Animal training involves manipulating animal behavior through reinforcement to foster animal welfare, manage behaviors, and educate the public. There are different models of training service animals, such as traditional programs that fully train dogs before pairing with recipients versus owner-training models where recipients train their own psychiatric service dogs with guidance. While owner-training can strengthen the human-animal bond and train for individual needs, it also risks inconsistent training producing poorly-behaved dogs. Proper training principles and oversight are important regardless of the model used.
1. Animal Training
Today, animal training, research, and behavior medicine are utilized to foster
animal health and welfare, shape and maintain prosocial behaviors, manage
breeding groups, contribute to a growing body of scientific literature, and educate
the public.
From: Encyclopedia of Marine Mammals (Third Edition), 2018
Related terms:
Animal Welfare, Dolphin, Veterinarian, Primate, Animal Behavior, Operant
Conditioning, Polygyny, Marine Mammal, Stallion
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Volume 1
Learning “Theory”
Animal training is, simply, the manipulation of behavior. Behavior is not the tool
with which the animal is trained, but rather the measure of the training
procedure: if the animal’s behavior changes, then learning has occurred.
There exists an argument that species-specific differences necessitate devising
unique training approaches for that particular animal, as though the principles of
learning differ between species. Similarly, some trainers believe that we need to
assess the animal’s temperament in order to know which techniques to use on a
particular animal. Labels such as friendly, nervous, shy, dominant, spooky, etc.
may serve to enhance communication between professionals if these are clearly
defined; however, there is much misinterpretation of these labels. Additionally
these labels themselves do not help us define the actual behaviors that the animal
is exhibiting or that we wish to train.
Most animal professionals recognize that species show a repertoire of innate
behaviors that serve certain functions for the animal. These behaviors are
influenced and shaped further by an animal’s experiences. As the Brelands noted,
these behaviors can at times interfere with training goals. Nevertheless, these
innate behaviors also can be used to enhance the success of training goals. Horse
trainers utilizing negative reinforcement for “natural horsemanship” have done
this with the manipulation of a horse’s instinct to run when threatened. Escape
behaviors (running away) are easy to condition in an animal that is already
predisposed to running away. The weakness in the approach is that too few
trainers understand the principles of learning. They rely solely on ethological
concepts to explain behavior, e.g. the horse runs because it is a prey species
Melissa Bain, in Encyclopedia of Animal Behavior (Second Edition), 2019
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2. and/or is acting submissive, rather than understanding that avoidance behavior is
conditioned via negative reinforcement.
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Assistance animals
Philip Tedeschi, ... Jana I. Helgeson, in Handbook on Animal-Assisted Therapy
(Third Edition), 2010
20.9 Training models
Some service animal training organizations, such as Assistance Dogs International
(ADI), set standards which define individual training as “deliberately teaching the
animal through the use of rewards and/or corrections to perform a task in
response to a command or another stimulus such as the onset of a seizure” (ADI,
2009). Assistance Dogs International has developed an accreditation manual
defining standards for training service dogs and by 2010 all programs that apply
for membership in ADI must be accredited. The major difference, other than the
breed and type of dog, between traditional service dogs and some psychiatric
service dogs is how they are trained and who does the training. This can be
illustrated by comparing traditional and psychiatric service dog training.
Traditional training places an emphasis on predictability and control. If they
control the breeding, selection, training, and finally the pairing of the dog with
the service recipient, they can predict the results of that pairing. In general,
puppies stay with their littermates until they are eight weeks old and then each
puppy is sent to live with a trained puppy raiser. The puppy raiser keeps the dog
for approximately 12 to 16 months and does the initial socialization of the dog
and trains the puppy to respond to many basic commands. Following this
socialization period, the dog is generally sent for formal training that includes
Canine Good Citizenship (CGC) training and completion of public access training
along with specified task training. In other words, the dog is completely trained
prior to meeting its paired recipient handler. Then, team training assists the dog
to learn to respond to the recipient, and for the recipient to learn how to handle
the dog.
