Santino, a chimpanzee at the Furuvik Zoo in the city north of Stockholm, surprised visitors as well as zoo keepers, when they came to know that the chimp calmly collected and stored stones to use them as missiles, to throw them at the zoo visitors, in "agitated" state. But, the chimp behavior really did attract the attention of the Swedish researchers, who started their study on Santino.

The Swedish researchers revealed their study in the journal Current Biology on Monday, in which they wrote that apes can plan things ahead just like humans. The team researchers led by Mathias Osvath, a cognitive scientist from Lund University in Sweden, found that Santino, the chimpanzee planned hundreds of stone-throwing attacks on zoo visitors at the Furuvik Zoo, about 93 miles (150 kilometers) north of Stockholm.

Osvath and his team found that the 30-year-old Santino collected the stones in a calm state, in the morning, before the zoo opening, and the chimp started hurling stones at the zoo visitors, when it got agitated due to the visitors gathering on the other side of the moat to view it.

"These observations convincingly show that our fellow apes do consider the future in a very complex way. It implies that they have a highly developed consciousness, including lifelike mental simulations of potential events," said Dr Osvath, who authored the study.

The study found that Santino collected rocks knocking out disks from concrete boulders inside his enclosure, and waited until around midday to launch its stone attacks at the visitors. The chimp got agitated when too many visitors gathered around it, or when it saw a group of visitors including less number of males and large number of females. It suggested that that Santino was anticipating a future mental state.

The researchers noted that Santino didn't attack the other chimpanzees, and the attacks were only aimed at the humans viewing the animal. The stones rarely hit visitors because of the Chimp's poor aim.

Dr Osvath said, "We've done experimental studies, and the chimps in my mind show very clearly that they do plan for future needs, but it has been argued that perhaps this was an experimental artefact, but now we have this spontaneous behaviour, which is always in some sense better evidence."

Dr Osvath and his team observed Santino and interviewed three senior caretakers who had followed the chimp's behavior for 10 years at the Furuvik Zoo to conclude that chimps can plan for future events.

Dr Osvath said, "I'm personally convinced that at least chimps do plan for future needs, that they do have this autonoetic consciousness. I hope that other zoos or those in the wild will look more closely at what is happening. I bet there must be a lot of these kinds of behaviours out there, and I wouldn't be surprised if we find them in dolphins or other species."