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Review
Ecological functions and ecosystem services provided
by Scarabaeinae dung beetles
E. Nichols
a,*
, S. Spector
a
, J. Louzada
b
, T. Larsen
c
, S. Amezquita
d
, M.E. Favila
d
,
The Scarabaeinae Research Network
1
a
Invertebrate Conservation Program, Center for Biodiversity and Conservation, American Museum of Natural History, Central Park West at
79th Street, New York, NY 10024, United States
b
Departamento de Biologia, Universidade Federal de Lavras, Lavras, Minas Gerais, Brazil
c
Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ 08544, United States
d
Instituto de Ecologı´a, A.C. Apartado Postal 63, Xalapa 91000, Veracruz, Mexico
A R T I C L E I N F O
Article history:
Received 25 October 2007
Received in revised form
31 March 2008
Accepted 11 April 2008
Keywords:
Nutrient cycling
Secondary seed dispersal
Waste removal
Bio-control
ABSTRACT
Clear understanding of the links between ecological functions and biodiversity is needed to
assess and predict the true environmental consequences of human activities. Several key
ecosystem functions are provided by coprophagous beetles in the subfamily Scarabaeinae
(Coleoptera: Scarabaeidae), which feed on animal excreta as both adults and larvae.
Through manipulating feces during the feeding process, dung beetles instigate a series
of ecosystem functions ranging from secondary seed dispersal to nutrient cycling and par-
asite suppression. Many of these ecological functions provide valuable ecosystem services
such as biological pest control and soil fertilization. Here we summarize the contributions
of dung beetles to nutrient cycling, bioturbation, plant growth enhancement, secondary
seed dispersal and parasite control, as well as highlight their more limited role in pollina-
tion and trophic regulation. We discuss where these ecosystem functions clearly translate
into ecosystem services, outline areas in critical need of additional research and describe a
research agenda to fill those gaps. Due to the high sensitivity of dung beetles to habitat
modification and changing dung resources, many of these ecological processes have
already been disrupted or may be affected in the future. Prediction of the functional conse-
quences of dung beetle decline demands functional studies conducted with naturally
assembled beetle communities, which broaden the geographic scope of existing work,
assess the spatio-temporal distribution of multiple functions, and link these ecosystem
processes more clearly to ecosystem services.
!2008 Elsevier Ltd. All rights reserved.
0006-3207/$ - see front matter !2008 Elsevier Ltd. All rights reserved.
doi:10.1016/j.biocon.2008.04.011
*Corresponding author: Tel.: +1 212 496 3684.
E-mail address: nichols@amnh.org (E. Nichols).
1
This review was fostered by the Scarabaeinae Research Network (ScarabNet), of which the authors are members. ScarabNet is a
collaborative group of dung beetle taxonomists, biogeographers, ecologists and conservation biologists dedicated to developing the use
of the Scarabaeinae as an invertebrate biodiversity focal taxon. The following additional ScarabNet members contributed to this effort:
Jorge Noriega. ScarabNet is supported by the National Science Foundation’s Research Coordination Network program under Grant DEB-
0043443 to S. Spector (P.I.).
B I O L O G I C A L CO N S E R V AT I O N xxx (2008) xxx–x x x
a v a i l a b l e at w w w . s c i e n c e d i r e c t . c o m
journal homepage: www.elsevier.com/locate/biocon
ARTICLE IN PRESS
Please cite this article in press as: Nichols, E. et al, Ecological functions and ecosystem services provided ..., Biol. Conserv.
(2008), doi:10.1016/j.biocon.2008.04.011
Contents
1. Introduction.................................................................................... 00
2. Ecologicalfunctions.............................................................................. 00
2.1. Nutrientcycling............................................................................ 00
2.2. Bioturbation............................................................................... 00
2.3. Plant growth enhancement. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 00
2.4. Secondaryseeddispersal .................................................................... 00
2.5. Parasitesuppression........................................................................ 00
2.6. Entericparasites........................................................................... 00
2.7. Parasitedispersal........................................................................... 00
2.8. Flycontrol................................................................................ 00
2.9. Trophic regulation and pollination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 00
3. Ecosystemservices............................................................................... 00
4. Dung beetle response to anthropogenic threats . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 00
5. Conclusion..................................................................................... 00
Acknowledgments............................................................................... 00
References..................................................................................... 00
1. Introduction
Human economy, health and wellbeing are intimately linked to
functionally intact ecosystems (MEA, 2005), and well charac-
terized relationships between biodiversity and ecosystem
function are key to predicting the ecological and economic
impacts of human activities (Armsworth et al., 2007). In terres-
trial systems, insects play important ecological roles in diverse
ecological processes such as nutrient cycling, seed dispersal,
bioturbation and pollination. Dung beetles in the coleopteran
subfamily Scarabaeinae mediate several of these processes.
Dung beetles are a globally distributed insect group, with
their highest diversity in tropical forests and savannas (Han-
ski and Cambefort, 1991). Largely coprophagous, dung beetle
species feed on the microorganism-rich liquid component of
mammalian dung (and less commonly that of other verte-
brates, as well as rotting fruit, fungus and carrion) and use
the more fibrous material to brood their larvae (Halffter and
Edmonds, 1982; Halffter and Matthews, 1966).
Most dung beetles use one of three broad nesting strate-
gies, each with implications for ecological function. Paraco-
prid (tunneler) species bury brood balls in vertical chambers
in close proximity to original deposition site. Telocoprid (roll-
er) species transport balls some horizontal distance away, be-
fore burial beneath the soil surface. Endocoprid (dweller)
species brood their young inside the dung mass itself (Halffter
and Edmonds, 1982). Ecological linkages between dung bee-
tles and mammals have played an important role in shaping
the evolution of the Scarabaeinae and the structure of extant
dung beetle communities for at least the last 40 million years
(Cambefort, 1991). Recent fossil evidence of dung-provisioned
burrows strongly suggests that dung beetles evolved coproph-
agy through association with dinosaurs even before the diver-
sification of mammals (Chin and Gill, 1996).
