Museum and literature records of Malagasy dung beetles

The existing knowledge on the systematics, phylogeny, distribution and ecology of endemic Malagasy dung beetles in the subtribe Helictopleurina and the tribe Canthonini have been summarized in a series of recent papers, mostly based on studies conducted since 2002 (Hanski et al. 2007; Orsini et al. 2007; Viljanen et al., in prep.; Wirta et al. 2008). The vast majority of both Helictopleurina and Canthonini species occur in wet forests, using lemur dung and carrion (Koivulehto 2004; Viljanen 2004; Viljanen et al., in prep.).

Concerning species in the other tribes with clearly fewer species, previous limited information on habitat selection and diet of the introduced and endemic Aphodiini, Didactyliini, Onthophagini and Scarabaeini in Madagascar and mainland Africa is summarized in Table 1. Bordat et al. (1990) has summarized the distributional data for Aphodiini and Didactyliini.

Sampling

During the course of our extensive sampling of dung beetles in forest localities across Madagascar since 2002, small-scale manual searching of cattle dung pats in open habitats and wet forests has been conducted in Ranomafana National Park (NP) and in Andringitra NP in December 2003, in open areas in Manombo on the east coast in November 2004, in Ambila in November 2005, and in Sambava in December 2007 (Appendix 1, Fig. 1). In addition, Viljanen (2004) conducted a smallscale pitfall trapping (30 trap-nights) in wet forest in Ranomafana NP.

Fig. 1.

A, Sampling localities in open areas. B, Cattle density in Madagascar: black 230–410, dark grey 175–230, grey 122–175, light grey 60–122, and white 44–60 heads/km².

A large-scale inventory of dung beetles in cattle dung pats in open areas was conducted in 2006 and 2007 (Appendix 1, Fig. 1). First, a transect of 47 localities was sampled by four people from the capital Antananarivo to southern Madagascar during six weeks from March to May in 2006. The second transect included 22 localities from Antananarivo towards north, sampled in November and December 2006. This transect was sampled by five people in three weeks. The third transect in northern Madagascar included six localities sampled by three people in two weeks in May 2007.

Samples were collected at roughly 50 to 150 km intervals while driving along the main roads (Fig. 1). The time spent at each locality was roughly proportional to the numbers of dung pats present and varied from approximately 10 minutes to 2 hours. At each site, we checked all dung pats that appeared to be of suitable age (not too dry). All individuals encountered were collected for subsequent identification and counting, with the exception of the often very abundant Digitonthophagus gazella, which was mostly counted in the field. Due to differences in search effort and sample size, the observed species numbers in different localities are not directly comparable. To account for variation in sample size in regression analyses of the number of species in local communities, we used the logarithm of sample size as a covariate. An alternative analysis was conducted by rarefaction, modelling the number of species in a random subsample of 30 individuals per locality.

Ordination of dung beetle communities

We used Kruskal's non-metric multidimensional scaling (NMDS) to characterize the species composition in the 73 local communities in open habitats sampled across Madagascar (Fig. 1). We examined whether cattle density, altitude, latitude and longitude explained the structure of the local communities in a three-dimensional ordination. We used the same method to study possible effects of the introduced and numerically dominant species, Digitonthophagus gazella, on the species composition of the remaining species in local communities.

Table 1.

Dung beetle species collected in cattle dung or which potentially occur in cattle dung in Madagascar (the latter for Aphodllnae only). Habitat: O = open habitats, DR = dry forest, WF = wet forest. Other resource types apart from cattle dung (CD): H = human faeces, LF = lemur faeces, PD = Propithecus diadema faeces, BD = buffalo dung, Ba = baboon faeces, D = dog faeces, BP = bush pig dung, T = tortoise dung, C = carrion, L = light trap, UV = UV light, ^*P. Bordat (pers. comm.), ^**Paulian (1992), () = data from Africa (P. Bordat, unpubl.). For details of our own trapping results see Appendix 2.

continued

NMDS is an unconstrained ordination method used for exploratory analyses of the relationships between species occurrences and environmental variables (Legendre & Legendre 1998; Venables & Ripley 2002). NMDS does not assume any particular functional forms for the responses of species to environmental variables, and it is not severely affected by the zero observations that are typical for community data. By fitting a monotonie regression to the data, NMDS places sample plots into the ordination space in such a manner that the ordination distances correspond to differences in species composition and abundances. The locations of the species in the ordination space are calculated as locality (sample) averages weighted by species abundances (Legendre & Legendre 1998; Venables & Ripley 2002; Oksanen et al. 2008). The distances between the localities were calculated using the Bray-Curtis dissimilarity index. We applied square-root transformation and Wisconsin doublestandardization to use relative abundances and to reduce the weight of the most abundant species in the analysis (Faith et al. 1987, Oksanen et al. 2008).

