Cover letter to all parties interested in Mexican wolf
reintroduction
We regret that our proposal is coming so late in the Mexican wolf
reintroduction effort. We
believe that we may be able to substantially reduce conflicts between
Mexican wolves and domestic livestock using procedure known as conditioned
taste aversion (CTA) as described in the following report.
We understand that the readers of this report are very diverse in background
and interest. We have prepared
it so that anyone reading only from the main text of the report can
understand the essence of what has happened and what we are recommending.
For all wishing to examine our claims more carefully, we offer a
series of appendices that explain things more closely.
We also provide a list of scientific publications that substantiate
our claims, conclusions and recommendations.
We hope that all of you will take a little time to consider this possible
solution to this problem and support an effort to test it.
With the minimum required support, we are willing to do what is
necessary to see to it that a good first effort gets under way, to be sure
that the effects of this effort are openly and objectively measured and that
personnel are adequately trained in this new procedure.
We do not consider ourselves the final source of wisdom on this subject and
so please send us your suggestions and comments.
We will respond quickly and fully if you just say who you are.
We will not respond to anonymous persons.
It may well be possible that someone might suggest something that is
missing from the report or that ought to otherwise be changed and so its
final form and what is ultimately done might be changed somewhat from what
we are presently submitting.
Thanks,
Lowell Nicolaus, Contact:
wolfishnicolaus@earthlink.net
Dan Moriarty, Contact:
moriarty@sandiogo.edu
FINAL REPORT: A CONDITIONED AVERSION PROTOCOL FOR
MITIGATING CONFLICTS BETWEEN LIVESTOCK AND WOLVES DUE TO BE RELEASED INTO
LIVESTOCK HABIAT
Lowell K. Nicolaus, Ph.D.
Emeritus, Northern Illinois University
And
Daniel D. Moriarty, Ph.D.
University of San Diego and the California Wolf Center
Introduction
Mexican wolves
were reintroduced into the Blue Range Wolf Reintroduction Area of Arizona
and New Mexico in 1998.
Then,
wolves began to prey on livestock in the region, averaging 20 depredations
of cattle per 100 wolves per year.
Of course this led to conflicts between those advocating
reintroduction of the wolves and cattlemen with their livelihoods at risk.
Livestock depredation has led to control action including lethal
removal of wolves.
The
Interagency Field Team has also employed some non-lethal methods to
discourage wolf depredations upon domestic livestock including hazing of
wolves and fladry barriers but the depredations continue.
Here we report
and discuss the results of some recent research using a process known as
conditioned taste aversion (CTA) that suggests a powerful alternative method
for reducing conflicts between Mexican wolves and domestic livestock.
It has long been
known that when humans and animals experience a severe gastrointestinal
illness after consuming food, the taste and scent of this particular food
become disgusting even when the food was earlier very preferred and
familiar.
In humans, this has
been shown, for one example, among cancer patients who consume food just
before the onset of nausea induced by chemotherapy or radiotherapy.
Long after recovering from the nausea caused by the cancer therapy,
patients respond to the smell and taste of this food with pronounced
disgust, often retching and vomiting at the mere scent of the now offending
food.
These aversions result
after just a single illness and can be extremely persistent.
So, before this process began to be prevented by physicians with
understanding of what was happening, patients that underwent repeated
chemotherapy treatments often formed aversions to each of their favorite and
most nutritious foods in sequence until loss of body weight became a
critical factor in their cancer treatment.
Paradoxically, these people can intelligently discuss the fact that
the chemotherapy is what made them ill and not the food, but they still gag
and wretch rather than to swallow the food and often vomit at a distance
based only on the food smell (Appendix 1).
Conditioned
taste aversion has been tested experimentally upon bird and mammal predators
both in captivity and in the field (Appendix 1).
The procedure usually requires that predators consume a meat bait
with the same taste and scent as of live target prey, but laced with a
hidden dose of some substance that induces a severe but temporary illness
after it is consumed.
If the
illness-inducing substance is successfully hidden in the bait, then the
predator forms an aversion to the taste and scent of the target prey rather
than to the taste and scent of the aversion agent.
When predators consume poorly constructed baits that taste and smell
different from live prey, they may begin to avoid the baits but nevertheless
will continue to attack and consume live prey (Appendix 2).
Paradoxically
even though a well constructed meat bait that induced the illness was
inanimate, predators nevertheless tend to be dissuaded from live prey with
the same taste and smell as the bait because, like their human counterparts,
that taste and smell has become disgusting to them.
We have recently
demonstrated the potential usefulness of Thiabendazole (TBZ) as an aversion
agent among captive wolves.
The
focus of this work was to develop a clinical protocol that safely and
effectively produces aversions to the taste and scent of target domestic
livestock among captive predators before they are released into livestock
habitat.
But with modification,
this same procedure could also be used to produce aversion in other
applications.
These include
producing aversions among recently caught predators while they remain in
captivity and could readily be extended to the treatment of free-ranging
predators. It could also be used to reduce conflict by inducing aversions to
the taste and scent of livestock carcasses.
In all cases, the intent is to produce a disgust for the scent and
taste of target prey so that rather than being attracted at a distance to
these prey, predators are dissuaded from approaching and conflicting with
livestock at a distance.
That
is, we expect the critical events affecting depredation upon target
livestock to take place at night several kilometers down wind from occupied
pastures without any human witnesses when predators choose not to move in
the direction of the cattle because for them the scent has become disgusting
rather than attractive.
We
expect that since the taste and scent of cattle will have become disgusting
to treated wolves, wolf and calf will seldom come nose to nose.
All recently
released Mexican wolves can be tracked with radio collars while others
already in the field are monitored and wolf depredations upon cattle are
also recorded.
As long as these
efforts continue in this situation and those with successful experience in
the use of CTA see to it that properly constructed baits are distributed and
monitored as needed, it ought to become clear whether or not our attempts to
produce aversions among wolves reduce livestock conflicts.
The process of producing aversions is relatively inexpensive, can do
no harm and at this time there is no better option.
Thiabendazole as a Suitable Aversion Agent
Baits designed to produce conditioned aversion among
wolves must contain an appropriate dose of some substance that safely but
effectively induces a temporary illness after predators consume the bait.
Many substances are known to induce illness but few have the
particular combination of features required for an effective aversion agent.
To function as we wish it to, an aversion agent must fulfill all of
the following requirements:
·
It must induce an illness severe enough to
produce a strong aversion to the taste and scent of the target food.
·
This illness must commence some time after
the bait is fully eaten so that the full, intended dose of the substance is
consumed before illness onset terminates the meal.
·
The substance must be safe enough so that
when the intended dose is consumed the predator fully recovers after a
relatively short time. And, if
there is a possibility that any one predator might consume a greater amount
of the aversion agent, the safety margin between an illness dose and a
lethal dose must be broad.