The amount of dung buried by a beetle species is primarily
related to mean female body size (Horgan, 2001), though fac-
tors such as soil type and moisture (Sowig, 1995), pair cooper-
ation (Sowig, 1996) and dung quality (Dadour and Cook, 1996)
also play a role. These varied patterns of consumption and
relocation of dung by beetles drive a series of ecological pro-
cesses that include nutrient cycling, soil aeration, secondary
seed burial, and parasite suppression.
Where they are directly relevant to humans, these ecosys-
tem functions often provide important and/or economically
beneficial ecosystem services (De Groot et al., 2002). Here we
summarize our current knowledge about dung beetle ecosys-
tem functions. We outline the circumstances wherein these
functions become ecosystem services and highlight areas in
need of further empirical study. We frame the importance of
these ecological processes with a discussion of the numerous
threats to dung beetle persistence.
2. Ecological functions
2.1. Nutrient cycling
A significant proportion of the nutrients consumed by verte-
brates are voided in excreta (Steinfeld et al., 2006) and the ex-
tent to which these nutrients can be returned to the plant
growth cycle has strong implications for plant productivity.
The transfer of freshly deposited waste below the soil surface
by tunneler and roller dung beetle species physically relocates
nutrient rich organic material and instigates micro-organis-
mal and chemical changes in the upper soil layers.
Nitrogen is an often critically limiting element that struc-
tures plant productivity (Vitousek et al., 1997). A recent FAO
report estimates that 12 of 30 million tons of N excreted by
extensive livestock production systems in the mid-1990s were
lost through NH
3
volatilization (Steinfeld et al., 2006). By bury-
ing dung under the soil surface, dung beetles prevent the loss
of N through ammonia (NH
3
) volatilization (Gillard, 1967), and
enhance soil fertility by increasing the available labile N avail-
able for uptake by plants through mineralization (Yokoyama
et al., 1991a). While a high estimate of NH
3
volatilization from
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livestock excreta (ca. 80%, Gillard, 1967) has been cited in
studies estimating the impacts of dung beetle activity on soil
fertility (e.g. Bang et al., 2005; Losey and Vaughan, 2006), more
recent estimates from the Food and Agriculture Organization
of the United Nations and the Intergovernmental Panel on Cli-
mate Change project more moderate rates of around 22%
(FAO/IFIA, 2001).
One mechanism by which dung beetles affect the nitrogen
cycle is by accelerating mineralization rates. Nitrogen volatil-
ization and mineralization are bacteria-mediated processes,
and dung beetles alter the microorganism fauna in dung pats
and brood balls during feeding and nesting (Yokoyama et al.,
1991a). Several studies suggest that the aerobic conditions in
dung and elevated C and N levels in the upper soil layers
stimulated by dung beetle activity foster bacterial growth,
including ammonifier bacteria responsible for continued
N-mineralization (Yokoyama and Kai, 1993; Yokoyama et al.,
1991a,b). In the absence of dung beetle activity, nitrogen min-
eralization rates in freshly deposited dung initially increase,
accompanied by a release of inorganic N (Yamada et al.,
2007; Yokoyama and Kai, 1993; Yokoyama et al., 1991a,
1989). This mineralization processes declines or ceases within
5–7 days, yet continues to increase in beetle-colonized dung
and brood balls (Yokoyama and Kai, 1993; Yokoyama et al.,
1991a, 1989). Dung beetles may also affect N-volatilization
rates by physically diluting the available concentration of
inorganic N as they incorporate it into the soil (Yokoyama
et al., 1991b). This action may enhance N-fixing activity
through increasing the availability of easily decomposable or-
ganic matter, but the net positive benefits of this mobilization
remain unknown (Yokoyama et al., 1991b).
The influence of dung beetle action on denitrification rather
than NH
3
volatilization remains uncertain. Yokoyama et al.
(1991a) demonstrated that dung beetles significantly inhibited
the volatilization of NH
3
, principally from brood balls. How-
ever, denitrification in brood balls caused an N loss signifi-
cantly greater than that from un-manipulated dung. They
postulated this was a consequence of dung beetles increasing
the endogenous NO
3
–N pool, enhancing denitrifying activity.
Increased denitrification rates in dung beetle-colonized dung
could partially offset the benefits of increased N-mineraliza-
tion, however a full accounting of the influence of dung beetles
on nitrogen flows and distributions has yet to be done. Work by
Rougon et al. (1990) reported high concentrations of amino
acids in dung beetle brood ball casings, which potentially accu-
mulate following gaseous nitrogen fixation by microorganisms
in the digestive tracts of dung beetle larvae.
Several authors have reported an increase in soil nutrients
(P, K, N, Ca and Mg) found in soils exposed to dung beetle
activity in experimental dung masses (Bertone, 2004; Galbiati
et al., 1995; Lastro, 2006; Yamada et al., 2007). Bertone (2004)
also found dung beetle activity spurred an increase in soil
pH and cation exchange capacity of soils, though had little ef-
fect on humic matter content. Yamada et al. (2007) report a
significant positive relationship between the magnitude of re-
leased inorganic N and available P and K in cattle dung and
dung beetle abundance.
Our understanding of dung beetles’ role in soil fertility
comes exclusively from pasture and grassland studies, and
the importance of these processes is poorly understood for
other natural systems. Further research is needed in tropical
forests, where dung beetles are typically capable of transfer-
ring all deposited mammal feces into the soil within hours
after deposition (Arrow, 1931; Slade et al., 2007), and highly
localized differences in soil fertility are important in structur-
ing plant communities in nutrient-poor soils (John et al.,
2007). Necrophagous dung beetles may affect also affect
nutrient cycling by relocating carrion below the ground sur-
face. Carrion consumption is most strongly developed in Neo-
tropical Scarabaeines (Gill, 1991), though no present estimates
exist for the amount of vertebrate or invertebrate typically
biomass consumed.