For each continuous explanatory variable (cattle density, altitude, latitude and longitude), a vector was fitted onto the ordination space to yield maximal correlation between the variable and the locality (sample) values. Thus each vector points to the direction in the ordination space where its value increases most rapidly. The relative length of the vector is proportional to the strength of the variable's effect on the ordination. To compare the communities in northern, central and southern Madagascar, and communities with small (relative abundance <10 %), medium (10–50 %), and high (>50 %) numerical dominance by D. gazella in the sample, we calculated averages of the ordination scores for the factor levels (Legendre & Legendre 1998; Venables & Ripley 2002; Oksanen et al. 2008). The significance of the explanatory variables was tested with a permutation test. Ordination analyses were carried out with version 1.11–0 of the community ecology package vegan (Oksanen et al. 2008) as implemented in version 2.6.2 of R (R Development Core Team 2008).

Species composition

Table 1 summarizes the data on the dung beetle species that occur in cattle dung in Madagascar. For completeness, we have included in this table all species of Aphodiini, Didactyliini, Scarabaeini and Onthophagini known from Madagascar, though especially the poorly known wet forest species of Aphodiini may use mostly resources other than cattle dung.

In the systematic sampling conducted at 73 localities in open habitats across Madagascar in 2006–07 (Fig. 1), we sampled altogether 21 species, including 3 Canthonini, 6 Helictopleurina, one Scarabaeini, 4 Onthophagini, 6 Aphodiini, and 1 Didactyliini (Table 1). Our trappings in eastern Madagascar in Manombo, Andringitra NP, Ranomafana NP, Andasibe NP, Antalaha and Sambava added five more species, of which Helictopleurus rudicollis has been sampled in wet forests only (Table 1).

Habitat selection and diets

There are only three species that use cattle dung regularly in wet forests in Madagascar, and none of them is a cattle dung specialist. The most frequent species is Helictopleurus rudicollis, which is a generalist feeding on both dung and carrion across the entire eastern wet forest belt. In the well-studied Ranomafana NR cattle dung-baited pitfall traps yielded regularly two species of Neoemadiellus, N. humerosanquineum and Neoemadiellus sp. 2 (Appendix 2; Viljanen 2004). Six other species, all common on some other resources, were caught in very small numbers and most likely accidentally rather than being attracted by the bait.

In contrast to the lack of cattle dung-using species in wet forests, in open habitats there are several species that are true cattle dung specialists, including both native species and all four introduced Onthophagini species and all ten introduced Aphodiini. In Helictopleurina, there are four species that can be classified as cattle dung specialists in open habitats and in semi-open dry forests (see also Wirta et al. 2008, Hanski et al. 2008), and further four species that use cattle dung to some extent in dry forests (Table 1). Canthonini includes four cattle dung-using species in open habitats, while all the three Scarabaeini species occur in open habitats and semi-open dry forests, with some ecological differences among the species that are discussed in the Discussion.

Fig. 2.

Geographical ranges of selected dung beetle species that use cattle dung. Upper row: Four species of Onthophagini and three species of Scarabaeini. The lower row shows the distributions of two Helictropleurus species using cattle dung in open areas and, for comparison, the much more restricted ranges of two common forest-inhabiting Helictopleurus species.

Practically all species using cattle dung in open areas occur across Madagascar (Fig. 2, Appendix 2), including Labarrus madagassius, Mesontoplatys dorsalis and Pseudopharaphodius apicesetosus (Aphodiini) (Bordat et al. 1990), though they were not included in our northern samples. The exceptions are the three species of Scarabaeini and two Onthophagus species, which have more restricted distributions in western and southern Madagascar (Fig. 2, Table 1). The three most numerous dung beetle taxa in cattle dung, Helictopleurina, Onthophagini, and Aphodiinae, are rather equally represented across Madagascar and each taxon is numerically the most abundant in many individual local communities. Thus of the 73 local communities sampled, 16 were numerically dominated by Helictopleurina, 24 by Onthophagini, and 25 by Aphodiinae.

