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Resource competition between spotted hyaenas, Crocuta crocuta, (Erxleben 1777), and brown hyaenas, Parahyaena brunnea, (Thunberg 1820)
Field data were collected and analysed on the feeding and spatial ecology of spotted
hyaenas and brown hyaenas living in the Madikwe Game Reserve. Methods used to estimate the
population of spotted and brown hyaenas include audio call-in surveys, photographic records and
mark-resighting. The localized convex hull method was used on data collected from latrine
surveys, radio-telemetry, sighting records, and camera-trapping to determine the spatial ecology
of hyaenas in Madikwe. Faecal analysis and carcass observations were used to determine the
prey consumption and dietary components of hyaenas.
Population estimates of spotted and brown hyaenas in Madikwe using the NOREMARK
method proved smaller than originally presumed by park officials. The brown hyaena population
in Madikwe is critically small at 11 to 13 individuals and needs to be monitored. Spotted hyaenas
are slightly more abundant at 20 to 30 individuals, but still merit monitoring of their numbers.
The audio call-in survey method is effective when used for the first time or when surveys are
separated by extended time periods during long-term monitoring. Hyaenas appeared to become
habituated to successive repeated uses of the surveys and the numbers of hyaenas responding to
the survey decreased accordingly. Hyaena responses to the audio call-in surveys also fluctuated
with respect to the presence or absence of other predators, showing a decrease in response when
lions responded to surveys.
Range sizes of spotted hyaenas and brown hyaenas were large and covered nearly the
entire reserve, and overlapped considerably with each other. The localized convex hull method is
one of the most robust tools used in spatial analysis and was employed to determine the
utilization distributions and range sizes of Madikwe’s hyaenas based on spatially fixed points of
hyaena presence. Utilization distributions obtained from latrine surveys and camera-trap data indicated seasonal differences in the area use and range sizes of hyenas. Spotted hyaenas had
smaller range sizes in the dry season, with larger range sizes in the wet season. Brown hyaenas
had larger range sizes in the dry season, which contracted considerably in the wet season.
Hyaena utilization distributions overlapped for 581.4km2 of the reserve, with an average overlap
of 343.0km2. The overlapped area was significantly larger than areas which were exclusively
used by spotted hyaenas (± 68.8km2) or brown hyaenas (± 92.3km2).
Dietary analysis of hyaenas living in Madikwe depicted a near perfect overlap in food
groups and prey remains. Brown hyaenas were shown to exploit a slightly wider dietary breadth
than spotted hyaenas, utilizing birds and reptiles in their diets, but both hyaenas exploited larger
mammals more often than smaller mammals. Impala and blue wildebeest were the most
important food source for hyaenas in Madikwe and other less important food types were
seasonally important. Invertebrates featured prominently in hyaena diets in the wet season, while
seeds featured prominently in hyaena diets in the dry season. Spotted and brown hyaenas
temporally and spatially avoided one another while foraging and at carcasses. Hyaenas often
foraged alone or in small numbers in Madikwe, and were never observed to hunt large prey.
The spotted hyaena population in Madikwe appears to be functioning relatively well and
not under any immediate threat. However, the low numbers of brown hyaenas presents a concern
as to the viability of the population. Competition for the same resources is significant between
spotted and brown hyaenas, and efforts to reduce the number of spotted hyaenas through
translocation to other reserves may be beneficial in ensuring that brown hyaena populations in
Madikwe remain stable. As the lions in Madikwe provide much of the carcasses for hyaenas to
feed on, future research may also look at the effect of lions in regulating the spotted hyaena
population, and how this may or may not benefit the brown hyaena population.