African Forest Biodiversity - Earthwatch Institute

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6.3.3 Sweep surveys In practice, field workers make the most of all their field records by combining information on sightings and calls. This can be done during transect walks, but even more information can be gained when the surveys are carried out along parallel transects on a survey grid by a number of surveyors working simultaneously. These are called sweep surveys (Whitesides et al., 1998). Equipment/personnel ● survey grid cut and mapped (see below) ● at least three experienced field observers Procedure i) A rectangular survey area has to be prepared, with three or more survey transects running parallel to each other, spaced at 100-m intervals, and extending for at least 1km. They should be linked at either end by perpendicular trails, to get surveyors to the start points quickly and quietly. All paths are marked at 50-m intervals. ii) Soon after dawn, the surveyors should assemble at the start of their survey trails and travel slowly and quietly along the path, beginning at a prearranged time (having synchronised watches beforehand). The surveyors move forwards in a single front, stopping occasionally to make field records. To keep the line of surveyors coordinated, several pre-determined restart points should be marked along the survey routes. Recording i) When a primate is sighted, its position and the group-spread are marked on a scale map (e.g. 10mm: 50m). All primate group sightings and calls are recorded (as noted in sections 6.3.2 and this section above). ii) By noting the time of all records (sightings and calls), simultaneous records of the same group by different observers can be mapped, thereby avoiding double-counting of the same groups. Data analysis i) At the end of the survey, all surveyors reassemble and a map is compiled for each species from all records collected. Once the map has been completed for a number of repeat surveys, separate primate home ranges can be marked, and the number of groups within the survey area and its vicinity can be counted. 114
ii) Some groups’ home ranges will fall wholly within the survey grid, but others will be partly outside. Whitesides et al. (1988) considered groups having home ranges in excess of 80% inside the survey grid as being within the area surveyed, groups having 80–30% inside the survey grid as half a group, and groups with 30% or less of their home ranges inside the grid were regarded as falling outside the survey area. By adding whole groups and half groups, the number of groups/km 2 can be calculated. iii) Detailed information on the size of primate groups, and their age/sex composition, combined with information on the body weights of different types of animals (eg adult males, juveniles, females, etc.), can then be used to calculate population densities and biomass. Advantages/limitations This method provides very reliable and accurate estimates of absolute group densities, plus solitary individuals, within a known survey area. It can be verified by repeated sweep surveys over time to take account of seasonal biases. If the sample area is representative of the forest as a whole, then the results from these surveys can be extrapolated to wider areas. The disadvantages of this method include the time taken to build up an accurate picture of group densities, the large number of surveys required, the need for a team of three or more experienced surveyors (although a team of just two can allow triangulation on calling groups), and clearing and maintenance of the transect grid. Rapid sweeps Using the same principle as the sweep surveys, but in circumstances where there is only one surveyor, the system can be modified to a rectangular survey area (1km x 500m, depending on the species being surveyed), in which all sightings and calls of primates are recorded onto accurate maps. Over time, a picture of the number of groups in the area builds up, although the possibility of missing groups in the centre of the survey rectangle are higher than for the sweeps, and groups on the edge may also be missed. In Sierra Leone, data on relative primate abundance was gathered by a single observer using survey rectangles of 1km x 500m (e.g. Davies, 1987). Rapid sweeps have also been used in the small patches of forest along the Tana River in Kenya (Butynski & Mwangi, 1994), where pairs of observers searched in a zigzag fashion through parallel swathes of forest with each survey team’s route separated by about 100–150m. The survey routes were carefully mapped, and plenty of time taken to search for primates. At the end of the survey, all teams met and discussed results before group encounters were mapped and the numbers of groups in each patch calculated. 115
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A Field Survey Manual for Vertebrat
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African Forest Biodiversity: A Fiel
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Acknowledgements This manual has be
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4. Small mammals: bats, rodents and
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1. Introduction Glyn Davies 1.1 Bac
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Enlightened forest management requi
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2. Forest Surveys Glyn Davies 2.1 W
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A similar approach applies when sur
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multiple-use management plans to ad
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2.4 Ethical and legal standards Whe
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The advent of hand-held computers o
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At the local level, even more impor
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twig snake (Thelotornis kirtlandii)
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spp. toads, Arthroleptis spp. frogs
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3.3.1 General surveys When visiting
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emains in mammal faeces, may all pr
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● a hoe and pick suited to cuttin
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Advantages/limitations i) The advan
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Recording Information on captured s
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3.3.5 Capture, mark, recapture When
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3.3.7 Time-constrained searches In
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3.3.10 Sound recording surveys Park
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3.5 Health and safety Both amphibia
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3.7 References Barbault, R. (1975).
