Plenty poses for­est pest plague

Mast­ing in our beech forests, which pro­duces a bounty that once sus­tained our na­tive species, now threat­ens their ex­is­tence.

The Tribune (NZ) - - ENVIRONMENT -

Con­ser­va­tion­ists are brac­ing them­selves for ex­plod­ing pop­u­la­tions of rats and stoats this year.

Re­spon­si­ble for this men­ace is an ex­cep­tion­ally plen­ti­ful sup­ply of seeds in New Zealand’s beech forests dur­ing the au­tumn.

In a process known as ‘‘mast­ing’’, some 50 mil­lion beech seeds will fall per hectare. For each hectare that’s about 250 kilo­grams of seeds.

At one time, the su­per­abun­dant seed would have nour­ished kakapo and other na­tive species, en­cour­ag­ing them to breed.

But with those species on the brink of ex­tinc­tion, it’s rats and mice that feast on the bounty in­stead, lead­ing to dra­matic pop­u­la­tion rises.

A fe­male rat reaches sex­ual ma­tu­rity at five weeks of age and can pro­duce ten off­spring ev­ery eight weeks—that’s a lot of rats!

All these rats and mice mean a feast for stoats. Their num­bers ex­plode as well.

Next spring, the beech seed will rot or ger­mi­nate, mak­ing it use­less as a food source. Threat­ened with famine, preda­tors will turn their at­ten­tion to bird eggs, nestlings, na­tive bats and snails.

Among the species put at risk are kiwi, ta¯kahe, ka¯ka¯, kea, whio (blue duck), mo¯hua (yel­low­head), ka¯ka¯riki (na­tive para­keet) and pekapeka (na­tive bats).

Stoats, by far our worst preda­tor, kill an av­er­age of 40 North Is­land brown kiwi chicks a day, equiv­a­lent to 60 per cent of the an­nual brood.

Mak­ing the situation still more crit­i­cal, 2015 will be the sec­ond beech mast year in a row.

In re­sponse to the 2014 mast year the Depart­ment of Con­ser­va­tion (DOC) launched its ‘‘Bat­tle for the Birds’’, which saw

Stoats, by far our worst preda­tor, kill an av­er­age of 40 North Is­land brown kiwi chicks a day.

rat num­bers crash­ing at most sites and averted a plague of stoats.

How­ever, For­est & Bird is con­cerned that fund­ing for a sec­ond ‘‘bat­tle’’ will not be avail­able this year.

Kevin Hack­well, For­est & Bird group man­ager for cam­paigns and ad­vo­cacy, will be talk­ing about the threat posed to our na­tive species by these two suc­ces­sive beech mast years at the monthly For­est & Bird meet­ing on Tues­day, April 12.

All are wel­come to hear Kevin’s talk in City Li­brary at 7.30pm.


Rats feed­ing on eggs in the nest of a song thrush. Rats are skilled tree clim­bers and do not dis­crim­i­nate be­tween na­tive and in­tro­duced birds.

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