•  
  •  
 

Document Type

Research

Keywords

snail, population estimation, algific slopes, Discus macclintocki, endangered species, Iowa Pleistocene snail

Abstract

Discus macclintocki Baker, the Iowa Pleistocene snail, is a federally endangered species found only on algific talus slopes in northeastern Iowa and northwestern Illinois. Population size estimates for fourteen D. macclintocki populations in Iowa and Illinois ranged from 182 to 22,125 individuals. Estimates from the program CAPTURE as well as Bayesian estimation procedures gave similar results, although the Bayesian method allowed estimation of populations that could not be estimated with CAPTURE due to small sample sizes. A comparison of two methods of sampling, visual counts of quadrats and cover boards, showed that using cover boards resulted in much higher probabilities of capture and more recaptures. Snail activity was highly variable over time and space, making precise estimation difficult. Several populations are much larger than previously thought, although it is not clear whether this is due to bias in previous sampling methods or actual increases in populations since the previous estimates were made.

Publication Date

June 2000

Journal Title

Journal of the Iowa Academy of Science

Volume

107

Issue

2

First Page

34

Last Page

41

Copyright

© Copyright 2000 by the Iowa Academy of Science, Inc.

Language

EN

File Format

application/pdf