PRIMATES, 16(2): 231-234, June 1975 231

A Case of the Adoption of an Infant Chimpanzee by a Suckling Foster Chimpanzee

T. VAN WULFFTEN PALTHE and J. A. R. A. M. VAN HOOFF

University of Utrecht

ABSTRACT. Chimpanzees in captivity have grown up in a rather unnatural social environ- ment and there frequently are problems when they have to nurse their own offspring. It is most remarkable that a chimpanzee mother in a captive colony, who had lost her child al- most immediately after birth, adopted without problems a five-week-old infant, which had been reared by humans from the day of its birth. Successful adoption has not been reported for feral chimpanzees; similar cases in captivity are not known.

Due to the fortunate concurrence of events, the chimpanzee colony of Burgers' Dieren- en Safaripark in Arnhem, the Netherlands, now has an infant chimp and his foster mother within its mids t - -an infant which would otherwise have been deprived of the privilege of being brought up by a member of its own species.

The reason for reporting on this is that to our knowledge a similar case has not been described anywhere in the literature on the social behaviour of chimpanzees.

VAN LAWlCK-GOODALL (1968), who observed wild chimpanzees, describes three instances of orphaned infants, two circa 3 years old and one 14 months old, all of whom were adopted by an older sibling. The 14-month-old infant died after 2 weeks. Its brother could provide it with the security and protection it needed, but not with the milk it needed most. VAN LAWICK-GOODALL (1971) mentions another case of an infant, Cindy, who was orphaned at 3 years old and who was an only child. Since she and her mother had often been seen together with another suckling mother (the mothers were believed to be sisters) it was expected that this mother would adopt Cindy. This did not happen, and she died after 2 months. KOLLAR, BECKWlTH, and EDGERTON (1968) report how among the chimpanzees of the ARL colony, an adult male would play a protective role towards a juvenile chimp. This same behaviour of males towards motherless infants and juveniles, is seen in the Arnhem colony. How- ever, never is as intense a tie established as in a genuine mother-child relationship or an adoption.

'Kidnapping, ' or an at tempt to 'k idnap ' an infant from its mother is seen both in feral (VAN LAWiCK-GOOOALL, 1968) and in zoo chimp groups. In cases such as these, the mother is always nearby and can collect her child when it seems necessary.

Before describing the case at hand, we may first say something more about the chim- p a n z e e consortion in Arnhem (for an extensive description see VAN HOOFF, 1973).

In 1971, the consort relation was established under the auspices of the second author of the Laboratory for Comparat ive Physiology, University of Utrecht, the Nether- lands. The object is to provide a habitat which is sufficiently spacious and structured in such a manner that permits keeping a social group of chimpanzees like that of

232 T . v . W . PALTHE t~ J. A. R. M. VAN HOFF

Fig. 1. Foster mother Tepel with her adopted step-son Wouter.

natural composition, and providing an opportunity for behavioural studies. At first there were 18 animals in the colony, 13 of these were collected from other zoos, private individuals and circuses, and the remainder were part of Burgers Zoo's own chimp population.

During February-March 1974, the time-span with which this report deals, the colony consisted of 24 individuals. Such was the composition of the group:

three newly introduced adult males, ten adult females, of whom three gave birth during the period February-March

1974, two sub-adult males, one sub-adult female, one juvenile male, four juvenile females, and three infants, one of whom died at age 3/4 of an hour (approximately).

On the 8th of February 1974 Spin, one of the adult females gave birth to a healthy child, her first. It immediately became obvious, however, that Spin had no experience nor interest in caring for an infant. Her newly born infant lay screaming on the floor, while she climbed high onto the bars of her nightcage, ignoring it. This situation re- mained unchanged during 5 hours in which she was closely watched. Not once during this time did she approach her infant. It was decided to remove the infant and rear it by hand until sufficiently independent to reintroduce it into the colony. He was named Wouter and made excellent progress but, to all intents and purposes, was an orphan.

On Tuesday the 12th of March, 31 days later, Tepel, another adult female, gave birth to what later proved to be a premature infant. This was her second infant; she had given birth before in another zoo and nursed her child successfully for sometime. In contrast to Spin, Tepel appeared to be the perfect mother. Immediately after its birth, Tepel gathered her infant in close embrace and started building feverish-

Adoption of Infant Chimp by a Suckling Foster Chip 233

ly her nest of straw, stopping every now and again to look at, nuzzle or groom her infant, while making faint vocalizations. She held it in the crutch of her leg and sup- ported it with one arm while she was arranging and re-arranging the nest with the other. The little one seemed rather weak. It was heard to squeak three times. The first and loudest squeak was given at birth and the last, squeak audible on the tape-recorder, 43 minutes after birth. Soon afterwards it was ascertained that the infant was dead. Despite her infant's death, Tepel's behaviour remained the same. The following morning she still supported the dead infant and carried it around with her in the night-cage.

