SciBlogs

Archive April 2010

Today’s Crocodile Photo Brendan Moyle Apr 29

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This was one of the earlier shots we got on our expedition to the Mary. You’ve got a nice colour variation to the scales with this particular animal.

Given we’re on a small boat, and the engine is throbbing and causing a constant tremor, I’ve increased the ISO value for these shots to push the shutter-speed higher.

I’ve also opted to keep the 300mm lens as is, and eschew the 1.4x TC. This reduced the effect of camera shake further.

It’s an old, old earth Brendan Moyle Apr 28

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As mentioned yesterday, geology, chemistry and biology have all converged on the conclusion that the earth is very old. Patterson went on to demonstrate a more precise age of 4.55bn years in the early 1950s using radiometric dating.

For those of us not blessed with PhD’s in chemistry however, there are some straightforward reasons to accept a very old age of the earth.

One of these is just to recognise that lots of biomass from dead organisms is stored in the earth’s crust. Over time, animals and plants die. Some animals- small marine organisms- had their shell’s preserved as chalk. This has lead to massive accumulation of these deposits- e.g. the cliffs of Dover.


It’s easy to recognise that there’s really no way, hundreds of metres of animals would have piled up on each other in a very short space of time.

Another big source of old biomass are fossil fuels. These include peat, coal, oil and natural gas. There is so much carbon in this stored biomass, that its release into the atmosphere is actually changing green-house-gas levels.

With only some geological formations are conducive to the fossil fuel formation, even the massive oil deposits were using represent a tiny fraction of the plant and animal life that used to live on this planet.

All of this stored biomass outweighs the current biomass of this planet by a very large margin. So even with only a fraction of the biomass being captured, there’s a lot more in the earth’s crust than can be explained by a young earth. Every time you fill your car with petrol, you’re contributing to the proof that the earth is old.

A related problem is just the sheer brittleness of rocks. Rocks you might have noticed, aren’t very plastic. That contributes to some of New Zealand’s erosion problems. The East Coast has a lot of soft gray-wacke rocks, but is also an area with lots of active fault lines. That means earthquakes, less stable bedrocks, and hills and soils that are apt to being washed away in bad storms.

If scientists are wrong and the formations we see around us, was laid down much faster via accelerated, cataclysmic events, then that pretty much would shatter all those lovey mountains and hillsides we see around us. Instead of the Southern Alps rising slowly under the collision of two tectonic plates, it would have been reduced into many tiny fragments in low mounds.






Theory of Evolution isn’t a religion- it’s science Brendan Moyle Apr 27

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A somewhat bizarre and recurrent claim on some social media sites, is that the theory of evolution requires faith to believe in. Hence it’s analogous to a religion. (Often that prefaces an assertion that it requires an extraordinary amount of faith).

The theory of evolution however, doesn’t require faith or beliefs. It’s accepted in the scientific community (and in most secular countries, by a large chunk of the population) because of evidence.

We only need to establish four basic facts for evolution to be- at the very least- deductively correct.

First, it has to be the case that a population of organisms varies in their traits. This is readily observable. This variation is a necessary condition of evolution.

Second, there has to be a mechanism of inheritance. Again, this has been firmly established. Chromosomes carry DNA. DNA is the molecule of inheritance.

Third, selection[1] has to operate on populations or organisms. Again, this is observable. The example of the pepper moth is a classic example from the wild. Pesticide resistance in insects is another example.

So these three things means that evolution is going to occur. Evolution is about shifts in gene frequency. Some genes become more common, some genes become less common. So these facts mean that some traits will be selected for. They will have some evolutionary advantage. Mosquitoes that are resistant to common insecticides will be more successful than those without this resistance. These will pass this trait on to their descendants. And there will be a lot more resistant mosquitoes in the population as a result.

That leads to the last condition for evolution. That’s just time. There is a lot of time available. Early geologists pondering the rock stratas in Europe and North America deduced that Earth is very old. Biologists appreciating the slow, incremental nature of selection, deduced that the Earth is very old. And finally, Clair Patterson nailed the age of the earth down with a lot more precision when lead isotope analysis showed that the earth was 4.5 bn years old.

