Seely, M.K.

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1977 SHORT COMMUNICATIONS 247 was maintained. This fact probably explains the constancy of the RBC and Hc values compared with freshwater-transported animals where the decrease in blood Na+ concentration is known to be associated with a decrease in blood osmotic pressure (Hattingh & Van Pletzen 1974). This eventually leads to haemolysis. Maintenance of a constant blood Na+ concentration during trans-portation therefore seems to be crucial for these animals and they most probably do this by ab-sorbiRg NaG from their medium. Finally, although it is apparent that addition of salt to the transportation water aids the fish, the decrease in blood pH on the second day is indicative that some stress is still experienced. The cause of this remains to be investigated. REFERENCES BOUCK, G. R. & BALL, R. c. 1966. Influence of capture methods on blood characteristics and mortality in the rainbow trout (Salmo SAND SOLIDIFIED BY GEMSBOK URINE AS SELECTED BURROW SITES BY GERBILS M. K. SEELY Desert Ecological Research Unit, Walvis Bay Accepted: August, 1976. Gerbillurus paeba is widely distributed throughout the arid parts of southern Africa (Roberts 1951). Its range extends into the central Namib Desert where it is most often found on sandy areas of the central Namib plains or in the interdune valleys (Coetzee 1969). Its semi-permanent burrows are excavated in the sand either in the open (Laycock 1975) or, more often, close to dune-grass clumps (Coetzee 1969) and other vegetation. The sand gairtineri). Trans. Am. Fish. Soc. 95: 170-175. FUJlYA, M. 1961. Use of electrophoretic serum separations in fish studies. J. Wat. Pollut. Control Fed. 33: 250-257. HATIlNGH, 1. & VAN PLETZEN, A. 1. 1. 1974. The influence of capture and transportation on some blood parameters of freshwater fish. Compo Biochem. Physio/. 49A: 607-609. HATTINGH, J., FOURIE, F. LE R. & VAN VUREN, J. H. J. 1975. The transport offreshwater fish. J. Fish. Bioi. 7: 447-449. MANN, K. H. 1965. Energy transformation by a population of fish in the River Thames. J. animo Ecol. 34: 253-275. NARASIMHAN, P. V. & SUNDARARAY, B. I. 1971. Effects of stress on carbohydrate metabolism in the teleost Notopterus notopterus (palles). J. Fish. Bio/. 3: 441-452. WEDEMEYER, G. 1972. Some physiological con-sequences of handling stress in the juvenile coho salmon (Oncorhynchus kisutch) and steelhead trout (Salmo gairdneri). J. Fish. Res. Bd Can. 29: 1780-1783. at the base of perennial vegetation clumps (e.g. Acanthosicyos horrid a, Stipagrostis sabulicola, Trianthema hereroensis) is solidified by fog pre-cipitation falling from the plants and by the presence of the roots which facilitate burrow construction. Distribution of gerbil burrows in dunes is thus limited by the occurrence of peren-nial vegetation or other suitable burrow sites in the more compact pebbly soils of the interdune valleys. Unconsolidated sandy interdune valleys can be successfully colonized only under special conditions. One such opportunity is presented by the occurrence of sand patches which have been solidified by gemsbok (Oryx gazella) urine. The concentrated gemsbok urine lightly cements a block of sand averaging 0,025 ml (n = 20) in diameter which is more resistant to wind erosion and other disturbance than the surrounding loose Reproduced by Sabinet Gateway under licence granted by the Publisher (dated 2010). 248 ZOOLOGICA AFR ICAN ..... VOL 12 " " " > ~ • " ~~ ~ • • c ] • • ,~ • ~ • ~ • • " • c , '0 0 • u: ~ .8 " E ::, .8 ~ " ~:2 1l ~ c • " • e ] :E " <0 Reproduced by Sabinet Gateway under licence granted by the Publisher (dated 2010). 1977 SHOR l' COMMUNICATIONS 249 sand. This provides a suitable location for the entrance to gerbil burrows which can then be extended into the more cohesive subsurface sands (Figure 1). Gemsbok occur widely and regu1arly throughout the dunes thus providing numerous suitable burrow sites. In one sandy interdune valley 16 km south of Natab on the Kuiseb River in the Namib Desert Park a one-hectare plot was surveyed for gerbil holes and patches of sand solidified by gemsbok urine. Multiple entrances at one gemsbok urine patch were counted as one burrow. Of 134 gemsbok urine patches, 106 (79 per cent) were used for gerbil burrow entrances with from one to three entrances each. In this area there were 17 other gerbil burrow entrances. Thus of all burrow entrances in this area 86 per cent were situated at gemsbok urine patches. The surface area solidified by gemsbok urine totalled 13,4 m l or 1,34 X 10-6 per cent of the total area surveyed: Using the chi-square test a non-random distri-bution of burrow sites was demonstrated (p < 0,001). This valley supports a sparse cover of dried annual Stipagrostis gonatostachys, Monsonia Ignorata and Asthenatherum glaucum, none of which is suitable for gerbil burrow entrances. Gerbils are highly mobile, crossing high dunes (Cpet7ee 1969) and are sometimes found far from their burrows (Laycock 1975). At such times they are subject to predation, primarily by jackals (Canis mesomelas). Access to escape BABOONS AS DISPERSAL AGENTS FOR ACACIA CYCLOPS CHRISTINE DAVIDGE Zoology Department, University 0/ Cape Town Accepted: October, 1976. provided by foraging in the vicinity of burrow systems probably reduces the possibility of being preyed upon. Thus the advantage gained by a more even distribution of burrows relative to food sources is facilitated by the use of solidified gemsbok urine sand patches as burrow sites. ACKNOWLEDGEMENTS Mr P. K. Mostert and Miss A. Henderson are thanked for their assistance in the field. The continued financial support of the CSIR and Transvaal Museum is gratefully acknowledged. Permission to work in the Namib Desert Park was granted by the Division of Nature Conserva-tion and Tourism, South West Mrica. REFERENCES COETZE!, C. G. 1969. The distribution of mammals in the Namib desert and adjoining inland escarpment. Scient. Pap. Namib Des. Res. Stn, 40: 23-36. LAYCOCK, P. A. 1975. A brief gerbil trapping survey in an interdune valley in the Namib Desert. Madoqua (2) 4: 95-97. ROBERTS, A. 1951. 17re mammals 0/ South A/rica. Johannesburg: Trustees 'The mammals of South Mrica Book Fund.' Baboons, many birds and a few rodents in the south-west Cape include significant proportions of seeds of the Australian wattle (Acacia cyclops-'rooikraoz') in their diets (Middlemiss 1963. 1974). These animals may, therefore, act as dispersal agents for A. cyclops by distributing undigested seeds in their droppings. A one-year study (March 1975-February 1976) of a troop of chacma baboons. Popio ursinus, in the Cape of Good Hope Nature Reserve provided oppor-Reproduced by Sabinet Gateway under licence granted by the Publisher (dated 2010). 

Sand Solidified by Gemsbok Urine as Selected Burrow Sites by Gerbils

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Sand Solidified by Gemsbok Urine as Selected Burrow Sites by Gerbils

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