In contrast, PSDS advocates that recipients train their own psychiatric service dog
with one-on-one assistance from a professional dog trainer. According to
www.psychdog.org, there are numerous benefits to training one’s own service
dog. In an interview with the President of the Psychiatric Service Dog Society, Joan
Esnayra discussed the various strengths and weaknesses of the owner-trainer
model. She comments that the owner-trainer model is an empowerment model.
In learning how to train one’s own service dog, the handler learns to better
communicate with the dog. This in turn leads to the creation of a stronger bond
which sets the stage for keener alerting abilities (i.e. the ability of the dog to “cue”
to the handler’s physiology). She believes owner-training is the optimal way to
train psychiatric service dogs because no one else can train the dog to “cue” to
changes in the handler’s physiology, which is what most PSD handlers need their
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3. animal to do. Esnayra (2009) also believes that when a handler learns the
fundamental principles of dog training, s/he is better equipped to maintain a high
behavioral standard with their service dog. Esnayra believes that these principles
cannot be adequately learned in the two-week placement window of most
traditional service dog training programs. Learning how to train one’s own PSD
also puts the handler into a behavioral mindset that focuses his/her attention on
stimulus/response interactions in the environment, with the dog and within
his/her own body.
Nevertheless, in our discussions, Esnayra (2009) points out that the owner-trainer
model is not for all candidates. Lack of consistency in training produces a poorly
trained and confused, even frustrated, dog. Since there is no established oversight
for owner-trainers, it is easy for some to slip into bad handler habits and this can
cause a dog’s public decorum to slip in noticeable ways.
At best, basic obedience training teaches individuals how dogs learn and how a
handler must act to achieve desired behaviors. Also, embarking on the training
process together enhances the bond and builds trust between the
handler/recipient and the service dog in training as well as offering therapeutic
benefits as it teaches the handler to “think like a behaviorist.”
As the handler learns to critically observe the behaviors of the service dog in
training, he or she can learn how to observe his or her own behaviors. PSDS
philosophy toward training can be partially summed up as follows: “the Psychiatric
Service Dog Society is committed to the ongoing and empirical articulation of
PSD work. Whether psychiatric symptoms are mitigated through the execution of
trained physical tasks, or by subtle non-verbal interactions between dog and
handler, does not matter to us. PSDS is focused quite singularly on the
therapeutic effect of psychiatric service dog partnership, as well as how to leverage
and sustain those effects over time.” For PSDS, the training process is a very
necessary part of achieving these therapeutic effects.
There are several models, most commonly related to dogs, of training service
animals, all of which have advantages for the people who are recipients but may
have limitations for the animals involved. Prison puppy raiser programs have also
become popular as a way for young service dogs to be started, socialized and
receive basic obedience training. The dual benefit to this model reportedly is that
responsibility for training these young dogs offers psychosocial benefits for the
inmate, and it remains unclear if this is a safe method of training for the animals
involved.
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Neural-Network Models of Cognition
Vijaykumar Gullapalli, in Advances in Psychology, 1997
Shaping
Shaping is an ancient animal-training procedure that has been studied by
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4. experimental psychologists interested in animal learning (Honig & Staddon,
1977). The term "shaping" itself has been attributed to the psychologist Skinner
(1938), who used the technique to train animals, such as rats and pigeons, to
perform complicated sequences of actions for rewards. Skinner describes how the
technique is used to train pigeons to peck an illuminated spot on a pecking disk:
We first give the bird food when it turns slightly in the direction of the spot from
any part of the cage. This increases the frequency of such behavior. We then
withhold reinforcement until a slight movement is made toward the spot. … We
continue by reinforcing positions successively closer to the spot, then by
reinforcing only when the head is moved slightly forward, and finally only when
the beak actually makes contact with the spot…
The original probability of the response in its final form is very low; in some cases
it may even be zero. … By reinforcing a series of successive approximations, we
bring a rare response to a very high probability in a short time. … The total act of
turning toward the spot from any point in the box, walking toward it, raising the
head, and striking the spot may seem to be a functionally coherent unit of
behavior; but it is constructed by a continual process of differential reinforcement
from undifferentiated behavior, just as the sculptor shapes his figure from a lump
of clay. (Skinner, 1953, pp. 92-93)
The phrase "reinforcing a series of successive approximations" expresses the
essence of shaping. Given the task of training an animal to produce complex
behavior, the trainer must (1) judge what constitutes an approximation to, or a
component of, the target behavior, and (2) determine how to differentially
reinforce successive approximations so that the animal easily learns the target
behavior.