·
The substance must have the physical capacity
to be adequately mixed in the bait material and remain stable in the bait
long enough to remain effective by the time it is consumed.
·
Importantly, the taste and scent of the
substance must not alter that of the bait in any detectable way.
Poorly constructed baits that induce illness but that do not taste or
smell like live prey will themselves be avoided by predators that acquire an
aversion to them, but predators will still attack and consume live prey that
do not taste and smell like the baits they ate.
Thiabendazole (TBZ) appears to meet all of these
requirements.
·· Although it
might not be the most effective aversion agent in terms of the nature and
severity of illness it induces, it has produced clear and lasting food
aversions among Black bears, wolves, dingoes, foxes, hunting dogs and other
predators (Appendix 3).
· The
physiological effects of TBZ appear to begin some time within about an hour
after a suitable dose is consumed and so this delay should provide adequate
time for a full meal to be consumed before illness onset reduces willingness
to eat (Appendix 4).
· TBZ has a very
long history as both a human and a veterinary pharmaceutical and as a
fungicide applied broadly upon human foods.
In these roles, its toxicity and safety are documented by a very
extensive literature demonstrating its safety (Appendix 5).
· As an organic
compound, it mixes easily in meat baits containing animal fat and appears to
remain stable in meat baits for a sufficient time to remain effective under
field conditions.
In fact, the
baits used in the current study were manufactured in the state of Oregon and
frozen for several months before they were used at the California Wolf
Center.
·
Most important,
although it is probably not fool-proof and so should be mixed very carefully
in meat baits, TBZ does not appear to have a strong scent or taste of its
own and so it can be added to food in recommended amounts without enabling
predators to discriminate between the all-important taste and scent of bait
and that of live prey (Appendix 2).
A DEMONSTRATION OF THE CONDITIONED TASTE AVERSION PROTOCOL
The Wolves and the Setting
The procedure
reported here was demonstrated at the California Wolf Center (CWC) near
Julian, California over the month of September, 2008.
A pack consisting of 9 Alaskan gray wolves (Canis
lupus), including 6 males and 3 females, was maintained in a common
outdoor enclosure approximately 30 meters (90 feet) on each side.
All of the pack members had been raised in captivity and until
shortly before being moved into this relatively restricted space to
facilitate observation, had been maintained together long term in a much
larger portion of the facilities at CWC in addition to the enclosure within
which they were recently limited.
Three of the wolves were old and to some extent crippled by injuries
and age.
The remaining pack
members ranged from two years of age to 8 years of age.
The enclosure
had clean water available at all times and shade trees were dispersed
largely on the sloping upper half of the space.
With the exception of one low area surrounded by logs, nearly all of
the interior of the enclosure was visible from the outside.
No objects or devices were provided in the enclosure for the purpose
of enriching the environment for the wolves.
Prior to the
start of the demonstration, in order to minimize strife and stress, the
wolves were fed a ration of meat and/or fish at a rate of almost 8 Kg (20
pounds) per wolf in each of two weekly feedings.
Each of the weekly totals of 16 Kg was more than the wolves
ordinarily consumed immediately and so there was usually food left from
earlier feeding at all times and so the feeding regimen was essentially
ad lib.
The wolves were
largely free of immediate human contact other than the brief occasions when
volunteers and staff entered the enclosure to feed them and to remove
obvious articles of offal.
Visitors to the CWC were required to remain in an observation area
approximately 30 m from their enclosure and warned not to make noise or
otherwise threaten the wolves.
The Sequence
The essential logic of this protocol is that wolves must
voluntarily consume illness-inducing baits whose exterior and interior
maintain the unique taste and scent of live target domestic livestock prey.
After fully recovering from the effects of the aversion agent, they
must then demonstrate that they have acquired an aversion to the taste and
scent of target prey before being released into habitats where they may
conflict with livestock.
Food Deprivation.
The protocol requires that wolves be subjected to a feeding
regimen including sufficient food deprivation to induce them to voluntarily
participate in the protocol.
This is because they must voluntarily consume baits that, because they may
initially be unfamiliar to them, might not be readily eaten and includes
times when they are offered treated baits that they must fully consume in
order to acquire an aversion.
Food deprivation should induce predators to consume their maintenance ration
when offered to show that they are fully recovered from the effects of the
aversion agent. Finally,
deprivation provides assurance that wolves that refuse baits during the
post-test after acquiring an aversion are doing so because of the aversion
rather than because of satiety.
In order to
achieve the food deprivation we needed to apply the protocol, we fed the
wolves every other day for 4 days per week and completely withheld food on
the intervening 3 days per week.
When fed, each received only 3 Kg (about 6.5 pounds) in a single meal
lasting several hours. These feedings took place several hours after our
morning trials when we introduced baits designed to induce aversions.
The greatest difference between the old and this new feeding regimen
was that few hours after each feeding, we removed all of the uneaten food
and so we completely food deprived the wolves between feedings.
In this way, 4 days per week before each morning trial we had
completely food deprived the wolves for approximately 20 hours and on three
intervening days per week we deprived them for over 40 hours before the
morning trials.
This was the
first time that the wolves had been subjected to a feeding regimen that
included any food deprivation but they withstood it well without evidence of
weight loss or of increased strife.
The protocol should include an initial pre-test; a period
of time when predators consume meat baits with the taste and smell of target
livestock but without the aversion agent. This achieves several things.
Predators allowed at first to consume baits without the aversion
agent become familiar with the taste and scent of this food and so are more
willing to fully and quickly consume treated baits that deliver the intended
dose of TBZ when offered a little later.
The pre-test also demonstrates whether wolves are normal candidates
to participate in the aversion protocol.
Obviously, wolves unable or unwilling to consume target prey in the
normal manner during the pre-test are probably poor candidates.
The pre-test should provide opportunity to adjust procedural details
so that wolves fully consume uncontaminated baits during treatment and can
be fairly tested during the post-test.
Since under captive conditions, wolves often display idiosyncratic
behavior, the pre-test provides an individual history of the behavior of
each wolf that can be used to compare with post-test behavior in determining
the extent to which each wolf has acquired an aversion during its treatment
period.
The protocol must include a period of time during which
baits with the same external and internal taste and scent cues as those
consumed during the pre-test deliver a dose of hidden aversion agent
sufficient to induce the requisite physiological effects that produce the
aversion. The aversion agent
should be mixed within the inner meat of the bait such that its taste and
scent are not detected by the consumer.
The protocol requires that treated wolves demonstrate that
they are fully recovered from the effects of the aversion agent before being
tested to establish whether or not they have acquired an aversion.
This can be accomplished only by offering them their ordinary
maintenance ration 6-8 hours after they are treated with TBZ.
