Dolphins Essay Research Paper Bottlenose dolphins are

Dolphins Essay, Research Paper

Bottlenose dolphins are among the most vocal of the nonhuman animals and

exhibit remarkable development of the sound production and auditory

mechanisms. This can be seen in audition, which is shown in the animal?s

highly refined echolocation ability, and in tightly organized schools in which

they live that are made up by sound communication. In testing the

communication skills of dolphins, extensive studies have been done on vocal

mimicry, in which the animal imitates computer-generated sounds in order to

test motor control in terms of cognitive ability. Language comprehension on

the other hand has been tested through labeling of objects, which has proven

to be successful regarding the association of sound and object stimulus. The

biggest question in dolphin communication, is whether or not the species is

capable of intentional communicative acts. Though results from studies have

been debatable, the key to understanding the extent to this ?language? is to

determine whether they have a repertoire of grammatical rules that generate

organized sequences. In determining this, the greatest accomplishment for

both the scientist and all of humanity, would be to accomplish interspecies

communication, creating a bridge between humans and animals which could

open up a new understanding of the unknown world of wildlife. Most

importantly, it is necessary to understand the incredible aptitude of dolphin

communicative skills, and the impressive intelligence the animal possesses

which allows for a great deal of intraspecies and interspecies communication

(Schusterman, Thomas, & Wood, 1986). The acoustical reception and

processing abilities of the bottlenosed dolphins have generally been shown to

be among the most sophisticated of any animal so far examined (Popper,

1980 as cited by Schusterman et al. 1986). In order to understand the

complexity of these highly mechanized acoustic systems, it is necessary to

learn the process for which the dolphin hears. In most water-adapted

cetaceans, tissue conduction is the primary route of sound conduction to the

middle ear. The isolation of the bullae shows an adaptation for tissue

conducted sound. The lower jaw contains fat that is closely associated with

the impedance of seawater. The lower jawbone of most odontocetes

becomes broadened and quite thin posteriorly, and the fat forms an oval

shape that closely corresponds to the area of minimum thickness of the jaw.

This fat body leads directly to the bulla, producing a sound path to the ear

structures located deep within the head. Paired and single air sacs are

scattered throughout the skull, which serve to channel these tissue-conducted

sounds (Popov & Supin, 1991). Other than this description, there are still

more studies needed to determine the function of the middle ear and the type

of bone conduction that occurs within the bulla. Due to detailed audiograms,

dolphins have been shown to have the ability to detect high-frequency

sounds. In an experiment by Johnson (1966) as cited in Schusterman et al.

(1986), sine-wave sounds ranging in frequency from 75 Hz to 150 Hz were

presented to a bottle-nosed dolphin. The animal was trained to swim in a

stationary area within a stall and to watch for a light to come on. Following

the light presentation a sound was sometimes presented. If the dolphin heard

the sound, its task was to leave the area and push a lever. Sound intensity

levels were varied by a staircase method of 1, 2, or 3 dB steps. The resulting

audiogram, compared to the human aerial audiogram, showed that at regions

of best sensitivity for each, thresholds for human and dolphin are quite similar,

but separated by about 50 kHz in frequency, showing that the animal?s inner

ear function is very similar to a human. The experiments done on dolphin

auditory functions have generally shown a finely adapted sound reception

system. This would be expected due to the highly adapted echolocation

ability of the bottlenosed dolphin and other cetaceans. Results of work on

absolute thresholds, critical bandwidths, frequency discrimination, and sound

localization all indicate that the dolphin auditory system is at least as good or

better than the human system. This is in spite of the fact that sound travels five

times as fast under water as it does in air (Popov et al. 1991). The

bottlenosed dolphin in captivity produces two categories of vocalizations: (a)

narrow-band, frequency-varying, continuous tonal sounds referred to as

?whistles? and (b) broad-band pulsed sounds expressed as trains of very

short duration clicks of varying rates (Evans, 1967, as cited in Schusterman

et al. 1986). The pulsed sounds are used for both communication and

echolocation, and the whistles are found to be used primarily for

communication (Herman & Tavolga, 1980, as cited in Schusterman et al.

