By Ella Davies
Earth News reporter
Black-tufted marmosets living in Brazil's city parks are going to surprising lengths to avoid unusual predators - domestic cats.
The small urban-dwelling monkeys return to favoured sleeping sites - something jungle-dwelling marmosets do not do.
Cats often make multiple attempts to catch the monkeys each day, but have difficulty accessing tall trees with smooth bark and fewer low branches.
So the monkeys habitually return to these tall trees to thwart the cats.
The marmosets favour tall palms
Details are published in the International Journal of Primatology.
Marmosets usually live in rainforest canopies but have adapted to life in Brazil's urban green spaces.
Marmoset researchers observed the behaviour whilst investigating the affect of city noise levels on urban populations in Belo Horizonte City Park in Minas Gerais, south-eastern Brazil.
In their study, Marina Duarte and Professor Robert Young revealed how the black-tufted marmosets make sleeping site choices.
The park contains more than 3,000 trees, but the nine resident marmosets only slept in 12 particularly tall trees, all of which had high first branches and smooth bark.
The monkeys also showed a preference for trees that could only be accessed by jumping from neighbouring trees.
This behaviour has not been observed in black-tufted marmosets living in more traditional rainforest habitats.
"Normally, in nature the animals prefer to sleep in several different trees so that predators do not learn to find their sleeping places," explained Ms Duarte.
Approximately 115 domestic cats live in the park and researchers recorded an average of three attempts at marmoset predation by cats per day.
However, the cats were unable to scale the tallest trees or those without suitable climbing supports like rough bark or low hanging branches.
By adapting their choice of sleeping sites, the marmosets were able to evade the exceptionally high number of predators.
Unwanted pets have been abandoned in the park for the last 20 years, greatly increasing the cat population.
Cats can only access certain trees
Scientists studying how marmoset and tamarins adapt to urban environments have also recorded their communication in groups and interaction with humans.
In the past, these sap-feeding species have been identified as particularly adaptable to urban environments where they can find suitable food sources.
The small monkeys are also popular with exotic collectors and it remains unclear how many of Brazil's urban marmosets were once pets.