Toowoomba Field Naturalist: TFNC Members Talk

New member Natasha Preston showed photographs taken by Laurie Perks, of tree kangaroos on her relative’s property in North Queensland, and spoke about their characteristics and habits which in some cases are quite different from those of ground-dwelling kangaroos. Blade Preston, who is also one of our new members then showed images of birds he had taken in the Bunya Mountains area, including the Brown Falcon, Golden Whistler, Red-tailed Black Cockatoo, Pink-eared Duck, and many others. It’s great to see a young person so enthusiastic and keen to learn about natural history and share his knowledge with us. Some of us missed being involved with Neil McKilligan’s egret-counting venture some years ago, but we were pleased to see Neil’s images of some of the 14-heron species found in Australia. Some but not all, are found in the Toowoomba area, and Neil spoke briefly about each. Rod Hobson did not come prepared to speak at this meeting, but kindly filled in for member Jane Orme who was unable to be present. Rod had brought the jaws of a tiger shark and some fossil shark’s teeth for “show and tell”, and spoke about the enormous extinct shark, Carcharocles megaladon, which lived from 23 to 2.6 million years ago, growing to 15 metres long. Rod’s article about this giant creature also appears in this newsletter. Thank you to Natasha, Blade, Neil and Rod – your presentations were enjoyed by all.

(Glenda Walter)

Tree Kangaroos (Natasha Preston)

The tree kangaroos found in Far North Queensland are called the Lumholtz tree kangaroo. They weigh up to 14-20 kilograms, and are about 75 centimetres long with their tail about 85 centimetres. Their face is quite black with their fur many shades of brown. Their babies are called joeys and grow inside a pouch. They live for about 20 years, due to not having many predators. They eat Bollywood leaves, fruit, berries, lantana, Black bean leaves and even bark. They are a master of disguise, you may be looking at them and they simply tuck their head down and fade into the flora. An interesting fact is they don't hop on land; they walk. They are very agile in a tree, jumping up to eight metres from tree to tree. On land, they are extremely clumsy and awkward. Ten percent of their day is spent eating, cleaning themselves and socializing, the rest of their time is sleeping. They are extremely fascinating creatures with strong forelimbs, shorter legs for climbing. Their rubbery wide feet are equipped with rubbery soles and their tail is used as an anchor for balance when they are up very high in the trees. I encourage everyone to go and discover this amazing animal for yourself.

Herons of Australia (Neil McKilligan)

There are in excess of 60 species of heron worldwide of which Australia has 14 resident species plus occasional visitors from the islands of the tropical north. Our herons are differentiated in three groups.

· The Night Heron - Nankeen Night Heron (one species),

· Bitterns (three) - Australian, Black, and Little,

· Day Herons (10) - Pied Heron, Great Billed Heron, Pacific Heron, White-faced Heron, Striated Heron, and the Great, Intermediate, Reef, Little, and Cattle egrets. They all have a pectinate (comb-like) middle toe and powder down feathers. Both being used to keep their feathers clean. Egrets are simply white herons. Reef egrets come in black and white morphs.

They show a large degree of habitat specificity and species-characteristic choice of feeding methods. Most feed in water or swampy areas, the Cattle Egret being a notable exception frequently following large ungulates on dry pasture land. The Great Egret is a stand and wait predator up to its belly feathers, the Intermediate searches reedy and weedy situations, and the Little actively pursues its prey in shallow open water.

I spent 20 years studying the Cattle Egret at its nesting sites in the Lockyer Valley. Nest counts yielded over 4000 in a good year and were only achieved with the help of TFNC members and other volunteers. These hardy souls seemed not to mind the knee-deep mud and aerial bombardment from chicks scrambling among nests overhead. All in all our herons are a very beautiful and interesting group of birds.