Unfortunately, neither of these two components of shaping has been formalized
rigorously in the psychology literature, even though shaping is widely used both
in psychological studies and to train pets and circus animals. Staddon (1983), for
example, observes that the trainer often has to rely on an intuitive understanding
of the way the animal's behavior is generated when determining which behavioral
variations are precursors to the target behavior and how to reinforce these
precursors. Variations in the behavior of individual animals also must be taken
into account when making these judgments.
The limitations of relying on intuition when judging approximations to the target
behavior are especially apparent when the behavior under consideration is
cognitive (covert) in nature. However, when the overt behavior of the animal is
being shaped, behavioral approximations become equivalent to physical distances,
and it is therefore easier to determine a sequence of approximations that will lead
to mastery of the target behavior. It is therefore not surprising that shaping has
been used most often for teaching motor skills to animals. For the same reason,
shaping can also prove useful for training artificial learning systems to perform as
controllers of motor behavior.
Several neural-network researchers have noted that training a controller to
perform one task can facilitate its learning a related second task (e.g., Selfridge,
Sutton, & Barto, 1985; Gullapalli, 1990; Wieland, 1991). Selfridge, Sutton, and
Barto (1985) studied the effect of shaping a controller to balance a pole mounted
5. on a cart. They observed that overall learning times were typically shorter when a
previously trained controller was retrained on a modification of the cart-pole
system than when an untrained controller was trained from scratch. This was
demonstrated for several types of modifications including increasing the mass of
the pole, shortening the pole, and shortening the track. (See Barto & Sutton, this
volume.)
Wieland (1991) illustrated the utility of shaping using a different version of the
cart-pole task in which the controller had to simultaneously balance two poles
mounted on a cart. Because it is easier to solve the two-pole balancing problem
when the pole lengths are very different than when the pole lengths are almost
equal, Wieland trained a controller by starting with poles of lengths 1.0 m and
0.1 m and gradually increasing the length of the shorter pole to 0.9 m. Although it
is very difficult to balance poles with lengths as close as 1.0 m and 0.9 m, the
shaping process resulted in a controller that was able to do so. Wieland and
Leighton (1988) also studied the utility of shaping schedules for accelerating other
learning methods based on gradient-descent procedures.
Other applications of shaping in neural-network research have been in the area of
training recurrent nets. Allen (1989) trained recurrent nets to generate long
sequences of outputs using a shaping procedure that involved initially training the
nets with short target sequences and introducing longer sequences gradually over
training. Another related form of shaping was studied by Nowlan (1988). In this
case, a robust attractor state for a recurrent network was developed by first
training initial states near the attractor, and then gradually increasing the distance
of the initial states from the attractor.
In this chapter, we focus on the utility of shaping for training controllers via direct
reinforcement-learning methods. The behavior of a controller was shaped over
time by gradually increasing the complexity of the control task as the controller
learned. At the same time, the evaluation function used to compute the
reinforcement delivered to the controller was also changed to reflect the
increasing complexity of the task. This procedure is analogous to the manner in
which shaping is used to train animals, and to the manner in which shaping was
used in some of the studies cited previously.
