Environmental Enrichment for Captive Wildlife
Through the Simulation of Gum-feeding
Kathy Kelly
Department of Pathology, National Zoological Park
Washington, DC
The author is an animal records technician.
(Animal Welfare Information Center Newsletter
4(3):1-2, 5-10. July-September 1993)
Exudativory, or the use of plant gums,
saps, resins and occasionally latex as a food source in an
animal's diet, has been increasingly documented by field studies
performed during the past 40 years (Nash, 1986) (Figure 1).
Animals known to eat plant exudates are found among the
prosimians, marmosets, tamarins, squirrels, marsupials, old world
primates, and birds (Fleagle, 1988; MacDonald, 1984; Rylands,
1984; Post, 1983; Smith, 1982; Wrangham, 1981; Bearder, et al.,
1980; Charles-Dominique, 1977; Hausfater, et al. 1976; Izawa,
1975; Kilham, 1975; Tate, 1973; Radman, 1969). A literature
search done in 1990 resulted in documentation of exudate-feeding
in 45 species of animals (see table 1). However, the degree of
dependency of animals on this food source is variable. For
example, plant exudates are the major component of the natural
diet of the Pygmy marmoset (Cebuella pygmaea) (Fleagle, 1988;
Hershkovitz, 1977; Nash, 1986), Fork-marked lemur (Phaner
furcifer) and other prosimians (Charles-Dominique, 1980; Oxnard,
et al., 1990). These animals are considered primary gum-feeders
based on their morphological, anatomical, physiological, and
behavioral adaptations (Fleagle, 1988). Secondary gum-feeders
are species that feed on plant exudates as a response to
decreased fruit and flower availability, or climatic changes such
as wet or dry seasons. Another factor that influences the degree
to which animals rely on plant exudates is whether these exudate
sources are water stressed, which results in low exudate
production (Garber, 1984a; Nash, 1986; Lacher, et al., 1984).
Exudate use also includes animals that ingest them
opportunistically when they are found and animals that ingest
exudates coincidentally when they eat, or perforate, bark down to
the cambium layer during insect- or browse-feeding.

Fig. 1. Black-tailed marmoset licking gum that is dripping down
a tree limb. (Photo by Lee Miller)
Between March 1988 and September 1990, I was a member of a
behavioral research project at the Small Mammal House, National
Zoological Park (NZP), Washington, D.C. Our objective was to
apply the information, documented by field research about
gummivory, to the captive management of our Pygmy marmosets,
Black-tailed marmosets (Callithrix argentata melanura), and
Geoffrey's marmosets (C. geoffroyi). We also offered gum arabic
to other animals in the collection such as Lion tamarins
(Leontopithecus spp.), Goeldi's monkey (Callimico goeldi), Low's
squirrel (Sundasciurus lowi), Sugar gliders (Petarus breviceps),
Prevost's squirrels (Callisciurus prevosti), and Cuban hutias
(Capromys pilorides). All of these animals, except for the Sugar
gliders, were on exhibit during our study. Since our experience
is with gum-feeding, I will use the term gummivory, or
gum-feeding, to be synonymous with the term exudativory. The
following information presents the results of our research
experiences, gained knowledge, and the unexpected side benefits
we obtained from simulating gummivory in captivity.
