Message Number: YG6537 | New FHL Archives Search
From: RRC
Date: 2001-08-21 19:23:00 UTC
Subject: Bob C: Feral Ferrets and California

Q: "I heard through the grapevine that you allowed [California ferret
legalization advocates] use of a paper that proves ferrets cannot go
feral in California like in New Zealand. ...Can I get a copy? I try to
answer those sort of questions all the time."

A: I did allow use of the article in question, but only on a limited
basis. The scope of the paper—as you describe it—appears to be
exaggerated. It is NOT a paper that has been submitted for publication,
but is rather what I consider a working draft. While the paper will
ultimately be submitted for publication, I plan on making major
revisions, and (believe it or not) expansion.

I've had three other requests for this work, so IF the list moderators
feel it is appropriate for publication on the FML, I'll post it here and
people with an interest can use it for PERSONAL USE ONLY. Because I plan
on using it for eventual publication, I will evaluate requests for use
on web pages and newsletters on a case-by-case basis. Sukie can post it
to the FML as long as this caveat is in place.

When reading the article, keep in mind it is a largely unedited piece,
and designed as a working paper only. Because the references support the
core of the paper and the research represents intellectual property,
they have been removed. However, I will supply then upon request to
people with a legitimate interest.


By Bob Church ©2001

The California Fish and Game objects to ferrets being legal in
California because there exists feral ferret colonies in New Zealand.
True, but it is a white lie; the well documented conditions in which
ferrets became feral in New Zealand are vastly different than those
found in California.

1. Ferrets, preconditioned to eat rabbits, were deliberately released by
the government of New Zealand, dozens of acclimation societies, and
private citizens for decades. The government and the acclimation
societies gradually stopped releasing ferrets as the populations
stabilized, but ranchers continued to raise ferrets for deliberate
release decades longer, exacerbated by accidental and purposeful
releases from fur farms. While the total numbers of ferrets released in
that time period is unknown, those totals probably exceed the total
number of ferrets lost or released in the entire United States during
the last century (based on shelter populations). For the release
conditions between New Zealand and California to be the same, tens of
thousands of ferrets would have to be annually released in California
for several decades, with smaller numbers released periodically for
nearly a century. 1

2. Ferrets released in New Zealand were 100% sexually intact. Pet
ferrets in California are neutered to prevent seasonal odors in male
ferrets, and to prevent anemia and death from prolonged estrus in female
ferrets. For the sexual conditions between New Zealand and California to
be the same, all ferrets in California would have to remain sexually
intact. 2

3. The government of New Zealand proactively protected ferrets by
banning hunting, and sheltering and feeding them. Legal protections
lasted for decades, preventing citizens, wildlife societies, or
government agencies from reducing or controlling feral ferret
populations. For the protective conditions between New Zealand and
California to be the same, laws prohibiting removal or control of feral
ferrets would be required. 3

4. Ferrets were released in New Zealand in an environment devoid of
native terrestrial mammals and suffering from widespread ecological
disturbances caused by over populations of introduced rabbits, rats,
livestock (including cattle, horses, sheep and goats), poultry, and
wildlife (including various marsupials, deer, elk, and game birds). A
study of those few instances where feral ferrets have managed to exist
show they share a common trait; they all existed where widespread
populations of the introduced European rabbit (Oryctolagus cuniculus)
occurred. For the introductory conditions between New Zealand and
California to be the same, widespread feral colonies of European rabbits
would have to exist throughout California. 4

5. Most feral ferret sightings in the United States are based on single
observations rather than from verifiable collections, and are limited in
scope to a particular time and location. While there are often reports
of “feral ferrets in the area,” sightings and collections are never
repeated. Such anecdotes are paraded as clear and empirical evidence of
the existence of feral ferret colonies, yet return visits never produce
more captures, sightings, photographs, tracks, signs, carcasses, or
scats from the hypothesized feral colonies. In New Zealand, feral
ferrets are readily found, photographed, captured and hunted in those
areas in which they have been introduced. The excuse for the lack of
repeated observations in the United States is blamed on the difficulty
of locating ferrets, which apparently does not exist in Britain despite
the rarity of European polecats (road kill is frequently used to
establish population and health demographics in most European
countries). For the signs of introduced ferrets between New Zealand and
the United States to be the same, repeated observations, captures,
photography, recovered carcasses, scats, tracks and other signs of
sustained and established populations would also have to occur in areas
of reported feral ferret colonies within the United States. 5

