A REPORT ON INVESTIGATIONS IN THE DENEHOLES 7
typical smoothness and roundness which flowing water produces
in chalk. The holes are shallow and of various shapes and extend
at least a foot into the chalk, and probably even further. In
places a chalky sediment appears to have been deposited. These
holes have been observed only in two or three other chambers
apart from No. 3.
Fauna of the Deneholes
Investigations of the fauna have been concerned mainly with
the collection of invertebrates and study of the bats, which occur
in the holes, and have been only of a preliminary nature. No
work has been done on the fauna or flora of these deneholes
before, apart from an occasional observation of the bats, and it
appears that no deneholes in Great Britain have been at all
extensively investigated biologically.
Collection of invertebrates has been performed on two visits:
May 23-24, 1959, and January 6-7, 1962, while study of the bats
has been done on various dates.
Conditions in the holes are generally similar to the conditions
to be found in more extensive, natural, underground systems, viz.:
(i) Uniform absence of light. No measurements of light have
been made, but only a small circle of dim light is present at the
base of one shaft (No. 5) which remains open. The chambers of
No. 5 possibly receive some light from this source, but chambers
of other holes receive no light from outside. With visitors
frequently entering the holes, artificial illumination may now be
of some importance.
(ii) Uniform temperature. A maximum-minimum thermo-
meter and a recording thermometer placed in a chamber of No. 9
for 18 hours (March 8-9, 1959) recorded a constant temperature of
between 42° and 43°F. Similar results were obtained in No. 9
with the same instruments on May 23-24, 1959, while the same
maximum-minimum thermometer recorded a constant tempera-
ture of 45°F. on January 6-7, 1962.
(iii) Uniformly high humidity. Humidity in the holes was
determined by means of a wet and dry bulb hygrometer and varies
between 95 and 100%. Drops of water have been observed on
flints protruding from the chalk walls, and on metal wall tags
used to number the holes.
(iv) Still air. Very little movement of air through the holes
can take place, especially since the blocking of shaft No. 3.
(v) Restricted food supply. As a result of (i). no green plants
occur.
Bats
Three species of bat have been observed, Daubenton's Bat
(Myotis daubentoni Kuhl) and Natterer's Bat (Myotis nattereri
Kuhl) being most frequently taken, and in about equal propor-
tions. A few Long-eared Bats (Plecotus auritus L.) have also