Have we got any poisonous spiders in New Zealand?
Are there any snakes in New Zealand?
Were there ever dinosaurs in New Zealand?
Why does New Zealand seem to have so many threatened species?
When did humans arrive in New Zealand?
What causes phosphorescence?
What is the difference between a skink and a gecko?
Which way do snails coil in their shells?
What is New Zealand’s tallest species of tree and what is the world’s tallest tree?

Q. Have we got any poisonous spiders in New Zealand?

New Zealand is home to around 2000 species of spiders and although all spiders bite very few of those found in New Zealand are actually dangerous to humans. The katipo (Latrodectus katipo) is perhaps the most venomous but most people will never see one due to their shy nature and the habitat in which they live. The closely related Australian immigrant the redback (Latrodectus hasselti) is also known to occasionally bite the unsuspecting causing a painful bite, swelling and numbness which may lead to nausea, vomiting and if left untreated potentially death. Another Australian immigrant species, the white-tailed spider (Lampona cylinrata), has become well known for its painful bite. In addition, several victims have required treatment after the bite caused flesh to rot (a state called necrotising fasciitis). It is highly likely however that this is a result of the spider having injecting (along with venom) a virulent, although common, soil bacterium.

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Q. Are there any snakes in New Zealand?

Yes and no. New Zealand has no terrestrial (land) snakes either native or introduced. However due to New Zealand’s sub tropical climate it is visited irregularly by two species of sea snake. The yellow-bellied sea snake, Pelamis platurnus, (the most widely distributed of all sea snakes) is an infrequent visitor to our shores with more than 35 sightings around New Zealand shores since 1930. An even more unusual visitor is the banded sea krait, Laticauda coumbrina. The banded sea krait is distributed from India and South-east Asia through New Guinea, Australia and the Pacific Islands. Both species of snakes are highly venomous but, due to their size, are highly unlikely to be able to penetrate human skin.

Yes. Considering it’s relatively small size New Zealand had a reasonable dinosaur representation. However it wasn’t until fairly recently, when amateur palaeontologist Joan Wiffen uncovered dinosaur bones in the Hawkes Bay, that scientists even knew that dinosaurs had roamed New Zealand. We now know that at least five types of dinosaurs were once found on the land in New Zealand:

• the carnivorous theropod which stood around 2m tall and weighed in at 400kgs
• the Ankylosaurus an armour plated monster weighing around 500kgs
• a sauropod called Diplodocus which was the largest of all New Zealand dinosaurs at around 10m tall
• the well known, flying pterosaur
• a herbivorous ornithopod
  

In addition, two marine species were relatively common around the New Zealand coastline:

• Plesiosaur
• Mosasaur

Q. Why does New Zealand seem to have so many threatened species?

During it’s first 1000 years of human occupation New Zealand has lost a third of all native land and freshwater birds, a fifth of all seabirds, three of seven frog species, one species of bat, at least twelve invertebrates and eleven plant species. In addition, 75 species of birds, 50 species of marine fish, 50 species of reptiles and close to 600 species of terrestrial invertebrates have been assigned ‘threatened’ status. Botanical records tell us that toward the end of the 20th century the number of introduced plant species in New Zealand surpassed the number of indigenous species. New Zealand is now home to over 2100 introduced higher plants many of which are considered problem weeds. As a direct result of this in excess of 750 species of plants are currently classed as threatened.

The reasons for this are two fold. Firstly New Zealand wildlife evolved for 100 millions years without the influence of mammals (except for three small species of bats). There were no large mammals such as bears, dogs, cats and the like common in continental countries. As a result the native fauna evolved in such as way that little emphasis was put on defense ie. many bird species lost the ability to fly, many insect species evolved gigantism (and as a result were very slow moving) and reproduction rates became very slow (some birds such as kiwis only laying a single egg each season).

Secondly, with the arrival of humans came the arrival of predatory mammals that found their new food sources, native animals, to be easy pickings. This coupled with the fact that humans undertook massive forest clearance resulting in habitat loss meant that many native species were put under pressure to survive.

Q. When did humans arrive in New Zealand?

It is though that Maori (the indigenous people of Aotearoa/New Zealand) arrived by way of waka (canoe) in a series of migrations sometime after 1150AD. They brought with them the kuri (Pacific dog) and kiore (Pacific rat/Rattus exulans). Where they arrived from is still unclear although legend tells of a homeland called Hawaiiki. Debate still continues as to where exactly this was, with some proponents suggesting Hawaii (based on linguistics) others (citing recent DNA work) Tahiti. Either way what is more ambiguous is where Maori originated from prior to their appearance in the Pacific.

