Mountain Wildlife - Mountain Geography: Physical and Human Dimensions - page 423

that the fecal droppings and continual mixing of soil have a beneficial effect on soil and
vegetation development in mountain meadows (Ingles 1952; Turner et al. 1973; Lay-
cock and Richardson 1975).
These examples come from mid- and high-latitude mountains where strong seasonal
contrasts exist and the chief problem for survival is posed by winter. No similar pro-
longed period of stress exists in tropical mountains, where the environmental extremes
occur on a daily basis. In tropical mountains, there is very little migration or hiberna-
tion; instead, animals are heavily dependent on burrowing and use of microhabitats.
Most animals are diurnal and are most active in early morning and late afternoon,
between the periods of high sun intensity. At night, they retreat to sheltered sites amid
rocks and vegetation or in shallow burrows. Most tropical mountain animals are not
well adapted to cold and find alpine conditions only marginal; if small animals are live-
trapped at night and left without bedding, they cannot survive freezing temperatures
for more than an hour or two (Coe 1969). These animals capitalize on the fairly constant
temperatures found in cavities under rocks or shallow burrows, however, and their own
body heat raises the temperature of the confined space. The huddling together of cer-
tain species, as in middle latitudes, also aids in heat conservation.
A good example of a high mountain mammal in the tropics is the Mount Kenya
hyrax ( Procavia johnstoni mackinderi ) (Fig. 8.9), which lives above timberline on Mount
Kenya, occupying rocky habitats below cliffs and in glacial moraines (Coe 1967; Roder-
ick and Roderick 1973). Like many tropical mountain animals, it emerges early in the
morning and basks in the sun by stretching out on its side to expose maximum body
area to the sun; this compensates for the night chill. It then feeds for several hours,
seeks cover during the hottest time of day, and appears again toward late afternoon to
finish feeding (Coe 1969). Another animal on the same mountain, the groove-toothed rat
( Otomys orestes orestes ), finds shelter from night frosts and the intense sun by crawl-
ing underneath the drooping basal leaves of the giant Senecios, and frequently spends
its resting hours in a cavity it has excavated in the trunk (Coe 1967).
Reptiles, being cold-blooded, are even more strongly controlled by the diurnal cli-
matic regime in tropical mountains. The low night temperatures force them to be inact-
ive and immobile. In early morning, they are barely able to crawl into the sunlight that
will raise their internal temperatures and allow them to operate efficiently. When they
emerge, they orient themselves to receive the maximum sunlight, and bask on rocks or
dark surfaces so they are also heated from the underlying surface. Unlike warm-blooded
mammals, they remain in the sun as much as possible. In fact, their periods of activity
are almost entirely limited to sunshine; even a passing cloud will send them scurrying
for cover. As a result, their feeding periods are generally limited to four hours or less
per day. At night, they seek shelter under rocks, in shallow burrows, and in vegetation
to escape the full extent of the cold (Pearson 1954; Pearson and Bradford 1976). Most
reptiles select rocks at least 20 cm (8 in) thick—a size large enough to moderate the
temperature extremes (Swan 1952, 1967; Coe 1969).
Invertebrates in tropical mountains also escape the daily extremes through timing
of activities and clever use of microhabitats. In contrast to the highly active and visible
insects of lowlands, those above timberline are sedentary and secretive. Consequently,
there are very few insects visible at any given time. Insect collectors in tropical moun-
tains have found most of their specimens beneath rocks and amid vegetation. This re-