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Studies on the Two New Zealand Bats



The present area of distribution of New Zealand bats is considerably less than it was over a century ago. Early records are available from many major urban centres such as Wellington and Dunedin and a well authenticated colony beneath a bridge over the river Avon in Christchurch persisted to the early 1900's. Smaller townships such as Dannevirke (Hawke's Bay) and Ross (Westland) also had their colonies.

Before 1930 sightings were scattered and were generally nearer the coast or townships than is now the case. They were seldom far distant from the extensive forest areas. The general pattern has been a decrease in the distribution correlated with the restriction of forest during the last century. Both species of bat have failed to urbanise, and small populations isolated from the forest generally have not survived.

There is no evidence that the density of bats has decreased within unmodified forest. Rivers and lakes provide an abundance of suitable insect food and clearings near bush provide favourable hunting grounds. Bat colonies have therefore survived in these localities. In open limestone country isolated colonies sometimes occur in caves. Such small colonies are present in the Te Kuiti-Waitomo district (South Auckland).

Altitudinally the bush line limits the distribution of bats. The single record. above this limit is at 3,460 feet in the Tararua Range (South Wellington).

In the North Island bats are regularly reported from southern South Auckland, Rotorua-Taupo, Gisborne and the northern parts of North Wellington and Hawke's Bay. Within. the Rotorua-Taupo and Gisborne districts the greatest number of sightings are from the Urewera and Lakes Waikaremoana-Rotorua districts. page 20A large colony is well established at Aniwaniwa (Waikaremoana) with flights of 40 or more bats being observed over the lake during the summer. Some recent records are derived from the Whakatane-Opotiki district. In North Wellington the upper reaches of the Wanganui River drainage system account for many sightings. The many records from South Wellington have usually been of isolated bats or small flights. It appears that here bats are restricted to a few small scattered colonies in the Rimutaka and Tararua ranges. Little Barrier Island and Kapiti Island have a long history of sightings, but again numbers appear to be relatively few.

In the South Island, north-western Marlborough, Nelson and northern West-land seem to be well populated. The Wairau, Pelorus, Motueka, Karamea, Buller and Grey River drainage systems account for these records. The few recent records for Canterbury come from the Geraldine County. In Southland the few records are perhaps deceptive and the recent nature of these, excepting those coastal, suggests that a general absence of observers in previous years accounts for an apparent absence of bats. Stewart Island and its subsidiary islets still support small but flourishing colonies.

I would suggest that the Urewera in the North Island and the Buller River drainage in the South Island support the highest densities of bats in New Zealand. For only two localities is it possible that one species may occur in the absence of the other. In the North Island only Chalinolobus has been recorded from the Wanganui River drainage, and in the Stewart Island region only Mystacina has been taken.