After wolves have fully recovered, it requires that untreated baits
again be offered in order to
document that predators now avoid the outer surfaces of baits on the basis
of taste and scent before each wolf is released.
Our
demonstration of this protocol was therefore divided into three phases: a
4-day pretest, a 10-day treatment period and a 4-day posttest.
During the pretest, for 4 consecutive mornings beginning at first
morning light we threw two untreated sheep meat baits over the enclosure
wire, one at a time (Appendix 6).
The wolves were allowed to interact with the first bait for 60
minutes before the second bait was provided for a second 1-hour period.
Each of the baits consisted of 100 g of plain ground mutton without
TBZ wrapped with fresh, clean sheep hide.
The hide was securely sutured with double square knots with double
cotton thread at intervals of 1 cm (0.5 inches) along each edge of the bait
package.
In this way, we
intended that wolves be exposed to the unique exterior taste and scent of
sheep by being forced to spend substantial time and effort chewing their way
into the bait to get to the interior meat.
During each of these hour-long episodes, we remained outside of the
enclosure and as unobtrusively as possible video taped all of the
interactions during each period.
At the end of this time, we entered the enclosure briefly to remove
any unconsumed portions of the baits to be examined and weighed.
This was
immediately followed by a treatment period of 10 consecutive mornings during
which wolves were offered one TBZ treated bait for 60 minutes and we
recorded all events as before.
The TBZ treated baits consisted of 250 g of ground mutton with 5.4 g of TBZ
well mixed with the meat.
This
TBZ treated meat was then securely wrapped with fresh, clean sheep hide and
sutured closed as before.
At the
end of each of these episodes we entered the enclosure to recover all
remains of the baits.
Since the
average body weight of the wolves was estimated to be 38.5 Kg (98 pounds),
an absolute amount of 5.4 g of TBZ would deliver an average dose of 140 mg
TBZ/Kg wolf body weight.
But
some of the largest males weighing about 50 Kg (125 pounds) would receive a
dose of TBZ as little as 113 mg/Kg and some of the smallest females that
weighed only 27 Kg (69 pounds) would receive 200 mg TBZ/Kg their body
weight.
Finally, there
was a posttest composed of 4 consecutive days during which just the same
procedure including untreated meat baits as used for the pre-test was
repeated.
Analysis
We scored the
video record of wolf interactions with the baits to characterize any changes
in the frequencies of common predatory/feeding behaviors that have been used
in earlier studies of animals with food aversions and that might be of use
in a practical effort to evaluate whether or not captive predators had
actually acquired an aversion to the taste and scent of baits prior to their
being released.
Our statistical
analysis of the database was the simplest, most intuitive, most
conservative, and least dependent upon statistical assumptions that we could
logically use.
RESULTS
Safety of Thiabendazole
Of the four
wolves in the pack that fully consumed a TBZ-treated bait, two were small
females that each received a dose of approximately 200 mg TBZ/Kg their body
weight.
The other two were
larger males receiving relatively less of a dose.
Four other wolves that did not consume a full bait received less TBZ
still.
Since only one bait was
offered each day during the treatment period,
each of the TBZ treated wolves received treatment on separate days
during which we could monitor their recovery.
Since the symptoms of TBZ treatment are mainly just lethargy, after
consuming the bait each of the treated wolves found a place in shade to lie
down and sleep.
At about this
time of the day with rising temperatures the other wolves of the pack found
shade for sleep also.
As a
result, no wolf that was treated was molested by any of the other wolves
while potentially disabled under the influence of the TBZ.
All fully treated wolves consumed their maintenance ration in the
normal fashion when it was offered approximately 6 hours after they consumed
TBZ.
Consequently, we concluded
that the physiological effects of this dose of TBZ persisted less than 6
hours, but cannot say precisely when recovery occurred before the 6 hours
when they were fed.
Aside from
changes in willingness to approach and consume baits subsequent to this,
there were no changes in the social rank or physical capacity of any of the
fully treated wolves of the pack.
Effectiveness of
This Demonstration (Problems)
Because we were
obliged to conduct this demonstration under the prevailing conditions at the
CWC where wolves had to be maintained all together in a common enclosure, we
identified three problems that must be avoided in the future.
These were:
· Bias.
Our presence near the enclosure and
our having to throw the baits over the enclosure wire introduced a bias
strongly favoring the least shy members of the pack.
Of the nine wolves in the enclosure one, Kuma, was a large male so
shy of humans that none of the volunteers or staff at the CWC had ever seen
him consume food in their presence.
Though he paced broadly and actively, he never interacted with baits
throughout the demonstration and so will not be mentioned further.
Naomi was a shy low-ranking female who eventually consumed treated
bait but did so under such cover that we could not say precisely how much
she consumed.
On the
opposite spectrum, Taku, a young low ranking male, and Minka, a potential
alpha female, were the least shy and tended to dominate the baits.
Typically, Taku first seized a bait, dragged it around and played
with it before opening it, often spreading the interior meat over the ground
and urinating on it before higher ranking individuals took the bait. Taku
never consumed a full treated bait and so although he stopped consuming any
of the bait material, he continued to play with the baits, contaminate the
outer surfaces of baits and spread the meat onto the ground. Until she
finally consumed a full treated bait, Minka also seized baits but this
ceased after her treatment.
Because of these interactions, many wolves that might have fully consumed
treated baits without contamination of the taste and scent of the exterior
merely scavenged portions of meat from contaminated baits.
· Contamination.
Our intention was for wolves to consume baits whose outer surfaces
retained the unique taste and scent of target livestock.
Requiring wolves to chew their way through the hide was to force them
to be exposed to these taste and scent cues before illness that followed
eating treated interior meat.
But, the exterior taste and scent of all of the baits were both
substantially altered by at least three different sources of contamination.
No bait escaped being urinated upon at least once and sometimes
several times and by up to three or four different wolves.
This occurred before, during, and after baits were opened.
Wolves also often rolled over and rubbed their faces onto the
surfaces of baits and in so doing, probably imparted their particular scent
gland secretions.
Finally, the
ground of the enclosure was a very fine, almost powdery dry material
containing the urine, dried fecal material and decomposed offal that had
accumulated over many years.
All food, including all of the baits, became thoroughly coated with this
highly familiar and highly scented residue and so the exterior of all of the
baits became much less distinguishable from everything else that the wolves
consumed as food.
The result of
all of this was that no wolf had a single, clear exterior taste and scent
cue before becoming ill from eating treated meat and so the exterior of
baits did not become a barrier to some of the wolves.
· Under Dosing.
Several wolves competing for baits
resulted in treated meat being broadly spread and so scavenging resulted in
4 of the wolves receiving only partial treatment with TBZ.
Because of these
difficulties, none of the baits remained unopened by wolves throughout the
entire protocol.