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Reproductive biology of the red panda
Erin Curry, in Red Panda (Second Edition), 2022
Ultrasonography
In many zoological institutions, animal training programs are regularly
implemented to habituate an animal to participate in medical examinations, such
as ultrasonography (Fig. 7.6). Ultrasonography is a powerful tool that enables
diagnosis and monitoring of pregnancy. In pregnant females, gradual
enlargement of the uterine lumen has been documented and may be useful in
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6. predicting the timing of parturition [6] as has been shown in mink [43]. In a study
utilizing transcutaneous ultrasonography of unrestrained pregnant red pandas at
the Cincinnati Zoo & Botanical Garden, the earliest a conceptus could be
visualized was 62 days postbreeding/50 days prepartum [6]. Uterine fluid,
presumably a gestational sac, was detectable much earlier, approximately 1 month
postbreeding/76 days prepartum. This is in contrast to carnivores of similar size
that do not experience delayed implantation, such as the domestic cat (Felis catus),
in which a gestational sac and embryo proper were visible as early as 10 and 18
days postbreeding, respectively [44]. The long delay between breeding and the
ability to visualize a foetus is consistent with the findings of two other species that
experience delayed implantation: mink [43] and fishers (Martes pennant) [45]
providing further corroboration for embryonic diapause in red pandas.
Furthermore, ultrasonography can be useful in diagnosing twins and monitoring
foetal growth and development (Fig. 7.7, Fig. 7.8, and Fig. 7.9).
Figure 7.6. Illustrates different mounting positions.
7. Figure 7.7. Shows a female red panda standing voluntarily for an ultrasound examination. She receives favorfavoured food items as a reward for
participating in training sessions.
Figure 7.8. Depicts changes in faecal progesterone (reported in nanograms of progesterone per grams of dried faeces) and gestational sac growth
in a pregnant red panda. Breeding was observed on 25 March and pregnancy lasted for 107 days, with parturition occurring on 11 June.
Progesterone increases around the time of breeding and then undergoes a secondary rise approximately 70 days prior to parturition, presumably
following CL activation.
From Erin Curry.
Figure 7.9. Depicts the changes in weight (% gain) of seven female red pandas throughout the year. Using trans-abdominal ultrasound, four of
these individuals were diagnosed as pregnant (Preg1-Preg4), two were pseudopregnant (Pseudo1 and Pseudo2) and one experienced a lost
pregnancy (Lost). There were no significant differences in weight gain between parturient and nonparturient females.
From Erin Curry.
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Update on the Great Ape Heart Project
Hayley Weston Murphy, Marietta Dindo Danforth, in Fowler's Zoo and Wild
Animal Medicine Current Therapy, Volume 9, 2019
Echocardiograms
Standardization and accuracy of echocardiographic examinations done in great
apes have been essential in detecting and monitoring great ape CVD, and the
GAHP has developed standardized guidelines for great ape echocardiography. A
great ape's size, positioning, and conformation may all affect imaging. It is
generally recommended to perform echocardiography on anesthetized apes
placed in left lateral recumbency, with the left arm extended cranially (Fig. 82.3).
Accurate and complete examinations require a skilled examiner and consist of a
comprehensive, two-dimensional transthoracic echocardiogram with Doppler
color flow study capabilities, and all GAHP recommended measurements stored
as DICOM (Digital Imaging and Communications in Medicine). While it is
possible to review measurements saved as movie and jpg files, DICOM standard
29,30
8. possible to review measurements saved as movie and jpg files, DICOM standard
capabilities are the gold standard, especially if participation in the GAHP is to be
maximized. This capability allows for postprocessing measurements and
assessment of images, ensuring data validity and remote storage capability.
