Puku are very abundant in the study regions. This makes them a possible prey for every predator. Although not preferring puku, a lot of the large carnivores might prey upon puku just because it is abundant. Occurrence of large predators that probably kill puku was found to be higher in Kafue Region than in Kasanka NP. However, few sightings and hints are available for Kasanka NP, especially concerning the leopard (FRANK WILLEMS, pers. comm.).
Systematic search for scats and also the camera trap study could not clearly prove the presence of large terrestrial predators, but revealed the presence of medium sized carnivore species. However, caracals and perhaps side striped jackals might exercise predation on (young) puku in Kasanka NP, but rather fractionally compared to Kafue Region. The occurring medium sized carnivore species, like mongooses or civet, consume meat of puku but without exercising a predation pressure on the puku’s population. The abundance of puku influences the amount of available carrion.
The absence of predators enables herbivores to increase many more times than
‘normal’ which causes a trophic cascade (TERBORGH et al. 2001). Intense grazing favours unpalatable grasses and thus increases the resistance of the vegetation which then reduces carrying capacity for grazers (TERBORGH et al. 2001). Large predators do no longer occur on much of the Earth’s surface: top-down regulation is replaced by bottom-up regulation becomes more and more widespread (TERBORGH et al. 2001).
The characteristics of the puku’s population were different in each study region (see Chapter 2). The puku’s population in Kasanka NP was characterised by high densities at specific localities as well as generally in more open habitat than in Kafue Region. The males of various African ungulates have been shown to be especially vulnerable to predation (POLE et al. 2004) – and male groups of puku were observed more often in Kasanka NP. Moreover, zebra population in the Serengeti might be limited by the first year survival of zebra (GRANGE
et al. 2004). Thus, the high numbers of male and juvenile puku in Kasanka NP might be a further indication of less predation pressure on the puku in Kasanka NP.
On the other hand, biodiversity of both bovid and carnivore species was apparently higher in Kafue Region. In systems with diversity of predators and prey, top-down and bottom-up regulation affect simultaneously herbivore populations (SINCLAIR et al. 2003). Thus abundance of herbivores is limited by predation and by resources (SINCLAIR et al. 2003). The presence of top predators can increase the diversity of prey species via intermediate disturbance effects (SINCLAIR & BYROM 2006). Despite that, predators can reduce the diversity
as shown for lizards and spiders in the Caribbean (SINCLAIR & BYROM 2006). Taken as secondary prey, rare species are reduced by predators that depend on more common prey (SINCLAIR & BYROM 2006). Barida NP, Nepal, was resurveyed after 22 year of protection. The abundance of ungulates increased but this was mainly due to the increase of a few species (WEGGE et al. 2009). The predators occurring on that site, namely tiger (Panthera tigris) and leopard, did not choose the most abundant prey. In this case, as with the lizard example, the large carnivore might not maintain or stabilize the ecosystem (WEGGE et al. 2009). WEGGE et al. (2009) recommend improving the habitat conditions that changed due to shifts in the ungulate society. Further, conservation planning needs to take into account the needs and impacts of predator and prey to prevent negative effects on ungulate populations (WEGGE et al. 2009). This might take place similarly in Kasanka NP, if densities of predators increase due to conservation effort and management. Thus, this should encourage to monitor and survey population density and distribution of carnivore and herbivore species, not only in Kasanka NP but in all protected areas.
Each predator needs a specific amount of meat to fulfil its nutritional requirements.
These amounts are different for each carnivore species (HAYWARD 2006, HAYWARD et al.
2006a, HAYWARD et al. 2006b, HAYWARD et al. 2006c, WEST & PACKER 2013); generally they increase with increasing body size of the predator. This means that the predators have a different impact on puku in respect to their general preference of particular prey and to their amount of meat needed. This makes a general evaluation of the exact predation pressure difficult. Furthermore, ‘Predation needs to be analysed for each particular situation and its influence may vary not only spatially, but also temporally within a certain area’
(SMUTZ 1978, cited from HAYWARD & KERLEY 2005). This citation summarises that predation upon puku as in general upon the antelope society changes in time and space. When looking at the distribution of the kills through the course of a year (MITCHELL et al. 1965), puku appear to suffer more from predation during the dry season. On the one hand, during the rainy season the growing vegetation, as well as the wet soil, might generally reduce the carnivore’s hunting success. Further, puku in Kasanka NP showed different patterns in habitat use during the rainy season (see Chapter 2) which might affect positively their susceptibility. Additionally sexes might be killed differently because of weight constraints or because of differences in habitat use or sociability. This means that there are many aspects that need to be assessed about the relation of predator and herbivore population. Dietary analyses of nearly all predator species are rather lacking in the miombo ecoregion. This research should be emphasized as one basis for the understanding of the animal community in Zambia.
5 Activity patterns of puku
Abstract
The aim of this study was to find out about different behavioural patterns of puku (Kobus vardonii) in the course of a day, during different seasons and in different study regions. This was complemented by behavioural observations of impala (Aepyceros melampus) to check for a possible interference competition.
Observations were conducted from viewpoints at Kabwe Plain in Kasanka NP during the cool dry season 2009, the hot dry season 2010 and the late rainy season 2011 and at Puku Pan in PPKR during the cool dry season 2010. This was complemented by data from transect line sampling. At the viewpoints behaviour was measured every 10 minutes in a way that all hours of a day were covered twice. Behaviours were measured by scan sampling and the recording rule was instantaneous sampling.
Distribution of grazing and resting was rather similar in all study regions, especially during the cool dry season. In all study regions and seasons, puku were found active and thus grazing mainly at dawn and at night, confirming earlier statements by DE VOS & DOWSETT
(1964). Puku were not dayactive, although some diurnal activity took place. During the main parts of day, puku rested. Results implied peaks of resting during the morning, around midday and during the afternoon that were more or less pronounced in the different surveys. This might be related to increasing temperatures but also to the need to ruminate.
The need to ruminate, which, at least in Kasanka NP, appears higher during the hot than during the dry season. A probable explanation might be the food quality, which is suggested to be lower during the hot dry season and which makes puku spend more time on resting.
Impala were found to move more than puku, reducing by this interference competition. The two species were observed grazing only. In contrast to puku, impala are predominantly diurnal and forage mainly during the day, although some foraging behaviour can happen at night (JARMAN 2011). Although not observed at night during this study, the time schedule might be the main difference in activity patterns between these antelope species.
Concerning resting behaviour, puku were observed very often lying down while resting in contrast to impala that kept standing. Unlike puku, impala are a preferred prey of several predators which might justify this behaviour. Although more possible predators are available in PPKR, puku there did not show any increased vigilant behaviour in comparison to the findings from Kasanka NP.
As puku exhibit differences between sexes according to habitat choice (see Chapter 2) and also concerning their diet (see Chapter 3). Further, the territoriality might influence the behaviour. Dimorphism in behaviour patterns between sex and age classes are expected as well as a particular activity patterns in the rainy season which would underline the need for further analysis of the available data as well as for expanded observations.