So, none of the above facts actually require any faith. Evolution is just a necessary consequence of these factors. Now in science, we also go a bit further than this. We also try to make predictions based on this. One very important area of prediction are fossils. The Theory of Evolution is going to make some pretty bold claims about the order in which fossils appear and the types of features these fossils will exhibit.

An excellent example of this is Tiktaalik roseae[2]. This is an important fossil that shows some of the transitional properties we expect between fish and tetrapods (the early vertebrates that first conquered land). From the theory of evolution there should be transitional forms in the late Devonian (375-363 Myr). Palaeontologists looked, and yes, we got it right. It’s there in the Late Devonian and its got dorsally mounted eyes and a neck and head capable of independent movement.


Image linked to National Geographic
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[1] Selection isn’t the only mechanism of evolution. Other factors such as genetic drift or hybridisation also can play a role.
[2] Downs, J.P., Daeschler, E.B., Jenkins, F.A. & Shubin, N.H.(2008) The cranial endoskeleton of Tiktaalik rosae Nature 455: 925-929


Knowing your invasive pests Brendan Moyle Apr 26

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The late 19th century and early 20th century saw the release of many mammalian species in New Zealand. One of the lesser known invasives is the dama wallaby or Macropus eugenii. This species was released on Kawau island around 1870. More of these wallabies were then released in 1912, but we don’t know if these came from Kawau Island or were another Australian import.

By the 1950s the wallaby had established itself in the central Bay of Plenty. It’s range at the moment is being curtailed by a combination of geography and pest control. The current range is bound by a number of lakes and rivers in the Bay of Plenty.

The dama wallaby is also the smallest extant wallaby species. It is also a pest and its browsing inflicts significant damage to emerging native plants.

I took the following photos of a young wallaby feeding at a local zoo (Rainbow Fairy Springs) in Rotorua.

#1


#2


#3

A feathered friend for Friday Brendan Moyle Apr 23

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On a less guinea-pig related note, here’s a photo of a red-crowned parakeet (or kakariki) from NZ.



NZ is not exactly swarming with native parrots and parakeets. Australia on the other hand, has a lot more of them. The kakariki is a native parakeet that is still reasonably common. Photographing them of course, is an entirely different challenge.

Guinea pigs are the answer for the Congo Brendan Moyle Apr 22

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Getting enough food is a challenge for much of the world’s population, but for war-affected counties, the problem is even worse. The answer it seems could be ‘microstock’.

Last year researchers from CIAT[1] in the Congo found that villagers in the North and South Kivu districts were keeping guinea pigs. This came as a bit of surprise, because nobody has any idea how guinea pigs (rodents native to South America) how they got there. The guinea pigs are being used to provide meat to these households.
[2]

Guinea pigs turn out to be a better choice than traditional large, livestock (pigs, goats etc). The animals are small and easy to conceal, and that reduces the risk of theft. Looting of larger, domestic stock is sadly common, something to do with the poverty and lawlessness of the area. Having small animals that are easy to conceal, turns out to be a very smart, local solution (still, where did they get the guinea pigs to begin with?).

Guinea pigs have other advantages as well. On the farming side of things, they require little investment to begin with. They reproduce very quickly so stock-numbers grow much faster than many other animals. They’re also a lot more resistant to diseases than pigs, chickens or rabbits.

The other advantage of these little critters, is that they’re monogastric. For those of you worried about greenhouse gas emissions, it means they’re going to produce a lot less emissions than our favourite ruminants (cows, sheep).

CIAT is now working on ways to increase guinea pig production, and link it to ways to expand livelihoods in these regions.







