BRU Blog

Adult male baboon. Photo: John Burnside

What is a dispersing male?

Unlike female baboons that remain with their natal troops throughout their lives, male baboons typically leave their troop when they reach adulthood. These males are known as dispersers. Dispersal in baboons is often not a discrete event, but a gradual process which may take months or even years. Individuals acquire information about neighbouring troops and individuals within their own troops over the course of their lives which they may then use to make decisions on when to leave and for how long and which troop(s) to join. 

If baboon dispersal is a natural process, why does management intervene?

Urban development on the Cape Flats prohibits baboon movement from the Cape Peninsula to other areas of the Western Cape. Thus, local baboon managers are dealing with a ‘closed’ population of baboons (no animals can get out and none can come in of their own accord) – a situation which necessitates active management by local authorities. Human management does not and cannot replicate the natural process but must attempt to mimic it wherever possible.

 How does the urban environment of the Cape Peninsula affect male dispersal?

 The urban sprawl that covers much of the Peninsula acts as a barrier to dispersing male baboons. In their dispersals, or investigative pre-dispersal forays, males who enter the urban space may encounter conflict (e.g., being shot at with an air rifle) and once on the move can become further isolated by human hysteria, dogs, police, security guards, etc. – all attributes that are unique to the urban space and very different from the landscape in which baboons and their dispersal behaviour evolved. Additionally, males might become quite accustomed to the treats of the urban space that are readily available in dustbins and gardens, and might decide to set up camp among humans rather than baboons (e.g. Bart).

Baboons that choose to live amongst humans pose a threat to the general health of the rest of the baboon population for they are exposed to human parasites and pathogens and the threat of cross transmission is greatly increased. A recent PhD thesis by BRU member Damiana Ravasi has shown that baboons have acquired human gut parasites as a result of their commensal lifestyle and furthermore baboons in the Western Cape beyond the Peninsula are known to have been infected with human tuberculosis (TB). Male baboons that live in urban areas and periodically visit troops may thus pass pathogens that they have acquired within the urban setting to baboons that still live within natural areas and in doing so compromise the health of the Peninsula baboon population. There are no absolutes in this scenario, only probabilities and the authorities adopt the ‘precautionary attitude’ that more time with humans equates to a higher risk of cross transmission.

Bart entertaining the crowds at UCT campus

 Is there a protocol for managing dispersing males?

Yes. The Baboon Management Team (BMT) devises many protocols that are used to guide baboon management in the Peninsula. The dispersing male protocol is one of them, and stipulates what action should be taken when baboons enter the urban space and remain in it for extensive periods.

Was the dispersing male protocol devised recently?

No. the dispersing male protocol has been in existence for 10 years. However, baboon management has seen many changes in 2009, and these changes have brought with them revisions to protocols that were considered too harsh on the animals. For this reason the dispersing male protocol has been recently amended.

Who was involved in making the amendments to the dispersing male protocol?

The new protocol was devised and approved by all of the Peninsula operational managers (Cape Nature, SANParks and the City of Cape Town) in addition to the Baboon Research Unit, the SPCA and a civic representative .  The list of representatives present from each group included Natasha Wilson from Cape Nature, Gavin Bell from SANParks, Dean Ferreira and Linden Rhoda from the Nature Conservation Corporation, Justin O’Riain, Esme Beamish and Shahrina Chowdhury from BRU, Kira Joshua from the SPCA, and Jenni Trethowan from Baboon Matters.

How does the old dispersing male protocol differ from the revised dispersing male protocol?

Old protocol

The old dispersing male protocol recommended that “where the same baboon enters a built up area a third time it may be euthanized in the most humane way possible, namely trapped, darted or drugged and euthanized, rather than shot”.

Revised protocol

The revised dispersing male protocol has done away with the “three strikes and you’re out” policy, and instead tries to better replicate the natural dispersal process in a number of ways. Assisted dispersal includes one trip back to the male’s natal (home) area. If he then chooses to disperse again, he is relocated by vehicle across the urban space and deposited near to other troops that he can then attempt to join. Successful integration with a new troop, however, is up to the baboon – managers cannot assist in this part of the dispersal process! Two assisted relocations may be granted for each individual to maximise their chances of integrating with a new troop. Should the male not integrate, then he could be translocated off the Cape Peninsula or euthanized. Details of these latter management options, which are as complicated from a conservation point of view as they are controversial, will form the basis of our next two blog posts.

Who makes the decisions about what happens to dispersing males?

All decisions are made by the Wildlife Advisory Committee (of Cape Nature) and based on detailed case histories of each animal.