Instead, while
fully treated wolves avoided baits largely at a distance, partially treated
wolves opened bait exterior with the altered taste and scent but they
rejected the interior meat, ending up spreading it all over the enclosure.
On two occasions during the pre-test, empty hides composed of belly
hide were thin enough to enable wolves to chew them enough to be swallowed.
All other hides were left for us to recover after tests.
Though
problematic in this particular demonstration, it is well that these
difficulties alerted us to what might take place under similar circumstances
and this greatly contributed to our certainty concerning what to recommend
for future efforts.
Effectiveness of
Thiabendazole (Measures of Effect)
During the pre-test, all but one of the wolves that
ultimately participated in the protocol partially or wholly consumed at
least one untreated bait. We observed no hesitation on the part of any of
the wolves to approach, open and consume uncontested baits.
The absence of any evidence of neophobic behavior (the tendency to
treat new foods with suspicion) toward this initially unfamiliar sheep meat
may have been partially due to the fact that the wolves at CWC were fed an
extremely varied maintenance diet and so may have become accustomed to novel
foods (Appendix 6). On no
occasion at this time was anything left other than the hide after the first
30 minutes. The usual pattern
was for a bait to be seized, opened with the use of all of the complement of
teeth and the interior meat quickly consumed either all at once or scavenged
when it was spread around.
Other than the fact that Kiana and Taku tended to be the first to seize the
baits during the pre-test, there was no other obvious pattern indicating
that the first bait in any way predisposed which wolf might open and consume
the second bait.
Even under the unfavorable conditions described above,
treated wolves demonstrated the most common indications of having acquired
an aversion to the baits (Appendix 7).
One of the most obvious changes in behavior attributable to treatment
with TBZ was an absolute suppression of the willingness of these predators
to consume the baits once each of them had been treated (See Table 1 below).
Four of the wolves fully consumed a bait and then abruptly stopped
consuming bait. So, in their
case the amount consumed and TBZ dose received was certain.
The other four wolves scavenged broadly distributed meat.
At these times our estimates of amounts consumed by each wolf were
based upon careful analysis of the video record and the recorded weights of
bait material recovered from the enclosure after each trial.
We reentered the enclosure to collect all of the remains
of baits that we could find, but it is certain that we did not recover all
unconsumed bait. Some of the
meat, for example, was mixed into the enclosure soil and/or divided into
extremely tiny pieces. In
addition, the meat attracted swarms of carnivorous wasps, each of which
removed meat so that in the aggregate we might have lost appreciable amounts
within the hour before be recovered the meat.
The amount of recovered inner meat indicated below was the aggregate
per cent of all that was offered for that day (100g offered twice during
each of the pre-test and post-test days, 250g during each of the treatment
days). Hides varied according
to thickness and amount of material they accumulated in the enclosure and so
were not weighed.
Table 1. Consumption record
of wolves participating in the
Thiabendazole aversion protocol at CWC.
Wolf
PRE-TEST
TREATMENT
POST-TEST
1
2
3
4
1 2
3 4
5 6
7 8
9 10
1 2
3 4
FULLY-TREATED
WOLVES
Kiana
YES
YES
YES
YES
100%
[NO FURTHER
CONSUMPTION…………………………………..…...]
Minka
YES 100% [NO FURTHER CONSUMPTION…….…………..……...…]
Ketchikan
YES
YES
100% [NO FURTHER CONSUMPTION………….…..…]
Barrow
YES 97% [NO FURTHER CONSUMPTION……….….]
PARTLY-TREATED
WOLVES
Taku
YES
YES YES
20%
30% [NO FURTHER CONSUMPTION……….…...…….…...]
Inuk
YES YES
15%
30% [NO FURTHER CONSUMPTION…….….……….……..]
Tundra
YES 30% [NO FURTHER CONSUMPTION………….….….……..]
RECOVERED
MEAT
(%)
0
0
0
0
0
60 0
10
0
3
90
20 60
80
75
99 90
75
Inspection of the above data reveals several important
features of this process:
· By mid-way
through the treatment phase of the protocol, all of the wolves destined to
be treated other than Naomi had been treated and ceased consumption of
baits.
As expected for a
successful aversion, the most active predators tended to be the first
treated and these wolves simply left TBZ meat to be consumed by others in
their own turn.
· Those that had
become most familiar with the baits during the pre-test were as likely to
cease consumption of baits after a single full treatment or partial
treatments as those least familiarized with baits during the pretest.
Therefore, familiarity with prey did not seem to impair the
acquisition of an aversion to it.
· Wolves that were
treated early underwent up to 17 subsequent post-tests (including 2-1 hour
trials during each of the 4 post-test days) during which no food other than
the bait was available and on almost half these occasions after having been
food deprived for over 40 hours.
· Of the wolves
that received only partial treatment with TBZ, two consumed some of the bait
meat twice and then ceased eating baits, one ceased consuming bait meat
after only a single incomplete dose.
This indicates that even partial treatment can have some effect upon
food preference though partial treatment might not produce lasting and
robust effects for wolves destined to be released.
·
Once treated
with TBZ, wolves continued to refuse baits in spite of the near and
continuous presence of other untreated wolves actively consuming baits.
· Since all of the
wolves continued to reject the interior meat of baits during the post-test
when no TBZ was present in the bait, it appears that the wolves failed to
detect the TBZ in the bait during the treatment period.
That is, instead of forming an aversion to the TBZ, the illness
induced by TBZ was associated with the taste and scent of the meat itself.
In addition to complete suppression of actual consumption
of bait contents, wolves demonstrated a change in willingness to approach
the baits from a distance. Two
obvious measures of this tendency were identified on the video record and
have been used before as measures of aversion (Appendix 7).
We assumed that it was most unlikely that any wolf that moved within
1 meter (three feet) of any available bait but then continued past the bait
without any observable hesitation had done so because it did not know the
bait was present. Wolves that
engaged in this behavior were therefore scored as having “ignored” the bait.
Another behavior was the tendency to reject the bait on the basis of
its scent. In this case, wolves
were scored as having “Smell-Rejected” a bait if they came head-on toward a
bait within 1 meter, hesitated with the nose near the bait, and then chose
to move on without making physical contact with the bait.
The total frequency of these two behaviors is reported on Table 2.
Table
2. Frequency of avoidance of baits at a distance (Ignoring baits and
smell-rejecting baits).