1986). Descriptions in literature emphasizing either the whistles or the pulsed

sounds have led to contradictory hypotheses concerning the communication

system of the dolphin. It has been reported that individually specific whistles

often make up over 90% of the whistle repertoire of captive bottlenosed

dolphins (Popov et al. 1991). A number of observations of apparent vocal

mimicry have been made, though with no systematic investigation of the

degree of vocal flexibility. The observed variability in the whistles, combined

with the difficulty of identifying individual vocalizing dolphins in a group, has

led to speculation that the whistles might be a complex, shared system, in

which specific meanings could be assigned to specific whistles. Consideration

of vocal mimicry has been taken to understand its relation to cognitive

complexity, and to the potential use of vocal response for communication in

an artificial language. In one study done by McCowan, Hanser, & Doyle,

(1999), the dolphin was able to learn to mimic a number of

computer-generated model sounds with high fidelity and reliability. The

dolphin using its whistle mode of vocalization imitated all of the sounds, and

all were distinct from the unreinforced whistles produced prior to training.

The large majority of each dolphin?s whistle vocalizations were individually

specific acoustic patterns, described as a ?signature whistle?; the rest of the

whistles were short chirps. The results of the mimicry training have shown that

dolphins can mimic tonal sounds with frequencies between 4 and 20 Hz. Due

to this research, scientists can now learn from these mimicry skills how to

understand and develop natural communication based on a stronger emphasis

on the animal?s cognitive abilities (Brecht, 1993). In object labeling, the

dolphins seemed to understand the task of associating model sounds with

displayed objects. Progress was most rapid when the model sound was

always presented at full intensity, but the probability of its being presented on

any given trial was systematically decreased over successive trials. There

wasn?t any confusion of the objects themselves, but only a tendency to drift in

the quality of the rendition of the labels. This demonstration of symbolic use

of vocalizations could lead to the investigation of the potential of animals to

form referential concepts, thus creating a new understanding of dolphin

communication and its uses in the wild. The main purpose of study in dolphin

language, is the interest in whether the animal?s speech is intentional

communication like our own human speech. The fact that awareness as

applied to the phenomena of human communication also implies something

we would not attribute to animals-and this is the awareness that

communicative acts are behaviors about behaviors (Crook, 1983, as cited in

Schusterman et al. 1986). Language, as we know it, could not exist without

the capacity for intentional communication, as all linguistic communications

are, by definition, intentional. Dolphins have been observed to have some of

these intentional communication characteristics, as their behaviors have

shown in captivity. For example, dolphins have been observed to squirt or

splash water at strangers who come near their tank. After squirting the water

the dolphin will raise itself out of the water to curiously observe what effect

their behavior had on the stranger. Although this behavior is not communitive,

nonetheless, it seems to suggest that the dolphin is aware of the effect of its

behavior on others, showing that it has the cognitive ability for intentional

communication (Erickson, 1993). Communication between humans and

dolphins occurs mostly through a gestural language that borrows some words

from American Sign Language. The trainers make the gestures with big arm

movements, asking the animal to follow commands such as ?person left

Frisbee fetch,? which means ?bring the Frisbee on the left to the person in the

pool?. In one study, two bottlenosed dolphins were tested in proficiency in

interpreting gestural language signs and compared against humans who

viewed the same videos of veridical and degraded gestures. The dolphins

were found to recognize gestures as accurately as fluent humans, and the

results suggested that the dolphins had constructed an interconnected

network of semantic and gestural representations in their memory (Herman,

Morrel-Samuels, & Pack, 1990). Such requests probe the dolphins

understanding of word order and test the animal?s grammatical competence.

It has also been determined that dolphins can form a generalized concept

about an object: they respond correctly to commands involving a hoop, no

matter whether the hoop is round, octagonal, or square. The animals seem to

have a conceptual grasp of the words they learn, showing an understanding of

the core attributes of human language, those being semantics and syntax

(Erickson, 1993). Though this information seems compelling for dolphin

language abilities, to determine whether or not they are capable of complex

intentional communications, researchers must continue to investigate their

receptive capacities, and to attempt to provide them with a communication

system that would tap their productive capacities. Is interspecies

communication possible? Could we someday be having philosophical

discussions with a bottlenosed dolphin? Though these questions seem

ridiculous, there was much debate over these questions when a medical

doctor named John Lilly came out with hopeful findings of dolphin intelligence

in the 1960s (Shane, 1991). In the first true research of dolphin

communication and intelligence, Lilly set out to show that through the

correlation of brain size and IQ, the bottlenose dolphin was perhaps smarter

than humans and began a growing interest in dolphins and their language

through whistles. Though dolphins are exceedingly intelligent creatures, no

real scientific evidence has yet been found to totally support the many

conceptions about the animal?s intelligence. Lilly (1966) states, ?A dolphin . .

