Desert Lions

History

Demography

Habitat

Socio-ecology

Behaviour

Dispersal

Habitat utilisation

Habitat preferences
Home ranges
Nocturnal movements
Coastal movements

Habitat preferences
During 2006, four lionesses in the Hoaruseb and Hoanib Rivers were monitored. They occupied an area of 4,309 km2 between the two river systems (see Figure 29). This area was divided into eight distinct habitat types, using ArcView Spatial Analyst (Table 4). Mountains, rocky outcrops, dunes, and plains comprise 90% if the habitat, whilst the ephemeral river systems and the coastal belt add up to only 10% (Figure 24). Habitat selection by the lions was calculated from 1696 radio tracking fixes using Spatial Analyst. The lions did not use the available habitat uniformly and spent significantly more time in the two ephemeral river systems and the Hoanib floodplain, than expected (Figure 25). Rocky outcrops was the only habitat type that lions used equal to its availability. Lions killed prey animals in all eight habitat types, and mostly in the same proportions when compared with the time they spent in each habitat (Figure 26). They were most successful in catching prey along the Coast, whilst the Mountain and Hoanib habitats produced less than the expected number of kills.

Table 4. The surface areas of eight habitat types between the Hoanib and Hoaruseb Rivers, and the number of radio tracking fixes and kills in each habitat type by four lionesses in 2006.

Figure 24. Proportions of eight habitat types in a area utilised by four lionesses between the Hoanib and Hoaruseb Rivers in 2006.

Figure 25. Preferential habitat selection, expressed by the 2 value, of lions between the Hoanib and Hoaruseb Rivers in 2006. The proportions of the eight habitat types and the number of fixes in each habitat were compared using a 2 goodness-of-fit test. If lions selected a habitat equal to the proportional size of that habitat type, the Chi-sqr value [Sqrt(Observed/Expected)] would be 1, and the value would increase if the habitat were favoured.
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Figure 26. Preferential selection of habitat types, expressed by the 2 value, where lions killed prey animals, between the Hoanib and Hoaruseb Rivers in 2006. The number of fixes and kills in each habitat type were compared using a 2 goodness-of-fit test. If lions killed prey animals in a habitat equal to the number of fixes in that habitat type, the Ch-sqr value [Sqrt(Observed/Expected)] would be 1, and the value would increase if they were most successful in that habitat.
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During daytime radio tracking sessions (N = 597) lions were observed in eight habitat categories (Fig. A15). Ephemeral rivers, mountains (28%) and springs are the three most important habitat types (total = 92%) that lions utilise for daytime resting. During nocturnal movements and foraging, lions are expected to utilise the habitat more uniformly

Fig. A15. Summary of habitats favoured by Kunene lions (N = 597).

Home ranges
The areas occupied by the Kunene lions are the largest home ranges ever recorded for the species (Table A4). With the increase in sample sizes the two methods (MCP and Kernel) are calculating similar estimates of home ranges size for most individuals. The home ranges of the Aub and Agab prides, that utilise similar habitats, are similar in size, for both the MCP and Kernel methods. There is extensive overlap between the different groups, and especially so for the male groups, where the size of the habitats they utilise increase continuously. Land tenure systems appear to be driven by ecological factors, such as prey availability, and density dependent factors, but more research is needed to address this.

Table A4. Home ranges of Kunene lions.

1 The percentage of fixes where the MCP home range estimate reached an asymptote of at least 95% of the total MCP-estimate, based on bootstrap analyses.

Detailed maps showing the home range size and areas utilised are presented here for each group of lions. (Click to view enlargement of maps)

Aub Xpl-2, 5, 9

Agab Xpl-17,18

Hoaruseb Xpl-10

Huab/Ugab (1) Xpl-4

Huab/Ugab (2) Xpl-16

Hoanib Xpl-3

Hobatere Xpl-20

Secumib Xpl-29

The home range of the Hoaruseb lionesses is dynamic. During 2006 the group ranged in an area of 3,604 km2, between the Hoanib and Hoaruseb Rivers (Figure 29). However, the founding female of this group has been monitored since the age of 14 months, starting in October 1999. The long-term results highlight a dynamic and evolving pattern of home range use (Table 6 & Figure 30). Xpl-10 was born in the Aub pride (see above) in September 1998. Up to 2000 she moved in the area occupied by the Aub pride, but dispersed in November 2000, extending her home range to the Hoanib River in 2001. At the end of 2001 she moved to the Hoaruseb where she remained for the period between 2002-2004. During 2005, Xpl-10 expanded her home range to the Okongwe area, south east of the Hoaruseb River. Intensive daily monitoring during 2006 highlights the fluctuating pattern of range-use, and demonstrates a gradual expansion to the Hoanib River that started in May 2006. By September 2006 Xpl-10 were spending most of her time on the Hoanib floodplain.

Figure 29. Locations and home range estimate (Kernel Contour) of Xpl-10 and the Hoaruseb females during 2006.
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Table 6. The home ranges used by Xpl-10 and the Hoaruseb females during eight periods between 1999 and 2006 (95% Kernel Contour).

