Daily Archives: October 9, 2006

What’s black and white…?


z., originally uploaded by frischmilch.

 

There are four extant species, as well as several subspecies. Zebra populations vary a great deal, and the relationships between and the taxonomic status of several of the subspecies are well known.

The Plains Zebra (Equus quagga, formerly Equus burchelli) is the most common, and has or had about twelve subspecies distributed across much of southern and eastern Africa. It, or particular subspecies of it, have also been known as the Common Zebra, the Dauw, Burchell’s Zebra (actually the subspecies Equus quagga burchelli), and the Quagga (another, extinct, subspecies, Equus quagga quagga).

The Mountain Zebra (Equus zebra) of southwest Africa tends to have a sleek coat with a white belly and narrower stripes than the Plains Zebra. It has two subspecies and is classified as endangered.

Grevy’s Zebra (Equus grevyi) is the largest type, with an erect mane, and a long, narrow head making it appear rather mule-like. It is an inhabitant of the semi-arid grasslands of Ethiopia, Somalia, and northern Kenya. The Grevy’s Zebra is one of the rarest species of zebra around today, and is classified as endangered.

Although zebra species may have overlapping ranges, they do not interbreed. This held true even when the Quagga and Burchell’s race of Plains Zebra shared the same area. According to Dorcas McClintock in “A Natural History Of Zebras,” Grevy’s zebra has 46 chromosomes; plains zebras have 44 chromosomes and mountain zebras have 32 chromosomes. In captivity, Plains Zebras have been crossed with mountain zebras. The hybrid foals lacked a dewlap and resembled the Plains Zebra apart from their larger ears and their hindquarters pattern. Attempts to breed a Grevy’s zebra stallion to Mountain Zebra mares resulted in a high rate of abortion.

 

Stripe convention, originally uploaded by Jean Marc Dieu.

 

Zebras are typically herd animals. They usually stand one to two meters tall, two to three meters long, and weigh 250-500 kilograms as adults (depending on the species). They are most notable for their black and white stripe pattern.

A zebra can travel at a top speed of fifty-five kilometres per hour, slower than a horse. However, it has much greater stamina. During the course of a day the plains zebra can walk around eighty kilometres.

 

Zebra’s eye [Portfolio Magazine], originally uploaded by markeveleigh.

 

They are black with white stripes[1]. These stripes are typically vertical on the head, neck, forequarters, and main body, with horizontal stripes at the rear and on the legs of the animal. The zebra crossing is named after the zebra’s white on black stripes.

Originally, most zoologists assumed that the stripes acted as a camouflage mechanism, while others believed them to play a role in social interactions, with slight variations of the pattern allowing the animals to distinguish between individuals. A more recent theory, supported by experiment, posits that the disruptive coloration is an effective means of confusing the visual system of the blood-sucking tsetse fly.

 

zebra baby, originally uploaded by photo707.

 

Happy, originally uploaded by hvhe1.

Endangered: a living legacy of Steve Irwin

a living legacy of Steve Irwin

Leo Shanahan and Christine Sams
October 8, 2006
A RARE turtle named after the late Crocodile Hunter Steve Irwin could be under threat of extinction if a dam planned for construction in its habitat goes ahead.

The Elseya irwini – Irwin’s turtle – is named as a species at risk in a Queensland Government environmental impact report on a proposal to build the Urannah dam in the state’s north.

The Burdekin Basin draft water resource plan, which addresses environmental implications of the proposed Urannah dam, states: “Elseya irwini is known to occur in this reach. This species is of high conservation significance and is restricted to the Broken-Bowen River system and the lower Burdekin River.

“The dam impoundment would compromise the reproduction and survival of the species in this area because of loss of riffle habitat and destruction of sandbars used for egg laying by inundation.”

Though yet to be approved, the dam was a given a major boost in August after the Queensland Government included it in the draft water plan. The Queensland Government has now backed away from the proposal, saying there are no “current plans to build the Urannah dam”.

The first person to catch the irwini was Steve Irwin’s father, Bob, on a fishing line during a family camping trip in 1990. The family were confused by the creature as nobody had seen it before. They suspected it might be new species.

Steve took pictures of the turtle and sent them to world renowned turtle enthusiast John Cann. “They took some photos of it and sent it to me, they didn’t know what they had,” Mr Cann said. “I saw the photos and jumped on the telephone because I knew it was a new species and asked Steve if I could do some work on it. He said, ‘go for your life’.

“That’s why I named it after him. I think if someone discovers something they should have a reward for it. It’s a good legacy for Steve.”

Meanwhile, Irwin’s voice will be used in a Hollywood film due for release in December. Before his death, Irwin voiced the role of a cartoon character, an elephant seal, which will appear in the film Happy Feet, which also stars Nicole Kidman, Hugh Jackman and Elijah Wood.

SMH: Endangered: aliving legacy of Steve Irwin