Echocardiograms on Nonanesthetized Great Apes
The GAHP has been able to utilize advances in animal training to encourage
cardiovascular monitoring in great apes without the aid of anesthesia. The
advantages of performing echocardiography and BP monitoring on
nonanesthetized apes include less frequent anesthetic episodes, more frequent
monitoring, and lack of anesthetic effects on the cardiovascular system. The
disadvantages include training time and logistics, risk to the trainer and
equipment, less thorough echocardiograms, and a missed opportunity to do a
complete physical examination. Unfortunately, echocardiograms done on awake
animals may take several sessions to obtain all the necessary measurements.
Therefore, while not ideal, the GAHP recommends that measurements from
training sessions obtained within a 30-day period be submitted as one
examination.
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Reinforcement, Reward, and Punishment
Daniel T. Cerutti, in Encyclopedia of the Human Brain, 2002
IV Eliciting Effects of Reinforcers and Punishers
The eliciting effects of reinforcers can reduce variability in behavior by restricting
the range of responses available for reinforcement. The most dramatic examples
arising from the animal-training literature have been misnamed “misbehavior.”
An example is illustrated in Fig. 8. The operant contingency involved reinforcing
putting coins in a bank. Shortly after learning to do this, the raccoon began to
misbehave, rubbing the coins together for long periods of time. However, the
rubbing is actually a raccoon species-typical food washing behavior elicited by
food. As a result of earning food by depositing coins, the coins became a
conditioned stimulus for food and elicited washing.
9. Figure 8. “Misbehavior” in the raccoon. The operant contingency reinforced depositing money in the bank. However, the additional contingency
between coins and food resulted in the coins becoming conditioned elicitors of washing, interfering with the operant performance.
Many instances of punishment reduce the frequency of behavior in a similar
manner: An emitted response produces a painful stimulus that elicits defensive
behavior such as escape and avoidance. The result is that “punishment” reduces
the target behavior but not just by being a consequence of behavior. As a rule,
reinforcers are most effective when the responses they elicit are identical to or
compatible with a reinforced response and punishers are most effective when the
responses they elicit are incompatible with the punished response.
Conditioned aversive stimuli, stimuli that are paired with pain-eliciting stimuli,
can suppress operant behavior. They can do so by being made contingent on
operant responses or by their mere presence because they elicit defensive
behavior that is incompatible with the operant. Figure 9 illustrates the interaction
between conditioned-aversive stimuli and food-reinforced responding. As the
tone+shock trials proceed, less operant responding is seen during the tone. The
amount of suppression generated by a conditioned-aversive stimulus depends
greatly on the level of deprivation maintaining the operant behavior—a very
hungry rat will show less suppression of food-reinforced lever pressing than a less
hungry rat.
Figure 9. The development of a conditioned-aversive response as indicated by disruption of ongoing operant behavior.
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Conditioning and Behavioral Training in Reptiles
Gregory J. Fleming, Michelle L. Skurski, in Current Therapy in Reptile Medicine
and Surgery, 2014
10. Training
Since the early 1990s, there has been a dramatic increase in the use of operant
conditioning techniques to train exotic animals for husbandry purposes. These
animal training techniques can assist in facilitating day-to-day care, routine
medical procedures, and management of reptiles. The act of training becomes
enrichment for both the animal and the keepers as they interact. Any reptile
brought into clinics, such as dendrobatid frogs, Bearded Dragons, Green Iguanas,
monitor lizards, boas and pythons, and turtles and tortoises, can be trained to
calmly and voluntarily enter a crate instead of being physically restrained for
crating. Reptiles can also be trained to accept various veterinary procedures such
as ultrasounds, nail clipping, blood draws, or even being medicated. Reptiles with
chronic conditions requiring regular visits and or treatments can be trained to
cooperate for many types of procedures. This kind of training allows for treatment
with little to no stress to the animals and client.
To create a well-thought-out behavioral plan for a reptile, many facilities use the
“SPIDER” framework taught in several courses given by the AZA. The SPIDER
framework includes setting goals, planning, implementing, documenting,
evaluating, and readjusting (Table 11-1). More information on this process can be
found at www.animaltraining.org.
