Population estimation using line transects?

Michael Gochfeld gochfeld at eohsi.rutgers.edu
Sat Mar 27 06:28:54 EST 2004

I have tried this on an "all species" survey of a 300 m transect.  It hasn't
been useful.  My guess is that it is habitat AND species (and probably observer

1.  Butterflies don't sit still.
2.  Big butterflies are both more conspicuous and tend also tend to be more
mobile (i.e. most of the swallowtails on this transect are fly-bys).
3.  identification varies with size, distance and familiarity (as well as

But if you are only concerned with a single species, it should be possible to
work out a relationship with distance sampling.

However, if it is a limited area, we use a multitransect technique (for example
for a skippers in a large patch of grassland). We find them nectaring on Sand
Myrtle which is patchily distributed.

We run parallel transects about 5 m apart, across the area of the grassland that
has the nectar source.  We figure that the likelihood of duplicate counting
matches the likelihood of missing an individual altogether.

We have compared with with simply patch counting (that is examining every patch
in detail).

We often have several people walk the parallel transects, which may introduce a
problem comparing it with one person walking the transects.

Mike Gochfeld

Daniel Grosboll wrote:

> Does anyone know of anyone who has tried using "distance sampling" (i.e.
> Buckland et al. 2001; Burnham et al. 1980) to estimate populations of
> butterflies?  This is an often used method for vertebrates that essentially
> translates line transect counts and the distance to organisms from the line
> into a population estimate for a defined sampled area.  It would obviously
> be more labor intensive than the often used Pollard walk but that only gives
> an index of abundance.  I need a population estimate and given what we think
> is a very small population size, I can't potentially impact the population
> by doing capture-mark-recapture.  Any suggestions?
> Dan Grosboll
> Endangered Species Recovery Biologist
> Washington Department of Fish and Wildlife
> P.O. Box 385
> Littlerock, WA 98556
> 360.273.1820
> dangrosboll at earthlink.net
> References
> Buckland, S. T., D. R. Anderson, K. P. Burnham, J. L. Laake, D. L. Borchers,
> and L. Thomas. 2001. Introduction to distance sampling: estimating abundance
> of biological populations. Oxford: Oxford University Press.
> Burnham, K. P., D. R. Anderson, and J. L. Laake. 1980. Estimation of density
> from line transect sampling of biological populations. Wildlife Monographs
> 72:202.
>  ------------------------------------------------------------
>    For subscription and related information about LEPS-L visit:
>    http://www.peabody.yale.edu/other/lepsl


   For subscription and related information about LEPS-L visit:


More information about the Leps-l mailing list