BIOLOGY OF GUMMIVORY
Anatomical Adaptations
Generally, animals that use plant exudates are small bodied,
have a high metabolism, and are incapable of storing large
amounts of fat. Primary gum-eaters have most, or all, of the
following traits: small body size, clawed digits (for vertical
clinging at gum sources), long procumbent or semi-procumbent
incisors complimented by short lower canines (providing a level
gouging/scrapping surface), loss of enamel on the lingual side of
the lower incisors complimented by honing upper incisors
(providing a sharpening effect that permits gouging or scraping
abilities), a V-shaped configuration of the mandibular arch, a
long tongue (to reach gums within the plant bark), and an
enlarged cecum (to allow for fermentation of the gums) (Fleagle,
1988; Coimbra-Filho, et al., 1978; Rosenberger, 1978;
Hershkovitz, 1977). Nutritional Factors Associated With
Gum-feeding
Gums are a high-energy food source composed mainly of water,
complex polysaccharides, calcium, and trace minerals (iron,
aluminum, silicon, potassium, magnesium, and sodium) (Nash,
1986). Calcium is important to all animals, especially female
callitrichids (tamarins and marmosets) which commonly give birth
to twins twice a year. It is during the lactation period that the
females are usually impregnated by the male. Therefore, they are
developing fetuses while nursing their fast-growing infants,
resulting in an increased calcium demand. The
calcium-to-phosphorus ratio is high in gums which offsets its
ratio in insects, which is low. Because all known wild gummivores
also include insects in their diet, combining the two, in
captivity, may approach a desired nutritional balance and is
recommended to avoid the possibility of nitrogen loss and the
loss of protein from the body (Nash, 1986; Garber, 1984a;
Sussman, et al., 1984; Coimbra-Filho, et al., 1978; Moynihan
1976). Ecological Factors Associated With Gum-feeding
Gums from woody plants are reportedly available year round
and are constant in their location (Bouchardet de Fonseca, et
al., 1984; Ramirez, et al., 1978). This aspect allows marmosets,
which are capable of eliciting gum flow, to be non-seasonal
breeders and to subsist in small home ranges. Some tamarin
species have been noted by field researchers to travel in
association with marmosets and parasitize their gum sites.
It has been suggested that gums are an integral link in the
food chain of gummivores (Soini, 1982). Some insects (moths,
butterflies, ants) are attracted to the gum sites, while other
insects simply get stuck in the sticky substance. These insects
are often preyed upon by lizards and frogs. Gum-eaters prey on
all of these animals, which reduces the amount of time and energy
exerted in procuring animal protein in their diet. Gum-feeding
typically occurs at the lower levels of the forest canopy (about
3 meters from the ground) where fruits and flowers are usually
absent (Ramirez, 1978; Moynihan, 1976). The ability to subsist
at this level lessens competition with other forest animals,
which are predominantly frugivores or foliavores (Fleagle, 1988).
Gum-feeding is more than just another feeding strategy. It
is the merging of the nutritional, ecological, behavioral, and
evolutionary traits which allows species that are capable of
using this resource to coexist in the wild.
Captive marmosets will instinctively gouge holes in exhibit
furniture, despite the fact that they do not receive a food
reward. Offspring of captive-born parents also gouge wood
throughout their lives. The instinct to retain this behavior is
so strong that infant marmosets in captivity demonstrate
substrate "mouthing" behavior the prerequisite to gouging
behavior as early as 3 weeks of age in Pygmy marmosets and at 5
weeks in Black-tailed marmosets (person. observ.).
NZP Research
In 1988, we began our research project by offering
gum-feeders based upon McGrew's suggested artificial gum-feeder
for marmosets (McGrew, 1986). These gum-feeders consisted of
eight dowel segments with four drilled-out circular cavities (gum
reservoirs) that were stacked onto a threaded, metal rod,
secured with wing nuts, and wired onto the existing cage
furniture. The marmosets not only accepted and fed from these
gum-feeders, but became possessive of them when replacement was
needed. Although the artificial feeders functioned, there were
technical drawbacks. They required shop fabrication and needed
to be soaked in water weekly because the dowel was very hard and
dry. They were also unnatural in appearance, time-consuming to
fill (filling with gum, feeder assembly, and installation of four
feeders took approximately 2.5 hours per day), and they required
weekly replacement. We abandoned this type of gum-feeder after 2
months and substituted natural branches for the dowel (gum
reservoirs were simply holes drilled into the branch). Not only
was this type of feeder accepted but it served as additional cage
furniture that functioned as pathways and perches for the
animals. This type of feeder provides the animals with a
naturally textured substrate, is readily obtained, requires no
assembly, and if hard wood is used, needs less frequent
replacement (our hard wood feeders have been in place for 5
years). Filling these feeders can be accomplished in 5 to 10
minutes (Peterson, et al., 1988).
The following year we expanded the natural-branch idea to
the use of floor-to-ceiling-length tree limbs, oriented in
vertical and diagonal positions (Figure 2). This additional
length of the feeders allowed us to provide eight feeding sites
(gum reservoirs) in three locations on each feeder near the top,
in the middle, and near the bottom.

Fig. 2. Black-tailed marmoset waiting for the keeper to fill holes
on tree limb with gum arabic. (Photo by Lee Miller)
Using checksheets and 45 trained volunteer behavior watchers,
we observed for signs of differences in vertical versus diagonal
preference, hard wood versus soft wood feeders, and preference
of depth and dimension of drilled holes.
