Prey availability and consumption are major factors affecting rates of wild dog population change, survival and the spatial requirements for ensuring persistence of a resident wild dog pack. Wild dogs usually prey on the most abundant medium-sized to large prey species and generally utilize prey in proportion to abundance (Fuller & Kat 1990; Pole 1999; Lindsey et al. 2004). Reserves may need to manage their wild dog populations to ensure that prey consumption does not exceed a level which the reserve can sustain financially or ecologically. It is therefore important for metapopulation reserves to assess their prey population to ensure that sufficient prey species are present and in adequate density before reintroducing wild dogs. It is suggested that a management plan for reintroduction of wild dogs onto a reserve is compiled with input from an ecologist experienced with carnivore reintroductions.
Perimeter fencing of a reserve needs to be considered when assessing potential impact on prey since if wild dogs learn to use this boundary in their hunting strategy, it may enable them to catch larger prey than they would commonly do so in a particular area (Lindsey et al. 2004a). The consumption of prey by other predators in the area, as well as other factors contributing to prey mortality must also be carefully considered when measuring the impact of wild dogs on prey populations.
Prey populations should be periodically assessed after wild dogs have been reintroduced to ensure sufficient prey numbers are maintained. The following guideline for determining potential prey requirements may provide a useful model for managers although it needs to be remembered that this is only a guideline, despite being based on substantial research.
This method (Lindsey et al. 2004a) calculates the minimum population size of a prey species required to sustain predation by a pack of wild dogs over a period of one year (Nmin). It is important to remember that this model relies on several assumptions; 1) that the standard unit mass for prey species is used for estimates with no differentiation between prey sex weights accounted for; 2) that carrying capacities for prey populations are constant; 3) the impact of competing predators is not accounted for and that 4) prey-profiles of wild dogs reintroduced into small areas would represent those observed in large areas of similar habitat (Lindsey et al. 2004a).
To give a general, conservative idea of the prey and area requirement of wild dogs on your reserve, established prey-profiles of species consumed by wild dogs have been used to represent four regions in South Africa:
- Southern Kruger representing north-eastern South Africa (Mills & Gorman 1997)
- Save Valley Conservancy (south-eastern Zimbabwe) representing northern South Africa (Pole 1999)
- Hluhluwe-iMfolozi Park in KwaZulu-Natal representing eastern South Africa (Kruger et al. 1999)
- Pilanesberg in North-West Province
Using the known intrinsic growth rates of the particular favoured prey species for each region, and the calculated consumption rates of those particular species by wild dogs, the estimated prey population sizes to support a pack for a year were calculated. For more detailed interrogation of this model it is suggested to consult Lindsey et al. 2004a.
Minimum population sizes and areas required to support predation by a pack of 12 wild dogs (pack of seven dogs, plus one year’s offspring at one year of age), given each of four prey-profiles (Lindsey et al. 2004a). Estimated reserve area required is the sum of the two km2 areas listed in each prey profile. Useful conversion: 1 km2 = 100 ha.