Subject: Collecting adults vs. population

From: Kenelm Philip <[email-masked]>
Date: Mon, 1 Apr 1996 22:41:03 -0900

William Gerrard mentioned a paper by Hayes that, according to
Ehrlich, had '...shown that in some circumstances collecting adults from a
population can effect population size.' I was able to locate a copy of
Hayes' paper: 'The Population Ecology of a Natural Population of the Pierid
Butterfly _Colias alexandra_'. 1981, Oecologia 49:188-200.

        The paper is concerned with the various factors leading to mortality
at various stages of the butterfly's life cycle, and concludes that two
major factors in overall mortality are 'reduced natality' and diapause
mortality. Reduced natality derives from 'the failure of females to lay
their full potential of eggs.' This involves fecundity, adult mortality,
and dispersal.

        These key factors are considered to be density independent. Hayes
then concludes that 'The results reported here suggest that we may, by
removal of large series of adult female specimens for example, indeed pose
a greater threat in terms of population decline than we have chosen to
believe.' Note that no experiment was performed regarding the effects
of collecting.

        I don't think anyone would argue with the concept (as I mentioned
recently) that taking a large proportion of females from a population
before oviposition could affect the population, although in at least some
cases the population may have the potential to recover. In the so-called
'Ehrlich experiment', a deliberate attempt at overcollecting was unable to
capture a large proportion of the females. In my own field experience
(none of it in the British Isles) I have found the same thing: females
usually represent from 5% to 20% of the samples taken (and in these cases
the samples taken comprise a very small portion of the total population).
I recall _one_ exception--in 1972 at Noluck Lake on the western North Slope
a low rocky ridgetop came alive with female _Oeneis melissa_ (Melissa
Arctic) for one afternoon only. Since the ridge was some tens of miles in
length, there was no reason not to collect a good series at our location.
Males were rather uncommon at this location at the time. But this was a
very unusual event indeed...

        So, _if_ the population is small (which amounts to saying it's
endangered, and thus illegal to collect in the U.S., unless the status of
the population has not yet been made known to the authorities), and _if_
the collector has figured out a way to collect a large proportion of the
females before oviposition is completed, then damage can, in theory, be
done. How often this scenario occurs in practice I do not know, but I
suspect it's rare. Certainly there is little need to worry about legal
collecting of non-endangered species. As far as affecting the species
goes, even _illegal_ collecting is presumably harmless when the population
involved is not endangered (which is the case for many butterflies that
are protected by virtue of residing in large National Parks or Wildlife
Refuges, but are not actually endangered or threatened). There _is_ need
to worry about the major factors driving insect species to extinction:
habitat destruction and competition from introduced species--two factors
that the existing laws seem to disregard compared to collecting. That is
what is known as 'innumeracy'.  :-)

        It is of interest to note that in Ohio, the collecting of butter-
fly species declared protected by state law is allowed to members of the
Ohio Lepidopterists' Society. The state department of natural resources has
found that the information provided by such collecting is so valuable as to
outweigh any damage done.

                                                        Ken Philip
[email-masked]

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From: Henry Brodkin <[email-masked]>
Date: Tue, 2 Apr 1996 03:44:53 -0800

Kenelm Philip wrote:

> outweigh any damage done.

Ken-
Along these lines - In southern California the Nature Conservancy allows
 collecting
by at least one entomological society on some of their preserves - The bugs
collected are turned over to the Conservancy so they have specimens of species
 that
occur on these preserves.  I do not know if any of the species collected are in
 the
protected category.
Possibly other private reserves also have this arrangement in other states.

Interestingly enough, I was informed by FWS officers that
California state law does protect any insects.  For a while rare insects were
 protected
under a statute pertaining to fishes.  But this practice was stopped by the
 state
government.

--
               Hank Brodkin, Marina Del Rey, CA
                  33.58'24"N  118.27'39"W
             For Info on the Calbird-L Mail List
               Send mailto:[email-masked]

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From: [email-masked] (Carol Witham)
Date: 2 Apr 1996 18:06:18 GMT

I think that Hank Brodkin meant to say that California law does _not_ protect 
insects.

Carol Witham