Abstract
Despite a large number of studies on tick biology, there is limited information on long- term changes in tick populations. This study thus aimed to assess the long-term population dynamics of questing ixodid ticks in two landscape zones of the Kruger National Park (KNP). Questing ixodid ticks were collected in the KNP from August 1988 to March 2002 by monthly dragging of the vegetation in three habitats (grassland, woodland and gully) at two sites (Nhlowa Road and Skukuza). Findings pertaining to total tick numbers and Amblyomma hebraeum and Rhipicephalus decoloratus specifically are presented here. Fourteen tick species were collected, as well as four others that could be identified only to generic level. More ticks (211 569 vs 125 810) were collected at Nhlowa Road than at Skukuza. Larvae were the most commonly collected stage of all the major tick species. A. hebraeum was the most commonly collected tick (63.6%) at Nhlowa Road, whereas R. decoloratus accounted for 15.3% of the ticks collected there. At Skukuza, 31.6% and 27.1% of the collected ticks were R. decoloratus and A. hebraeum respectively. Most A. hebraeum larvae were collected in summer and the fewest in winter and early spring, mostly in woodland and least often in grassland habitats. Most R. decoloratus larvae were collected in spring and the fewest in autumn and winter, and were more frequently collected in woodland and grassland than in gullies. The largest collections of most tick species were made during the early 1990s, while numbers were lowest in the mid-1990s after a drought during 1991 and 1992 and then increased towards the late 1990s, followed by a final decrease. The changes in tick numbers over time probably reflect differences in their host communities at the two sites and the effect of climatic conditions on both hosts and free-living ticks. The population dynamics of questing ticks reflect a complex interaction between ticks, their hosts and the environment.
Highlights
Tick populations are influenced by a complex interaction between the ticks, their hosts and the environment
In the present communication we describe changes in the populations of questing ticks, and of two major species, A. hebraeum and Rhipicephalus decoloratus, collected from the vegetation in two landscape zones in the Kruger National Park (KNP) monthly over a period of 164 months
At Nhlowa Road, A. hebraeum accounted for 63.6% of the ticks collected and was the species most commonly collected in all years (Figure 2a)
Summary
Tick populations are influenced by a complex interaction between the ticks, their hosts and the environment. In South Africa, Horak and Boomker (1998) collected ticks from bontebok, (Damaliscus pygargus dorcas) and grey rhebok (Pelea capreolus) in the Bontebok National Park over a 10-year period. Horak et al (1993) and Horak et al (1995b) monitored the changes in tick populations on scrub hares (Lepus saxatilis) at Skukuza in the Kruger National Park (KNP) monthly over a period of 6 years. Most Amblyomma hebraeum larvae were collected from the hares between November and March or April and an erratic decline in numbers was observed over the 6-year survey period. The numbers of larvae of the two-host tick Hyalomma truncatum peaked on the hares between May and August every year and the nymphs between June and September. No noticeable decline in their numbers was evident during the 6 years of the survey
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