Wolf
PRETEST
POST-TEST
FULLY-TREATED
WOLVES
Kiana
0
46
-------------------------------------------------------------------------------------
Minka
0
4
-------------------------------------------------------------------------------------
Ketchikan
0
35
-------------------------------------------------------------------------------------
Barrow
0
21
-------------------------------------------------------------------------------------
TOTAL
0
106
------------------------------------------------------------------------------------------------------
PARTLY-TREATED
WOLVES
Taku
0
42
-------------------------------------------------------------------------------------
Inuk
8
34
-------------------------------------------------------------------------------------
Tundra
0
21
-------------------------------------------------------------------------------------
Naomi
3
2
-------------------------------------------------------------------------------------
TOTAL
11 99
The number of wolves that increased avoidance of baits at
a distance after treatment compared with before treatment was seven out of
eight. Although it is very
unlikely that very hungry wolves without a food aversion would otherwise
behave in this way, we arbitrarily assign the likelihood of hungry wolves
ignoring potential food as 50% (1 time out of two) for each wolf. The
computed likelihood of getting 7 out of 8 is actually less than one chance
in 100 trials (Sign Test, P=0.50, Alpha<0.01).
This is exactly the likelihood of getting 7 heads out of 8 tosses of
an honest coin. Therefore,
avoidance of these baits without aversion is very unlikely and so the
behaviors above are reliable and practical measures of whether or not
predators have acquired an aversion before being released from captivity.
This is not to
say that there were no occasions during the post-test when treated wolves
entirely avoided baits at a distance.
In fact, wolves did occasionally proceed to taste baits since
contamination of the outer surface prevented it from becoming the
unambiguous barrier that we intended.
By far, the most frequent rejection of baits on the basis of taste
took place with the two young wolves Kiana and Taku who continued to seize
baits when they were offered. Nothing in the enclosures enriched the wolf
environment and so the wolves were undistracted except upon occasions when
wind blew objects into the enclosure or a hapless Raven was caught by a wolf
that was then pursued by others before the Raven was finally dismembered and
left uneaten. CWC staff remarked that the behavior of the two youngest
wolves, Taku and Kiana, appeared more to be curiosity and playfulness than
feeding behavior since they tossed baits into the air and rolled playfully
over them before attempting to open them.
They spent much more time to open the baits than they did before
treatment since they now used only their incisors and took time with
exaggerated mouth and tongue movements in attempts to remove individual
pieces of hide from their mouths.
This accounts for the high frequency of recorded “Taste-Reject”
behavior.
On every occasion for
every wolf the taste of the hide and that of the interior meat was rejected
instead of being followed with normal consumption (See Table 1).
When the wolves encountered the taste of interior meat, they shook
their head, gagged, or stopped contact and simply left the bait.
Occasions when wolves made mouth contact with hide or meat without
going on to consume the bait were scored on the video record as
“Taste-Reject” behavior as reported in Table 3.
Table 3.
Frequency of rejection of baits based upon taste.
Wolf
PRE-TEST
POST-TEST
FULLY-TREATED
WOLVES
Kiana
0
23
-------------------------------------------------------------------------------------------------
Minka
0
1
-------------------------------------------------------------------------------------------------
Ketchikan
0
1
-------------------------------------------------------------------------------------------------
Barrow
0
8
-------------------------------------------------------------------------------------------------
Total
0
33
PARTIALLY-TREATED
WOLVES
Taku
0
31
--------------------------------------------------------------------------------------------------
Inuk
0
5
--------------------------------------------------------------------------------------------------
Tundra
0
8
--------------------------------------------------------------------------------------------------
Naomi
0
0
---------------------------------------------------------------------------------------------------
Total
0
44
Again, it is extremely unlikely for any hungry wolf to
reject the taste of potential food unless they have acquired some kind of an
aversion to the food or the food is laced with some kind of noxious
substance. Nevertheless, if we
set the likelihood of this kind of behavior being observed by chance as 0.50
(50% or 1 out of every 2 trials) as before, the chances of 7 out of 8
individuals engaging in this behavior during the post-test is very unlikely
indeed. The probability of this
occurring is much less than 1 occasion in 100 trials (Sign Test, P=0.50,
Alpha <0.01).
Please note, however, that although “taste-rejection”
behavior is very dramatic when it occurs, it only happens when aversion on
the basis of the external scent of prey is insufficient to produce avoidance
at a distance. This could occur
when wolves receive an insufficient dose of aversion agent, detect the
aversion agent in the bait or when the external taste and scent cues had
become confused or obliterated.
Conclusions
Our demonstration of this protocol assures that wolves can
be induced to voluntarily participate in the full protocol from pre-testing
through post-testing. In this
protocol, familiarity with target prey during the 4 days of the pre-test did
not prevent a single average dose of Thiabendazole of about 140 mg TBZ/Kg
wolf body weight from producing clear aversion to the taste and scent of the
inner meat. This was confirmed through practical measures of behavior
changes that have been used to measure aversions before.
It seems clear that wolves failed to detect TBZ when well mixed in
inner ground meat at a rate no greater than 2-3% of the weight of the meat.
It is equally clear that efforts must be made to eliminate the
influences of bias, contamination and under-dosing that affected the results
of this demonstration. If
wolves do not consume a full dose of TBZ or if the outer surfaces of baits
are contaminated so that the unique taste and scent of target livestock prey
is masked, reduced,or confused then there is little hope that an aversion
acquired under captive conditions will reduce predation on livestock.
We offer some recommendations for future use of this protocol
(Appendix 8). We hope
that the history of substituting poorly conceived procedures that produce
failures rather than simply following procedures known to produce desired
outcomes will not be repeated (Appendix 2).
APPENDICES
Appendix 1.
On their web site, Riley and Freeman (see literature cited
section below) list over 3000 research articles describing CTA.
Many of these are clinical studies dealing with the treatment of
alcoholism, food preferences of humans and animals, treatments for weight
loss or gain and many other subjects in addition to wildlife management.
The first studies reporting human cancer victims forming dramatic and
life-threatening food aversions resulting from chemotherapy were reported by
Bernstein, 1978; Bernstein and Webster, 1980; and Bernstein, 1985.
Successful research on CTA in which predators consumed
carefully constructed baits designed to produce illness began with Gustavson
who first reported that CTA could produce avoidance of live prey among
captive wolves and coyotes (Gustavson, et al. 1974; Gustavson, et al. 1976).
He later reported that meat baits placed into the field reduced
predation by coyotes upon sheep (Gustavson 1976).
These results were later confirmed independently by Ellins, et al.
1977 and by Stream 1976.
Gustavson again reported comparable results in Canada (Gustavson, et al.
1982). Nicolaus, et al. 1979
and Nicolaus, et al 1982 confirmed that aversions induced by inanimate baits
could inhibit predatory attack upon live prey.
But this was accomplished in the field rather than in captivity.
Individually identified free-ranging raccoons that had consumed
chicken carcasses carefully laced with an aversion agent later avoided live
chickens as well as the carcasses.
Later, Gustavson and Nicolaus, 1987 summarized all of the research on
this issue up to that date.