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Rodel, M.O. (2000). Herpetofauna of
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Form 3.2: Specimen Records: herptil
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golden-rumped elephant shrew (Rhync
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4.2 Management issues Small mammals
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4.3.1 General surveys General surve
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Fig 4.1: Live Traps Sherman ● Hav
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● full name of surveyor; sheet re
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Mist nets Mist nets for catching Mi
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Procedure i) Nets and traps should
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More detailed ecological research,
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There is a wealth of information th
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Page 75 and 76: 4.7 References Barlow, K. (1999). E
Page 77 and 78: Form 4.1: Small Mammal Catch Record
Page 79 and 80: zebra duiker (Cephalophus zebra) 5.
Page 81 and 82: identifying areas with concentratio
Page 83 and 84: Estes (1991). Although not a field
Page 85 and 86: Advantages/limitations This is a ti
Page 87 and 88: v) Some animals typically try to br
Page 89 and 90: Site selection i) As a general rule
Page 91 and 92: iii) Ideally, transects should be w
Page 93 and 94: tion between the scats of golden ca
Page 95 and 96: c 1 Transect route a c 2 b 1 b 2 ii
Page 97 and 98: If it is possible to distinguish in
Page 99 and 100: forest zone (Newing, 1990), disting
Page 101 and 102: camera to expose a frame when the f
Page 103 and 104: Davies, G., Heydon, M., Leader-Will
Page 105 and 106: 95 Start time Species No. of animal
Page 107 and 108: Notes: Distance from start = from s
Page 109 and 110: 6. Primates Glyn Davies 6.1 Biology
Page 111 and 112: angolensis) in Ituri (Zaire) and Ny
Page 113 and 114: gorilla hands); supplying animals f
Page 115 and 116: 6.3.1 Distribution surveys One of t
Page 117 and 118: A. Animal sightings Procedure i) Ea
Page 119 and 120: The transect width is influenced by
Page 121 and 122: section 5.3.4A. It is then possible
Page 123: Fig. 6.4: Mapping calls and sightin
Page 127 and 128: Davies, A.G. (1987). The Gola Fores
Page 129 and 130: Notes: Distance from start = from s
Page 131 and 132: Jameson’s wattle-eye (Platysteria
Page 133 and 134: forests present a particularly comp
Page 135 and 136: also be done by non-mechanical meth
Page 137 and 138: particular site. Entire bird commun
Page 139 and 140: Especially when you are starting of
Page 141 and 142: If a survey is being planned specif
Page 143 and 144: een recorded above 3m and within 25
Page 145 and 146: for shorter periods - the minimum o
Page 147 and 148: ory, line transects provide a measu
Page 149 and 150: ii) The species and numbers of indi
Page 151 and 152: are rarely encountered, there may n
Page 153 and 154: Site selection Mist nets work best
Page 155 and 156: line cut perpendicular to a survey
Page 157 and 158: considerable maintenance). Nets do
Page 159 and 160: The main limitation is how to keep
Page 161 and 162: 7.4 Specimen handling Casualties am
Page 163 and 164: Traditional transects can be diffic
Page 165 and 166: Fanshawe, J.H. (1995). The Effects
Page 167 and 168: Thirgood, S.J. & Heath, M.F. (1994)
Page 169 and 170: Form 7.2: Bird Recording Sheet for
Page 171: Form 7.4: Specimen Records: birds S
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