Wild Japanese macaques bathing in naturally warmed pools
Three of the Japanese snow monkeys introduced to the Highland Wildlife Park, near Aviemore, as a major tourist attraction have died.
The Scottish Society for the Prevention of Cruelty to Animals (SSPCA) said a male from one troupe was killed by the dominant male from another.
A second animal had to be put to sleep and a third one drowned.
The Royal Zoological Society of Scotland (RZSS), which runs the site, confirmed they died in February.
Campaigning group Advocates for Animals said the incidents highlighted why it was inappropriate to keep wild animals in captive conditions.
Iain Valentine, RZSS head of animals, said the deaths followed a struggle for dominance between the first group and a second introduced later.
He said: "As a result, the alpha male from one group killed the alpha male in the other. Two other members of the group also died.
"Primates are extremely unpredictable and conflict can happen at any time, whether it is within their existing group or when they are introduced to another group.
"This behaviour happens regularly in the wild and intervening would have resulted in serious repercussions for the social structure and long-term future of the group."
Mr Valentine said a third group has since been introduced and has settled down.
The SSPCA said one its senior officers had visited the park following the deaths.
A spokeswoman said: "Every new introduction needs to be carefully managed.
"We have been informed that there are no plans to introduce further animals to the group.
"There are currently around 24 macaques and the Scottish SPCA is satisfied with the animals' welfare at this moment in time."
At the time of the first troupe's introduction, RZSS said the new additions could increase visitor numbers from 67,000 to 100,000 a year.
The snow monkeys have been followed by the introduction of red pandas.
In 2006, a pack of Mackenzie River wolves that had been a feature at the park since 1972 were put down.
Experts said the six animals had to be euthanized because they were "not portraying their natural behaviour".