Biomedical Engineering Reference
In-Depth Information
Sensory Enrichment
All primates in the wild are exposed to a variety of sensory
stimuli, including visual, auditory, tactile, gustatory, and
olfactory information. The diversity of such stimuli is often
dramatically reduced in laboratory conditions. Sensory
enrichment is a way to provide animals with opportunities
to experience naturalistic stimulation of all five senses. As
with most other types of enrichment, it is important to take
the species' capabilities into account when providing
sensory enrichment; olfactory stimuli are far more impor-
tant to certain NHP species than they are to others.
Auditory enrichment often consists of music or natural
habitat sounds (e.g. “jungle sounds”). The provision of
auditory stimuli can be considered as enrichment, but may
also be used to mask other, assumedly stressful sounds
(carts going down the hall, animal handling and/or cage
cleaning procedures, etc.). Human studies have found that
certain kinds of music can produce a calming effect on
people (
Wells, 2009
). However, the results in NHP studies
are less clear. Certain types of music have been found to
reduce aggression in gorillas (
Wells, 2009
) and chimpan-
zees (
Howell et al., 2003
), yet when given a choice,
chimpanzees, tamarins, and marmosets chose silence over
“music” (
Richardson et al., 2006
). NHPs may prefer
naturalistic sounds to human music; tamarins exposed to
music based on species-specific affiliative vocalizations
responded with calm behavior (
Snowdon and Teie, 2010
).
Visual enrichment can take a variety of forms,
including videos, brightly colored mobiles, computer
screen savers and similar applications, or even something
as simple as a window. Chimpanzees and several monkey
species will spend time watching videos (
Platt and Novak,
1997; Bloomsmith and Lambeth, 2000
), with individually
housed primates spending more time “actively” watching
than is the case with socially housed animals (
Bloom-
smith and Lambeth, 2000
). Although NHPs will watch
videos, the presentation of uncontrollable video stimuli
has not been shown to have a dramatic effect on either
promoting species-typical behavior or reducing abnormal
behavior (
Platt and Novak, 1997; Bloomsmith and Lam-
beth, 2000
).
Olfactory enrichment, such as candles, scented oils, and
similar items, are infrequently provided to Old World
primates and great apes, since these species are not
particularly sensitive to olfactory stimuli. New World
Monkeys and prosimians, on the other hand, are quite
sensitive to olfactory cues, and species-appropriate olfac-
tory enrichment has been utilized with some of these
species (
Andrews and Iliff, 2005; Ablard and Nekaris,
2008
). For “scent marking” species, this may include the
leaving of dirty (i.e. scent marked) materials in otherwise
clean enclosures. It should be noted that some personnel are
adversely affected by particular fragrances.
Food-related Enrichment
Most nonhuman primates spend much of their day in food-
related activities, including foraging for, acquiring, pro-
cessing, and eating their food. This time is greatly reduced
in a laboratory setting, where food is typically provided
only once or twice a day. Food and foraging enrichment are
ways to provide laboratory NHPs with opportunities to
increase the amount of time they spend searching for,
processing, and eating their diet, and is one of the most
commonly utilized forms of enrichment (
Baker et al.,
2007
).
Food-related enrichment encompasses a wide variety of
enhancements. Ideally, it should encourage foraging and
increase the amount of time primates spend in the search
for food and its acquisition, processing, and/or consump-
tion. Food-related enrichment appears to be less susceptible
to the effects of habituation than are many other types of
enrichment. Examples of ways to provide opportunities to
increase time spent in species-appropriate, food-related
behaviors include scattering food on substrates, hiding
food, and providing treats frozen in ice. This kind of
enrichment has been found to reduce aggression in a variety
of species, including macaques, tamarins, squirrel
monkeys, lemurs, marmosets, and chimpanzees (
Baker,
1997; Honess and Marin, 2006; Maloney et al., 2006
).
Another commonly used feeding enhancement strategy is
to put food items in specially designed foraging devices,
such as foraging boards or puzzle feeders, which require
NHPs to work to obtain the food (
Crockett et al., 2001;
Honess and Marin, 2006
). These foraging devices have
been found to decrease the occurrence of some undesirable
behaviors, including stereotypies and overgrooming
(
Bayne, 1991; Pyle et al., 2002
), when kept on the cages
continuously. However, these beneficial effects tend to
dissipate when the device is empty or removed from the
cage (
Lutz and Novak, 2005
). Adding a small toy to
a feeding device can increase the amount of time that they
are utilized (
Rawlins et al., 2004
).
There are relatively few problems associated with the
provision of feeding and foraging enrichment. Obviously,
treats and/or high calorie food items should be provided in
moderation to prevent the development of nutritional
imbalances or obesity as a function of enrichment. Indi-
vidual primates may have food allergies or bad reactions to
specific items (
National Research Council, 2011
), although
that is infrequent. Some foods may be incompatible with
research protocols. For example, foods with phytoestrogens
might be contraindicated for animals participating in
reproductive studies. Foraging devices may increase
aggression if provided in limited numbers to social groups
of animals (
Honess and Marin, 2006
). On the other hand,
devices may be monopolized by dominant individuals as
they demonstrate their dominance status, and this reduces