Local communities In cattle dung

Sample size (number of beetles collected) decreased with increasing longitude and altitude (linear regressions, t = -2.32, P = 0.02 and t = -2.00, P = 0.05, respectively), though the amount of variation explained by the models was small, less than 6 %. Latitude had no significant effect. These results must be interpreted with caution because of great differences in the numbers of cattle in different sampling localities and consequent differences in the sampling effort.

As expected, sample size had a major effect on the number of species. Log-transformed sample size explained 53 % of variation in log-transformed species number (Fig. 3a). Species number ranged from one to 12 per local community.

We tried to explain variation in species number by cattle density, altitude, longitude, latitude, and annual precipitation. The effect of sample size on species number was corrected in two different ways. First, we modelled variation in the number of species in a random subsample of 30 individuals, in which case the rarefied species number increased with cattle density and altitude (Table 2). Second, we included sample size as a covariate in a multiple regression model. In this analysis, cattle density had a significant effect, altitude a nearly significant effect (Figs 3b and 3c, Table 2), and longitude, latitude and precipitation had no significant effects and were excluded from the model. Recall that sample size (number of beetles sampled) decreased with altitude (above), and hence high-altitude communities had many species with low density.

Fig. 3.

a, Number of species plotted against the logarithm of pooled sample size (number of individuals). In panels (b) and (c), the residual from panel (a) is plotted against altitude and cattle density, respectively. For statistics see Table 2.

In the NMDS ordination, latitude, longitude and altitude had significant effects on species composition, suggesting that the structure of local communities in the high central plateau of Madagascar differs from those at low coastal areas (Fig. 4a, Table 3a). This is supported by significant variation in community structure between northern, central and southern Madagascar. The significant effect of altitude is apparently largely due to the dominance of Aphodiinae in the central plateau, where the subfamily accounted for 75 % of the pooled sample of 1465 individuals, compared with 37 % (pooled sample 3624 individuals) in northern and 25 % in southern Madagascar (3843 individuals).

There was less variation among local communities in the ordination in northern than in central and southern Madagascar, which is at least partly due to the systematically high prevalence of the numerically dominant introduced species Digitonthophagus gazella in northern Madagascar. Local communities with dissimilar relative abundance of D. gazella did not differ from each other in terms of the species composition of the rest of the species (Fig. 4b, Table 3b). Cattle density had no systematic effect on the species composition in the local communities.

Table 2.

Least squares linear regression of species (log-transformed number of species collected) number and rarefied species number (species in a subsample of 30 individuals) explained by cattle density, altitude, and sample size (log-transformed number of beetles collected). Statistics for the full model: species (log) number, F _3,69 = 32.70, P< 0.0001, R ² = 0.57; and rarefied species number, F _2,45 = 4.38, P < 0.05, R ² = 0.13.

Use of cattle dung In forests and open habitats

Buffalo and cattle dung are widely used resources by dung beetles, particularly in tropical savannas in Africa and the western Orient, apparently because these resource types and other similar resources have been very abundant for a long time in grasslands with high density of large herbivorous mammals. Though the dung of ungulates (Artiodactyla, Perissodactyla and Proboscidea) is generally less abundant in forests than in grasslands, ungulate dung is used by a diverse community of dung beetles in tropical forests worldwide. For instance, in the Taï forest in the Ivory Coast, elephant dung and human excrement attracted about equal numbers of dung beetle species (Cambefort & Walter 1991). In striking contrast, in Madagascar there are only three species of dung beetles that have been caught in some numbers in cattle dung in wet forests, Helictopleurus rudicollis and two species of Aphodiini, and they all have a wide diet.

The likely explanation for the lack of cattle dung-using dung beetles in wet forests is the historical lack of Bovini in Madagascar. Even today, the vast majority of the seven-millionstrong cattle population occurs in open areas, though there is a significant feral cattle population in forests in many parts of Madagascar. In spite of no extant species using cattle dung, it is likely that the ancestors of Helictopleurina used the dung of comparable mammalian herbivores in mainland Africa some tens of millions of years ago (Wirta et al. 2008), as most of the other Oniticellini and many related Onthophagini do today (Cambefort 1991). Apparently, the evolution of Helictopleurina over the past 20–30 million years (Wirta et al. 2008) has modified them sufficiently to make the shift to cattle dung difficult. This shift has occurred, as we discuss below, but only in species that occur in open habitats at present.