The first step (S) in the SPIDER process is setting goals. It is beneficial to start a
training program by determining the overall behavioral goals (i.e., detailing the
specific behaviors to be trained). During this goal-development process, it is
important to include all parties involved with the management of the animals.
Goals should be based on the joint needs of owners, veterinary staff, and the
reptile. For example, if the monitor lizard can shift into a crate for transport to the
veterinarian, the lizard is more easily crated and less distressed when in the crate.
This outcome facilitates a better veterinary evaluation. The goals in this case
would then be to train the monitor lizard to enter a crate voluntarily and be calm
and comfortable in the crate.
The next step (P) is planning. This is where a training plan is created for the
behavior. The training plan is a series of steps for shaping the behavior. The plan
is meant to be a guide or a way for the trainer to think through the process before
beginning to training an animal. If crate training is used as the example, the first
step is to reinforce being comfortable with the crate itself. This process starts with
providing positive reinforcement when the animal merely approaches the crate,
which could occur randomly, and then slowly encouraging the animal to enter the
crate. The reinforcer or reward for learning to tolerate and enter the crate could be
small bits of a highly desirable food that are delivered as soon as the reptile
approaches and/or moves closer to the entry of the crate.
The third step (I) is implementing. The behavior should be trained over a period of
many sessions, and training should advance only when the animal is ready. If
more than one trainer is involved, having clearly laid out plans, assignments, and
timelines helps to facilitate a smooth process. Defining roles and creating clear
avenues of communication among all participants is also important.
Before the training is implemented, a decision should be made regarding how the
training sessions will be documented (D). Videotaping sessions is an easy way to
document and track progress of training. Taking notes, including session ratings
2
3
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11. document and track progress of training. Taking notes, including session ratings
and comments, is another useful way to document and track training outcomes.
The goals of documenting are to create a historical document, track the progress
of the animal, and look for trends in behavior.
The last two steps of the SPIDER process, evaluating (E) and readjusting (R),
require reviewing the documentation and training plan and making any changes
necessary to achieve the behavioral goals. For more information on how to apply
this process, visit Disney’s Animal Programs Web site or
www.animalenrichment.org1 or www.animaltraining.org.
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Training and Behavior Management
Ted Turner, ... Tyler Turner, in Encyclopedia of Marine Mammals (Second Edition),
2009
G Reintroduction Programs
The translocation of wild animals and the release of marine mammals held for
short periods (usually for research or rehabilitation purposes), has provided many
opportunities for behavioral management and in some cases, animal training
during the holding process. If managed correctly, the success rate of these
relatively short-term research projects can be an effective means of gathering
data. However, the release of animals born or housed long-term in zoological
facilities, should be approached carefully, and include specific behavioral plans as
well as health screening and scientific monitoring of released animals to ensure
their well-being and success of the reintroduction.
There have been instances where marine mammal releases have been over-
simplified by extremist and anti-captivity groups. Although emotionalizing their
concept of “freedom,” these groups generally discount the biological need of such
experiments, especially for non-endangered species, while often disregarding the
very real and complex survival obstacles an animal must confront successfully.
Therefore, thorough and unbiased scientific review must be completed before any
such permit can be granted in the United States. Attempts to release animals
without scientific review and permit authorizations are in violation of the US
Marine Mammal Protection Act. Past attempts to do this in the United States has
resulted in the needless suffering and death of animals. In one well-publicized
case in Florida (1996), this violation led to the prosecution and conviction of those
involved (US Department of Commerce, 1999). Unfortunately, not all
governments have laws protecting marine mammals from the naive actions of
some individuals and claims of success have been reported without proper
conditioning, scientific verification, or follow-up, and in most cases it is likely that
these animals succumbed to the challenges of life in the wild. However,
reintroducing captive-born animals is not without success.
