Albino little brown bat (Myotis lucifugus lucifugus) from Wisconsin, with remarks on other aberrant bats

Discussions and ConclusionsThe data collected in this study were based upon random samples of a natural population in which the animals' ages were not known beforehand.Nevertheless, counts of tooth annuli are believed to give absolutely accurate age determinations for known-age wild deer on Vancouver Island (Thomas and Bandy 1973).Therefore, individual lens weights could be easily assigned to specific age groups within the population.Unlike Longhurst (1964), who claimed success in estimating the age of individual black-tailed deer to 5 years of age by regressions of lens weights on age, we found that the mathematical expressions generated in this study did not serve to give reliable estimates of age for this population.Individual lens weights were so variable that linear models, although significant, were mostly impractical for inferences of age.Moreover, in attempting to minimize this variation by considering the mean lens weights for all age classes only, the polynomial expressions were impractical for age determination as well, as no confidence could be placed on the final estimates.At best then, the lens-weight method permits reliable separation of the fawn and adult classes only (cf.Lueth 1963).To place further emphasis on this growth structure as an age criterion for this population would be foolhardy where subjective characteristics of tooth eruption and wear serve equally well (Child 1970).Nevertheless, it has been shown that the eye lens grows continuously at a species-predictable rate, and the resultant growth curve awaits verification when tagged specimens of known age become available.