. naturally uses other sounds to convey and receive ?meaning?: creaking for

night-time and murky-water finding and recognition, putt-putting and whistles

for exchanges with other dolphins, and even air wailing to excite human

responses in the way of fish or applause. If a dolphin is copying our speech,

he?ll copy that part of what he hears which in his ?language? conveys

meanings.? Although this excerpt shows an incredible capability for dolphins

to produce intelligent communication, it is findings such as these, which lack

scientific support and have lost credibility among other dolphin researchers in

the past few decades. Though his findings lack support, Lilly was important in

bringing forth interest among people and therefore funds towards more

scientifically based research and experiments that have helped us learn more

about communication skills and intelligence of dolphins (Tyack et al. 1989).

In order to clearly understand if dolphins are creating intentional, intelligent

communicative sounds and meanings, it is necessary to break down the vocal

signals into repertoires and analyze those individually. The breaking down of

dolphin signaling into component units has just now begun and the task will be

to discover if, when, and to what extent they structure formalized sequences

of signal units. To determine whether they have a repertoire of grammatical

rules that generates organized sequences will be difficult, and it will be

necessary to obtain extended and continuous recordings. Patterns must be

found and compared to other dolphin recordings in order to obtain the most

accurate and universal findings for language among bottlenose dolphins

(Herman, Kuczjac II, & Holder, 1993). Through many more years of careful

study of these sounds, it is hopeful that our scientists can determine capacities

and meanings behind dolphin language. Though interspecies communication

seems unlikely at this point in time, through new studies being conducted our

conception of dolphins as communicative animals seems more possible.

Intentional communication through gestural understanding is the best finding

so far in the study of these intelligent animals, and leads many to believe there

is a lot more to dolphin?s communication skills than has yet been uncovered.

In tests done in mimicry and labeling of objects, it seems that the capacity the

bottlenose dolphin has for learning and understanding is large enough to make

taught communication a realistic goal in the future of dolphin training. The

highly specialized auditory and vocal mechanisms of the animal have helped

lead the way to a better understanding of cetacean ear anatomy and sound

production mechanisms, and these functions can now be seen as complex

structures unlike any found above water. Though more research needs to be

done before any true conclusions can be made about dolphin language, from

what we do know the bottlenose dolphin is among the most vocal of

nonhuman animals and exhibits remarkable development of sound production

and auditory mechanisms (Schusterman et al. 1986).

Brecht, M. (1993). Communications: A Predictive Theory of

Dolphin Communication. Kybernetes, 22, 39-53. Erickson, D. (1993,

March). Can Animals Think? Time, 146, 182-189. Herman, L. M., Kuczaj

II, S. A., & Holder, M. D. (1993). Responses to Anomalous Gestural

Sequences by a Language-Trained Dolphin: Evidence for Processing of

Semantic Relations and Syntactic Information. Journal of Experimental

Psychology, 122, 184-194. Herman, L. M., Morrel-Samuels, P., & Pack,

A. (1990). Bottlenosed Dolphin and Human Recognition of Veridical and

Degraded Video Displays of an Artificial Gestural Language. Journal of

Experimental Psychology, 119, 215-230. Lilly, J. C., (1966). Lilly on

Dolphins. Garden City, N.Y.: Anchor Books. Anchor Press/Doubleday.

McCowan, B., Hanser, S. F., & Doyle, L.R. (1999). Quantitative tools for

comparing animal communication systems: information theory applied to

bottlenose dolphin whistle repertoires. Animal Behaviour, 57, 409-419.

Popov, V. V., & Supin, A. Y. (1991). Interaural intensity and latency

difference in the dolphin?s auditory system. Neuroscience Letters, 133,

295-297. Schusterman, R. J., Thomas, J. A., & Wood, F. G. (1986).

Dolphin Cognition and Behavior: A Comparitive Approach. London:

Lawrence Erlbaum Associates, Publishers. Shane, S. H. (1991). Smarts.

Seafrontiers, 37, 40-43. Supin, A. Y., Popov, V. V., & Klishin, V. O.

(1993). ABR Frequency Tuning Curves in Dolphins. Journal of Comparitive

Psychology A, 173, 649-656. Tyack, P. L.,& Sayigh, L. S. (1989). These

Dolphins Aren?t Just Whistling in the Dark. Oceanus, 32, 80-83.