Over time, many studies both in captivity and in the field have confirmed
that predators quickly and dramatically alter predatory behavior when
affected by CTA. In addition to
research mentioned above, CTA has been shown to be effective when baits have
been distributed in the field to treat free-ranging predators such as
raccoons (Semel and Nicolaus, 1992), black bears (Polson, 1983; Ternent and
Garshelis, 1999), mongooses (Nicolaus and Nellis, 1987), whole assemblages
of predators converging to prey on the same prey species (Nicolaus, 1987;
Nicolaus, et al., 1989), Common Ravens (Nicolaus, 1987), American Crows (Nicolaus,
et al. 1983; Nicolaus, et al. 1989; Dimmick and Nicolaus, 1990) and Redwing
Blackbirds (Nicolaus and Lee, 1999).
In addition to this, a number of other researchers have reported
successful establishment of CTA among captive predators.
These include Gill, et al 1999; Massei and Cowan, 2002; Massei, et
al., 2003; Massei, et al., 2003 and a good summary of research in field and
captivity was produced in 2000 by Cowan, et al.
Appendix 2.
There is very good reason to believe that when applied properly in meat
baits, predators do not detect the taste or scent of the TBZ in the bait.
In the successful studies cited in Appendix 1 above in which TBZ was
used as the aversion agent, TBZ was variously added to such foods as meat
baits, bee’s wax and honey, and in military rations.
Since care was exercised to use carefully measured amounts well mixed
with a large enough amount of the food to mask its odor and taste, TBZ
induced aversion to the taste and scent of the food such that during post
testing, predators avoided the foods without the TBZ being present.
An extensive literature reveals what happens, however, when baits are
constructed so that the aversion agent systematically alters the taste and
scent of the bait.
Naďve and
hungry predators often willingly consume the baits but since the taste and
scent of the bait do not match that of live prey, they readily discriminate
between baits which they are no longer willing to consume and live prey that
do not taste or smell like baits that induced the illness (see: reviews of
this literature in Gustavson and Nicolaus, 1987; Bekoff, et al 1975; Ellins,
et al 1978: Quick, et al 1985; Nicolaus at
www.conditionedtasteaversion.net)
Appendix 3.
TBZ produced clear and lasting food aversions among free-ranging black bears
when applied to the problems of reducing depredations upon bee hives in
Canada (see: Polson, 1983) and in bear-human conflicts in a military
reservation in Minnesota (see: Ternent and Garshelis, 1999).
After a close analog of TBZ, Mabendazole, was seen to induce food
aversions among young wolves, TBZ itself was used to produce aversions among
Dingoes and Hunting Dogs (see: Gustavson and Nicolaus, 1987).
Later, TBZ was used to produce food aversions among foxes and other
predators (see: Masssei and Cowan, 2002; Massei, et al, 2003).
Appendix 4.
Some substances like Lithium Chloride produce very obvious illness symptoms
including gagging, vocalizations and vomiting and so the time for the onset
of illness is usually obvious.
The physiological effects of TBZ, however, are far more subtle and so the
onset of its effects is best judged by when predators treated with TBZ begin
to refuse food.
That is,
animals beginning to become ill cease feeding.
When such a thing has been indicated in the literature, the time
appears to be about 60 minutes (see Ternent and Garshelis, 1999; Gustavson
and Nicolaus, 1987).
For the
same reasons, animals can be judged to have recovered from the effects of
TBZ when they first are willing to consume alternative food normally.
Appendix 5.
TBZ is 2-(4-Thiozolyl) benzimidazole.
It has been approved for many years as both a human and a veterinary
pharmaceutical acting as a broad-spectrum preparation principally for
removal of gut worms (see: Merk Index, 1968).
Since the body weight of humans and animals largely determines the
effects of toxins, pharmaceuticals and nutrients, the dose of such
substances is expressed as so many milligrams (mg: meaning thousandths of a
gram) of the substance per Kilogram (Kg: meaning thousand grams) of the
human or animal body weight.
The dose of TBZ necessary to kill 50% of test rats is 3100-3600 mg per Kg
rat body weight, 3810 mg/Kg in mice and 3850 mg/Kg in rabbits (see: the
Veterinary Drug Handbook, 1991).
These doses are over 19 times greater than the 200 mg/Kg maximum dose
we propose to use with wolves. Dogs have been force fed doses of 200 mg TBZ/Kg
their body weight daily for a full two years without any observable ill
effects.
TBZ has been approved
and used extensively as a broadly applied fungicide applied to human foods
with a very good safety record.
The only environmental hazards so far identified in this agricultural use
involve potential toxicity to shellfish and other marine animals when
quantities of it wash into the sea.
As long as TBZ remains in baits that are then disposed of in a proper
manner, none of it should ever escape into the environment at all.
Appendix 6.
We do not recommend that in future baits continue to be introduced to wolves
in this manner.
We initially
attempted to introduce the baits in a more systematic, perhaps less biased
manner but since the wolves were hungry, there was a risk to the CWC staff
entering the enclosure to place the baits.
For safety concerns we opted to introduce the baits in this way and
admit the potential bias.
The maintenance
diet for wolves at CWC was varied, including chicken, fish, road killed deer
and other game, horses and mules volunteered by well-wishers.
It was important that we choose a target prey that was unlikely to be
donated to the CWC to help feed the wolves.
Since very few sheep were raised in the vicinity, this food had not
been fed to the wolves at CWC for many years and so we considered that
before we familiarized the wolves with it during the pre-test, sheep was
unfamiliar to them and that once established, aversion to sheep would not
materially affect their future maintenance.
Appendix 7.
Before acquiring an aversion, hungry predators typically approach, smell,
taste, and then fully consume familiar and preferred foods.
The 4-day pretest functioned to demonstrate that the wolves engaged
in normal feeding behavior and it also made the baits familiar enough to the
wolves so that they might more readily consume treated baits as required.
In nature, consuming nutritious prey provides an internal reward that
reinforces external feeding behavior.
That is, successful feeding on a particular food enhances the
attractiveness of the taste and scent of the food, directing feeding
behavior in a way that increases likelihood of successful feeding.
In nature, when the consequence of consuming prey with chemical
defenses is a severe internal illness rather than an internal reward, the
taste and scent of the particular food consumed before the illness becomes
disgusting. Rather then to
continue to be attracted by this prey at a distance, predators are dissuaded
and so seek other, more suitable prey.
Systematic studies of illness-induced change in the
attractiveness of the taste and scent of prey have identified several very
common and practical measures of this change that should be applied to
judging at the end of the proposed protocol whether or not a predator has
acquired an aversion before it is released.
These well known behaviors shown by predators with prey aversions
include “ignoring” or “smell-rejecting” target prey from a distance and
“taste-rejecting” foods that they allow to enter their mouths.
Often “taste-rejection” behavior is complete with head-shaking,
gagging and even vomiting at the taste of the now offending food.
