Communication in elephants

Communication in animals lies at the heart of the study of behavior. Animal communication mainly involves sight, smell, and sound, although other senses, including touch and electroreception, may also be specific to certain taxa. Communication can be looked at from its production by the organism, its transmission through the environment, its reception and analysis, and its functionality, including its evolutionary significance. There has been much discussion as to how to define communication. Most authors agree that communication involves the provision of information, as conveyed through a signal, by a sender to a receiver, and the use of that information by the receiver in deciding how to respond. A signal is distinguished from a cue in that the former reflects the intentional transfer of information, while the latter is not associated with any such intent (although determining the intent of an animal is not easy).

The theoretical evolutionary approach recognizes that communication is associated with benefits and costs, in terms of genetic fitness, to the signaler and the receiver. R. Haven Wiley thus recognizes four possible outcomes arising from an act of communication: (1) mutuality, when both the signaler and the receiver experience fitness increases; (2) deceit, when manipulation by the signaler increases its fitness, but decreases that of the receiver; (3) eavesdropping, when the receiver is able to increase fitness to the detriment of the signaler; and (4) spite, when both parties have decreased fitness. While these aspects have been applied to the study of communication in a variety of animal species, our understanding of communication in elephants is, with some exceptions, still largely descriptive.

Elephants actively communicate through a wide repertoire of tactile, visual, chemical, and acoustic signals. Several observers of captive and wild elephants have described the use of the trunk in a variety of contacts: reaching out to each other with extended trunks, entwining trunks, inserting the trunk tip in the other's mouth, placing the trunk over the back, caressing with the trunk, or just touching another with the tip of the trunk. Some of these contacts, such as making trunk contact with the temporal gland or the genitals, are obviously to obtain chemical signals, but many others are purely tactile contacts. Placing the trunk tip in another's mouth, for instance, seems to be part of reassurance behavior under times of stress (fig. 4.7). A calf may put its trunk into an elder's mouth to seek information about food. Leaning against or rubbing another's body is another form of tactile communication.

The African elephant has two fingerlike projections at the tip of its trunk, while the Asian elephant has a single finger. Several observers of the Asian species have noted the sensitivity of the trunk tip in functions such as detecting

Figure 4 .7

Female elephant placing trunk tip in the mouth of another adult cow. In addition to communicating through touch, chemical messages may be exchanged through breath.

Figure 4 .7

Female elephant placing trunk tip in the mouth of another adult cow. In addition to communicating through touch, chemical messages may be exchanged through breath.

ground vibrations, delicately picking up very small objects, and obtaining information on an object's texture, size, and perhaps even temperature. Histological examination of an Asian elephant's trunk tip by L.E.L. (Bets) Rasmussen and Bryce Munger revealed a high density of free nerve endings, convoluted branched small corpuscles, and "vellus vibrissae" or short hairs that barely protrude beyond the skin surface (fig. 4.8). These specialized structures are consonant with the advanced tactile abilities of an elephant, including sensing vibrations, performing delicate manipulations, and conveying chemical signals to other organs in the mouth.

While it is possible to assign a function to certain types or instances of tactile exchanges between two elephants, at other times it is not clear what information is being exchanged through such contact. This is especially true of exchanges between calf and mother. In his study of the Bandipur elephants, Vijayakumaran Nair recorded one young calf (<6 months) touching its mother 24 times an hour and one of its allomothers about half as frequently (fig. 4.9). The mother touched her calf about 9 times an hour, while the allomother did so 3 times an hour. On the other hand, the adults touched each other far less frequently. When Madhav Gadgil examined in detail the mother-calf exchanges

Figure 4.8

Life-size photograph of the trunk tip of an Asian elephant. Small vibrissal hair (SVH) and large vibrissae (LVH) can be seen on the skin surface (DT = dorsal tip, LDT = area lateral to dorsal tip, VT = ventral tip). (Photo courtesy of L.E.L. Rasmussen.)

Figure 4.8

Life-size photograph of the trunk tip of an Asian elephant. Small vibrissal hair (SVH) and large vibrissae (LVH) can be seen on the skin surface (DT = dorsal tip, LDT = area lateral to dorsal tip, VT = ventral tip). (Photo courtesy of L.E.L. Rasmussen.)

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Animal dyads involved

Figure 4.9

Number of contacts made per hour in different captive Asian elephant dyads between (1) two adult females, and between calf (hatched) and (2) mother, (3) I allomother, (4) juvenile, and (5) II allomother at Bandipur in southern India. (From Gadgil and Nair 1984. Reproduced with the permission of the Indian Academy of Sciences, Bangalore.)

recorded for the Bandipur elephants, he found that, in about 80% of instances, no immediate function could be attached to an exchange. He has suggested that these exchanges contribute to monitoring the state of well-being of the calf by its mother and other adults. In a highly social, long-lived animal, it would be advantageous for the mother to have regular information about her offspring's state so that she could then regulate her investment according to its needs. An active calf would indicate that it is healthy while one with lower activity would be signaling that it needs assistance. The basic idea, of course, is to optimize investment in a manner that maximizes the genetic returns to mother and offspring (or, broadly, the "inclusive fitness" to any individual making such investment). Just as too little investment may not serve this purpose, too much investment in an offspring that has crossed a certain threshold in its health status would not be worthwhile. In principle, a calf may try to misinform the adults to extract extra investment, but Gadgil and colleagues showed through modeling that this is not easy as the calf could also run the risk of receiving lower investment than its actual needs.

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