Current evidence points to an origin in South East Asia by way of Melanesia. Recent DNA work indicates that the ancestors of the Maori explorers derived from a migration of people of the Taiwan Tapenkeng culture known as the Austronesians and that this migration occurred around 3500BC. The Austronesians slowly expanded southward and, by 1500BC had moved down through the Phillipines, the Malaya Peninsula, down through Java, Borneo, Sumatra, and the Celebes and across to the Solomons. It appears they had made their way to New Caledonia, Fiji and Samoa by around 1200BC. They then continued to extend east to the Society Islands, the Cook Islands and the Marquesas by around AD1. Within five hundred years the Easter Islands were inhabited, and by 1000 AD, so too was Pitcairn Island. The final major island group of the South Pacific to be inhabited was New Zealand.

Q. What causes phosphorescence?

Phosphorescence, of the kind often observed during the summer months, is caused by single celled (unicellular) algae called Dinoflagellates. These microscopic organisms are present throughout the ocean and emit light when they are disturbed, for example by a boat, a swimmer or more commonly wave action. The result is a chemical reaction within the organism, resulting in the production of light. Dinoflagellates breed all year round. However, there are several factors that increase their numbers, these are: light, water quality, temperature, availability of nutrients, and depth or tidal exposure. As dinoflagellates depend on photosynthesis to get their energy for growth, light is a major factor in their survival. Interestingly the intensity of phosphorescence by photosynthetic dinoflagellates is strongly influenced by the intensity of sunlight the previous day, ie. the brighter the sunlight, the brighter the flash. The other thing that can contribute to a particularly impressive display can be a concentration of nutrients in the water, most commonly caused by runoff from pollutants, such as sewage. This results in a build up of dinoflagellates.

Q. What is the difference between a skink and a gecko?

Skinks and geckos both belong to the class of animals known as reptiles (Reptilia). This class also includes tuataras, snakes, turtles and tortoises. Both fall into the order Squamata and are therefore known as lizards. Skinks and geckos are well known for their powers of dispersal and accordingly are well distributed throughout the Pacific. New Zealand is home to 16 species of geckos and 28 species of skinks. New Zealand native lizards are unique in that all but one species of skink give birth to live young. The differences between geckos and skinks however, are numerous. Geckos tend to be restricted to warmer areas of the world while skinks are spread throughout tropical and temperate regions. Geckos cannot blink (their lower eyelid has fused shut and a single scale has enlarged to cover the eye). As a result they clean their eyes with their tongues. Skinks on the other hand blink. Skinks also tend to move very quickly while geckos move much more slowly. Skinks have very shiny, tight skin (a result of their scales overlapping) while geckos have a more granular, loose fitting skin that is regularly shed. Most reptiles are silent except geckos. The New Zealand species have a chirping or chattering communication and some can croak and squeal. New Zealand geckos tend to be omnivorous while New Zealand skinks seem to prefer a carnivorous diet only occasionally feeding on fruits. Skinks have long tails that they can easily shed to escape danger. These can grow back but don’t seem to acquire the length of the original. Geckos are expert climbers with long toes and pads on the underside of their feet to assist them.

Q. Which way do snails coil in their shells?

The direction a snail’s shell coils is called the handedness, chirality or screw sense and reflects the body plan of the animal that lives within. There are two possible types - a left handed coil is called sinistral, a right handed coil is called dextral. Most snail species are dextral (right-handed), with fewer being sinistral (left-handed). However, in some species both types of coiling can be observed. The direction of handedness appears to be determined during the second stage of snail embryo development, when the single-celled egg splits into two new cells. Within these cells, the way that the chromosomes line up determine whether an individual will display dextral or sinistral coiling.

Q. What is New Zealand’s tallest species of tree and what is the world’s tallest tree?

The tallest native tree species in New Zealand is the kahikatea or white pine (Dacrycarpus dacrydioides). They are known to grow to 60m and are found throughout New Zealand up to around 600m altitude. Kahikatea are often the dominant tree species in swampy areas, although they also grow well in drier areas. Unfortunately today there are few large pure stands of kahikatea to be found. This is mainly due to forest clearance for farming. Eucalyptus regnans (mountain ash) is the tallest tree species in the world.One particular speciman at Mt. Baw Baw, Victoria, Australian, is believed to have measured 143 m (470 ft.)1885. Formerly, another Australian eucalyptus, at Watts River, Victoria almost certainly had been over 150 m (492 ft.) tall. Both however have since died. The tallest living tree today is the Mendocino Tree, a coast redwood (Sequoia sempervirens) found at Montgomery State Reserve near Ukiah, California, USA. In September 1998, it measured 112 m (367.5 ft) tall, with a diameter of 3.14 m (10 ft). Neither genus, Sequoia nor Eucalyptus, are native to New Zealand.