(kim) 17. Trophic cascades 'Masting'

Question 1

Define ‘Masting habit’

Answer 1

-Silultaneous production of seed by all plants in a local community

(typical of plants with large seeds vulnerable to seed predators)

Question 2

What is the advantage of masting?

Answer 2

Advantages

• Evolved as predator swamping technique: helps reduce losses of seed to predators (eg insects, rodents, birds) by satiation *supply beyond capacity
• Flowers are wind poillenated so increased chance of fertilisation
• Seeds are expensive prodicts = masting increased chance of some seeds surviving and germinating

Disadvantages

-Depends on effective synchronisation

Question 3

What is the main endemic predator to seeds?

Answer 3

Endemic insect

• Larvae feed on developing seeds in Autumn
• During winter within the seed
• Emerge in spring

Question 4

Consequences of masting for forest fuana (maori times)

Answer 4

• Huge amounts of food available some years whilst none in others
• Effect well know to pre european maori

(response of kiore, pigeons, kaka vital for winter food supplies)

(Kiore traps set in traditional places after a masting event)

Question 5

Consequences of masting for forest birds (maori times)

Answer 5

Birds were significant resource: rights to known bird catching places guarded jealously

• Kereru and kaka were caught at traditional, named sites on fruiting trees belonging to particular hapu and protected by tapu.
• Pigeons loved miro but fruit made them very thirsty (maori knew this)

Hunters provided a bird through, waka manu, a wooden vessel up to 1.5m long and sometimes carved.

-Snares would be set over it, or the snarer would hide nearby with his tahere (noose) on a rod

Question 6

Podocarp masting stimulates breeding in..

Answer 6

..Kakapo

• connection between masting and kakapo (south island)
• Rimu takes 3 years to fruit
• Once the green fruit began to grow, male start booming cycle in spring
• Mating and egg laying in summer
• sexually mature at 5 years (lek breed)
• ‘Freezing camouflage’ defence mechanism

(innefective against introduced scent predators)

• Common in early european times, staple food for explorers
• Declined to 18 known birds in 1970’s, all males in Fiordland
• Last breeding pop found on Stewart Island
• Transferred to Whenua Hou after it was cleared of kiore
• 1995, increased to 50
• Breeding depends on rimu fruiting + supplements (male infert problems)
• N = 154 in 2016, all offshore islands, now 149

Question 7

Consequences of masting for forest fuana (post european)

Answer 7

• Effects still reverberate throughout forest community
• Litter-feeding insects, rodents, carnivores, even parasites all benefit

Male flowers > Beech seed & leaves

increase of nutrition for isects/inverts >

Mice now have more insects/inverts to eat >

increase of protein to mice which stimulates breeding

(breeding success of mammals down to protein which builds bodies of youns)

All of the mice younglings survive due to lots of nutrition >

More food availability for stoats >

stoats eat all the birds/birds also benefit from insect increase.

Critical native species so the only benefactor from this trophic cascase is the introduced species (scream emoji)

Question 8

What happened at Okarito forest between 2002 and

Answer 8

• Masting year in 2002
• Extra food = Rat & young rats population went up
• October rats killed (800)
• Stoats numbers soured because of higher rat population
• More stoats than usual
• Second Masting 2003 the following year

Numbers or rats soared because the population starting base was already so high (1600 killed)

Stoats followed the rat soare and the kiwi was affected..tbc