In contrast to the cattle dung pats in wet forests that are devoid of dung beetles, in open areas cattle dung is used by a characteristic community of dung beetles. In our samples, there were typically two to six species per locality (average 4.6, standard deviation 2.5, range 1 to 12), which is an underestimate of the true number, as our samples were collected within a short period of time and were typically rather small. The total number of about 30 species for the whole of Madagascar (Table 1) is however reliable, as most species are widely distributed and were sampled repeatedly in multiple localities (discussed below).

Compared to dung beetle communities using cattle dung in mainland Africa, the Malagasy communities are species-poor. In the Ivory Coast, more than 100 species use ungulate dung in humid and dry savannas (Cambefort 1991). In a single locality, Abokouamekro in the humid savanna biome, 64 dung beetle species were sampled from cattle dung. In South Africa, local communities have typically 40 to 60 species in bush and grassveld areas and grasslands (Doube 1991; Davis et al. 1999, 2004; Krüger & Scholtz 1998). The lowest numbers have been sampled from cattle dung in improved pastures, but even then the number of species in a local community is typically over 30 (Davis et al. 2004). Thus the Malagasy communities have roughly an order of magnitude fewer species than local communities in mainland Africa. Incidentally, the total number of dung beetle species known from African savannas is around 1500 species (Cambefort 1991).

Apart from being species-poor, the dung beetle communities in open areas in Madagascar are strikingly homogeneous, as most of the species occur across the entire island. The only exceptions are the three endemic scarabaeines and one endemic onthophagine. Scarabaeus sevoistra (Scarabaeini) has been collected in only one area in southernmost Madagascar (Fig. 2), and S. radama and S. viettei, though locally abundant, have restricted ranges in southern and northwestern Madagascar, respectively. The endemic Onthophagus delphinensis has been collected from only Forth Dauphin in the south, and it may have already gone extinct, as there are no records since 1901. In the high plateau of central Madagascar, the relative abundance of Aphodiinae is higher than at lower altitudes. This pattern fits the global distribution of dung beetle subfamilies, as Aphodiinae are most numerous in temperate and Scarabaeinae in tropical regions (Hanski & Cambefort 1991).

Lack of radiation in Scarabaeini and Onthophagini

Scarabaeini and Onthophagini have colonized Madagascar over a prolonged period of time, including recent colonizations by the two introduced species of Onthophagus (they are considered to be introduced based on their occurrence in mainland Africa and elsewhere). Scarabaeini are represented by three species in Madagascar. The species are considered endemic because they are not known from elsewhere, but the monotypic Malagasy genera Neomnematium and Madateuchus have been synonymized with Scarabaeus by Mostert & Scholtz (1986) and confirmed by Forgie et al. (2005). Given that Scarabaeini and probably also Onthophagini with four endemic species are likely to have colonized Madagascar multiple times (H. Wirta, pers. comm.) and have been there for a long time, we may ask why they have not radiated like the Helictopleurina and Canthonini (Orsini et al. 2007; Wirta et al. 2008)

First of all, no species of Scarabaeini or Onthophagini occurs in wet forests in Madagascar. In the case of Scarabaeini this is not entirely surprising, because in mainland Africa Scarabaeini typically occur in arid regions, and especially the most speciose genus Scarabaeus is proportionally most prominent in the dry southwestern parts of southern Africa (Davis 1997). In the case of Onthophagini, lack of forest species in Madagascar is unexpected because hundreds of Onthophagus species worldwide occur in forests (see many chapters in Hanski & Cambefort 1991). For instance, in the Taï forest in the Ivory Coast (Cambefort & Walter 1991) and in the Gunung Mulu NP in Borneo (Hanski 1983) there are 27 and 37 Onthophagus species, respectively. Lack of forest species in Madagascar cannot be easily explained by diet either, because Onthophagus have adapted to use practically any kind of decomposing animal and even plant material that any dung beetles use (Cambefort 1991; Hanski 1989). The most probable reason for lack of forest-dwelling Onthophagus in Madagascar is competition with the diverse communities of Canthonini and Helictopleurina. Helictopleurina resemble greatly Onthophagini in appearance and ecology. The ancestors of Helictopleurina have been inferred to have arrived at Madagascar 37 to 23 million years ago and radiated rapidly soon afterwards (Wirta et al. 2008). It is probable that by the time Onthophagini arrived at Madagascar, the Onthophagini-type dung beetle niche in forests was already taken up, and hence Onthophagus have been unable to colonize forests. It would be helpful and informative to have a time-calibrated phylogeny of African Onthophagus including the endemic Malagasy species to infer the likely time of their arrival in relation to the colonization and radiation by Helictopleurina.

