Mountain Wildlife - Mountain Geography: Physical and Human Dimensions - page 424

clusiveness is viewed as a major adaptation to the rigors of the environment. Like mam-
mals, insects largely restrict their activities to early morning and late afternoon. They
are forced to this behavior because the low night temperatures make them lethargic
and even comatose (Salt 1954).
An excellent example of vegetation serving as a micro-habitat for insects is provided
by the giant senecios and lobelias. These plants open their leaves each day and close
them at night, and a number of insects take advantage of this habit to escape the nightly
frosts. Temperature measurements on a giant lobelia revealed that, while the surround-
ing air cooled to −2.4°C (27.7 °F), the base of the flower remained at 3.3°C (37.9°F) and
the center of the hollow stem was 4.0°C (39.2°F) (Coe 1969). Some insects live their
entire lives without ever leaving the plant. This is true for a bibionid fly that lives within
the flowers of the giant Lobelia keniensis on Mount Kenya. It feeds and reproduces in
the flowers, where it may be found in all stages: adult, egg, larvae, and pupae. These
flies form the primary food source for the scarlet-tufted malachite sunbird ( Nectarinia
johnstoni johnstoni ), which hovers in front of the plant or moves up and down the trunk
feeding on the insects (Coe 1969).
FIGURE 8.9 A rock hyrax from South Africa. The body temperature of this species varies diurnally.
(Photo by iStockphoto.com/G Purdey.)
Another excellent plant shelter is provided by the large grass tussocks on Mount
Kenya. Measurements within these tussocks reveal that temperatures fluctuate viol-
ently on the outer perimeter, less so halfway down the leaves, and remain fairly constant
at the leaf base (Fig. 8.10). Temperatures on the outer leaf area during the measure-
ment period showed a range of 13.3°C (23.9°F), while those at the leaf base revealed a