We also experimented with presenting the gum arabic/water
solution in a rodent water bottle with a sipper tube (do not use
tubes with a ball-bearing). We offered this modified gum-feeder
in three ways: 1) inserted through one of our feeders, with the
stem protruding; 2) hidden inside a piece of cork bark, with the
stem protruding; and 3) affixed directly onto the wiring of a
holding cage. The third method could be used for an animal that
has been separated for health reasons or because of preshipment.
It could also be used for enrichment in a laboratory situation
where individual housing may be necessary for compliance with
research protocol. Our objective was to make the gum available
ad libitum, in hopes that the marmosets would teach us how often
they use it.
Results of Providing Natural Wood Feeders to Marmosets
Data analysis (850 observation hours) revealed that the
Pygmy marmosets (1.1.2, 1.1, 1.1) [Ed. Note: the first digit
indicates the number of male animals, the second digit indicates
the number of females, and the third, if present, indicates that
the sex is unknown] used all gum sites on all feeders provided to
them regardless of position, type of wood, or depth and dimension
of drilled gum holes. The Black-tailed marmosets (1.1.2)
demonstrated a preference for gum sites that were mid to upper
level on vertical feeders. The Geoffrey's marmosets (1.1) used
all feeders and feeding sites provided to them regardless of
orientation, type of wood, or hole dimension.
Marmoset Behavioral Responses
The Pygmy marmosets shared feeders and even feeding sites
without conflict. Over time, the Black-tailed marmosets became
territorial over the feeders and a pronounced hierarchy system
emerged within the family. The male Geoffrey's marmoset hung
back and allowed the female first access to the gum sites. This
behavior has been documented in some species of wild prosimians
(Charles-Dominique, 1977).
One observation consistent among our marmoset species was
that the use of soft wood feeders stimulated more scent marking
and gouging behavior which resulted in marked damage to the
feeders as well as to the existing cage furniture.
By providing gum feeders in vertical and diagonal
orientations, we had unintentionally provided the marmosets with
the opportunity to employ their widely recognized abilities as
vertical clingers and leapers. When eating gum from the feeders,
the marmosets often fed from an upside-down, clinging position a
posture not seen at other times. Gouging on feeders and eating
gum from them required the marmosets to use muscles that are not
used when locomoting quadrupedally on horizontal vines and
branches the typical exhibit furnishings provided in captive
settings (Newman, et al., 1990; Garber, 1984b).
Benefits Resulting From Providing Gum-feeders to the Marmosets
1.) Increased animal activity level: The marmosets immediately
come down to the feeders while the keeper is injecting the gum
into the drilled holes via a syringe. They would also return to
the feeders, at various times in the day, to scrape off and eat
the dried gum overflow that adhered to the feeders' bark. This
replicates the feeding pattern of their counterparts in the wild
(Fleagle, 1988).
2.) Increased animal visibility: The Pygmy marmosets in all
three exhibits will come within 2-3 inches of a caretaker while
the gum is injected into the drilled holes, while the four
Black-tailed marmosets and both Geoffrey's marmosets will eagerly
eat the gum arabic directly from a syringe (Newman, et al.,
1990). This simplifies the task of performing daily head counts
of these animals.
3.) Close proximity to exhibit animals allows for health
observations: Since the marmosets either eat the gum directly
from a hand-held syringe or come within inches of the caretaker,
we have been able to detect early signs of pregnancy and detect
and monitor minor injuries (cuts, scratches) and dental problems
that do not require immediate treatment. We used the gum-filled
syringe to encourage our young Black-tailed marmosets to stretch
out for sex confirmation. We also used the gum-filled syringe to
administer antibiotics to our adult, female Black-tailed marmoset
who was diagnosed with a flagyl parasite infection (Figure 3).
She refused her medication, even when hidden in her favorite food
items, but accepted it when it was mixed into the gum arabic
solution (Kelly, et al., 1989) and offered to her in the familiar
syringe. Feeding gum arabic has proven to be a useful tool for
animal caretakers to keep abreast of their animals' general
health. The aspects of close proximity to the animals with its
resulting observational benefits can be performed without
physical manipulation or stress to the animals (Newman, et al.,
1990).