The three Malagasy Scarabaeini show some differences in their ecologies, apparently reflecting their long history in Madagascar. Thus only Scarabaeus radama is common in open areas in most of southwestern Madagascar using cattle dung, human excrement, and carrion. Scarabaeus viettei occurs in dry forests and may mostly use carrion, Scarabaeus sevoistra is very rare, only ever collected from two localities in southern Madagascar: Analavondrove in Antanimora (1901) and Marovato (1939). These localities used to have the characteristic spiny forest vegetation, which has, however, been greatly reduced in area and quality by cutting and invasion by Opuntia. Scarabaeus sevoistra has not been collected for 70 years and may be extinct or effectively extinct.

We do not know which resources Scarabaeini and endemic Onthophagini used following their arrival at Madagascar, but possible candidates include faeces of the now-extinct megafauna, especially the large-bodied lemurs. Following the arrival of cattle in Madagascar, Onthophagini and at least S. radama were able to switch back to cattle dung, or perhaps they had never lost their ability to use ungulate dung.

Endemic and introduced species of Aphodiinae

We have compiled (Table 1) all of the information available for Aphodiinae regardless of whether the species use cattle dung, which is not known for most species. Of the 30 species, 10 are considered to be introduced and 20 endemic to Madagascar. As a rule, the endemic species occur in wet forests, while the introduced species occur in open areas and many if not all of them use cattle dung. The same pattern is found in Scarabaeinae (above), though in Scarabaeinae there are only two introduced species.

One striking exception is Didactylia pictipennis, one of the four endemic Didactyliini, which occurs in cattle dung in open areas and is strikingly abundant in many local communities (Appendix 2). Apparently D. pictipennis has made a shift of resource use and habitat selection similar to the shift made by the few species of Helictopleurus discussed below. Two genera, Pharaphodius and Pleuraphodius, include both introduced and endemic species (Table 1).

Of the 20 Aphodiinae not sampled in our study (Table 1), 11 species (10 endemic) have been found only in the eastern wet forest region and may be generalists like the three endemic Neomadiellus species in Ranomafana NP (Viljanen et al., in prep.). They may also have restricted geographical ranges, as so many wet forest dung beetles (Wirta et al. 2008) and many other taxa do (Wilmé et al. 2006, and references therein). Four endemic species have been found only in the westernmost or southernmost Madagascar, where we did not conduct sampling in 2006–07. The remaining five species include species with a wide range and species with unknown distributions in Madagascar (Bordat et al. 1990). Three of these species have been sampled from cattle dung in the African mainland (Aganocrossus amoenus, Mesontoplatys parvulus, and Pleuraphodius leo), and the two other species have been sampled with carrion (Didactylia rosickyi) or with light (Paradidactylia dionysii) in Madagascar.

In contrast to Onthophagini and Scarabaeini, Aphodiini have entered and speciated in wet forests, where many endemic species now occur. A probable reason for the success of Aphodiini in entering forests is their much smaller size and hence different biology compared with the forestdwelling Helictopleurina and Canthonini. Aphodiinae are generally most active around dawn and dusk, while Helictopleurina are diurnal and Canthonini are mostly nocturnal (Viljanen et al., in prep.). In contrast to forests, Aphodiini have not radiated in open areas, perhaps because of shortage of appropriate resources until the arrival of cattle in the past 1000 years. This agrees with lack of radiation in Scarabaeini and Onthophagini.

Shift to cattle dung in Helictopleurina

Helictopleurina arrived at Madagascar 37 to 23 million years ago and went through an adaptive radiation concurrently with the adaptive radiation of lemurs (Wirta et al. 2008). Most species have evolved a broad diet and they feed on both carrion and dung, especially on lemur faeces, the dominant herbivorous mammals in Madagascar. Following the arrival of cattle to Madagascar about 1000 years ago (Burney et al. 2003), four species have been able to switch to cattle dung in open habitats: H. quadripunctatus, H. marsyas, H. neoamplicollis and H. sinuatocornis. The first three species are very abundant and occur, exceptionally for Helictopleurina, across all of Madagascar, while H. sinuatocornis is less common.

