Resource competition between spotted hyaenas, Crocuta crocuta, (Erxleben 1777), and brown hyaenas, Parahyaena brunnea, (Thunberg 1820)

[摘要] Field data were collected and analysed on the feeding and spatial ecology of spottedhyaenas and brown hyaenas living in the Madikwe Game Reserve. Methods used to estimate thepopulation of spotted and brown hyaenas include audio call-in surveys, photographic records andmark-resighting. The localized convex hull method was used on data collected from latrinesurveys, radio-telemetry, sighting records, and camera-trapping to determine the spatial ecologyof hyaenas in Madikwe. Faecal analysis and carcass observations were used to determine theprey consumption and dietary components of hyaenas.Population estimates of spotted and brown hyaenas in Madikwe using the NOREMARKmethod proved smaller than originally presumed by park officials. The brown hyaena populationin Madikwe is critically small at 11 to 13 individuals and needs to be monitored. Spotted hyaenasare 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 areseparated by extended time periods during long-term monitoring. Hyaenas appeared to becomehabituated to successive repeated uses of the surveys and the numbers of hyaenas responding tothe survey decreased accordingly. Hyaena responses to the audio call-in surveys also fluctuatedwith respect to the presence or absence of other predators, showing a decrease in response whenlions responded to surveys.Range sizes of spotted hyaenas and brown hyaenas were large and covered nearly theentire reserve, and overlapped considerably with each other. The localized convex hull method isone of the most robust tools used in spatial analysis and was employed to determine theutilization distributions and range sizes of Madikwe's hyaenas based on spatially fixed points ofhyaena 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 hadsmaller range sizes in the dry season, with larger range sizes in the wet season. Brown hyaenashad 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 overlapof 343.0km2. The overlapped area was significantly larger than areas which were exclusivelyused by spotted hyaenas (± 68.8km2) or brown hyaenas (± 92.3km2).Dietary analysis of hyaenas living in Madikwe depicted a near perfect overlap in foodgroups and prey remains. Brown hyaenas were shown to exploit a slightly wider dietary breadththan spotted hyaenas, utilizing birds and reptiles in their diets, but both hyaenas exploited largermammals more often than smaller mammals. Impala and blue wildebeest were the mostimportant food source for hyaenas in Madikwe and other less important food types wereseasonally important. Invertebrates featured prominently in hyaena diets in the wet season, whileseeds featured prominently in hyaena diets in the dry season. Spotted and brown hyaenastemporally and spatially avoided one another while foraging and at carcasses. Hyaenas oftenforaged 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 andnot under any immediate threat. However, the low numbers of brown hyaenas presents a concernas to the viability of the population. Competition for the same resources is significant betweenspotted and brown hyaenas, and efforts to reduce the number of spotted hyaenas throughtranslocation to other reserves may be beneficial in ensuring that brown hyaena populations inMadikwe remain stable. As the lions in Madikwe provide much of the carcasses for hyaenas tofeed on, future research may also look at the effect of lions in regulating the spotted hyaenapopulation, and how this may or may not benefit the brown hyaena population.

[发布机构] University of Pretoria