The life of a baboon

By John Yeld Time of article published May 31, 2011

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LOVE them, hate them… but it’s almost impossible to ignore the baboons of the Cape Peninsula. Surprisingly, perhaps, for an animal that has made newspaper headlines so often over decades, these baboons have not been comprehensively studied until quite recently.

But now, new research has produced fascinating empirical evidence about the local troops that disproves the claim, so often heard, that there are “too many” baboons on the peninsula and that the troops should therefore be culled.

More importantly, perhaps, this research also offers the most practical and effective methods of reducing human-baboon contact during which the animals invariably come off worst, often at the cost of severe injuries or maiming, or even death.

Much of this research has emerged in the PhD study of Tali Hoffman of UCT’s Baboon Research Unit, who studied the spatial ecology of the peninsula’s baboon troops through field tracking and the use of GPS satellite-tracking collars.

After three years’ field work, she had more than 25 000 GPS points to analyse, as well as numerous field observations from more than 40 assistants.

“My study aimed to provide data that could enhance the understanding of their landscape requirements and preferences, and thereby improve baboon management and conservation approaches, with the ultimate objective of achieving a sustainable baboon population that is not in conflict with its human neighbours,” she explained during a zoology post-graduate student seminar at the university last week.

Hoffman found that the peninsula baboons displayed probably the most interesting and varied population dynamics of any primates anywhere in the world, perhaps matched only by one population of Japanese macaques (snow monkeys).

She says she always asks audiences at her various talks how many baboons they think live on the peninsula.

“Most pupils answer ‘A million!’ while adults usually say ‘Thousands’.”

But Hoffman and colleagues put the baboon population on the peninsula at just 475, living in troops that vary in size from 16 to 115 animals.

One of her critical findings is that there is no relationship between the size of a troop and the size of its home range or its average daily range.

The Kanonkop troop in the Cape Point area is probably the most “pristine” troop in the peninsula with the least interaction with humans and hence least access to human food. These 49 animals, which have a home range of 37km2 at a density of about 1.3/km2, move furthest and fastest during their daily foraging.

In contrast, the 16 baboons in the Red Hill troop spend nearly half their time in the Simon’s Town urban area, eating mostly human food. At a density of 10/km2, they travel the shortest distance at the slowest pace.

In Tokai, the 115 animals also have a tiny home range of 9km2 at a density of 12/km2. This is because more than 90 percent of this home range consists of alien vegetation – pine and eucalyptus plantations, and vineyards – that offers the troop an abundance of non-indigenous food sources in close proximity to suitable tree sleeping sites.

When baboons are able to easily source “unnatural” food like this, they are able to satisfy their nutritional needs more quickly, leaving them more social time and more time for rest. The age at which females first reproduce is lower and they have an increasing number of infants during their lifetimes, with obvious population implications.

The average population growth rate on the peninsula is 6 percent, but 8 percent in Tokai and just 3 percent in the far south (such as the Kanonkop troop).

So the first management implication is that it’s not baboon numbers that need to be controlled, but the animals’ access to certain habitats, Hoffman says.

This is confirmed by her estimates of how many baboons the peninsula can sustain.

Her “most generous” scenario assumes that only the urban areas are excluded from the animals’ access, while the “most conservative” estimate assumes the removal of all alien food sources such as vines and pine trees, as well as human food.

The “most generous” figure is 612 baboons and the “most conservative” 488. The “most realistic” figure Hoffman puts at 586.

“So even under the most stringent spatial restrictions, baboons can still not be considered over-abundant on the peninsula, and the current population is well within the carrying capacity of the landscape.

“So management should not be looking to control numbers, but at managing habitat access”

Unfortunately, baboons are “hard-wired” to seek out the most profitable foraging areas and, for various reasons – including the natural attributes of the landscape – these are nearly all at low altitude, she adds.

Of course, these are also the areas where human development has occurred, so they are where baboons now suffer their highest incidence of injury and mortality as they compete for this habitat.

“All space is not equal space for baboons,” Hoffman explains, which is why the high mountainous spine of the peninsula has never supported permanent baboon troops.

Because of the UCT research, authorities are now aware of the baboons’ home ranges, and these must be taken into account when considering any possible future land transformation, she adds.

Her research also reveals that more than half of the baboons sleep at roosting sites less than half a kilometre from the urban edge. If the troops are pushed by baboon monitors to roosting sites further than 500m, or at least one hour away, this will reduce the amount of time they are able to spend in urban areas where they are most vulnerable, says Hoffman.

“It would be a challenge to move them there, a big ask, but I think with the right kind of collaboration it could be done and it’s worth the effort.”

There are two major findings of Hoffman’s thesis. The first is that “unnatural” resources – like food from urban areas and artificial roosting sites – must be properly managed and secured so that baboons don’t have access to them.

“And the best means is electric fencing, and a particular kind of baboon-proof electric fencing, because if there’s a reward on the other side, baboons will go through just about anything.”

And the second major finding is that remaining areas of natural land suitable as baboon habitat on the peninsula must be conserved.

“All the results from my thesis point to this,” she says.

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