Fig. 3. A female Black-tailed marmoset is being given
an antibiotic gum arabic solution without being removed from
her family, who are watching the procedure. (Photo by Lee Miller)
4.) Visitor experience enhancement: Throughout our study, all of
the gum-feeders were positioned near the public viewing side of
each exhibit. The public responded to our gum-feeding project
with interest and enthusiasm, and countless questions about the
animals. It is exciting for zoo visitors to see a captive animal
active and interacting with its environment. Other visitors
appreciated the opportunity to get close-up photographs of the
animals engaging in a natural behavior.
Gum-feeding Results in Lion Tamarins, Goeldi's Monkey,
Marsupials, and Rodents
In the summer of 1989, we offered floor-to-ceiling-length wood
feeders to a mixed bachelor group of Golden Lion tamarins
(Leontopithecus rosalia) and Golden-headed
Lion tamarins (L. r. chrysomelas) that were exhibited outdoors.
The feeders became a source of interest and stimulation for the
tamarins. Use of these feeders again illustrated
species-specific behavior responses.
The Golden-headed Lion tamarins stripped off the bark over
the gum sites to gain access to the gum that had been injected
into the holes, whereas the Golden Lion tamarins were observed
probing the gum-filled holes and then eating the gum from their
fingers. The Golden-headed Lion tamarins also returned to the
feeders later and stripped off additional bark from over the gum
holes to gain access to any gum residue. At no time did we
observe conflicts between the tamarin species over the gum
(Kelly, et al., 1989).
When we injected the gum into a wide, circular depression on
one of the feeders, both species of tamarins were observed using
their cupped hand to scoop up the gum and eat it. This is the
same method used in the wild to obtain rainwater from the cups of
bromelids.
Our trial with Goeldi's monkey was limited to
an individual female that was housed with our Black-tailed
marmosets during our initial study in 1988. She did taste, and,
on occasion, eat some of the gum, but she did not demonstrate
strong attraction to it as did the marmosets and tamarins. We
believe she was simply mimicking the Black-tail's responses to
the gum. We have since learned that wild Goeldi's are not known
to eat gums from woody plants, but do eat a sticky gum substance
found on seed pods.
We were disappointed by our results with the Low's squirrel
and the Sugar gliders. We offered a natural wood gum-feeder to a
Low's squirrel and although the gum always disappeared, we never
actually saw the squirrel using the feeder. It has been our
experience that Low's squirrels are typically shy and secretive.
The Sugar gliders (family group of five), however, stripped off
large areas of bark from the feeders but ignored the gum sites.
Further literature searches suggest they were probably searching
for insects under the bark. Providing natural branches to Sugar
gliders, even without gum, provides a stimulus to them which
increases their activity level. Although both of these species
are documented gum-eaters (MacDonald, 1984; Smith, 1982), the
types of gum utilized by animals vary among species because of
differences in geographic ranges and environmental factors. We
used acacia gum extract in our trials which may not be the type
of gum eaten by Low's squirrels and Sugar gliders.
One pair of Prevost squirrels in our study ate gum from the
feeders as well as directly from the syringe. We do not place
emphasis on their acceptance of the gum-feeders since this
particular pair of squirrels were hand-raised and seek human
interaction. The other pair of Prevost squirrels (parent-raised)
in our study showed little-to-no interest in the gum or the
feeders.
The responses of the Cuban hutias were surprising. Our four
hutias were recently acquired, wild-caught animals. We do not
have any documentation of gum-feeding in this species, but based
on our theory that wood-eating species ingest gums, we offered
the gum to them. The hutias, especially the females, ate the gum
directly from the syringe but at no other time would they allow
us close proximity to them. We have noticed that the females in
all the trials, especially when pregnant, are usually the first
animals to come for the gum.
Although we did not intentionally include Acouchis
(Myopracta pratti) in our gum-acceptance trials, we
learned that some acouchis will eat gum. The pair of acouchis housed
in our mixed Geoffrey's and Pygmy marmoset exhibit began eating
any gum that accidently landed on the floor. One of these acouchis
would eat the gum directly from the syringe and would stand up on its
hind legs, waiting to be fed the gum.
All of the above animals, except for the Low's squirrel and
the Sugar gliders, would come surprisingly close to keepers
feeding gum or they would accept hand-feeding via the syringe.
This provided us with the same side benefits previously listed
for the marmosets.