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[1] CIAT is the International Center for Tropical Agriculture (www.ciat.cgiar.org)
[2] Figure is sourced from the CIAT news letter

The beleagured grey duck Brendan Moyle Apr 21

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The New Zealand grey duck (Pārera) is a subspecies of Anas superciliosa. While the species is considered secure over its range, it is in decline in New Zealand. The major source of decline is competition and hybridisation with the mallard.

The mallard occupies much the same habitat as the grey duck, and is a strong competitor. Hybridisation is also causing a decline in gray ducks as they will mate with mallards also.

I took this photo in the aviary at Rainbow Fairy Springs

Native Grey Duck or Pārera


In contrast, the female mallard (in the wild)

Thinking about Captive Breeding Brendan Moyle Apr 20

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Captive breeding remains a vital approach in the conservation of many species. In addition to building up numbers for reintroductions, captive breeding also provides an outlet for research, advocacy and medicine. For some species where habitat is not secure enough, captive breeding is the last chance to preserve a population long enough to keep open the option of reintroduction.

In New Zealand we don’t seem to make a lot of use of captive breeding options. This has long puzzled me. There is little in the way of genuinely secure habitat outside a few offshore islands. If we’d had a backup population of say, little-spotted kiwi or some of our weka species, the dramatic collapse in the population of these birds would have been far less serious.

I am leaning to the idea that the Wildlife Act is part of the problem. The Wildlife Act is a decades old piece of legislation. One of the motivations was the rediscovery of the takahe- a native rail previously thought extinct- in the late 1940s. The passage of the Act in 1953 had three basic aims. These were to protect some native animals, manage introduced animals, and kill pests.

Somewhat telling is that nowhere in the legislation are zoos or zoological parks mentioned at all. This is not suprising. The Act is old, and predates the current era where zoos have conservation missions, and where sustainable use is employed as a conservation tool. Nonetheless, because the Act effectively gave the Crown all property-rights in a select number of species, captive breeding of these animals is mediated via this Act. So we have an Act that has to be used by zoos and the like (e.g. Otorohonga Kiwi House, Rainbow Fairy Springs, Orana Park, the various city zoos) that doesn’t recognise zoos.

Compounding this is the uneven treatment of species. For instance, birds and reptiles are automatically given protected status unless specifically exempted. Insects and other arthropods only get protection if specifically listed.

In the absence of any legislated role or objectives for captive breeders, much of the policy-making is thus devolved onto the Crown’s authority. Currently this is the Department of Conservation.

This use of discretionary mechanims can lead to decision-making on the fly and a lack of consistency across species, or over time. For instance, restrictions have at times, been placed on the actual captive breeding of species. In some seasons, potential breeding opportunities have been forestalled by decisions out of DoC.

In policy terms this is not ideal. Having clearly set out legislation that recognises and supports the contribution captive breeding can play, is just good policy. The issue is about reducing the level of discretion to a point where policy-making is fair and transparent. Where too much discretionn is involved, breeding programmes are vulnerable to short-term, reactive interventions.

Miromiro or NZ tomtit photos Brendan Moyle Apr 09

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I’ve had the opportunity to do a bit more bird photography recently. This wasn’t entirely planned, and rather than employing my heavier and faster 300mm prime, I was making do with a slower (but much lighter) zoom.

New Zealand is home to a number of native birds from the family Petroicidae. These are commonly known as the Australian robins. While these birds were given common names based on similar European species, they are unrelated. The miromiro was given the name of NZ tomtit. Its scientific name is Petroica macrocephala. It’s close relatives include the NZ robin and the black robin from the Chatham Islands.

The miromiro is an insectivore. Fortunately the species does not appear to be in any risk of extinction. Nonetheless, it is often heard but rarely seen by many New Zealanders.

While in Rotorua near the Redwoods, I spotted one such male miromiro chasing insects on the tree trunks of the trees. With a bit of patience and a lot of luck, I managed to get some shots in before it flew off.


Link to larger image

If you look closely at the larger image, you should be able to see traces of spider-silk on the face.

The male has the characteristic black hood.

The second shot is a longer distance photo taken with the bird on the leaf litter

Link to larger image