Finally, dung beetles are not exclusively responsible for the
relocation of fecal material into the soil. Many wood, litter
and soil feeding termites are also documented coprophages,
though dung does not appear to be a preferential food source
(Freymann et al., 2008). Termites may proportionally remove
more waste in arid areas and dry seasons relative to dung
beetles (Coe, 1977; Herrick and Lal, 1996). Termites impact
nutrient cycling through the comminution and spatial redis-
tribution of dung, which increases its availability to microbial
decomposers. Termite modified soil is often richer in nitro-
gen, organic carbon, and exchangeable cations than non-
modified soil, but these impacts have not been clearly attrib-
uted to feeding on dung, rather than other detritus (Freymann
et al., 2008). Earthworms also incorporate feces into the soil,
and alter organic materials that pass through their gut – spur-
ring microbial interactions that alter N availability in complex
ways (Groffman et al., 2004). In north-temperate systems
where coprophagous beetle communities are dominated by
the genus Aphodius (Coleoptera: Scarabaeidae), earthworms
often play a significant role in waste burial (Gittings et al.,
1994; Holter, 1977, 1979).
2.2. Bioturbation
Bioturbation (the displacement and mixing of sediment parti-
cles by animals or plants) may influence soil biota and plant
productivity by increasing soil aeration and water porosity.
Tunneler dung beetles play a role in bioturbation through
moving large quantities of earth to the soil surface during
nesting (Mittal, 1993). While particular nesting styles vary
greatly among tunneler species, most construct underground
tunnels with branching brood chambers. These tunnels canbe
up to several meters deep, and are often lightly backfilled with
soil to protect the developing larvae. The tunnel depth and
amount of soil removed are positively related to beetle body-
size (Edwards and Aschenborn, 1987; Halffter and Edmonds,
1982; Lindquist, 1933). While this tunneling activity is gener-
ally assumed to increase soil aeration and water porosity in
the upper soil layers, these effects have rarely been empiri-
cally assessed (Miranda, 2006). A single study has measured
the impact of dung beetles on soil permeability beneath dung
pats, and reported that of three species (Copris ochus,C. tripar-
titus and Onthophagus lenzii), only the largest-bodied species
(C. ochus) had a significant positive effect on permeability (Bang
et al., 2005). Their results also indicated that beetle activity did
not affect soil permeability at depths greater than 10 cm.
We found no studies that assessedwhether soil aeration by
dung beetles is sufficient to offset soil compaction by grazing
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livestock (Fincher, 1981). Neither were there studies that
empirically separated the relative effects of soil aeration
and nitrogen mobilization on plant growth. In situ studies
assessing the physical affects of dung beetles on soil struc-
tural properties and subsequent impacts on plant productiv-
ity and biodiversity are needed, given that dung beetle
behaviors that affect soil structure are often altered in the
laboratory environment (Mittal, 1993).
Other organisms, specifically termites and earthworms
also create tunnels and redistribute soil. The mass of dung
buried and soil removed by termites has a strong linear rela-
tionship with an average 2–1 ratio (Herrick and Lal, 1996).
While several studies have demonstrated that some earth-
worms are efficient dung removers in Europe (Holter, 1977,
1979), Australia and New Zealand (Baker, 1994), their dung-
related contribution to bioturbation in areas with a higher
diversity of Scarabaeine dung beetles is unknown.
2.3. Plant growth enhancement
A series of experimental studies link dung beetles’ role in bio-
turbation and nutrient mobilization to increases in plant bio-
mass. These experiments often contrast the biomass of
plants grown in soil with dung mixed by hand, mixed by dung
beetles, and with chemical fertilizer applications. Studies
have reported that dung mixing actions by dung beetles result
in significant increases in plant height (Galbiati et al., 1995;
Kabir et al., 1985), above-ground biomass (Bang et al., 2005;
Lastro, 2006), grain production (Kabir et al., 1985), protein lev-
els (Macqueen and Beirne, 1975a) and nitrogen content (Bang
et al., 2005). Galbiati et al. (1995) also reported that dung beetle
activities had positive (though inconsistently significant) ef-
fects on corncob diameter and below ground biomass. Borne-
missza and Williams (1970) reported a two-factor yield
increase in above-ground biomass of millet planted in soil
mixed with cow dung relative to dung-free soil, but biomass
was not influenced by the mechanism of dung burial. In some
studies, the positive impacts of dung beetle activity on both
above and below ground plant biomass required several
months to manifest (Miranda et al., 1998, 2000). In the only
in situ study conducted with both natural vegetation and
un-manipulated dung beetle abundances, Borghesio (1999)
found that dung beetle mixing significantly increased net pri-
mary productivity (NPP) of heathland plants in Italy over dung
without beetle activity, or dung-free controls. A repetition of
their experiment the following year found significant differ-
ences in NPP between the control and both dung treatments,
but could not distinguish between the effects of the latter.
They attributed this to the comparatively lower number of
dung fauna in the second year, possibly as a consequence of
lowered cattle stocking rates in the area.
In several studies, the effects of nutrient mobilization by
dung beetles on plant growth rival that of chemical fertilizers.
Miranda et al. (2000) found dung beetle activity outperformed
chemical fertilizer application in increasing plant height and
leaf production at an application of 100 kg/ha of N, 100 kg/ha
of P
2
O
5
and 100 kg/ha of K
2
0. In an in situ pasture study, Fincher
et al. (1981) contrasted the yield of Bermuda grass fertilized
with two levels of ammonium nitrate application (112 kg/ha
and 224 kg/ha) or cattle dung exposed naturally to dung bee-
tles. Dung beetle activity resulted in significantly higher yield
than the lower fertilizer application and dung unmanipulated
by beetles, but could not be distinguished from the yield found
in the higher fertilizer treatments. In a second study, Fincher
et al. (1981) reported that dung beetle activity significantlyele-
vated the yield of wheat plants relative to chemical fertilizers
and unmixed dung in one of three trials, though results in the
other two trials were equivocal. Maqueen and Beirne (1975a)
reported that while dung-beetle mixing of cattle dung in-
creased crude protein levels in bearded wheatgrass by 38% rel-
ative to a hand-mixed control, both low (67 kg/ha) and high
chemical fertilizer application (269 kg/ha) had a much greater
effect (increases of 95% and 144%, respectively).