We also placed natural wood gum-feeders in some of our
indoor mixed-species exhibits. The feeders became a source of
interest and activity to the gum-eating species as well as to the
non-gum-eating species. Curiosity was stimulated and intra- and
inter-species activities resulted, thus creating a more interesting
environment for the animals.
DISCUSSION
Our research project has shown that natural branch
gum-feeders can be used to simulate gummivory in captivity for a
variety of animals. Use of natural branches/tree limbs is an
inexpensive, readily available, and low maintenance method of
providing environmental enrichment in an artificial setting.
Simulating gummivory in captivity can be accomplished with
minimal time investment and energy demand on the part of animal
caretakers.
Modern zoos are attempting to exhibit animals
in naturalistic settings. Ideally, the goal should be to exhibit
animals in a naturalistic setting that stimulates behavioral
interactions between the animals and their environment. We feel
our natural branch gum-feeders help accomplish this goal.
When captive environments lack stimulus, animals are
deprived of the opportunity to engage in some of their natural
behaviors, which may be replaced by atypical behaviors
characterized by excessive inactivity, grooming, and/or sleeping
(Schoenfield, 1989). Duplicating natural habitats as much as
possible in captivity encourages animals to use their innate
behaviors (Hancocks, 1980).
Having the opportunity to demonstrate their natural
gum-foraging behavior stimulated some of the animal's other
natural behaviors, i.e., compatible sharing of feeders and
feeding sites (Pygmy marmosets), methods of food acquisition
(marmosets and tamarins, Golden Lion tamarins and Golden-headed
Lion tamarins), and territoriality and dominance (Black-tailed
marmosets). Providing feeders allowed our captive animals to
emulate, to some extent, the behaviors of their wild
counterparts. Gum-feeders also served as a source of interest
and entertainment for young marmosets (Shepardson 1989).
Providing natural wood gum-feeders to NZP animals resulted
in: increased animal activity, increased animal visibility for
record- keeping and general health observations, sexing of young
animals, early detection of pregnancy, non-stressful medicating
of sick animals, and detection and monitoring of minor injuries
or dental disorders that do not require immediate medical
attention (Figure 4).

Fig. 4. Hand-feeding gum via a syringe provides keepers with
the opportunity to closely examine animals and dispense medication
in a non-stressful manner. (Photo by Lee Miller)
Full-length feeders presented in vertical and diagonal
orientations promote and compliment the locomotor abilities of
known vertical clingers and leapers. Using the gum-feeders
required the animals to use muscles that are not exercised during
quadrupedal locomotion (Garber, 1984b). They provided the
animals with the opportunity to assume postures not demonstrated
prior to the introduction of the feeders, and they increased the
amount of available, usable cage space. Simulating gummivory
improved the condition of our animals and enhanced the interest
and experience of our zoo visitors.
Providing interactive ways for captive animals to gain some
control of their environment results in an aesthetic,
interesting, potentially educational, and functionally useful
exhibit. Attempts at environmental enrichment, such as simulating
gummivory, could simultaneously be used to help visually
demonstrate the evolutionary niche of various species while
illustrating the need to conserve entire ecosystems as well as
individual species.
This paper is dedicated to the memory of Yoda, a 4-year-old
Black-tailed marmoset who was the catalyst for this research project.
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Sussman, R.W. and Kinzey, W.G. (1984). "The Ecological Role of
the Callitrichidae: A Review," American Journal of Physical
Anthropology 64:419-449.
Tate Jr., J. (1973). "Methods and Annual Sequence of Foraging by
the Sapsucker," The Auk 90(4):840-856.
Wrangham, R.W. and Waterman, P.G. (1981). "Feeding Behavior of
Vervet Monkeys on Acacia tortilis and
Acacia xanthophloea: with Special Reference to Reproductive
Strategies and Tannin Production," Journal of Animal Ecology 50:715-731.