6. The claims of possible damage to the California ecosystem by ferrets
is based largely on the ecological damage which has occurred in New
Zealand. Paramount in those claims are the loss of native bird species;
a claim which is cited as caused by introduced feral ferrets. The
California Fish and Game ignores the effects of urbanization and
industrialization, lost of habitat due to agriculture, introduced
disease, introduced carnivores (including pigs, rats, cats, dogs, fox,
stoats, and weasels), vehicular traffic, introduced livestock (including
rabbits, cattle, horses, sheep and goats), poultry, and wildlife
(including various marsupials, hedgehogs, deer, elk, and game birds),
amid others. Also ignored is the evolutionary history of the bird life
which inhabited New Zealand, where birds adapted to environmental
conditions which precluded the presence of terrestrial mammalian
predators. Long term studies have failed to pinpoint blame for any bird
extinction on feral ferrets. For the ecological conditions between New
Zealand and California to be the same, prey species in California would
have had to evolve in an environment devoid of terrestrial predators. 6

7. Ferrets were introduced into a New Zealand which lacked established
predators which would have competed for food and other resources. Well
established predators native to California include short- and
long-tailed weasels, American mink, spotted and striped skunks,
raccoons, bobcats, gray fox, coyotes, badgers, pine martens, owls and
raptors, and introduced red fox, opossums, cats (both feral and pet),
dogs (both feral and pet), rats, and pigs. When the ferrets were
introduced in New Zealand, the populations of introduced rabbits and
rats were so high that in those few areas where competition existed, it
was a minor factor. For the niche and competitive conditions between New
Zealand and California to be the same, widespread populations of native
predators would have to be removed or some other way found to prevent
their competition with ferrets. 7

8. Ferrets were introduced into New Zealand when ferret predators were
generally absent, allowing ferret populations to reach self-sustaining
levels without danger of predation. California has abundant predators
capable of killing and eating ferrets, including gray and red fox,
coyotes, dogs (both feral and pet), bobcats, mountain lions, cats (both
feral and pet), badgers, feral pigs, snakes, and various raptors and
owls. Weasels could prey on immature ferrets, and the American mink is
known to kill and consume the domesticated ferret’s wild progenitor, the
European polecat. For the predatory conditions between New Zealand and
California to be the same, widespread populations of native predators
would have to be removed or some other way found to prevent their
predation on ferrets. 8

The California Fish and Game argues New Zealand and California are very
similar, and allowing ferrets into the state places wildlife at risk
because if it could happen there, it could happen here. The white lie
told by the California Fish and Game is that while superficially the
conditions between the two regions appear the same, the conditions in
which ferrets were introduced are markedly different. For analogs to
have value in modeling probabilities, they have to have as many similar
conditions as possible; something which is clearly not the case—in terms
of introductory conditions—between New Zealand and California. Indeed,
between New Zealand and the rest of the United States, which explains
why in more than two centuries of the presence of ferrets, including
mass excapes and releases from numerous ferret farms, not a single,
repeatable or verifiable feral ferret population has been demonstrated.
The best example, the ferrets that may have formed a feral colony on one
of the San Juan Islands in Washington, the ferrets died out when
introduced European rabbit populations dropped below predator
sustainability. Feral ferret populations appear to be so tied to the
presence of introduced European rabbits that ferrets may not be able to
form feral colonies without them (worldwide, there is not a single,
confirmed instance where ferrets have managed to establish feral
populations without the presence of European rabbits). Clearly, the use
of analogs in the manner chosen by the California Fish and Game is
inappropriate. The conditions which allowed the introduction of ferrets
into New Zealand are so vastly different from those found in California
as to render arguments based on analogy invalid. 9, 10, 11, 12

While the California Fish and Game has not presented outright lies
regarding the ferret’s ability to become a feral predator, from the
pattern of evidential use, they either lack a clear, concise
understanding of the history of ferret introduction in New Zealand, and
the concepts of competition, predation, and niche theory, or they are
guilty of blatant duplicity by spreading half-truths twisted to
emphasize negative aspects. Clearly, they are presenting anecdotes,
unconfirmed sightings, and rescues of lost or abandoned ferrets as
empirical evidence, and not presenting the facts in a clear and unbiased
fashion to allow lawmakers to perform their job free of bureaucratic
manipulations which suggests purposeful duplicity is intended.
Ultimately, they rely on nonspecific, negative, uncorrelated, and
anecdotal evidence to substantiate claims. Still, even if duplicity
and/or self-promotion is not intended, the lack of clear understanding
of the issues is a sign of scientific incompetence, tainting whatever
evidence is presented in open debate. In other words, the arguments
presented by the California Fish and Game are untrustworthy because they
are either poor scientific evidence or simply white lies. 13, 14, 15,
16, 17, 18, 19, 20, 21