The studies outlined above predominantly consisted of
single dung beetle/single plant species experimental systems,
in laboratory settings. Incorporating naturally assembled
dung communities with multi-species plant assemblages
and non-crop plant species will be important for future work.
There is a conspicuous lack of dung beetle nutrient mobiliza-
tion studies in tropical forests. Non-native earthworms often
have demonstrable effects on nutrient cycling in natural posi-
tive effects on yields in agroecosystems (Baker, 1994), but
these effects have not been linked to coprophagy. Similarly,
termite effects on plant yield as a consequence of dung con-
sumption have been inconclusive (Freymann et al., 2008).
2.4. Secondary seed dispersal
Vertebrate seed dispersal mechanisms are extremely wide-
spread in tropical and temperate ecosystems (Howe and
Smallwood, 1982; Jordano, 1992; Willson et al., 1990). For
seeds, the risks between initial deposition in frugivorous ani-
mals’ dung and final seedling emergence include predators,
pathogens and unsuitable placement for future germination
(Chambers and MacMahon, 1994). Secondary seed dispersal
is believed to play an important role in plant recruitment
through interactions with these post-primary dispersal risk
factors (Chambers and MacMahon, 1994). From a dung bee-
tle’s perspective, most seeds present in dung simply represent
contaminants, since they occupy space in the dung and are
not consumed by the larvae. However, with competition for
dung usually intense and burial occurring rapidly, dung bee-
tles often bury seeds, perhaps accidentally, as they bury dung
for their larval brood balls. At other times, dung beetles pur-
posefully remove seeds before or after burying dung, typically
‘cleaning’ the dung from a seed and abandoning it on the soil
surface or within the tunnel (Andresen and Feer, 2005).
Dung beetles relocate seeds both horizontally and vertically
from the point of deposition. The combined impact of this dis-
persal by tunneler and roller species benefits seed survival (and
therefore plant recruitment) by (i) reducing seed predation and
mortality due to seed predators and pathogens (Andresen,
1999; Andresen and Levey, 2004; Chambers and MacMahon,
1994; Estrada and Coates-Estrada, 1991; Feer, 1999; Janzen,
1983a; Shepherd and Chapman, 1998); (ii) directing dispersal
to favorable microclimates for germination and emergence
(Andresen and Levey, 2004); and (iii) decreasing residual post-
dispersal seed clumping (Andresen, 1999, 2001), with potential
effects on density dependent seed mortality, seedling
competition, and predation risk (Andresen and Feer, 2005).
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The probability and depth of a seed’s vertical burial by a
dung beetle depends on seed size (Andresen and Levey,
2004), the composition of the dung beetle community (Andre-
sen, 2002; Slade et al., 2007; Vulinec, 2002) and both the
amount (Andresen, 2001, 2002) and type of dung (Ponce-Sant-
izo et al., 2006). Dung beetle communities bury between 6 and
95% of the seeds excreted in any given fecal pile, and this per-
centage ranges widely across studies (13–23% Feer, 1999; 26–
67%; Andresen and Levey, 2004; 35–48%; Andresen, 2003; 6–
75% Andresen, 2002; 47–95% Shepherd and Chapman, 1998).
As they bury a disproportionate amount of dung, larger-
bodied and nocturnal species perform a disproportionate
amount of secondary seed burial (Andresen, 2002; Slade
et al., 2007).
The horizontal movement of seeds away from the original
deposition site may increase seed fitness by (i) reducing den-
sity dependent predator or pathogen attack or by (ii) increas-
ing seedling survival by reducing seedling density and
competition (Howe, 1989; Peres et al., 1997). The probability
and distance of a seed’s horizontal dispersal depends on seed
size (Andresen, 2002, but see Andresen and Levey, 2004) and
the beetle community composition. Both the amount and ori-
gin of dung deposits affect the composition of the attracted
dung beetle assemblage, but not the probability or distance
of horizontal seed burial (Andresen, 2001, 2002; Ponce-Santizo
et al., 2006). Overall, dung beetles communities move approx-
imately 5–44% of available seeds horizontally (Andresen,
2001, 2002; Andresen and Levey, 2004). Maximal recorded dis-
tances of dung beetle brood balls (presumably containing
seeds) up to 15 m in the Afrotropics (Heymons and von
Lengerken, 1929 cited in Halffter and Matthews, 1966) and
10.6 m in the Neotropics have been reported (Canthon pilularius,
Halffter and Matthews, 1966, though shorter distances are
more common (6–17 cm Andresen, 2002; 18 cm Andresen and
Levey, 2004; 82–112 cm Andresen, 1999; 200–500 cm Canthon
humectus and Canthon indigaceus Halffter and Matthews, 1966).
Both vertical and horizontal secondary dispersal assist
seeds to avoid the extremely high seed predation rates often
seen in tropical forests due to rodents (Estrada and Coates-
Estrada, 1991; Sa
´nchez-Cordero and Martı´nez-Gallardo,
1998). Seed detection and predation risks decline with deeper
seed burial depths (Andresen, 1999; Estrada and Coates-Estra-
da, 1991; Shepherd and Chapman, 1998). Seed ‘cleaning’ dur-
ing brood ball creation may reduce the likelihood of rodent
predation of those seeds by reducing the attractive dung scent
(Andresen, 1999), though this impact remains speculative.
While deeper seed burial depths decreases rodent detection
and predation, buried seeds must also be shallow enough to
permit germination and emergence (Andresen and Feer,
2005; Dalling et al., 1995). The ability of a seed to emerge from
a given depth depends on seed size, cotyledon morphology
and microclimate requirements (Andresen, 1999; Estrada
and Coates-Estrada, 1991; Shepherd and Chapman, 1998).
