Human Conflict
Evaluating Chacma Baboon Deterrents in the Cape Peninsula
Introduction
In a world with a human population that is expanding numerically and spatially at an appreciable rate, human-wildlife conflict is becoming a particularly relevant field. This conflict is typified in the Cape Peninsula of South Africa.
Human developments in this area range from agricultural (vineyards in Constantia and Tokai), to residential and governmental (e.g. a naval base in Simon's Town). The Peninsula is also home to a number of baboon troops. Some of these troops live within the boundaries of the Cape of Good Hope Section of the Table Mountain National Park (CoGH) and never enter human developments. Several troops, however, live outside the CoGH and frequently enter the urban fringe. These troops are largely motivated by the attraction of human food. Raiding by troops often results in property damage, stress to both humans and baboons and the injury and mortality of baboons (often by car collisions, E. Beamish, unpubl. data). Unsurprisingly there are a number of methods that have been proposed and in some cases, employed to discourage baboons from entering the urban environment.
Deterrents
Deterrents can be classified as either disruptive or aversive. Disruptive deterrents use fairly simple concepts, such as loud bangs, light flashes or unusual images (e.g. fladry, pictured below) to surprise animals that venture into 'no-go zones'. In theory, these animals will dislike the surprising cue and will avoid the areas where these deterrents are located.
Aversive deterrents aim to condition the behaviour of an animal. Essentially the deterrent is only activated when the target animal performs a certain unwanted behaviour (e.g. feeding on crops). Theoretically the animal will learn to associate the deterrent with a particular behaviour and in an effort to avoid the deterrent, will stop exhibiting that offending behaviour.
Importantly, aversive deterrents are not necessarily more complex, more expensive, or more effective than disruptive deterrents. Arguably however, aversive deterrents may be less susceptible to habituation than disruptive deterrents.
Habituation
Overexposure to a stimulus can result in habituation. This overexposure can limit the response a stimulus originally evoked. For example, the banging of pots and pans as a deterrent may initially startle a baboon, but in time the baboon will become accustomed to the sound and will cease to be startled. This must not be confused with conditioning. In the case of conditioning, a stimulus is paired with a particular outcome. The animal will learn to associate the outcome with the stimulus to such an extent that when the stimulus is used, the animal expects the outcome. Thus, if a baboon feeds on oranges (stimulus) and those oranges contains a chemical that makes the baboon nauseous (outcome), in time the animal will associate oranges with nausea. Subsequently, when seeing an orange, the baboon will expect nausea, and will presumably make an effort to avoid it. In this way, deterrents susceptible to habituation (pots and pans) and those relying on conditioning (chemical in orange) work in opposite ways. Greater exposure to the pots and pans, the less likely they are to work, while greater exposure to the oranges makes them more likely to work. Thus, the mechanism of habituation limits the length of time over which certain deterrents will be effective. The time over which a deterrent is effective, however, is only one way in which a deterrent's success can be measured.
Measuring Efficacy
A deterrent's efficacy can be measured using two basic parameters: percentage exclusion and
habituation-susceptibility. Both parameters rely on measuring the habitat use of a troop.
Habitat use is determined by recording the troop's position at a set time interval (e.g. every 30 minutes)
throughout the day. Over time, these recordings can be grouped and a troop's habitat use,
calculated (e.g. Urban area: 40%; Natural vegetation: 40%; Alien vegetation: 20%).
This habitat use is then used to quantify success in the two measures of deterrent efficacy.
Percentage exclusion is measured by comparing the habitat use of a selected baboon troop before
(baseline) and after (treatment) applying a deterrent. Specifically, the use of the urban area
(or no-go zone) will be examined. A successful deterrent is one that is able to significantly
reduce the percentage time spent in the urban area over a given time period (e.g. 10 days).
Habituation-susceptibility (or long-term success) will be measured by comparing the habitat
use of a troop (esp. the urban area) between selected time periods (e.g. 10 days) after a
deterrent is applied.
For example, a deterrent is activated on day zero. After this,
habitat use in period 1 (days 1-10); period 2 (days 11-20);
period 3 (days 21-30)
and period 4 (31-40) will be recorded and compared with one another. This will assess
whether the efficacy of the deterrent remains constant over time. Habituation to a
deterrent might show an increase in urban space use in periods 3 and 4.
Testing a deterrent on the percentage exclusion it can effect and its susceptibility to
habituation will give a balanced idea of its value. In addition, this will also
prescribe the situations in which the deterrent in question should be used.
The most effective method of excluding baboons from the urban area will be
one that utilises the strengths of each deterrent and one that considers a combination thereof.
Toolkits
The application of a single deterrent to exclude a baboon troop from an area is unlikely to be highly effective over an extended period of time. The efficacy of deterrents will be restricted by various factors including cost, time of year, susceptibility to habituation and geographical and social factors. Importantly, deterrents will differ in their restrictions. Applying two deterrents that complement one another in their abilities might prove to be more successful than applying either of those deterrents in isolation. The outcomes of the testing mentioned above will be able to quantify the abilities of each deterrent. Then, based on the profiles of individual human-baboon conflict sites, several deterrents can be pulled out of the deterrent 'toolkit' and used as needed. For example, in an area where baboons only enter the urban edge seasonally, the deterrent employed need not be 'habituation-proof', and can thus be of a disruptive nature (see above). An aversive deterrent can also be deployed simultaneously and over time, as the troop habituates to the disruptive deterrent, so the aversive deterrent becomes more effective. For now, these are only concepts and they will be explored as the project unfolds.
The Holistic Approach
A holistic approach to management will increase the success of any deterrent strategy.
Baboons entering an urban environment can be considered to be using a trade-off approach. That is, balancing the rewards obtained (human food) versus the risk taken by entering the urban environment (chance of stress, injury or mortality). Successful deterrents should increase the risk of entering the urban environment. Reducing the availability of food in the urban area will reduce the incentive to enter the urban edge and increase the efficacy of any deterrent. While this aspect of management may be difficult to quantify through measurement, its impact may be significant. This reduction in the availability of human food will come about through intensive educational programmes, communication with residential bodies and the support of conservation authorities. Through this, the difference between risk and reward of entering the urban space can be increased. This will hopefully reduce the time that baboons spend in the urban environment. This project will directly assess the efficacy of baboon deterrents and predict the success of a wide range of strategies. Following my assessments, collaboration with scientists, local residents, managers and authorities will provide a platform from which human-baboon conflict in the Peninsula can be addressed.
