Brief communication
Fire in Africa and the effect on herbivore behaviour
African herbivores have for a long time interested researchers all over the world and the questions and aims have been many. African herbivores and their behaviour have been the interest in this study and mainly the Thomson’s gazelle. Thomson’s gazelle is one of the great migratory species which moves between Serengeti and the Masai Mara every year. In these parks/reserves, fire is a common tool for maintaining savanna diversity (Lunt and Morgan 2002). Why fires are commonly used is low costs, universal ability and can be used over large areas (Mistry 1998). After a fire the nutritional quality and release of nutrient is high in turn leading to high re-growth of the grass ( Russel-Smith et al. 1998 ). We observed a total amount of 18 herbivore and the behaviours used for analysis was grazing, lying, stand/self-lick and walk/run. The behaviours and preferences were compared at three different treatment, control, early fire and late fire and were conducted in the Masai Mara National Reserve 2004, Kenya , and the aim was to see if; fire affected the choice of habitat, if fire affected the behaviour of African herbivores, or if fire affected the diurnal behaviour. For the sampling of data the we used the line transect method (Buckland et al. 1993). A total amount of 36 transect were used: nine transects burned in June 2004 (early fire), nine transects burned in October 2004 (late fire) and 18 transects not burned within the last year (control). For estimations of the fire intensity, biomass was cut on twenty 0.125 m2 squares before fire, to determine type of fire. Fuel loads ≤150 g/m2 is a cold fire and fuel loads >300g/m2 is a hot fire, hot fires cause more damage ( Dublin 1995). The biomass was on all transect above 300 g/m2 which resulted in hot fires. The total count on herbivores was 3447 observations and 19571 individual observations. These observations was pooled together in one group and analysed as all herbivores. Thomson’s gazelle was also analysed separately. When comparing different habitats (control, early fire and late fire), the majority of animals preferred the late fire then early fire and last the control areas. The same result was found on Thomson’s gazelle. (Table 1).
Table 1. P-values of habitat usage for group all herbivores and Thomson’s gazelle (Mann-Whitney U-test)
|
Species |
Treatment |
Z-value |
P-value |
|
All herbivores |
Control: Early fire Control: Late fire Eary fire: Late fire |
-2.984 -3.550 -2.605 |
0.003 <0.001 0.009 |
|
Thomson’s gazelle |
Control: Early fire Control: Late fire Early fire: Late fire |
-4.324 -4.491 -3.578 |
<0.001 <0.001 <0.001 |
When doing the analysis on behaviour the results concluded that all herbivores preferred grazing at late fire treatment over the early fire (P<0.001). Lying is a behaviour that is somewhat associated with ruminating and comparing the control areas with high grass (low visibility) and early fire areas with low grass (high visibility) the early fire was more used (P=0.045). This was also seen when comparing the control areas with the late fire treatment (P=0.005) where late fire was preferred. There was no significant difference between the two different fire treatments. Stand/self-lick (standing and self-lick was treated as one group) is also a behaviour associated with ruminating or a relaxed state and was preferred at early fire (P<0.001). Also when looking at the behaviour walk/run (walk and run was treated as one group) the early fire compared to control was favoured (P<0.001). For the Thomson’s gazelle the control areas were excluded in the analysis due to low counts. They preferred grazing at late fire treatment (P>0.001) where grass is fresh and were nutritional values are high (Russel-Smith et al. 1998) lying did not differ between the fire treatments, stand/self-lick (P>0.001) and walk/run (P=0.033) was preferred at the early fire. For analysing the diurnal behaviour the day was divided into three different periods. Morning (06.30-08.29), midday (08.30-16.29) and evening (16.30-18.30). The group all herbivores preferred grazing during morning, lying was preferred during midday when temperature was higher. Stand/self-lick during midday and walk/run during morning. For the Thomson’s gazelle grazing was preferred during evening, lying during the hottest hours as all herbivores. Stand/self-lick did not differ significantly between the periods and walk/run was preferred during morning when activity begins and when walking to daily pastures. (Table 2)
Table 2. Diurnal behaviour of all herbivores and Thomson’s gazelle (Mann-Whitney U-test)
|
There is a lot of reasons for why a species prefers an area the recently been burned over others, for example nutritional requirements, predation, competition, migration and so forth. I have not gone in to all different reasons for why this is, but simply if fire affects the behaviour of some species, the conclusion is that for some species it does whilst for some it do not.
References
Lunt, ID, Morgan JW (1999) Effects of time-since-fire on the tussock dynamics of a dominant grass (Themeda triandra) in a temperate Australian grassland. Biological Conservation 88, 379-386.
Mistry J (1998) Decision-making for fire use among farmers in savannas: an exploratory study in the Distrito Federal, central Brazil. Journal of Environmental Management 54,321–334.
Russel-Smith J, Ryan PG, Klessa D, Waight G, Harwood R ( 1998). Fire regimes, fire sensitive vegetation and fire management of the sandstone Arnhem plateau, monsoonal Northern Australia. Journal of Applied Ecology. 35:6, 829-846.
Dublin HT (1995) Vegetation dynamics in the Serengeti- Mara ecosystem. The role of elephants, fire, and other factors pp 71-90. In: Sinclair ARE, Arcese P (eds) Serengeti II: Dynamics, Management and conservation of an Ecosystem. University of Chicago Press, Chicago.
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05/31/05