While the emergence success of most seeds is greatly reduced
at depths below 3 cm (Feer, 1999; Hingrat and Feer, 2002; Pear-
son et al., 2002), a recent review by Andresen and Feer (2005)
found that dung beetles bury most seeds at depths of 1–5 cm.
Consequently, the secondary burial of a seed by a given dung
beetle may impact that seed positively or negatively.
Determination of the net effect of dung beetle seed dis-
persal on plant recruitment will require studies that (i) track
seed fate through germination and emergence, (ii) assess
the response of small seeds to dung beetle burial, (iii) relate
changes in beetle community structure to overall profiles of
burial depth and (iv) assess the effect of dung beetle burial
on invertebrate seed predation and fungal pathogens. The
germination of a seed secondarily dispersed by a dung beetle
may be influenced by local physical alteration of the soil, the
seeds’ final dispersal location (within a brood ball or within
the tunnel itself), or the size of the brood ball in which it
was incorporated, but these factors remain uninvestigated.
The effect of dung beetles on small seeds (63 mm) is broadly
unknown given the logistic challenges in following the fate of
very small seeds (Andresen and Feer, 2005). Many small seeds
are light-demanding pioneer species (Dalling, 2005) that rep-
resent a large proportion of the seed bank (Murray and Garcia,
2002). Dung beetles bury nearly all small seeds present in
dung, but as small seeds face real constraints on maximal
burial depth for successful germination (Dalling et al., 1995),
the average burial depth by dung beetles may contribute to
more to small seed death than survival. The relative impor-
tance of beetle seed dispersal in areas with elevated rodent
seed predator densities, such as partially defaunated or sec-
ondary forests (Asquith et al., 1997) will be important infor-
mation for predicting the quality of recovering forests
(Gardner et al., 2007).
The importance of dung beetle secondary seed dispersal
outside of the Neotropics (and Afrotropics to a lesser extent)
is poorly known, particularly in savannas, temperate and
Mediterranean systems and the (primarily wind-dispersed)
Dipterocarp forests of south-east Asia (McConkey, 2005).
While there are several reports of dispersion of invasive plant
species by livestock (Campbell and Gibson, 2001; Constible
et al., 2005) and wild mammals (Myers et al., 2004; Shiponeni
and Milton, 2006) in anthropogenic and natural ecosystems
worldwide, it is not known whether dung beetles play a role
in the seedling establishment and success of invasive plants.
In northeastern Brazil Phanaeus kirbyi and Dichotomius (Seleno-
copris)aff. bicuspis are known to positively affect germination
rates through scarring pequi seeds (Cariocar brasiliensis) (Vaz-
de-Mello pers. comm), but it is unknown if scarification is a
common dung beetle function.
Secondary seed dispersal is not unique to dung beetles.
Earthworms may have a strong effect on seeds, as seeds are
occasionally ingested and redeposited in surface-level casts
or deep within the soil profile, though the net effects of these
movements are unknown (Dalling, 2005). Secondary dispersal
by ants (myrmechory) is also relatively common in tropical
forest systems (Dalling, 2005; Pizo et al., 2005).
2.5. Parasite suppression
Through feeding and nesting, adult and larval dung beetle
activity serves to control the abundance of dung-breeding
hematophagic and detrivorous flies and dung-dispersed nem-
atodes and protozoa. As these ecological processes poten-
tially have enormous implications for livestock, wildlife and
human health and wellbeing (Byford et al., 1992; Miller,
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1954). Much of our understanding of these functions has aris-
en from the study of livestock parasites and pests.
2.6. Enteric parasites
From an early study in Australian cattle pastures, Bryan (1973)
reported a significant decrease in emergent strongyle nema-
tode larva from cattle dung manipulated by Digitonthophagus
gazella. In a subsequent study, Bryan (1976) reported that con-
trol pats with no dung beetles contained 50 times more hel-
minth larvae than those with 10 or 30 D. gazella pairs.
Fincher (1973) experimentally elevated the dung beetle popu-
lation 5-fold in a cattle pasture in the southeastern United
States and reported a nearly 15-fold reduction in the emer-
gence in Ostertagia ostertagi relative to dung beetle free-pas-
tures and a 3.7-fold reduction relative to pastures with
natural dung beetle levels. In a second experiment, Fincher
reported that calves grazed on pastures without dung beetles
acquired nine times more endoparasites (Ostertagia and Coo-
peria) than those in pastures with experimentally elevated
levels dung beetles and four times more than pastures with
natural beetle abundances (Fincher, 1975). Bergstrom (1983)
reported an 84.7% reduction in the number of emerging elk
lungworm larvae (Dictyocaulus hadweni) when elk dung was
manipulated by an Aphodius dominated dung beetle commu-
nity. Dung beetles have also been implicated in the reduction
in abundance of the exploding fungus Pilobolus sporangia,
which forcefully disperses nematodes in pasture systems
along with its own spores (Gormally, 1993).
Laboratory studies reveal that passage through certain
dung beetle species significantly reduces the abundance of
viable helminth eggs and protozoan cysts, including Ascaris
lumbricoides,Necator americanus,Trichuris trichiura,Entamoeba
coli,Endolimax nana,Giardia lamblia (Miller et al., 1961) and
Cryptosporidium parvum (Mathison and Ditrich, 1999). Miller
et al. (1961) reported the feeding actions of four Canthon and
Phanaeus species reduced the passage of hook and round-
worm eggs by nearly 100%, while Dichotomius carolinus had lit-
tle effect. Miller understood dung beetle feeding to involve a
grinding action between the molars and attributed the re-
duced control of helminth eggs by D. carolinus to its large mo-
lar size and spacing (Miller, 1961). Subsequent work indicates
that scarabeine beetles strain out, rather than comminute
large particles, using their soft, filtering setae to ingest only
minute particles (8–50 lm) and squeezing the smaller remain-
der between the molar surfaces to remove excess liquid (Hol-
ter, 2002); consequently the specific mechanism for this
parasite suppression remains poorly understood.