A number of captive-born terrestrial mammal species have been released into
historical home ranges with success. Endangered animals such as red wolves
2
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12. historical home ranges with success. Endangered animals such as red wolves
(Canis rufus), golden lion tamarins (Leontopithecus rosalia), and black-footed Ferrets
(Mustela nigripes) are some examples of well-managed and scientifically sound
protocols that are helping in the recovery of wild populations. Due to their
endangered status and the biological necessity to make their genetic material
available to the wild population, the risks of such programs are deemed
acceptable. These animals are carefully managed at reputable facilities, candidate
animals are selected based upon specific criteria, population and environmental
dynamics carefully reviewed, behavioral repertoires (such as predator avoidance
and foraging skills) are strengthened, tracking and follow-up protocols
scrutinized, unbiased scientific review completed, and legal permits obtained
before such an undertaking begins. Research into the release of captive-born
marine mammals, or animals housed long-term, must include an analysis of
behavior, a strict behavioral management plan, and the measurable observation of
behaviors that enhance survivability in the wild.
In addition, in order for this program to fulfill a biological imperative, the
candidate animal must be assimilated into a social group so that breeding and
reproduction completes the conservation objective. If a future opportunity to
collect endangered marine mammals for captive breeding finds strong support,
then using non-endangered marine mammals such as bottlenose dolphins as a
concept model for successful captive breeding and reintroduction of endangered
species is certainly prudent. Animal training and behavior management will
undoubtedly play a role in the future of reintroductions.
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1.
2.
3.
4.
Infrared Thermography in Zoo and Wild Animals
Sabine Hilsberg-Merz, in Zoo and Wild Animal Medicine (Sixth Edition), 2008
METHOD
Infrared thermography makes use of the physical characteristic of bodies or
materials to emit electromagnetic waves, and with the aid of a special detector,
these rays are visible. Therefore, surface temperatures are measured over a greater
distance.
The advantages of IR thermography compared with other imaging techniques
(e.g., ultrasonography, radiography, magnetic resonance imaging, endoscopy) are
as follows:
Is completely noninvasive because no contact with the animal is necessary,
and therefore no animal training, immobilization, or sedation is required.
Offers an ideal, instantaneous first screening method to help the veterinarian
in decision making, monitoring, and determining whether other measures
need to be taken.
Yields real-time visual imaging in gray or false-color coding.
6
13. 4.
5.
6.
7.
8.
Provides surface temperature imaging of a whole animal, or parts of the
animal, as well as easy comparison with herd mates at the same time.
Permits examination of motion and direction (e.g., inflammation, reproductive
evaluation).
Allows easy monitoring of a condition over time (e.g., lameness, inflammation,
pregnancy).
Facilitates documentation and preservation of primary data.
Is portable and uses battery packs and thus is conducive to zoo and wildlife
field conditions.
As with other techniques, however, IR thermography presents specific challenges
in zoo and wildlife medicine that are not encountered as often in human medicine
and classic veterinary medicine. For example, detailed knowledge of the
morphology of many different species is required; no control exists over the
animal under investigation (e.g., movement, position relative to the sun, muddy
or wet surface parts, positioning of animal for best investigation); and no specific
examination room in a veterinary clinic with controlled environmental parameters
(e.g., temperature) is available.
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Hearing in Cetaceans: From Natural History to
Experimental Biology
T. Aran Mooney, ... Brian K. Branstetter, in Advances in Marine Biology, 2012
6.2 Advancements in AEPs
As described above, there are many types of studies which address hearing in
odontocetes. However, a large proportion of them now involve AEP
measurements (Fig. 4.4). AEP is an appealing method because data can be
gathered rapidly with minimal or no animal training investment. A complete
audiogram can be obtained in an untrained animal in less than 20 min, enabling
hearing tests even during situations where time is severely limited (Nachtigall et
al., 2004, 2005). Recording times can be dramatically decreased by simultaneously
recording responses to multiple frequencies (Finneran and Houser, 2007) and
using automated methods of response detection (Finneran et al., 2007a).
