Tuatara Tuesday – Stephens Island

September 21, 2010

This little guy lives on Stephens Island in the Marlborough Sounds, and is affectionately known as “tree tut” to the Victoria University researchers who frequent the island.  Because he lives in a tree, of course.  His tree is along the pathway between the house occupied by the DoC rangers and the house where the researchers stay, so he has plenty of passing foot traffic to keep an eye on.

Stephens Island is tuatara central, home to a staggering 30,000 – 50,000 individuals.  Given that the island is only about 150 ha in size, this means that tuatara are EVERYWHERE on the island and it is sometimes difficult to avoid treading on them.  Stephens Island has an interesting history, which may have partly contributed to the high densities of tuatara found there.  A lighthouse was constructed on the island in 1893, and three houses were also built to accommodate lighthouse keepers and their families.  During World War II a radar station was set up there, and an accommodation building known as the “Palace” was constructed.  The Palace is still there and these days serves as a lab and storage shed.

The clearing of land for the construction of the lighthouse and houses, and the introduction of cattle and sheep decimated the Stephens Island forest, and photos of the island from 50 years ago or so show barren hillsides with only a few remnant patches of bush.   However, for the last 20 years a revegetation program has been in full swing and the forest is returning.  The lighthouse was automated in 1988, and the last lighthouse keeper left the island in January 1989.  The last sheep left the island in 2005, and today the only permanent human presence on the island are the DOC rangers, who live in one of the old lighthouse keeper’s houses.

Despite the human settlement and rampant habitat destruction, the only introduced predators that made it to the island were the lighthouse keeper’s cats.  These cats decimated some of the local wildlife, including the Stephens Island wren, an unusual flightless passerine which famously went extinct virtually as soon as it was discovered.  However, the tuatara population escaped virtually unscathed and cats were eradicated in 1925 after only about 30 years on the island.  Ironically, the clearing of forest on the island may have actually increased tuatara numbers, by increasing the availability of suitable nesting sites in open areas.  The island currently appears to be above its carrying capacity, and once the forest regeneration is complete tuatara numbers may decrease somewhat.

Stephens Island, with patches of regenerating forest clearly visible


What are the limits of non-stop flight?

May 14, 2010

In 2007, an Alaskan bar-tailed godwit (Limosa lapponica baueri) flew 11,000 kms over 8 days from Siberia to New Zealand.  Nonstop.  Thats without feeding, sitting down on the ocean to rest, or calling in for a break at a tropical island on the way.  In Plos Biology this week, Anders Hedenström looks at the physiological and aerodynamic requirements for such feats of endurance, and finds that current models can explain such feats.

Hedenstrom compared the rate of fuel consumption in godwits with that of other birds, and found that godwit’s fuel consumption is very efficient, but lies within a normal range.  The godwits body shape and flight speed also mean it is close to the “optimal design” for long-distance flight from an aerodynamic standpoint.  However, many shorebirds share these features and once again the godwit doesn’t stand out as being exceptional.  Hedenstrom suggests that the godwit may stand out from other birds in its ability to navigate, but exactly how the birds maintain their orientation during their non-stop flight across the ocean remains a mystery.

Satellite tracks of the Bar-tailed Godwit Limosa lapponica. Image created by USGS Alaskan Science Center.

Reference: Hedenström A (2010) Extreme Endurance Migration: What Is the Limit to Non-Stop Flight? PLoS Biol 8(5): e1000362. doi:10.1371/journal.pbio.1000362

Cloning extinct species #2: Should we bother?

May 10, 2010

Two weeks ago I posted about how, theoretically at least, one could go about bringing an extinct species back to life by cloning.  Its clear that for long-extinct species like the mammoth, where only degraded remains are available, cloning is still a very long way off and in fact may not ever be possible.  But for species that have only recently gone extinct, or are on the verge of extinction, correct preservation of tissues could see clones created (in fact this has already happened in the case of the pyrenean ibex).  But should we bother going down this path? Read the rest of this entry »

Cloning extinct species #1: A how-to guide

April 30, 2010
 Fancy seeing herds of mammoths running across the tundra, moa crashing through the undergrowth, or perhaps a tasmanian tiger lurking in the Aussie bush? Well in the near future these images might not just be the stuff of far-fetched Hollywood movie plots.  Advances in molecular biology and genomics mean that the ability to clone extinct species is getting closer. In theory, at least.  In this post I’m going to look at how one would go about bringing back to life their favourite extinct species, and in a later post I’ll discuss whether we should bother. Read the rest of this entry »

Rare giant gecko turns up (dead) in mainland sanctuary

April 22, 2010

Here’s one from the good news but bad news file:  The good news is that a Duvaucel’s gecko (Hoplodactylus duvaucelii) has been found on the New Zealand mainland for the first time in nearly 100 years.  The bad news is that it was found dead in a mouse trap.

Duvaucels geckos are the largest of our native geckos, and one of the biggest geckos in the world, growing to up to 30cm in total length.  They are found on a number of offshore islands off the north-east of the North Island and in Cook Strait, and were thought to be extinct on mainland New Zealand.  The last recorded sighting of this species on the mainland was near Thames in the 1920s, but subfossil remains have been found on both the North and South Islands, suggesting it was once widespread across the country. 

The dead gecko was found at Maungatautari, in the Waikato.  Maungatautari is a 3400 ha nature reserve ringed with a predator-proof fence, making it the largest pest-free area on the mainland.  Many rare species have been released into the sanctuary, including kiwi, kaka, takahe and hihi, and reintroductions of many more species are planned.  The Duvaucel’s gecko find suggests that there is a remnant nautral population of the species in the sanctuary, which somehow survived the years when the area was overrun with introduced predators. The hunt is now underway for more of the geckos (which will hopefully be found alive).

This discovery shows that you never know what you might find when you protect an area instead of mining it.

More on the discovery on Stuff.