Most Helictopleurina (63 %) occur in wet forests in Madagascar, but none of these species has shifted to use cattle dung in open areas (Wirta et al. 2008). Species inhabiting wet forests are poorly adapted to change their habitat selection, which would involve moving to a very different environment in terms of temperature and humidity, particularly in the case of diurnal species such as Helictopleurina (Cambefort 1991; Viljanen et al., in prep.), which experience the maximal contrast in temperature and humidity between forests and open habitats. Koivulehto (2004) has shown that the wet forest-dwelling Helictopleurina simply do not cross the forest edge.

If not coming from wet forests, the species of Helictopleurus now using cattle dung in open areas are likely to have originally occurred in different types of dry forests, where they probably used the dung of lemurs and the dung of the extinct Malagasy megafauna: giant tortoises, elephant bird, and hippopotami, which appear to have occurred especially in dry forests in southeastern Madagascar (Goodman et al. 2003; Hawkins & Goodman 2003). There is a gradient in environmental conditions from entirely open habitats to dosed dry forests, via various kinds of intermediate savanna-type habitats, in which the open habitat Helictopleurus can be found even today. This concerns particularly H. neoamplicollis, H. marsyas, and H. quadripunctatus (Wirta et al. 2008). The situation may be somewhat different in the case of H. sinuatocornis, which occurs as an uncommon species at high elevations along the western range boundary of H. giganteus, its closest relative. These two species occur in sympatry, but H. giganteus occurs in forests while H. sinuatocornis occurs primarily in open habitats.

Apart from the difficulty of changing habitat selection from forest to open habitats, the shift to cattle dung from lemur dung involves a shift to a very different type of resource in terms of texture, fibre content, and size of droppings. Most dung beetles exhibit selectivity for the dung of particular animals based on the size of the dropping and qualities such as moisture, nitrogen and fibre content. Most of the strictly coprophagous dung beetles are specialized to use either herbivore or omnivore dung, although there may be seasonal changes in preference or differences in resource use for adult feeding versus provisioning the nest for oviposition (Hanski & Cambefort 1991).

Regardless of exactly how the shift to cattle dung took place in H. neoamplicollis, H. marsyas and H. quadripunctatus, resource shift has apparently allowed the species to greatly expand their geographical ranges. At present, the species that occur in wet forests have significantly smaller geographical ranges than these three common cattle dung-using species (Wirta et al. 2008). The most likely explanation is that reduced competition in open areas allowed the latter species to expand their ranges, while any expansion of the forest species is hindered by competition with other species outside the ranges of focal species. Rapid range expansion is supported by exceptionally low genetic diversity across the ranges of the three cattle dung-using species (Hanski et al. 2008).

Impact of the introduced Digitonthophagus gazelle

Digitonthophagus gazella, an Afro-Eurasian species, is one of the most frequently introduced dung beetle species worldwide, and a species that has become successfully established in Australia, North America, and Madagascar (Hanski & Cambefort 1991). Howden & Scholtz (1986) reported changes in the abundances of native species ten years after the introduction of D. gazella to Texas in 1972. The previously dominant O. pennsylvanicus, and probably a few other species, appeared to have declined due to competition with D. gazella. In Australia, the previously introduced Euoniticellus intermedius declined following the establishment of D. gazella (Doube et al. 1991). In contrast, the more than 300 native Australian species have not been greatly affected by the many introduced dung beetle species, largely because the native and introduced species exhibit clear habitat segregation, the former living in forests and the latter in open habitats.

The situation in Madagascar is similar to that in Australia: the vast majority of the endemic species occurs in forests and is hence not affected by the abundant and widespread D. gazella, which occurs only in open habitats. Concerning the species in open habitats, our results indicate that the relative abundance of D. gazella in the community did not have a systematic effect on the species composition among the rest of the species, suggesting that D. gazella has no major influence on community structure. Nonetheless, occasionally D. gazella is so abundant that the population uses a substantial fraction of the cattle dung available and there is likely to be competition with the endemic Helictopkurus species living in cattle dung in open habitats. More detailed quantitative studies are required to elucidate these interactions.