Figure 30. Locations and home range estimate (Kernel Contour) of Xpl-10 and the Hoaruseb females during eight period between 1999 and 2006.

2000

2001

2002-2004

2005

April 2006

May 2006

July 2006

September 2006

Hobatere: Two male lions (Xpl-19 & 20), born in the Aub pride during August 2000, utilised an area of 2,457 km2 up until May 2005 (Figure 31). They then dispersed and settled permanently on Hobatere. This was the first documented case of lions from the desert population, dispersing towards the east and joining the Etosha population. At the age of five years the two males arrived at Hobatere late in June 2005. They ousted the local male lion, took over tenure of the pride that live on Hobatere and the Otjovasandu area of Western Etosha, and were seen mating with the lionesses on 2 July 2005. Steve Braine of Hobatere Lodge monitored their movements intensively. Since their arrival the two males have remained in the Hobatere Concession (Figure 32), using a home range of only 187 km2 (95% Kernel Contour).

Figure 31. Locations and home range of Xpl-19 & 20 between December 2001 and May 2005, prior to dispersing to Hobatere. Figure 32. Locations and home range estimate (Kernel Contour) of Xpl-19 & 20 between June 2005 and December 2006, after they dispersed and settled on Hobatere (N = 148, Steve Braine).

Nocturnal movements
Due to constraints imposed by the terrain, observations on marked lions are restricted to daytime radio tracking. Anecdotal observations suggest that lions move extensively at night and that they may utilise habitats not reflected by the conventional radio tracking data. To address this concern a GPS radio collar (courtesy of Ingrid Wiesel) was fitted to a lioness (Xpl-18) of the Agab Pride, for a three-month period in July 2005. The GPS radio collar was programmed to record daily position coordinates (fixes) every two hours, between 17h00 and 10h00 (UTC). Over the three months the GPS radio collar recorded 893 fixes during 104 nights (Table 5). The lioness moved an average calculated distance of 8.3 km per night, but utilised only 22% of the pride’s known home range (Table 5). Over the same period Xpl-18 was also located 17 times, using conventional VHF techniques (see Methods). These aerial radio-tracking locations reflected only 8% of the known home range, and 34% of the area recorded by the GPS collar (Fig. 16).

Table 5. Summary of data collected by a GPS radio collar and aerial tracking on the movements of Xpl-18 (Agab Pride), between 11 July and 22 October 2005.

1 Home range of the Agab Pride over 5 years 2656 km2 (MCP), see Table 4 & maps.

Fig. 16. Locations of Xpl-18, of the Agab Pride from a GPS radio collar and aerial radio tracking, 11 July - 22 October 2005. (Click to view enlargement of map)

Extended nocturnal movements to the north and northeast, and outside the ephemeral river systems (GPS collar data), was not captured by the conventional daytime methods. The GPS data on nocturnal movements of Xpl-18 revealed interesting patterns, not previously known, and in support of the anecdotal information on extended movements at night. In order to demonstrate these findings, a sub-set of six nocturnal movements, is presented (Fig. 17).

Fig. 17. Layout of nocturnal movements of Xpl-18 (Agab Pride) during six nights. (Click to view enlargement)

Table A6. Summary of distances moved during six nights by Xpl-18 (Agab Pride), as recorded by a GPS radio collar between 11 July and 22 October 2005.


1 Total distance moved, calculated by joining all the GPS fixes.
2 Distance between day-time-resting-spots (point-to-point).
3 Day resting distance as a percentage of the total distance moved.

The movements of Xpl-18 were often erratic, as she crossed over mountains, and between different tributaries of the ephemeral river systems. With the exception of 23 July 2005 (blue line), there were frequent and considerable changes in the direction of movements. The distance between one day-time-resting-spot and the next, is substantially less than the actual distance moved during the night, as recorded by the GPS collar (Table A6). Conventional radio-tracking techniques (daytime locations) clearly produce inadequate data on movements and habitat use, when compared with the GPS collar data.

Coastal movements
During the latter half of 2006 lions moved to the coast at four different locations. In August 2006 an adult male lions, from the Ugab/Huab group, walked down the Huab River and onto the beach at the Huab Lagoon, where he killed and ate a Cape fur seal (Figure 36). An adult male lion visited Sarusas spring and the mouth of the Khumib River in September 2006 (Figure 37). The last recorded record of a lion at this location was on 14 September 1987. The Hoaruseb lionesses were at the mouth of the Hoaruseb River during August & September 2006 (Figure 38) and then moved to the Hoanib River between September and December 2006, where they spent time at Auses spring and in the dunes, west of the floodplain (Figure 39). Click to view enlargements.

Figure 36. Huab River (August 2006)
Figure 37. Sarusas & the Khumib River
Figure 38. Hoaruseb River.
Figure 39. Hoanib floodplain.

Last data analysis & update - March 2007