Additional research is also needed to assess the relative
impacts of adult dung beetle feeding versus nesting on the
survival rate of parasitic eggs and cysts, and extent to which
these actions reduce disease incidence or parasite load in
wild and domestic animals. Male Canthon cyanellus cyanellus
are known to produce an antifungal compound that protects
brood balls. It is not known if this chemical protection is
widespread, nor has implications for fungal or other patho-
gen control (Cortez-Gallardo and Favila, 2007). While dung
beetles have been conjectured to be important suppressors
of human endoparasites (Miller, 1954), we know of no publica-
tion empirically relating dung beetles and human endopara-
site transmission. Hingston (1923) reported that dung
beetles in rural India were capable of interring 40–50 thou-
sand tons of human feces in the months of May and June. Un-
der similar removal rates, dung beetles use of human feces
may reduce transmission of fecal–oral pathogens, particularly
in rural areas with inadequate sanitation.
2.7. Parasite dispersal
Several studies have alternatively suggested that dung beetles
may transmit dung-borne pathogens within their gut or upon
their exoskeleton, acting as intermediate, incidental or
paratenic hosts. However few studies present convincing evi-
dence of the role of dung beetles in transmission.Other
coprophagous invertebrates (e.g. earthworms) have been
investigated for their role as endoparasite hosts, also with
generally inconclusive results (Roepstorff et al., 2002). With-
out targeted epidemiological study of the parasites in ques-
tion, it remains unknown if dung beetles commonly amplify
parasite transmission as frequently suggested.
Species in various dung beetle genera (including Anomio-
psoides,Eucranium,Megathopa,Canthon,Phanaeus,Dichotomius,
and Ateuchus) have been reported as intermediate hosts of
swine parasites (e.g. Ascarops strongylina,Physocephalus sexala-
tus,Macracanthorhynchus hirudinaceus and Gongylonema ver-
rucosum)(Alicata, 1935; Fincher and Marti, 1982; Martı´nez,
1959; Stewart and Kent, 1963), however simple presence of
infectious or non-infectious larval stages within adult dung
beetles is an insufficient demonstration of a dung beetle’s role
as host in a parasite’s development cycle. Stumpf (1986) sug-
gested that M. hirudinaceus used scarabeine beetle adults as
intermediate hosts in Brazil, though he reported more larvae
in non-infective (IV & V) than infective (VI) stages in adult
beetles. This suggests that M. hirudinaceus larvae may not de-
velop within the dung beetle, but simply be consumed at the
later infective stage.
Saitoh and Itagaki (1990) concluded that two species of
Onthophagus that emerged from cat feces infected with feline
coccidia (Toxoplasma gondii) carried infective oocysts both in
their feces and on their bodies. Mice that then consumed
these beetles were capable of infecting kittens (Saitoh and
Itagaki, 1990). Saitoh and Itagaki additionally detected two
additional strains of feline coccidia, Isopora felis and Isopora
rivolta on dung beetles collected from urban dog feces; these
dung beetles were also able to transmit feline coccidia to
three of four kittens via dung beetle-mouse consumption,
presenting a potential incidental or intermediate host role
for some beetle species in feline coccidia. In contrast, Xu
et al. (2003) tested 113 Catharsius molossus dung beetles for
two E. coli strains (O157:H7 and the virulent Shiga-toxin), both
with principle reservoirs in domestic pigs and cattle. Only six
beetles (ca. 5%) tested positive for E. coli O157:H7 and four of
the six for the Shiga-toxin 2 strain. They concluded that dung
beetles likely play no epidemiological role in E. coli O157:H7.
2.8. Fly control
Fresh mammal dung is an important resource for a variety of
dung-breeding flies as well as dung beetles. Several pestifer-
ous, dung-dwelling fly species (principally Musca autumnalis,
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M. vetustissima,Haematobia thirouxi potans,H. irritans exigua
and H. irritans irritans) have followed the introduction of live-
stock globally. Fly infestations reduce livestock productivity
(Haufe, 1987) and hide quality (Guglielmone et al., 1999), and
represent an enormous financial burden to livestock produc-
ers (Byford et al., 1992).
When and where dung beetles and dung flies co-occur, fly
survival tends to decline as a consequence of asymmetrical
competition for dung resources, mechanical damage of eggs
by beetles, and fly predation by mites phoretic on dung bee-
tles. A series of experimental manipulations of dung beetle
and fly densities in artificial dung pats report elevated fly mor-
tality in the presence of Scarabaeine beetles, both in the labo-
ratory and field (Bishop et al., 2005; Blume et al., 1973;
Bornemissza, 1970; Doube, 1986; Feehan et al., 1985; Hughes
et al., 1978; Macqueen and Beirne, 1975b; Mariategui, 2000;
Moon et al., 1980; Ridsdill-Smith, 1981; Ridsdill-Smith and
Hayles, 1987, 1990; Ridsdill-Smith et al., 1986; Ridsdill-Smith
and Matthiessen, 1984, 1988; Wallace and Tyndale-Biscoe,
1983).Fly mortality caused by dung beetle activity is a com-
bined consequence of (i) direct mechanical damage to fly eggs
and early instars caused during adult beetle feeding (Bishop
et al., 2005; Ridsdill-Smith and Hayles, 1990), (ii) unfavorable
microclimates for fly eggs and larvae caused by dung distur-
bance (Ridsdill-Smith and Hayles, 1987) and (iii) resource com-
petition with older larvae, primarily from removal of dung for
brood balls (Hughes, 1975; Ridsdill-Smith and Hayles, 1987,
1990). The relative impact of these dung beetle activities is
modulated by several factors, including dung quality (Mac-
queen and Beirne, 1975b; Ridsdill-Smith, 1986; Ridsdill-Smith
and Hayles, 1990), beetle abundance (Bornemissza, 1970;
Hughes et al., 1978; Kirk and Ridsdill-Smith, 1986; Ridsdill-
Smith and Hayles, 1989; Ridsdill–Smith and Matthiessen,
1988; Tyndale-Biscoe, 1993), activity period (Fay et al., 1990),
nesting strategy (Edwards and Aschenborn, 1987) and impor-
tantly, arrival time (Edwards and Aschenborn, 1987; Hughes
et al., 1978; Ridsdill-Smith and Hayles, 1987). Phoretic preda-
tory macrochelid mites have also been implicated in fly con-
trol (Axtell, 1963; Doube, 1986). These mites rely on dung
beetles for transport between dung pats (Krantz, 1998) and
consume significant numbers of fly eggs and young larvae
(Wallace et al., 1979) when sufficiently abundant (Glida et al.,
2003). Anecdotal reports from Australia suggest that the level
of fly control achieved in dung pats with both mites and bee-
tles is superior to those with only beetles (Dadour, 2006).