Carcharocles megaladon (Rod Hobson, 10.10.17)

About a fortnight ago I was cleaning up a desk in our spare room after tolerance from the distaff side of my marriage had finally reached breaking point - “What do you need a dead stone fish for, anyhow.” That sort of thing. Anyway, during the subsequent flurry of activity I came upon a box of fossils that had been left to me by a close friend, the late Jeanette Covacevich. Jeanette spent her working career with the Queensland Museum eventually attaining the level of Senior Curator of Vertebrates specialising in herpetology. She was made a Member of the Order of Australia for her contribution to conservation and Science, particularly herpetology.

Great White Shark, North Neptune Island,

South Australia September 2010:

Photo credit Marcel Steinmeier

Aside from our shared passion for reptiles we both had an equal passion for faraway places especially islands and she had spent time on such oceanic outposts as St. Helena and Pitcairn. We both shared a great love for the isolated Chatham Islands. These islands lie in the middle of the Pacific about 660 kilometres off the South Island of New Zealand under which they are administered politically.

During a stay on the Chathams in February 2006, Jeanette visited the famous fossil fossicking site at Te Whanga Lagoon on the main island. Here, near the mouth of Blind Jims Creek she found the remains of a very large shark tooth plus several other smallersharks’ teeth. It was this tooth that I eventually inherited and that found its way to the TFNC’s October show and tell. The tooth belonged to the extinct sea monster Carchar-ocles megaladon commonly known by its specific epithet Megaladon (lit. large tooth). Years ago, while I was touring around California, I also bought the tooth of one of these fishes at a lapidary shop so I brought it along on the night, as well. This curio is a perfect example of this shark’s tooth albeit from a much smaller animal than the Chatham tooth. If I remember correctly the provenance of my Californian tooth was a Wyoming fossil bed?

Megaladon is the largest predatory shark that has ever lived. It had evolved by the start of the Miocene, about 23 million years ago. It is believed to have existed until about 2.6 million years ago. Early estimates of this species’ length have been grossly over-estimated but it is thought to have reached 15 metres, which is more than twice the length of the largest Great White Shark Carcharadon carcharias ever recorded. Megaladon was originally believed to be the ancestor of the Great White and was formerly placed in the same genus, however more recent work suggests that Megaladon actually belonged to its own extinct family of lamid sharks. Despite the similarity in tooth structure between the Great White and Megaladon the Great White is now thought to have evolved from an extinct Mako Isurus hastalis found worldwide in Miocene and Pleiocene deposits. This shark, by developing serrations on its teeth became the ancestor of the present-day Great White Shark. The teeth of Megaladon could reach up to 18 cm high whereas those of the Great White are only about a third of this size. This really enforces what a formidable predator Megaladon was. Speculation as to the extinction of Mega-ladon focuses on the cooling of the seas in the late Pleiocene about 2.6 million years ago. Megaladon is believed to have fed on marine mammals especially the great whales. Fossil baleen whales have been found in Antarctica recently and it is thought that they began colonising these waters around the end of the late Pleio-cene. It is not known if these whales shifted to these waters to escape predators or for feeding but irrespective it is believed that the cold-blooded predators such as Megaladon were unable to cope with these changed climatic conditions, unlike their blubber-encased prey, and subsequently died out.

My other exhibit on the night was a set of Tiger Shark Galeocerdo cuvier jaws taken at Waddy Point on K’gari (Fraser Island) in the mid 1990s. The Tiger Shark is common in these waters especially when following migrating Humpback Whales Megaptera novaeangliae. It is named in honour of the great French zoologist and taxonomist Jean Leopold Nicolas Frederic Cuvier (1769-1832).

I have included some images with this article including two that show the serrate dentation of the Great White.

Shark teeth for comparison with the images of Megaladon’s teeth. They are quite similar. It can be seen why these sharks, and the Tiger Shark, are/were such awesome predators. The detail of the Great White’s teeth was taken from a beach-washed female found at Inskip Point on 27.03.2005 whilst the photo of the shark attacking the trolled lure was taken on a trip that I attended off North Neptune Islands, South Australia in September 2010, one of the great highlights of my natural history life.