Table 1 - DOCUMENTED GUM AND SAP FEEDERS
Prosimians:
Euticus elengatulus - Needle-clawed Galago
Galago alleni - Allen's bushbaby
G. senegalensis - Senegal bushbaby
G. crassicaudatus - Thick-tailed bushbaby
Galagoides demidovii - Dwarf galago
Perodicticus potto - Potto
Lemur catta - Ring-tailed lemur
L. fulvus - Brown lemur
Microcebus murinus - Mouse lemur
Mirza coquereli - Coquerel's dwarf lemur
Phaner furcifer - Fork-marked lemur
Marmosets:
Callithrix argentata melanura - Black-tailed marmoset
C. a. aurita - Buffy tufted-ear marmoset
C. flaviceps - Buffy-headed marmoset
C. geoffroyi - Geoffrey's marmoset
C. humeralifer - Tassel-ear marmoset
C. jacchus - Common marmoset
C. j. pencillata - Black tufted ear marmoset
Cebuella pygmaea - Pygmy marmoset
Tamarins:
Saguinus fuscicollis - Saddle-back tamarin
S. imperator - Emperor tamarin
S. labiatus - Red-bellied tamarin
S. midas - Golden-handed tamarin
S. nigricollis - Black-mantle tamarin
S. oedipus - Cotton-topped tamarin
S. o. geoffroyi - Geoffrey's tamarin
Squirrels:
Hylopetes spadiceus - Red-cheeked squirrel
Microsceurus - Pygmy squirrel
Sciurus vulgaris - Red squirrel
Sundasciurus lowii - Low's squirrel
S. tenuis - Slender squirrel
Old World Monkeys:
Cercopithecus aethiops - Vervet monkey
Erythrocebus patas - Patas monkey
Papio c. cynocephalus - Yellow baboon
Macaca sylvanus - Barbary macaque
Pan troglodytes - Chimpanzee
Marsupials:
Gymnobelideus leadbeateri - Leadbeater's possum
Petaurus australis - Yellow bellied glider
P. breviceps - Sugar glider
Other Mammals:
Ursus americanus - Black bear
Loxodonta africana - African elephant (in Amboseli)
Birds:
Artideotis kori - Kori bustard
Coua cristata - Crested coua (Madagascar)
Sphyrapicus varius - Yellow-bellied sapsucker
The Research Resources Facility at the Geogetown
University Medical Center co- sponsored the Annual Otolaryngic
Cherry Blossom Conference with the American Academy of
Otolaryngology Head and Neck Surgery on March 22, 1992. The
purpose of the workshop was to give physicians in-depth training
on the use of lasers in otolaryngology. Lasers have been used in
the treatment of otolaryngological head and neck lesions since
the early 1970's. The course provided the basics of laser
physics, instrumentation and safety, and the future application
of lasers in otolaryngology. Surgeons were given the opportunity
to acquire hands-on clinical experience with soft tissue
application of lasers in otolaryngology-head and neck surgery,
while also being introduced to laser use in the international
otolaryngology-head and neck community. The course provided an
alternative to the use of live animals, which proved to be very
beneficial. In place of live animals, isolated tissues obtained
ex vivo, chicken, beef liver, eggs and inanimate objects were
used to reduce both animal use and cost for the course. After
speaking to several physicians after the course, it was found
that many of them preferred using isolated tissues and/or produce
rather than live animals.
The Animal Welfare Act (AWA) states that a principal
investigator must consider alternative methods to a procedure
that may cause momentary or slight pain or distress to an animal
(AWA - 2.31 8.D). An investigator should use sources such as the
U.S. Department of Agriculture's National Agricultural Library
(NAL) and the Department of Health and Human Services National
Library of Medicine (NLM) to obtain information on alternatives
to animal use in research and in educational training seminars.
The Animal Welfare Information Center (AWIC) of NAL can provide
written narratives to investigators that indicate possible
alternative models available for use in proposed procedures (AWA
- 2.32 C5). Assurance that alternatives have been considered
must be presented in the institution's annual report and when the
institution is inspected by the USDA (AWA -2.36 B.1).
Alternative models for animal research have become a major
consideration in the development of new protocols and in
continuing educational training seminars. However, implementing
alternative technologies and methods in research and in
educational workshops does not necessarily mean banishing the
animal model from the research environment. In current research
and training seminars, certain methods are available that allow
for the continued, but modified use of animals through the use of
inanimate objects and non-living animal systems. The
alternatives used in the Otolaryngology Head and Neck Surgery
training seminar consisted of specimens isolated ex vivo from
human and animal cadavers, inanimate models, and chicken eggs.
The tissues isolated from the human cadavers consisted of
tympanic membranes, inner ears, and cochleas. Tongues,
epiglotti, and tracheas were harvested from the animal cadavers.
The inanimate models provided a basis for the surgeons to
understand and become familiar with different available laser
types. These models consisted of moist and dry tongue
depressors, wet and dry gauze squares, plexiglass squares, and
metal spatulas.