Experimental simulations of field conditions typically re-
port a strong reduction in fly abundance by dung beetles in
individual dung pats (Hughes et al., 1978; Ridsdill-Smith and
Hayles, 1990), yet attempts to link the activity of a single dung
beetle species to demonstrable reductions of natural fly pop-
ulations have been unsuccessful to date (Eoniticellus interme-
dius,Hughes et al., 1978;Onthophagus granulatus,Feehan
et al., 1985, Digionthophagous gazella,Bishop et al., 2005). For
example, Tyndalebiscoe and Walker (1992) found that experi-
mentally elevated densities of Onthophagus australis reduced
bush fly survival by 74% and fly puparia size by 18% – however
O.australis densities were not observed to reach this critical
density in the spring, when bush flies populations first began
to grow. Fly abundance did not significantly differ before or
after the 1971 introduction of dung beetles and successful
establishment of Eonticellus intermedius in 1974 to Australia
(Hughes and Morton, 1985), despite anecdotal evidence to
the contrary (Hughes et al., 1978).
While dung beetles have a clear and negative impact on fly
breeding success under experimental conditions, in natural
settings this relationship is more complex. An entire dung
beetle assemblage (rather than a single species) is less likely
to demonstrate the mismatches in habitat use and seasonal
and daily flight activity that would reduce their effectiveness
in fly suppression. The two in situ field studies that have mea-
sured fly success after exposure to the entire dung beetle
assemblage (Fay et al., 1990; Horgan, 2005) both report a
strong fly reduction by dung beetles in individual dung pats.
Rather than concluding from these single species interactions
that dung beetles offer no practical pest fly control at the
landscape level (i.e. Macqueen and Beirne, 1975b), we advo-
cate that future investigations assess these functions with
the entire dung beetle assemblage.
Expanded future research on fly–beetle interactions to no-
vel ecosystems (e.g. outside of pastures or savannas), geo-
graphic regions (e.g. outside of Australia, southern Africa
and to a lesser extent Brazil) and fly groups (e.g. disease vec-
tors and wild mammal pests, though see Bishop et al., 2005)
would strengthen our understanding of the true role of dung
beetles as fly competitors in both natural and managed land-
scapes. While dung beetles are important competitors of pes-
tiferous flies, fly predators (e.g. Macrochelid mites, histerid
and staphylinid beetles) and parasites (e.g. parasitic wasps)
are also key biological control agents. This entire suite of
organisms likely produces the function of truly effective fly
control, and both the relative contribution by dung beetles
and the underlying functional relationships among these
coprophagous organisms (e.g. resource partitioning, facilita-
tion or a selection effect) are poorly known.
2.9. Trophic regulation and pollination
Some dung beetle species have additional unique ecological
roles in trophic regulation and pollination. Dung beetle preda-
tion potentially contributes to population regulation of leaf-
cutter ants (Atta sp.) – one of the Neotropics’ principal herbi-
vores (Costa et al., in press). Canthon virens (misidentified as C.
dives sensu Borgmeier, 1937) individuals attack leaf-cutter
queens during nuptial flights to provision their larvae (Forti
et al., 1999; Halffter and Matthews, 1966; Hertel and Colli,
1998; Silveira et al., 2006). Forti et al. (1999) estimated that a sin-
gle dung beetle individual could predate dozens of queens dur-
ing a reproductiveperiod, representing up to 10% of the recently
hatched individuals. Vasconcelos et al. (2006), observed that
61.8% of the predation events resulting in nest establishment
failure were instigated by Canthon virens. As Atta ants strongly
impact plant community structure and dynamics, soil proper-
ties and nutrient cycling (Farji-Brener, 1992; Hull-Sanders and
Howard, 2003; Moutinho et al., 2003), the enormous predation
pressure they face during nuptial flights may play an impor-
tant role in ecological processes. Further research on Atta pre-
dation by dung beetle species is needed to determine the
relative trophic importance of these predation events.
While restricted to only a few plant species, Scarabaeine
beetles are important (and often obligate) pollinators of
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decay-scented flowers in the families Araceae and Lowiacea.
Two species of Onthophagus dung beetles (O. ovatus and O. sell-
atus) are pollinators of the dung/carrion scented Arum dioscor-
dis (Aracaeae) in Lebanon (Gibernau et al., 2004; Meeuse and
Hatch, 1960). Gleghorn, cited in Arrow (1931) reported the pol-
lination of the carrion-scented Typhonium tribolatum (Arac-
aeae) in India by Onthophagus tarandus and Caccobius
diminitivus.Sakai and Inoue (1999) described the obligate pol-
lination of carrion-scented Orchidantha inquei (a member of
the highly relictual Lowiacea family) by carrion feeding Onth-
ophagus species. While these tight co-evolutionary relation-
ships may be rare, their obligate nature merits appropriate
conservation action.
