ELLIOTT ET AL.: THE CAVE FAUNA OF CALIFORNIA 
77 
0 20 40 60 30 100 120 
Figure 113. Scatterplot and linear regression of SR (species richness) for 221 caves vs. their vertical cave depth. 
Although the correlation is low, the positive regression is statistically significant (two-tailed test, p = 0.008) indicating that 
deeper caves are richer in species than shallow caves. However, the true ecological relationship may be with 
moisture/humidity rather than cave depth. Shallow caves tend to be warmer and drier, which are less hospitable for mois¬ 
ture-sensitive arthropods. 
The use of caves by porcupines was another subject studied by Graham (1962e). Porcupines 
nest in at least 38 caves in all California regions except the coastal regions and Sierra Nevada 
South, using a bed of quills and scats just inside the dark zone. The caloric value of the scats from 
these plant feeders may be low. 
Graham (1966a) documented the crane flies, Tipulidae (including Limoniidae, Figs. 87-88) 
and winter crane flies, Trichoceridae, in California caves. The trichocerids, which are smaller, are 
found in remote, dark portions of caves on the floor amongst debris as well as in the entrances; tip- 
ulids are limited to twilight, and favor high, open walls and overhangs. The largest species is 
Holorusia hespera, giant western crane fly, formerly H. rubiginosa. 
Graham (1966b) reported observations on the roosting habits of the Townsend’s big-eared bat, 
Corynorhinus (formerly Plecotus ) townsendii (Fig. 85). He thought that this bat did not often use 
Sierra Nevada caves, but was more drawn to cooler caves for hibernation, and warmer caves for 
nursery colonies. He reported on guano deposits as clues to former colonies, and the loss of this bat 
from some caves caused by human disturbance. 
In Graham’s 1967 study of the orb-weaving spider, Meta dolloff (formerly Pseudometa bio- 
logica. Figs. 43^14), in Empire Cave, Santa Cruz Karst, he mapped the occurrences of webs and 
prey from the cave mouth into deep twilight, and he estimated the potential catch of flying and 
jumping insects. He noted a shift in web locations owing to the near-closure of the cave by a con¬ 
creted gate at the entrance. His studies of the twilight moth, Triphosa haesitata (Fig. 89), in the 
same cave mapped the clustering behavior of this geometrid moth in twilight to deep twilight, and 
he applied biometric methods (Graham 1968a-b). The concreted gate had caused a change in moth 
roosts owing to the reduction in light, possibly damaging the cave community. This is one of the 
first papers to document an ecological shift in a California cave from human activity, in what is one 
of the most heavily abused caves in the state. 
Graham conducted an overall study of Bower Cave, Mariposa County, in three parts 
(1969a-c), all dealing with the outer vault, an unusual ecotonal sinkhole entrance with trees, 
columbine, animals falling in, and a deep lake with fauna. 
