Figure 1.
Western Namibia, showing the Hoarusib and Hoanib catchment areas of the western Kunene, and the Uniab and Huab catchment areas of the eastern Kunene together with the location of the Omusati region.
Isolines (mm) of mean annual rainfall are superimposed [6].
Figure 2.
(a) Surface and satellite-based rainfall study region, land areas from 12° to 16° east longitude by 17° to 21° south latitude (b) TRMM rainfall region—8° to 23° east longitude by 13° to 25° south latitude. TRMM located storms are shown for 30 December 2004.
Figure 3.
Daily total area rainfall is shown over the 400×400 km Study Region (a) for each of the five years (2002 to 2006) based on 0.25°x0.25° spatial resolution and determined from a hybrid climatology of surface raingage and satellite-based estimates of rainfall.
The extreme rainfall of 6360 cm over the Study Region (a) on 21 February 2002 is only partially shown.
Table 1.
Dry season to wet season transition days based on the climatological record of rainfall in Study Region (a), see Figure 2 for detail.
Table 2.
Wet periods within the dry season based on the climatological record of rainfall in Study Region (a), see Figure 2 for details.
Table 3.
Summary of GPS data availability for each elephant.
Figure 4.
Behavioral Change Point Analysis (BCPA) results for elephant EKF-01 in 2003 showing the elephant's persistence velocity (Vp).
The mean, variance, and autocorrelation of Vp are tracked by passing a moving analytical window through the data. Times when statistically significant changes in these three parameters are observed are indicated by the vertical bars, and their midpoints are labeled below the horizontal axis (e.g., the first break point is 9/9). Colors of the circles are coded according to the autocorrelation of the persistence velocity, as shown in the key on the lower right. The dry–wet season transition occurred on 22 October and is indicated by the thick vertical line. Horizontal red and green bars show the 24 days before (red) and after (green) a within-dry season wet event; blue horizontal bar depicts the wet season.
Figure 5.
Summary of Behavioral Change Point Analysis (BCPA) of 9 collared elephants totaling 16 tracking years from 2003 to 2006 when BCPA indicated a significant change in the mean, variance, or autocorrelation of persistence velocity.
Solid black dot is the dry-wet Transition Date (TD). Time on the horizontal axis increases to the right, i.e., movement changes occur after the TD and decreases to the left, i.e., movement changes occur before the TD; the horizontal axis, as shown in the key, is in increments of one week. Vertical arrow shows the direction of the parameter change: up = parameter increase; down = parameter decrease. Tagged elephants are identified by a three-letter code followed by a number: E (eastern) or W (western); K (Kunene) or O (Omusati); and F (female) or M (male).
Table 4.
Comparison of mean elephant movement rates (km/hr) prior to and after the dry-to-wet season transition dates and results of unpaired, two-sample t-test based on the rates 24 days before and after each transition.
Figure 6.
Statistically significant elephant movements in days before and after the transition date.
Only changes observed within 24 days of the transition date are included.
Table 5.
Summary of near simultaneous change of movements of more than one elephant relative to the timing and location of the nearest rainfall event.
Figure 7.
(a) TRMM 3-hourly rainfall distributions (grey) relative to the tracking rectangle for WKF-16a1 (solid rectangle) and WKM-10 (dashed rectangle) for 8 November 2003, with (b) tracks of elephant WKF-16a1 and (c) tracks of elephant WKM-10 for 2003 and 2004 (solid grey = wet season; dash-dot black = dry season; bar = 8 km, see also Table 5).
Figure 8.
(a) TRMM 3-hourly rainfall distributions (grey) relative to the tracking rectangle for EKM-06 (solid rectangle) and EKM-03 (dashed rectangle) for 5 December 2004, with (b) tracks of elephant EKM-06 and (c) tracks of elephant EKM-03 for 2004 and 2005 (solid grey = wet season; dash-dot black = dry season; bar = 8 km, see also Table 5).