Cost is always a major consideration when developing a
protocol or organizing an educational training seminar. Although
cost is not the main deciding factor, an investigator who uses an
alternative model may reduce overall research costs. In the
Otolaryngology Head and Neck Surgery training course, the cost of
using the alternative models was much less than for the
conventional animal model. By using the cadavers, inanimate
models, and the produce (Figure 1), there was no housing or
animal care fees incurred as there would have been with the
conventional animal model. The only pre-operative preparation
required was removing the tissues from the cadavers and arranging
them in their appropriate apparatus, buying the produce from a
grocery store, and arranging the various inanimate objects for
easy access by the participants. In contrast, conventional
animal models require pre-operative set-up that is much more
involved and requires technical skill and ability in animal
restraint, sedation, and patient monitoring during the training
seminar.

Fig. 1. An example of isolated tissues and products
used as models.
PROCEDURES
The training course familiarized surgeons with three types
of lasers: the KTP (Potassium Titanyl Phosphate) laser; the
Nd:Yag (Neodymium doped Yttrium Aluminum Garnet crystal) laser;
and the CO2 (Carbon Dioxide) laser. The differences between the
lasers are the wavelengths of light emitted. The KTP laser emits
a green visible beam at 532 nm; the Nd:Yag laser emits an
invisible infrared beam at 1064 nm; and the CO2 laser emits an
invisible infrared beam at 10,600 nm.
Laser applications were applied to moist and dry tongue
depressors and to wet and dry gauze squares. The results obtained
from these exercises indicated that the hydration of the target
site affected the laser þburnþ to the target area; too much
water reflected the laser beam away from the target site.
Dampened sites achieved similar þburnsþ as the dry sites but
required less power. The plexiglass square was used to
demonstrate the depth of damage from different power settings
from each of the different lasers. The metal spatula was used to
demonstrate the ability of the laser beam to be reflected 100
percent and have the same effect as a direct application of the
laser beam to a target site. The hard-boiled chicken eggs were
used to examine the laser application effects on a light-colored
tissue. This demonstration indicated that there is no absorption
of color from the laser beam by the white of the egg. Therefore,
in order to demonstrate an effect from the laser, a higher power
setting was needed. Tissue color effects were also examined using
animal tissues obtained ex vivo. White chicken meat simulated
effects on light-colored tissue, while red beef liver simulated
colored tissue effects. The red liver absorbed more of the
emitted light than the white meat which caused a more significant
"burn." Also, the water content in chicken meat is less than
that of the liver which will cause the applications of the laser
to be less pronounced. We also used the skin of the chicken to
provide a sense of various laser applications to epithelium.
Human and animal cadaver tissues were placed in holders in
order for the surgeons to access various target sites. Once the
trachea, epiglottis, and tongue systems were in place, the
surgeons used the lasers to perform epiglottectomies, excision of
an endolaryngeal mucosal lesion, cordectomy, and arytenoidectomy
(Figure 2). Surgeons specializing in otology used human cadaver
tissues to practice aural surgical techniques unique to their
field.

Fig. 2. A surgeon perfoming an epiglottectomy.
The seminar participants were required to evaluate the
workshop in a variety of areas. The participants, overall, felt
that the laboratory materials were good to excellent. The
surgeons also felt that the seminar will alter their practice
performance and that the information gathered will help them in
future otolaryngological surgical procedures.
The overall response to the workshop was positive, and the
participants felt that the information obtained was beneficial
and informative. The use of the alternative models satisfied the
3 R's of animal research: Refinement, Reduction, and Replacement.
By using alternative methods, the number of animal lives and the
cost of the surgical training course were greatly reduced.
References
The Animal Welfare Act.
AAO-HNS Bulletin: CME Update Vol. 11, No.4: 7 and 12, April,
1992.
Personal Communication with B. Paulette of AAO-HNS, May, 1992.
Russell, W.M.S. and Burch, R.L. 1959. Principles of Humane
Experimental Technique. C.C. Thomas, Springfield, IL.
The Animal Welfare Information Center
U.S. Department of Agriculture
Agricultural Research Service
National Agricultural Library
10301 Baltimore Ave.
Beltsville, MD 20705-2351
Phone: (301) 504-6212
FAX: (301) 504-7125
Contact us: http://www.nal.usda.gov/awic/contact.php