Conditions for Overcollecting

[John Shuey]

Bruce asks a question that I have pondered quite a bit over the last few years in
my role as gate-keeper for some of the most significant natural areas remaining
in Indiana.  My dilemma has always been, (1) how to get inventory of poorly known
taxonomic groups completed on these reserves, while (a) not jeopardizing any of
the taxa which may both depend upon the natural area for regional persistence
and  (b) which might be vulnerable to collecting pressure.   Here is what I've
come up with.

Populations (not species) are vulnerable if they meet certain requirements:

1) populations are isolated, such that gene flow, recolonization and rescue
events are almost impossible;

2) populations are small, such that collecting could represent a significant
source of mortality;

3) population represents a "desirable" species, such that collecting mortality is
consistent and persistent over time;

4) population subject to wild stochastic variation and/or species in question has
low reproductive capacity.

Based on these criteria, I think that in Indiana, there are exactly  three
butterfly populations representing two species that are potentially vulnerable to
over collecting.  These are:

_Speyeria idalia_ reduced to a single population in the state. Population very
isolated and occupies less than 200 acres.  Population fluctuates wildly,
especially in response to recent fire history of the habitat.   Females are very
easily collected at milkweeds that line adjacent agricultural fields.  A showy
species that is almost impossible to obtain in much of the eastern US -
collectors seek this one out.

_Neonympha m. mitchellii_ reduced to about 15 populations in the World - two in
Indiana.  Populations all isolated, especially relative to observed female
dispersal capacity which averages less than 50 meters.  Populations are usually
very small (based on MRR over two years at two "healthy" populations in adjacent
Michigan,  total adult brood size is between 200-300 per year.  The two Indiana
populations occupy habitats (fens) that are less than 3 acres in size.  Fecundity
is low, with females likely laying about 50 eggs per year.  Females are
especially easy to capture in this very sedentary species.  Desirability is high,
given the rarity of the species.

There is a relatively large list of species that fit most of the criteria above,
but are not likely to be subjected to persistent collecting pressure because they
are "less desirable".  Very rare skippers, Incisalia, etc - we have plenty of
small isolated populations of these types of animals, but collectors can readily
obtain specimens from many sites in adjacent states, and most collectors simply
don't care enough about these animals to be a threat.  Usually they  take a short
series for these species once in their lives.

My bottom line is that I would never grant access to collectors for these three
vulnerable populations.  This does not mean that general inventory has not been
encouraged at these sites.  For example, Eric Metzler ran bucket-type kill traps
for moths in the heart of the _S. idalia_ population over the course of a year.
While he certainly killed a bunch of moths (thousands), the collecting pressure
was limited to a single growing season - hence not likely to impact any unknown
species that might otherwise be vulnerable to persistent collecting pressure.
The potential positive impact to the site (better management based on inventory)
easily outweighed the potential risk to the site (in at least my mind).
--
John Shuey
Director of Conservation Science
Indiana Office of The Nature Conservancy

Bruce Walsh wrote:

> Some of the comments from the US Fish and Wildlife services contained in
> the recent posting (by Neil) on the potential listing of the Sacramento
> Mountains Checkerspot inspired me to think about the parameters underwhich
> overcollecting can be a serious issue.
>
> I'm interested in the thoughts of others on the Leps-l about which
> factors can make a population vulnerable  to overcollecting.  I'm especially
> interested in examples, either valid or cited by others, where overcollecting
> has caused significant harm to a population.
>
> I'm NOT trying to restart the collecting debate, so please let's start
> the last year of the old millennium with a truce on this issue.  Rather, I
> think that all sides will agree that there are certainly populations where
> modest collecting has at best a trivial effects.  Likewise, I think all
> sides will agree that there can be conditions underwhich very significant
> collecting can have a serious impact.  What are these conditions?  All
> thoughts are welcome.  You can send them to me or post them for the amusement
> of all of the list.
>
> Peace
>
> Bruce



phone:  317-923-7547
fax:  317-923-7582
email:  Jshuey at tnc.org