In the meantime it had been decided to offer Wouter to Tepel first thing in the morning, in the hope that she would accept this by now 4-5-week-old infant. We realized what a risk we were taking. Thereis every reason to believe thata chimpanzee and therefore Tepel, can distinguish between her own offspring and every other chimpanzee. Would she be content with the orphaned chimp Wouter and treat it as her own? On the other hand, would Wouter, so far raised exclusively in human companionship, accept Tepel? The ability of individual recognition was beginning to develop in him. He was starting to respond to human voices and to fix his gaze on human faces. Would he withdraw with fear from the unfamiliar features of a chim- panzee? We would only know by trying. Furthermore, if they accepted each other, would Tepel have en:mgh milk of the required nutritional quality to feed him?

The first thing to do was to separate Tepel from her dead youngster. She was coaxed into another cage where sh~ was offered an apple. Before coming to take it, she put the body aside. The slide-door was quickly shut and she was separated from her infant, which was then removed without her seeing it.

It was decided to offer Wouter to her in her own night-cage. Before letting her in again, the floor was covered with a thick layer of straw. In one corner a hollow was made resembling a nest in which Wouter was layed down. Tepel was let in. Sh" walked in calmly and immediately went over to the corner where Wouter lay. She stood over him and touched him with her knuckles upon which she smelt her hand. Then, with one quick, routinized movement, she picked Wouter up and held him in the correct cradling position. Wouter clenched his fists and held firmly onto Tepel's fur. She then walked with him to the far corner of her cage and proceeded to build a nest. When Wouter was picked up, he made no sound and nothing of fear for Tepel was noticeable. We could not have wished for a simpler and easier adoption!

The two of them were closely watched all during that day. Round noon, Wouter's next scheduled feeding time, he became restless and nuzzled at Tepel's breast. He happened upon one of her teats--she has rather prominent ones, hence her name- - and started to suck, forecefully and rhythmically. He drank for 4 minutes, then stopped. From then on he was seen to be drinking from both the left and the right breasts at regular intervals. Tepel proved to be an excellent mother.

Initially, Tepel and Wouter were kept apart from the rest of the colony. No undue risks were being taken at this early stage. Eighteen days later, on 29th March, 1974, another of the pregnant females, Kuif, gave birth to a healthy chimp. Although pri- miparous, she proved to be an adequate mother. Tepel and Kuif with their young

234 T. v. W. PALTHE & J. A. R. M. VAN HOFF

were put together. Another female, Splutter, who was suspected to be pregnant for the first time, was added to this group in order to confront her with an established mother-infant relationship.

By this time the weather was such that the rest of the colony spent the days in their large, open-air territory. On a particularly fine day, Tepel and Ku~f with their infants and Splutter, were allowed to join the rest of the group, where they were received most benevolently. Until this moment both infants are doing very well.

It is hoped that, apart from its theoretical interest, this report will prove to be of practical value since it has demonstrated that it is possible for an adoption, as de- scribed here, to take place, provided the circumstances are favourable.

ZUSAMMENFASSUNG

Schimpansen in Gefangenschaft sind meist in einer unnatiJrlichen sozialen Umgebung aufgewachsen, und sind deshalb spater nicht inamer f~ihig ihren Nachwuchs auf zu ziehen. Um so erstaunlicher erscheint es, dass eine Schimpansenmutter, die ihr Kind kurz nach der Geburt verloren hatte, ein ffinfw6chiges Flaschenkind problemlos adoptierte. Erfolgreiche Adoption bei wildlebenden Schimpansen ist bisher unbekannt; vergleichbare F~ille gibt es jedenfalls nicht. Hoffentlich ermutigt dieser Erfolg andere Tierg~irten wenn n6tig zu ~ihnlichen Versuchen.

REFERENCES

HOOFF, J. A. R. A. M. VAN, 1973. The Arnhem Zoo chimpanzee consortium: an attempt to create an ecologically and socially acceptable habitat, lnternat. Zoo Yearbook, 13: 195- 205.

KOLLAR, E. J., W. C. BECKWlTH, & R. B. EOGERTON, 1968. Sexual behaviour of the ARL colony chimpanzees. Nerv. Merit. Dis. 147: 444-459.

LAWlCK-GooDALL, J. VAN, 1968. The behaviour of free-living chimpanzees in the Gombe stream reserve. Anita. Behav. Monogr., 1 : 0-0.

- - , 1971. In the Shadow o f Man. Collins.

--Received June 17, 1974; Accepted September 7, 1974

Authors' Address: T. VAN WULFFTEN PALTHE t~r J. A. R. A. M. VAN HOOFF, Laboratorium voor Ver- gelijkende Fysiologie, der Rijksuniversiteit, Jan Van Galenstraat 40, Utrecht, Netherlands.