Rapid dung removal by beetles 181
per day (defaecation rate) and by mean dung decay time (White & Edwards, 2000; Marques et al., 2001; Thomas et al., 2010). To our knowledge, these parameters were estimated for the blue duiker Philantomba monticola and red duikers Cephalophus spp. for the first time in the Democratic Republic of the Congo (Koster & Hart, 1988), and are still used in most publications on duiker density. Of the 33 density estimates we are aware of, 27 used the va- lues of dung decay time from Koster & Hart (1988): 18 days for the blue duiker and 21 days for red duikers. These values are the maximum dung decay times estimated in a single, dry season from captive duikers. Two key problems hinder the accurate estimation of dui-
ker density from dung. Firstly, there is a lack of data on dung decay time and the effect of season on this. The use of dung decay time calculated in other localities or seasons to esti- mate duiker density in a given area is likely to result in biased duiker densities, as dung decay may be influenced by factors such as climate, diet and insect activity (Koster & Hart, 1988; van Vliet et al., 2009). Because most dung piles disappear not as a result of decay but as a result of other factors, we use the term dung survival time rather than dung decay time. Secondly, the effect of the freshness of dung on the mea-
surement of dung survival time needs to be considered. The few published values of dung survival time for duikers were calculated from dung piles 0–24 hours old (Beukou et al., 2019) or pellets collected from duiker intestines (van Vliet et al., 2009). Other studies have simply reported that fresh or intact dung was used (Breuer et al., 2009, 2021; Viquerat et al., 2013). We address these problems by monitoring the dung of
duikers and analysing factors influencing dung survival time in Nki National Park, south-east Cameroon. We also compare dung survival time for the blue duiker and red duikers across seasons.
Study area and species
This study was conducted in Nki National Park, south-east Cameroon, Central Africa (Fig. 1). The climate of the region is characterized as a four-season equatorial climate, with a major dry season during December–February, a minor wet season during March–June, a minor dry season during July–August and a major wet season during September– November (Ekobo, 1998). Mean annual rainfall is c. 1,660 mm and mean annual daily temperature is 23 °C (Sup- plementary Fig. 1). Themainvegetationtypeisamixtureof evergreen and semi-deciduous forests (Letouzey, 1985). Twomain groups of people live in this area: the Baka and
the Bantu. Both groups cultivate subsistence crops such as plantain and cassava. Cocoa farming is the main source of income for the Bantu. Bushmeat hunting and gathering of
non-timber forest products are also widely practised. The main hunted species are duikers, the porcupine Atherurs africanus and monkeys Cercopithecus spp. (Yasuoka, 2006, Bobo et al., 2015, Martin et al., 2020). There are six species of duiker recorded in the forests of
south-east Cameroon: the small blue duiker Philantomba monticola (3.5–9.0 kg), the large yellow-backed duiker Cephalophus silvicultor (45.0–80.0 kg), and four medium- sized species with reddish fur (Peters’sduiker Cephalophus callipygus, 17.5–25.2 kg; bay duiker Cephalophus dorsalis, 15.0–24.5 kg; white-bellied duiker Cephalophus leucogaster, 15.0–20.0 kg; black-fronted duiker Cephalophus nigrifrons, 14.0–18.0 kg). As the dung of medium-sized duiker species is difficult to distinguish, we grouped these four species into a single category, red duikers.
Methods
Data collection We established four 2-km transects, 400–800 m apart, in Nki National Park (Fig. 1). To maximize the number of dung piles, we opened two parallel paths, 4 m either side of each transect, giving a total of 12 observation paths. We surveyed the transects in January–May 2019, August– December 2019, January–February 2020 and May 2020. Together with three experienced local hunters, we searched for dung piles of duikers between 07.00 and 17.00. Each ob- server walked along a path but could move several metres away from the path if required. Only dung piles considered to be no older than 1 day (see below) were recorded. Dung of the yellow-backed duiker was rare and therefore not included in the analysis. When a dung pile was detected, we assigned a unique
identifier, measured the diameter covered by pellets, and estimated how many hours ago it had been deposited. Although it was not possible to know the exact time of the defaecation, experienced trackers and researchers can rea- sonably estimate their age (Viquerat et al., 2013; Elenga et al., 2020). We inspected the appearance of dung piles (shine, moisture) and other factors such as associated pres- ence of urine, time of last rain and exposure to sun. In discussion with the experienced hunters, we agreed upon when the dung was deposited, classifying dung piles into age classes of 3 hours (hereafter referred to as age class at detection). Dung piles were then visited twice per day to check
whether they had disappeared or still remained, and in the case of the former, to determine what had caused their dis- appearance: removal by beetles, decomposition, washed away by rain, covered by fallen leaves, or other. As we mon- itored the dung daily, we were able to identify the factor re- sponsible for disappearance with confidence.Wesometimes
Oryx, 2023, 57(2), 180–187 © The Author(s), 2022. Published by Cambridge University Press on behalf of Fauna & Flora International doi:10.1017/S0030605321001599
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77 |
Page 78 |
Page 79 |
Page 80 |
Page 81 |
Page 82 |
Page 83 |
Page 84 |
Page 85 |
Page 86 |
Page 87 |
Page 88 |
Page 89 |
Page 90 |
Page 91 |
Page 92 |
Page 93 |
Page 94 |
Page 95 |
Page 96 |
Page 97 |
Page 98 |
Page 99 |
Page 100 |
Page 101 |
Page 102 |
Page 103 |
Page 104 |
Page 105 |
Page 106 |
Page 107 |
Page 108 |
Page 109 |
Page 110 |
Page 111 |
Page 112 |
Page 113 |
Page 114 |
Page 115 |
Page 116 |
Page 117 |
Page 118 |
Page 119 |
Page 120 |
Page 121 |
Page 122 |
Page 123 |
Page 124 |
Page 125 |
Page 126 |
Page 127 |
Page 128 |
Page 129 |
Page 130 |
Page 131 |
Page 132 |
Page 133 |
Page 134 |
Page 135 |
Page 136 |
Page 137 |
Page 138 |
Page 139 |
Page 140