Mike (red ear tag) rummaging through refuse above UCT campus. Mike has since returned to his natal area in Tokai.

Why do some dispersing males have ear tags?

Each male who enters the urban environment during his dispersal attempts is captured and ear tagged. The tags make the animal recognisable to baboon managers and the general public and assist in the tracking of the animal after his release. This enables managers to compile detailed case histories (of health, ranging patterns, behaviour, etc.) for each individual, and allows decisions to be made on a case-by-case basis, with the best possible action being taken for each animal.

If dispersers are trying to leave their troops, why does the protocol suggest taking them back home the first time they’re captured?

Dispersal in baboons is a gradual process with individuals acquiring information about neighbouring troops and individuals within their own troops over the course of their lives which they may then use to make decisions on when to leave and for how long. The return of a first-time disperser to a natal (home) area allows the baboon an opportunity to assess the benefits (did they realise a mating opportunity?) and costs (did they experience potential risk?) of the dispersal attempt. A baboon with experience of an urban dispersal attempt (did not encounter any other troops and experienced extreme levels of conflict) may well use this information to reassess future dispersal options.

Returning a first-time disperser to a natal area thus provides the animal with the opportunity to use the information gleaned on the first dispersal attempt and hence assess subsequent benefits and costs of future dispersal. Thus for example a Tokai male that dispersed in an Northerly direction into dense urban areas (e.g., John wayne, Bart and Mike) would hopefully not make a similar attempt the second time for it did not encounter any other baboons nor did it have a pleasant experience. One would thus hope that this male would then use the information gathered in its first dispersal attempt and opt in its second dispersal attempt to move South where there are other troops (eight in fact!) that would provide an outbreeding opportunity. A male that moved south (e.g., Sebastian) and encountered an urban area (e.g., Sun Valley) could be herded on through the urban area until it encountered a new troops home range.

The intention is to allow baboons to learn from their experiences and hopefully use this information to make decisions that will not necessitate their subsequent recapture and relocation. Lastly, the recent paralysis in management of males on the Peninsula that ensued with change of service providers allowed us a unique opportunity to assess what males who disperse do when given freedom of choice. Both Bart and Mike left and returned to Tokai of their own volition. Bart failed to integrate with other troops and chose to go back to his natal area and Mike did not encounter any other baboons in the City bowl or at UCT and went back to his natal area too. Thus these baboons revealed that if left to their own devices males will return to their natal area if they fail to secure an outbreeding opportunity. The protocol attempts to mimic this pattern with the hope that baboons like Mike will move South and thus disperse naturally to other Peninsula troops.

A Bart's eye view: one of Barts favourite spots on campus on the Molecular and Cell Biology Building...perfect view of the food tents!

Has the strategy of returning dispersing males to their home area on the first capture shown signs of success?

 More than half of the baboons that were returned home have settled again (for periods varying from 2 months to more than 2 years). Perhaps even more illuminating is the fact that two males (Bart and Mike) who, because of management problems, have been allowed to range freely through urban areas for prolonged periods of time, both returned to their natal area. Bart achieved this despite being relocated to Cape Point!

Thus the precautionary principle that the dispersal subcommittee is applying to return baboons to their natal areas on first capture is not only based on baboon biology (dispersal is a gradual event and not a once off dash through vast tracts of baboon-less space) but furthermore has been shown to be a decision used by Peninsula baboons themselves if allowed freedom of movement. It is important to bear in mind that relocating an animal to an entirely new area, with which it has no prior experience and no accumulated knowledge of the local troops or their composition, is a highly improbable event in a natural population (how would a baboon effect such a move?) . In addition, this is arguably much more stressful (following the trauma of a preceding chase and subsequent capture by humans) than being returned to the natal area. If males continue to show readiness to leave their natal area (after being relocated back to it), the protocol accepts their intent and prescribes translocation to a new area.

In conclusion, whilst returning a baboon to its natal area increases the potential for a greater number of total catches required by a service provider (i.e., their job becomes exponentially more difficult) it defers to the best interests of the baboon. This will allow for those who wish to stay to do so (Myles, remained in Tokai for two years and completed his life history as a baboon within a troop outside of the urban edge). In addition, it will provide all baboons with an opportunity to directly assess the benefits of leaving their natal area against the costs of staying without being summarily relocated to a troop which may or may not accept a dispersing male. The latter point needs to be considered in light of the proximity of all Peninsula troops to urban areas, the propensity of males to be attracted to and raid urban areas, and the current lack of funding to actively monitor and herd individual dispersing males.