animal, but didn’t appear to annoy the sharks. A few sharks also had shark leeches on their fins, which feed on the flesh and blood of their host. Many of the sharks also have slender sucker fish living in association with them. Though more commonly seen on swimming sharks, some will grimly hang onto a leopard while in rests on the sand. They are thought to clean their hosts and share in their meals. I even witnessed several picking through the faeces trail of a swimming leopard.
It was at this time that I also discovered that leopard sharks love getting their bellies scratched. It happened completely by accident when I gentle patted a leopard on its side near its stomach. The shark shuddered, and settled down. I patted it again, it shuddered again and then rolled onto its back. This got me worried as I thought the shark was sick. Concerned I gently patted its stomach. It then started to twist and turn with delight. For the next few minutes I continued to scratch the sharks belly until my arm tired. When I stopped the shark remained in position for a little while, then flipped over, swam around me and settled right back beside me. So I scratched its stomach for a few more minutes.
I have since scratched the bellies of dozens of leopard sharks, but not all of them are receptive. I start by pat them on the side near the stomach, if the shark swims off I won’t harass it, but if the shark turns on its side I know it is responsive and scratch its belly for a while.
At the end of the 1993/1994 season I started to think about eggs and babies. If this was a mating congregation, then where were they laying the eggs? and when? On every dive I have done since I have searched for leopard shark eggs and babies, with no luck. Having found several other species of shark eggs in the past I thought it would be easy to find an egg 20cm long, but not so. I am either looking in the wrong places or they are depositing them in deep water. Also no sign of babies and juveniles, were they also hiding in deep water only to make an appearance when they reach 1.5m in length?
In February 1994 I had a very exciting dive with dozens of leopards at Cook Island, off Tweed Heads. About half the sharks were active, the other half resting, and surprising the ratio of females to males was 10 to 1, the opposite of The Group. Sexual segregation is known of in several shark species, but with so little known about leopard sharks this was probably the first time it had been recorded.
After the dive at Cook Island I found from talking to other local divers that leopards were nearly always seen there over summer. They were also regularly seen at Nine Mile Reef and Fido Reef, with the sharks at Fido Reef seen swimming around, was this another mating area?
I was starting to realise that South East Queensland was a hot spot for leopard sharks, no where else in the world was there such a concentration of these wonderful creatures. This could be quite an attraction for divers from around the world, like the whale sharks of Ningaloo Reef.
Later that year in December I received a phone call from Scott Michael, and American marine biologist, shark expert and author of ‘Reef Sharks and Rays of the World’. Scott was in Western Australia photographing wobbegongs and was chasing me up for some shark photos. I mentioned the leopard sharks to him and the possibility of a mating aggregation. He was amazed as he had done the only through study of any elasmobranch mating habits in the wild, on the round stingaree in the Sea of Cortez. He promptly cancelled a trip to the Great Barrier Reef and came to Brisbane the following week.
Scott has a leopard shark on his business card, but had in fact never seen one in the wild in all his travels around the world in search of sharks and rays. On the first day we headed to Middle Reef off North Stradbroke and found a leopard shark right under the boat. Scott was so excited he took several photos before realising that something was wrong with his camera. He had forgotten to put film in it. I told him not to worry as the next day we planned to head out to Flat Rock.
This day proved to be unforgettable. Diving mid week, when the conditions are always better than on the weekend, we anchored on the western side of Flat Rock. This was where the leopards usually congregate, but after 20 minutes we had found only one. I then saw two leopards swimming off in the distance. We followed and once over a ridge found ourselves on the rarely dived northern end of the island, and with dozens of leopards swimming around us. Being low on air we returned to the boat and moved it to where we had seen all the leopards.
Changing tanks we quickly descended to be surrounded by leopards. Some were swimming along the bottom, others in midwater, and even a few were close to the surface. With 20m viz. I did a quick head count as I turned around and counted over 20 sharks in view, so estimated that there was at least twice as many as that. This was the greatest concentration of leopards I had yet seen.
After a few minutes observing the sharks it soon become apparent that this was a mating aggregation. The ratio of females to males was even, but watching the sharks I soon saw the following behaviour again. Whether in pairs or groups it was always a female followed by one or more males. All the males looked sexually mature, with long battered claspers, a sign of sexual maturity in sharks. One of the pairs I observed came winding up the reef, the male very close to the female, almost like a pair of synchronised swimmers. The female then gave a shudder, stopped in midwater, then the male put his nose close to her cloaca (vagina). This lasted only a second before she continued up the reef with the male in hot pursuit. Was this male checking for chemical signals from the cloaca that this female was ready to be mated?
I was getting so engrossed watching this behaviour that I hadn’t taken any photos. I quickly fired off some photos as another female came close by with two male consorts. Out of the corner of my mask I saw another female shudder, I turned to see her actually swim at the bottom, turn on her side and rub it along the bottom, then swim off. Was she scratching an itch? removing an annoying parasite? or warning the males to keep away?
For the next 30 minutes I was absorbed watching these beautiful sharks. I had hoped to observed some mating or premating biting behaviour, which is a common factor in shark copulation. After the dive Scott and I were both ecstatic, and in agreement that this was a mating aggregation. But when are they mating? at night? in deep water? or was I just unlucky not to observe it.
Scott headed back to America impressed by Brisbane’s leopard sharks, and I spent the rest of the summer looking out, unsuccessfully, for mating behaviour.
In November 1995 I headed off to Thailand, the only other country were leopards were regularly observed. Staying at Phi Phi Don I did several dives around the area in less than favourable conditions. I couldn’t get out to the famous Shark Point, but
did see one shy
leopard at Hin Bida. But talking to the dive guides they did regularly see
leopards, but generally only solitary animals, and not swimming around or in
aggregations. Heading to Phuket the offshore conditions worsen, and I didn’t
get any diving at all. I again checked on the leopard shark situation with the
local dive guides. They regularly saw them, and even hand feed and patted them,
but did not see them in concentrated numbers. Since then I have continued my search for eggs, babies, juveniles and mating behaviour without success. I haven’t seen such a large mating aggregation at Flat Rock again, but there are always lots of leopards at The Group. The divers of South East Queensland don’t know how lucky they are to have such a concentration of leopard sharks on their door step.
We still know so little about the leopard shark and other marine creatures, as they live in a medium which makes it hard to study them for extended periods of time. But what I have learnt is almost surpassed by the sheer joy I get each time I am able to dive with these wonderful spotted sharks.
