Chimpanzees at Gombe National Park in Tanzania often become animated during rainstorms and around waterfalls. Our videographer, Bill Wallauer, answered a letter inquiring about this behaviour and we share his observations and thoughts below.

Waterfall DisplaysIn my time at Gombe I witnessed an average of two to three waterfall displays and rain dances per year. They ranged from single individual solitary events to a single individual participant within a social group, to multiple participant events. The displays I witnessed were performed by males of all age groups. Rarely have I seen adolescents or infants displaying in and around adult males, but it does occasionally happen. The displays are prolonged, lasting as long as five minutes, sometimes more. Aggression is occasionally an element of the display, but usually the event continues long after the subordinates have moved away. My feeling is that dominance plays a secondary role (if any) in most of this type of display. Rain dances are performed more often toward the beginning of the rainy season. I do not have a sense of seasonality in relation to waterfall displays.

I do not recall seeing a female perform an extended rain dance or waterfall display, but Dr Goodall has and I am not at all surprised that they do.

I have discussed these displays at length with Dr Goodall over the years. One of the most interesting and scrutinized events I recorded on video was a waterfall display performed by the alpha at the time, Freud. Freud began his display with typical rhythmic and deliberate swaying and swinging on vines. For minutes he swung over and across the eight-foot to 12-foot falls. At one point, Freud stood at the top of the falls dipping his hand into the stream and rolling rocks one at a time down the face of the waterfall. Finally, he displayed (slowly, on vines) down the falls and settled on a rock about 30 feet downstream. He relaxed, then turned to the falls and stared at it for many minutes. It was one of those times that I would give body parts to know what was going through a chimp's mind. Dr Goodall and I have seen several events in which the participants seemed to ponder or consider the natural event to which they were reacting.

During rain dance displays, lightning and thunder often, perhaps usually, precede and accompany the downpour. If you have experienced a storm in which the hair stands up on the back of your neck and you can feel or smell the electricity in the air, you can almost be certain that the chimps would display if they were there. In other words, the behaviour is predictable under some circumstances.

An excellent example of a respect and intense curiosity of chimpanzees to an animate object is in their reaction to snakes, particularly pythons. Pythons could pose a threat to young chimpanzees, but it is not likely that any snake would take on an adult. However, when a single individual or group of chimpanzees encounters a python (even a small one), the reaction is remarkable. One would expect the chimps to issue alarm calls to warn others and as an expression of their fear, but then to move well out of harms way as soon as possible. Predictably, the chimpanzees do issue a specific vocalization called a snake wraa, but when it is uttered, the group often draws near, to stare at the snake. Some climb above if possible for a better look. Typical facial expressions are those of fear and curiosity. Physical reassurance contact is often made (especially mutual embracing), and eye contact among individuals is frequent. After tens of minutes, members finally begin to disperse. Some individuals however, show exaggerated, prolonged interest. They will call repeatedly, even after other individuals have moved well away. I've seen chimpanzees stare and call for as long as 30 minutes.

It is difficult to explain why chimpanzees react to pythons in this way. It appears to be much more than keeping a close eye on a possible threat, as many species do. It also seems a great waste of energy and time. If pythons are dangerous, it would make much more sense to alarm call and move away as quickly as possible.

The only case of possible projected 'animation' on an inanimate object is that of a young female chimpanzee carrying and cradling rocks and sticks in mimicry of nurturing behaviour. I cannot be sure that this is exactly what I was seeing, but Gaia on several occasions has shown what appeared to be mothering behaviour toward objects, much as human children care for dolls. There is a fine line between hugging and holding on, but I have seen Gaia groom both rocks and sticks as she held them in her lap. There is a similar observation of a young female baboon at Gombe who was observed mothering a rock.

What does this all mean? We can't come to any real conclusions, but I honestly do believe that chimps have the capacity to contemplate and consider (even revere) both the animate and inanimate. Where the line is drawn between what is alive and what is not I fear will always remain a mystery.

I've spent many hours pondering how complex and sophisticated are the workings of a chimp's mind, but I still have far more questions than answers.

— Bill Wallauer, Gombe videographer