We simply used these standard measures of aversion as the criteria
for determining whether wolves in this demonstration had acquired an
aversion.
Appendix 8.
Recommendations
Please note: The
Mexican wolf recovery team may be in a position to monitor wolves and their
conflicts with domestic livestock.
None, however, have knowledge or practical experience with the
successful use of CTA.
Therefore, we consider it absolutely essential to a successful first effort
to use CTA to mitigate conflicts between Mexican wolves in each of the
applications described below that the work proceed with the guidance of
persons with knowledge and experience in the use of CTA.
In each of these three applications, this should include guidance and
supervision in the construction of baits, administration of baits whether in
captivity or in the field and the monitoring of the fates of baits and
behavior of the wolves. We
understand that incidences of conflict between wolves and livestock are
documented carefully and in a standard manner and so this procedure ought to
serve as a measure of success or failure of the CTA effort.
If the intention
is to produce an aversion that reduces predatory attacks upon live prey,
then we recommend the following:
· · Nothing
in our demonstration suggested that
the baits we constructed were flawed in any way and so the details of bait
construction described above including clean, fresh, dry hide typical of the
target livestock prey securely sutured around the TBZ treated inner ground
meat should be followed in future work.
Since the dose of 5.4 g of TBZ well mixed in 250 g of plain ground
meat was safe, effective and not apparently detected by the wolves, this
should be the standard preparation for baits intended to be consumed by
predators the size of these wolves.
· · Wolves
must be subjected to a food
deprivation regimen that meets their minimum feeding needs over all, but
that includes acute periods of food deprivation from 20-40 hours in duration
immediately prior to introduction of baits during all three phases of the
protocol. We consider that a
maintenance ration of 12 Kg (26 pounds) of meat per wolf per week
distributed in four feedings each of 3 Kg every other day is both adequate
to maintain fully grown wolves and sufficient also to induce them to
participate in the protocol.
The weekly maintenance diet for wolves proceeding through this protocol
should approximate 21% of their body weight as was the case in this
demonstration. The key to this
process, however, is to remove all unconsumed food 2-3 hours after each
feeding.
· ·
Barring unforeseen difficulties, presuming
that future practitioners can treat wolves separately, and presuming that
the intention is solely to establish aversion to live prey and not including
an additional effort to produce aversion to carcasses described below, the
total amount of time required to complete the protocol might be less than
that which we report here. That
is, the food deprivation regimen will require a few days to become
established before the protocol itself can begin.
Then, there should be a pre-test of up to 4 days, a single day of
treatment and recovery, and a post-test of up to 4 days.
This might total as little as a 10-12 days.
· · Our choice of 60-minute trials reflected our
desire to be able to document the full range of largely unpredictable
behavior of wolves all maintained together in the same enclosure at the CWC.
In the real world when predator chooses whether or not to pursue
prey, seconds are an eternity.
So, forcing hungry wolves to remain in close proximity to a food for which
they have an aversion with no alternative food available is a grossly
conservative measure of aversion.
If wolves are maintained separately in adequate facilities and
moderately deprived, then they should seize and open a bait within a few
minutes and very quickly consume the small amount of meat in the interior.
They may then interact with the hide for a time.
Therefore, pre-tests and the treatment might be terminated just as
soon as inner meat of baits is consumed and remaining hide is ignored.
Post-testing might require longer to provide assurance that the
criteria for successful aversion are met.
· · It
is essential that all of the details of
behavior throughout the protocol be documented with a video record.
It is simply not appropriate to attempt to surmise events on the
basis of leavings after a trial.
To reduce bias as much as possible, the videotaping may be conducted
as unobtrusively as possible.
In this way, review and scoring of events from the video record justify
procedure and policy decisions.
· · During the protocol, it is necessary that
predators be prevented from consuming any other food for several hours
before, during and after eating the baits.
In this way, only the taste and scent of well-constructed baits can
be associated with illness during the treatment period.
This is partially accomplished by subjecting wolves to food
deprivation as described above but in addition, care should be taken to
clean all remnants of earlier feeding so that none might be consumed within
three or more hours before or after the baiting period.
· Captive
predators should be proceed through the CTA protocol separately.
If this cannot be done, then baits should be introduced in such a way
as to absolutely minimize competition for any single bait that might produce
contamination or under-dosing.
The immediate environment should be clean and the substrate clean concrete,
gravel or some other substance so that all surrounding contaminants are
eliminated.
We strongly suggest
that wolves be maintained in a facility large enough for them to move freely
toward and away from baits without the introduction of bias that always
results from forcing them to interact with baits at close proximity.
If wolves are housed and observed separately, we suggest that
interaction with baits take place in facilities that are at least four times
the body length of the wolves, including the tail and excluding sleeping
areas and that clean water be maintained at all times away from where baits
are to be placed.
If wolves
have been transferred to their holding facility recently, it is necessary
that they demonstrate willingness to consume their maintenance diet and
otherwise behave normally before beginning the protocol.
· Since interest
in and interaction with the baits could well be more a function of boredom
than predation, we strongly recommend that the wolf environment be greatly
enriched with objects and devices designed to interest and occupy the
wolves.
An impoverished
environment combined with making all stimuli other than food essentially
irrelevant to the wolves strongly biases behavioral outcomes, especially
during the post-test of this protocol.
· Although ever
wolf in our demonstration required only a single full treatment to form an
aversion to baits, this may not always be so.
It is always possible that a wolf might need more than a single full
treatment with TBZ before it fulfills the criteria for a successful
aversion.
If captive wolves are
offered a TBZ bait only once during the treatment period, the first bait
offered during the “post-test” should also contain TBZ in case a second
treatment is needed.
A wolf
that has acquired an aversion to the taste and scent of target livestock
should demonstrate a dramatic change in behavior during post-testing
compared with its behavior during pre-testing.
That is, the outer surface smell and taste of the bait should be a
barrier to a wolf with a satisfactory aversion.
Evidence of this could take the form of ignoring the bait or
smell-rejecting the bait.
Wolves might attempt to bury the bait or cover it over.
Since the taste of baits will have become disgusting, if they pick
the bait up, they will tend do so only with the incisors dangling the bait
from the front of their mouth rather than to hold the bait fully within the
mouth.
Some individuals with
satisfactory aversion to the bait may nevertheless interact with it by
smelling or tasting it.
But
their response to the smell and taste of the bait should be pronounced
rejection of it and may be accompanied with head shaking, gagging and even
retching.
After a few minutes
of this, such animals often begin to avoid the bait at a distance and this
avoidance should continue during a second post-test. In all of these
interactions, if the wolf refuses to interact with the inner contents, the
TBZ in the inner meat is irrelevant.
To be assured that this is the case, these wolves can be exposed the
next day to another bait without TBZ.
If avoidance at a distance continues then the animal may be
considered to have acquired the desired aversion.
