Posted by:
RichardFHoyer
at Wed Jul 30 00:14:07 2003 [ Email Message ] [ Show All Posts by RichardFHoyer ]
Milt:
Concerning your question about size, I have only kept records on weights along with total and tail lengths. The weight of a boa is only some measure of the condition they are in relative to their length at any point in time. It can vary from year to year depending on prey availability and in the case of some females, whether they are in reproductive condition or have recently produced a litter. Thus, I have never taken grith measurements.
Concerning maximum lengths, there are a number of considerations involved. First, there is a sizable difference between mean and maximum length attained by males and females of any boa population with males being considerable smaller than females on the average. Secondly, there are now two rather distinct size morphs in C. bottae, a dwarf form that is found mostly on the isolated mt. peaks and mt. ranges in S. Calif. and a larger morph which occurs from at least southern Tulare County on north and east through the rest of the species distribution.
I have not been able to acquire a large enough sample of every dwarf population to make any precise statement as to how uniform or how much variation may exist in those populations with respect to mean and maximum male and female lengths. But as a group, the largest females approach or slightly exceed 22 inches and the largest males are in the neighborhood of 19 1/2".
A considerable mount of variation is known to exist between populations of the large morph with respect to mean and maximum lengths. Populations at high elevations tend to be smaller. Whether there is a genetic basis and/or this situation is due to shorter seasons along with reduced prey species and availability is unknown. However, all populations I have examined have females that reach at least 25' and males that reach about 21".
I have examined live specimens from Oregon and Calif. in which females have reached 30" or a bit more. Considerable shrinkage occurs when specimens are preserved yet a female boa in the Cal. Poly, Pomona collection from the Lee Vining area on the east slopes of the Sierra Nevada Mts. was 29". It would be my estimate that when alive, that specimen probably exceeded 31".
Regarding the size of prey that can be handled by this species, obviously the larger the snake, the larger the prey that they can consume. That being the case, large adult females can consume moderate size voles, smaller size moles, gophers, chipmonks, and the like. Adult males struggle but can consume adult deer mice as about the largest prey they can handle. But the species by and large is a nest robber specializing on the nestlings of small mammals. Depending on the region, they also consume lizards, lizard and snake eggs, and birds. There are some other species consumed such as bats, snakes, etc. but they are way down the list in the percentage of prey taken.
Richard F. Hoyer
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RE: Why 38 boas? - RichardFHoyer, Wed Jul 30 00:14:07 2003