Yawning is a widely recognized behavior in
mammalian species. One would expect that
elephants yawn, although to our knowledge, no
one has reported observations of yawning in any
species of elephant. After confirming a
behavioral pattern matching the criteria of
yawning in two Asian elephants (Elephas maximus)
in a zoological setting, this study was pursued
with nine captive African elephants (Loxodonta
africana) at a private reserve in the Western
Cape, South Africa, the Knysna Elephant
Park.
Observations were made in
June&endash;September and in December. In the
daytime, handlers managed seven of the elephants
for guided interactions with visitors. At night,
all elephants were maintained in a large
enclosure with six having limited outdoor
access. With infrared illumination, the
elephants were continuously recorded by video
cameras. During the nights, the elephants
typically had 1&endash;3 recumbent
sleeping/resting bouts, each lasting 1-2 h.
Yawning was a regular occurrence upon
arousal from a recumbency, especially in the
final recumbency of the night. Yawning was
significantly more frequent in some elephants.
Yawning was rare during the daytime and during
periods of standing around in the enclosure at
night. In six occurrences of likely contagious
yawning, one elephant yawned upon seeing another
elephant yawning upon arousal from a final
recumbency; we recorded the sex and age category
of the participants.
The generality of yawning in both African
and Asian elephants in other environments was
documented in video recordings from 39
zoological facilities.
In summary, the study provides evidence that
yawning does occur in both African and Asian
elephants, and in African elephants, yawning was
particularly associated with arousal from
nighttime recumbencies.
Introduction
Yawning is a widely recognized behavior in
many mammalian and avian species and even some
fish (1). In species with which we are familiar,
yawning is basically self-evident; no one argues
about whether a dog, cat, horse, rat, raccoon,
or human is yawning when shown a photo or video
clip, or seeing the behavior firsthand. But what
about a species where the anatomy is
considerably different from familiar mammals,
and where a yawn may not be very evident even to
experienced field investigators? We hypothesized
that elephants may fall into this category.
Prior to the initiation of our study, we were
aware of no published report of yawning for any
of the species of elephants in either a wild or
captive/zoological setting.
Research on the function of yawning has
increased markedly in the last decade or so,
with several schools of thought about its
function. Experimental evidence clearly shows
that yawning does not influence blood oxygen or
carbon dioxide levels (2&endash;4). While there
is some debate about the role of yawning in
arousal (5), investigators generally agree about
the association of yawning with brain activation
(2-4, 6). Another proposed function of yawning,
consistent with the brain activation role, is in
cooling of the brain after its heating due to
inactivity (7, 8).
If yawning does occur in elephants, one
would expect a fixed-action pattern, as
described in other species, with a slow opening
of the mouth, followed by a brief frozen open
posture, and then followed by a rapid, snap-like
closure (1, 2, 6), with the size of the mouth
opening varying from small to wide.
In this study, we first confirmed that
elephants could perform an oral gaping behavior
that met these descriptive criteria for yawning
in pilot observations of African and Asian
elephants at the San Diego Zoo and San Diego Zoo
Safari Park. Once a behavioral pattern for
elephant yawning was confirmed, we pursued a
quantitative study of yawning in captive African
elephants at a South African elephant park. Of
particular concern was the occurrence of yawning
as related to brain activation, particularly in
the transition from sleeping or resting to
wakefulness. Therefore, we focused on the
likelihood of yawning in early morning hours
compared with other times during the night.
Because the study group was very stable, and we
could observe the same individuals night after
night, we looked for individual differences in
the likelihood of yawning.
We also had an interest in whether or not a
specific type of infrasonic vocalization
occurred during yawning as in other
circumstances, such as elephants greeting other
elephants at waterholes or when leaving
waterholes (9).
A particularly interesting aspect of yawning
that has attracted considerable interest is
so-called contagious yawning that is documented
for humans, some non-human primates, wolves and
budgerigars, and which is especially noteworthy
among individuals that are familiar with each
other (10-17). Contagious yawning is sometimes
considered a manifestation of empathy, and
elephants in nature form stable social groups,
and their social empathic behavior is well
documented (18). Therefore, we took the
opportunity to observe the elephants for
possible occurrences of contagious yawning.
Finally, the generality of yawning in both
African and Asian elephants in other
environments was investigated by examining video
recordings from 39 zoological facilities in the
U.S.
Discussion
To our knowledge, this is the first
data-based report of the occurrence of yawning
in African and Asian elephants. The observations
reveal that yawning in African elephants at the
South African study site was a pervasive
behavior that occurs in a very specific
context&emdash;that is, in association with
arousals from nighttime recumbent
sleeping/resting bouts. Using observations from
this well-established group of nine elephants in
a South Africa reserve, where at night they were
maintained in an open-air enclosure with
infrared video recording, we were able to
compile data on virtually all yawning episodes
during the study periods. This unique
opportunity allowed us to document which
elephants yawned the least and the most, and
when yawning was most likely to occur. There was
no age or sex pattern with regard to which
elephants yawned the least or the most. For
example, of the two sub-adult males, Mashudu
yawned the most, and Shungu was one of those
yawning the least.
Of the 133 yawns associated with arousals
from recumbencies, over half occurred in
association with an arousal from the final
recumbency of the night, just prior to the
morning. There were significantly fewer yawns,
per elephant, associated with arousals from 1 to
3 nightly non-final recumbencies. This finding
is consistent with our prediction from the brain
activation theory of yawning, proposed by others
(2-4, 6). The recording of infrasonic
vocalizations in the enclosure at night revealed
that while the elephants did vocalize from time
to time, there were no evident vocalizations
associated with yawning.
The degree to which the pattern of yawning
we describe here might apply to wild
free-ranging African elephants remains to be
seen. Such observations would be difficult
because they would be expected to occur
primarily between midnight and early morning
when visibility would be restricted and the
observation distance would likely be much
greater. No vocalizations would be expected to
indicate that an elephant was yawning. That
said, the generality of yawning in both African
and Asian elephants in both sexes was evident in
examination of video recordings from North
American Zoos where 38 yawns were observed in
male and female African and Asian
elephants.
With the opportunity to observe a
well-integrated herd of elephants throughout the
night, via video recordings, we observed five
instances of what appeared to be contagious
yawning in pairs of elephants arousing together
from recumbent bouts, in which the yawning was
usually overlapping but differed in start times,
and one instance when a standing elephant yawned
after observing another arousing elephant that
yawned. The contagious yawning episodes seen in
pairs of elephants arousing together all
occurred in the final recumbencies of the night,
suggesting an association with the brain
activation theory of yawning that may even be
socially facilitated. We were able to establish
that contagious yawning occurred in pairs of the
same or different sexes and in pairs of the same
and different age categories (adults and
sub-adults). While our designation of some
yawning episodes as contagious is consistent
with descriptions of contagious yawning in other
species (10-7), the findings are unique with
regard to individual details pertaining to the
contagious yawning pairs. As with the occurrence
of yawning in general, observations on yawning
in an integrated group of elephants in natural
settings are needed to reliably establish the
occurrence and context of contagious yawning in
this species.
Conclusion
In addition to being useful in understanding
the occurrence of yawning as an essential aspect
of elephant behavior, this study adds an
important comparative component for current
research on the brain activation function of
yawning. Elephants now represent the first
megafauna species with data on when yawning
occurs and some variables that may influence
yawning. In addition, our finding of likely
occurrences of contagious yawning in elephants
adds to a comparative perspective on this aspect
of yawning.
