TOKOEKA

Apteryx australis

Tokoeka

HABITAT

The Tokoeka, also known as the Southern Tokoeka or Southern Brown Kiwi, lives mainly on New Zealand's South Island and Stewart Island. On the mainland, kiwis live in Fjordland and Westland. Refer to diagram below to find out about distribution.

This species of kiwi lives mainly in temperate/subtropical forests, and grassland. On the two islands, they also live on sand dunes. These are terrestrial environments. There is a high risk of predation from animals such as stoats and cats. The Tokoeka lives and incubates its eggs in a shallow burrow, or bowl to hide from these predators.

A forest in Fiordland - a typical habitat for the Tokoeka
Distribution of the Tokoeka; subspecies are shown

FERTILISATION

The Tokoeka reproduces by cross-fertilisation. Males and females attract each other using booming calls. They mate for life. Fertilisation is internal. The male fertilises the female by injecting sperm from his cloaca, a multi-purpose opening under the tail, into hers. Females only have a single oviduct through which sperm can pass through; however, they still have two functioning ovaries and can still release two eggs. This increases the chances of successful fertilisation. A low number of gametes are released. The advantages of internal fertilisation are that the number of gametes is lower due to higher chance of them joining, and also that the zygote can receive nourishment from the mother's body. External fertilisation can be a waste of sperm and eggs - the chances that the sperm and egg will actually make contact is lower. There is also a high risk of predation of the zygotes. A disadvantage of internal fertilisation is that the number of offspring is more limited and that the zygote depends on the mother for survival.

Tokoeka in a shallow burrow with eggs

DEVELOPMENT

The embryo of the Tokoeka develops externally - inside an egg, which is known as oviparity. The kiwi has the largest egg, in relation to body size, of any bird. The Tokoeka lays 1-2 eggs inside a burrow lined with plant materials. An advantage of oviparity is that the mother does not have to provide extra resources for her young except warmth. Labour and birth in viviparous animals also makes them vulnerable, while egg laying is quick and easy. The disadvantages of oviparity is that in some cases the parents must always incubate the eggs by sitting over them -this makes them more vulnerable to predators. The eggs can often not be moved quickly to get away from predators. Sometimes the young can be too underdeveloped to break out of the egg.

A newly hatched Tokoeka chick

PARENTAL CARE

The level of parental care in Tokoekas is high, known as K-selection. K-selection involves having fewer offspring, but taking more care of them - the mortality rate is low. The chick is cared for for up to five years until it is ready to breed and stake out its own patch of territory. This is due to the low number of offspring and also to the fact that the young Tokoeka needs to learn a lot about its environment in order to survive. The female lays only 1-2 eggs, usually just one, and occasionally 2 (2 in 15% of cases). Both parents incubate the egg and look after the chick. The advantage of using K-selection is that the mortality rate is lower than in species that use r-selection. The parents are able to abandon the eggs if they are in danger from predators. The disadvantage is that the young will die without the guidance of its parent. The parent is always kept busy caring for its offspring - feeding it and cleaning it.

REFERENCES

Melbourne Museum. (n.d.). Wild - Southern Brown Kiwi. Retrieved September 17, 2013, from Melbourne Museum: http://museumvictoria.com.au/melbournemuseum/discoverycentre/wild/biogeographic-regions/australasia/southern-brown-kiwi/

New Zealand Birds Online. (2013). Southern brown kiwi. Retrieved September 16, 2013, from New Zealand Birds Online: http://nzbirdsonline.org.nz/species/southern-brown-kiwi

Oiseux.net. (2013, August 28). Southern Brown Kiwi. Retrieved September 17, 2013, from Oiseux.net: http://www.oiseaux.net/birds/southern.brown.kiwi.html

Southern Brown Kiwi (Apteryx australis). (n.d.). Retrieved September 18, 2013, from BirdLife International: http://www.birdlife.org/datazone/speciesfactsheet.php?id=8

Wikipedia. (2013, June 1). Southern Brown Kiwi. Retrieved September 16, 2013, from Wikipedia: http://en.wikipedia.org/wiki/Southern_Brown_Kiwi

Wildscreen. (2013). Tokoeka photos, videos, and facts. Retrieved September 18, 2013, from ARKive: http://www.arkive.org/tokoeka/apteryx-australis/

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