One advantage of AEP-related methodology has been to opportunistically
measure the hearing of stranded animals, thus broadening the number of
individuals and species tested (Ridgway and Carder, 2001; André et al., 2007).
Early attempts at recording AEPs from stranded animals were conducted at
rehabilitation facilities and produced mixed results (Ridgway and Carder, 2001).
The animals tested were large and included a pygmy sperm whale (Kogia
breviceps), a grey whale (Eschrichtius robustus) calf, and a neonate sperm whale
(Physeter macrocephalus). The response records were somewhat noisy and full
audiograms were not acquired, perhaps because the large size of animals reduced
signal-to-noise ratios of the AEP (Szymanski et al., 1999; Houser et al., 2007).
14. signal-to-noise ratios of the AEP (Szymanski et al., 1999; Houser et al., 2007).
However, the study produced novel records, showed the efficacy of the technique,
and laid substantial groundwork for future research.
Improvements in methods and equipment between 2001 and 2005 led to
successful AEP recordings from a stranded neonate Risso's dolphin (G. griseus),
producing a full audiogram and an estimate of temporal resolution (Nachtigall et
al., 2005; Mooney et al., 2006). This animal had sensitive and broadband hearing,
discounting suggestions that there may have been permanent auditory damage
due to a potential noise-induced stranding event (Fig. 4.2). However, “profound”
hearing loss has been found in other stranded odontocetes including pilot whales,
bottlenose dolphins, and rough-toothed dolphins (Mann et al., 2010). The authors
speculated that the causes of hearing loss vary and could include congenital
defects, chemical contaminants, and normal presbycusis.
A major advance in AEP technology is the development of portable systems which
can be applied in field situations (Ridgway and Carder, 2001; Delory et al., 2007;
Taylor et al., 2007; Finneran, 2009). The AEP test on the stranded Risso's dolphin
involved flying a desktop computer from Hawaii to Portugal and was conducted
over 5 days. Since these tests, AEP systems have been reduced in size to laptop-
based systems, and audiograms are collected much more rapidly. To date, AEP
recordings in the field have been made with catch-and-release procedures on
white-beaked dolphins (Nachtigall et al., 2008) and beach-stranded delphinids
(Moore et al., 2011a), showing promising results despite logistical challenges.
Recently, novel AEP experiments have combined AEPs with morphological studies
to address form-and-function questions. Montie et al. (2011) examined the
hearing of two stranded pygmy killer whales. They moved electrode locations and
created 3D reconstructions of the brain from CT images (Fig. 4.1), while
concurrently measuring the amplitude of the ABR waves. Their results provided
evidence that the neuroanatomical sources of ABR waves I, IV, and VI were the
auditory nerve, inferior colliculus, and the medial geniculate body, respectively.
Other studies have combined AEP with CT and MRI to examine the hearing
pathways of odontocetes (Mooney et al., 2011). Using a jawphone transducer to
present stimuli, Mooney et al. showed that AEP responses can be generated from
multiple locations on the head and body. Jawphones placed at the mandibular fat
bodies (identified from MRI and CT) tended to produce higher amplitude AEPs,
lower thresholds, and faster responses, although this was somewhat frequency
dependent (Fig. 4.3C). Thus, the head receives and guides sound in multiple ways,
confirming earlier findings by Møhl et al. (1999) which mapped the areas of best
sensitivity in the bottlenose dolphin head using AEPs and jawphone-presented
stimuli. These areas of best sensitivity differ slightly between the few species
examined (bottlenose dolphin, beluga, finless porpoise; Fig. 4.3C and D),
suggesting that the diverse morphologies found among odontocete species affect
how each of them receives sound (Mooney et al., 2008).
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