· Regardless of
whether or not wolves meet the criteria for successful establishment of
aversion through this protocol, the taste and scent of the baits used in the
protocol must always be close approximations of the taste and scent of
livestock on the range where the wolves will be released.
· What to do with
“failures”.
Failure in this protocol is much
more easily prevented than corrected and the failures discussed below are
very unlikely if the protocol is carefully followed.
Possible failures to meet criteria for successful aversion can occur
in the following ways: 1. If the animal fails to engage in the sort of
rejection behaviors described above and instead, opens the first post-test
bait and then fully consumes the inner meat then aversion to both the
exterior and the interior of the bait failed in this particular case.
This could be because the TBZ in the interior was insufficient to
produce the effect or the wolf detected important differences in the inner
and outer scent and taste of the bait during treatment versus the post-test,
or the wolf might simply be an unusual individual responding to unusual
circumstances.
However, since
the wolf consumed the bait as before, it will be treated again with the TBZ
in the first “post-test” bait.
After recovering from this second treatment, this animal should meet the
post-test criteria for successful aversion on the basis of avoidance of the
outer surface as long as the outer taste and scent of treated bait is the
same as that for post-test baits. If required avoidance does not develop,
refer to #2 below. 2. If an animal is not dissuaded from the outer surface,
opens the bait but refuses to fully consume the inner TBZ treated meat then
it is possible that the TBZ was detected or, if not detected, aversion to
the outer surface failed but aversion to inner meat succeeded.
To resolve between these two possibilities it is necessary to
post-test a second time without TBZ in the meat.
If the bait is opened again and plain meat is rejected as before,
then aversion to the inner meat succeeded but aversion to outer taste and
scent of the bait has failed, almost certainly because of contamination of
the outer surface.
If plain
meat without TBZ is eaten, then it is likely that somehow the animal
detected the TBZ in the meat the first time.
Both of these problems will required an additional treatment to
correct but if wolves refuse to consume inner meat with or without TBZ, they
cannot be treated again using the same inner meat to establish aversion to
the outer surface of the baits.
It might still be possible to establish an aversion to the outer taste and
scent of baits and of livestock by changing the bait interior.
Very little is know concerning how to amend a failed aversion, but we
suggest that this might be attempted by including some kind of food other
than the ground meat originally used.
If it is apparent that the animal initially detected the TBZ in the
first meat bait, then the appropriate physiological dose of TBZ may be
placed into a larger volume of inner food to help mask the TBZ as long as
this volume does not exceed what the wolf is willing to consume in a single
meal.
After this, the wolf
should be again exposed to baits with the same outer taste and scent.
If this wolf finally avoids the bait from a distance then it may be
considered as a success.
If it
continues to consume the baits, then it should be scored accordingly and the
decision to release or not release this wolf should be made in the light of
programmatic needs.
It may be
possible to treat this particular animal in the field under more natural
settings, should the wolf conflict with livestock.
As with all of the other wolves released after the protocol, the
permanent record for wolves that have had difficulties should be maintained
and used to interpret future events in the field after their release.
· If they can be
induced to voluntarily participate in the protocol, this procedure may be
used to treat recently captured animals before they may be released again
into habitat with livestock.
The principal difficulty in this case may simply be one of inducing such
animals to consume food under the stress of captivity.
This may require that such animals be held in captivity for a longer
period of time than might otherwise be planned before their release and it
may require that other measures be attempted to induce them to participate.
·
Once treated
animals have demonstrated aversion to the outer surface of untreated meat
baits they may be released and then monitored carefully to determine whether
they engage in depredations upon target livestock.
It is during monitoring of wolves in the field that the proper test
of the strength and longevity of the aversion effect may take place.
Attempts at measuring these features under captive conditions will
inevitably introduce serious bias.
If the intention
is to reduce conflicts with livestock by also dissuading predators from
scavenging livestock carcasses, then a slight expansion of this protocol
could be highly effective:
· Predators may
begin to attack livestock after having scavenged livestock carcasses.
Even if scavenging does not act as a gateway for predation on live
prey there are many places where predators are shot or poisoned on sight and
so reducing the attractiveness of carcasses may generally reduce the
frequency of lethal conflicts with livestock.
To the human nose, decomposing carcasses do not smell like fresh live
animals and so non-human predators may also discriminate at some point
between carcasses and live prey.
In this way, predators with aversions established with fresh meat
baits may nevertheless be attracted to livestock carcasses whose taste and
scent sufficiently differ from the baits, with the usual lethal
consequences.
The process of
putrefaction of whole carcasses is time and temperature-dependent and the
products of anaerobic decomposition such as cadaverine, putrescine, and
hydrogen sulfide are highly predictable.
Consequently, a fresh bait composed of ground meat tightly wrapped
with hide should roughly follow the same course of decomposition events if
allowed to remain for a time under warm conditions.
It seems likely that the taste and scent cues of such baits could be
reasonable approximations of livestock carcasses and so might be used in an
expanded protocol designed to produce aversions that dissuade scavenging as
well as predation. This, then, is a microbiological process with important
behavioral and practical consequences.
We do not know at this time at what point a bait must decompose so
that its taste and scent become altered enough that a predator with an
aversion to fresh baits becomes willing to consume the decomposed bait.
Whatever that level of change is will be the limit of influence the
aversion protocol will have upon the critical problem of scavenging of
livestock remains.
We also do
not know how the presence of TBZ might affect the decomposition process.
It is possible that since it has been used as a fungicide TBZ could
alter the process in a way that might allow wolves to discriminate between
decomposed baits with TBZ and decomposing carcasses.
We also do not know if TBZ would survive in tact through the
decomposition process.
To our
knowledge, only one attempt to answer this kind of question has been
reported.
Nicolaus, et al. 1992
reported that oral estrogen retained its potency as an aversion agent when
allowed to remain in eggs through advanced decomposition. We therefore
recommend that an attempt be made to determine the safety and efficacy of
decomposed TBZ baits using “generic” wolves rather than the much more rare
Mexican wolves.
It should be a
relatively simple task to repeat the CTA protocol with TBZ meat baits that
have decomposed to a point at which they differ markedly from fresh baits
and the wolves are still willing to consume them. If it can be shown that
decomposed TBZ baits are safe and effective, captive predators with aversion
to the exterior of fresh baits may then be offered TBZ-treated baits that
have begun to decompose.
If
these predators avoid decomposed baits also, then they should systematically
be offered TBZ-treated baits with greater and greater decomposition until
they finally consume the bait and so are treated.
They should then be post-tested with equally decomposed bait to
demonstrate aversion before they may finally be released.
We presume if wolves are consistent in their behavior toward these
baits it might be sufficient to simply maintain baits at a known temperature
for a known time in order to streamline the second treatment designed to
reduce scavenging.