3. Ecosystem services
Ecosystem services are the subset of ecological functions that
are directly relevant or beneficial to the human condition (De
Groot et al., 2002). The few studies evaluating dung beetle eco-
system services have predominantly outlined their value to
the livestock industry, particularly in the context of the Aus-
tralian Dung Beetle Project.
Following European colonization, Australian livestock pro-
duction in the absence of a native ruminant-adapted dung
beetle fauna resulted in an estimated deposition of 33 million
tons of dung yr
!1
(Bornemissza, 1960; Bornemissza, 1976).
This vast fecal deposition increased pest fly populations
(Hughes, 1975) and caused extensive pasture loss (Ferrar,
1975), as livestock avoided grazing in the fouled areas sur-
rounding deposits (Anderson et al., 1984). In response, 55 spe-
cies of dung beetles were imported between 1968 and 1982,
principally from southern Africa. Eight species have success-
fully established (Macqueen and Edwards, 2006), and several
are widely distributed across the productive livestock regions
(Elphinstone, 2006). These introduced beetles have reduced
the area physically covered by cattle waste by approximately
4 percent (Hughes, 1975), representing a tremendous gain in
pasture, since an additional 6–12% of the area surrounding
each dung pat is generally avoided by grazing livestock (Fin-
cher, 1981; Weeda, 1967). However, while successfully increas-
ing dung removal services, introduced beetles appear to have
failed to successfully suppress fly population at the landscape
level (Hughes and Morton, 1985).
Beyond Australia, dung beetles play a key role in the sus-
tainability of extensive livestock production globally. Exten-
sive pasture systems account for 78% of all agricultural land
use and currently cover nearly 2.0 billion hectares – some
15% of the earth’s ice-free surface (Steinfeld et al., 2006). As
chemical additives and curative (rather than preventative) vet-
erinary care are often economically and logistically infeasible
in these areas, their long-term sustainability rests upon natu-
ral ecological processes to avoid forage fouling, suppress live-
stock pests and maintain forage productivity through
prevention of N-volatilization (Miranda, 2006). Losey and
Vaughan (2006) estimate the net value of dung beetles to the
extensively pastured beef cattle industry in the United States
at USD $380 million yr
!1
, based largely on estimates first pub-
lished by Fincher (1981) and Anderson et al. (1984). This sum
represents the estimated avoided costs in fertilizer application
and production losses from forage fouling, enteric parasites
and flies. An extrapolation of these values to extensive cattle
ranching globally is beyond the scope of this paper, but may
portend a significant economic role for dung beetles in main-
taining sustainable livestock production (Steinfeld et al., 2006).
Aside from the relevance of dung beetles to livestock pro-
duction, we can only conjecture about the importance of
other dung beetle ecosystem services. Soil conditioning and
nutrient recycling by dung beetles may increase crop yield
and plantation productivity as suggested by laboratory stud-
ies (Miranda et al., 2000; Yokoyama et al., 1991b). Isolation
and synthesis of the chemical compounds that suppress
pathogenic fungal growth on dung beetle brood balls may
have horticultural applications. Secondary seed dispersal
likely contributes to the timber and non-timber forest product
industries as well as reforestation or restoration projects
(Vulinec et al., 2007).
As with most ecosystem services, before dung beetle ser-
vices can be properly integrated with conservation planning
or practice, additional research on dung beetle biodiversity-
ecosystem function (BEF) relationships and links between eco-
system functions and services will be required. A bridging re-
search agenda suggested by Kremen (2005) provides a near
perfect fit to this task, suggesting future work that would iden-
tify: (1) the key species or traits providing ecosystem functions,
(2) the relationships between ecosystem function and commu-
nity assembly and disassembly processes,(3) the environmen-
tal factors influencing the production of ecosystem functions,
and (4) the spatio-temporal scales relevant to both providers
and their functions (Kremen, 2005). The most recent dung bee-
tle BEF work has begun to advance our understanding of points
1–3, by identifying the specific-specific and community traits
responsible for both ecological function (effect traits) and sen-
sitivity or resistance to environmental change (response traits)
(Horgan, 2005; Larsen et al., 2005; Slade et al., 2007).
To this we suggest a necessary fifth step, the specific rela-
tion of ecosystem functions to ecosystem services, through
identifying those socio-economics and ecological contexts
where a given function is directly relevant to humans. It is un-
likely that all dung beetle functions are relevant to humans in
all natural and socio-economic contexts. For example, dung
beetle secondary seed dispersal is unequivocally an ecosys-
tem function in a Neotropical forest. Is the burial of that seed
relevant or useful to humans, and therefore a service? If that
dispersal is important for the regenerative capacity of a na-
tional park that contributes to atmospheric and hydrologic
regulation, or has cultural values, is it then an ecosystem ser-
vice? Declaring an ecological process ‘‘important’’ to the hu-
man condition is heavily subjective to spatial, temporal and
even ethical considerations (McCauley, 2006; Srivastava and
Vellend, 2005; Wallace, 2007) compelling researchers to clearly
delimit the scale and intent of their study.
4. Dung beetle response to anthropogenic
threats
Multiple lines of evidence from temperate and tropical sys-
tems indicate that local and regional-scale changes in land-
use and mammal faunas can severely alter patterns of dung
beetle species diversity and abundance. The decline or local
extinction of dung beetles will likely have significant short
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and long-term implications for the maintenance of the eco-
system processes outlined above.
Globally, tropical forest loss, modification and fragmenta-
tion are driving high rates of local extinction across forest-re-
stricted dung beetle communities (Nichols et al., 2007),
effects that are likely exacerbated by concomitant declines in
food resources as mammal populations respond both to habi-
tat change and hunting (Nichols et al., unpublished data). Nat-
ural grasslands modified for livestock pasturing offer altered
vegetation density, soil temperature and moisture support –
leading to range expansion for some dung beetles species
and contraction for others (Davis et al., 2004). New evidence
demonstrates that re-forested habitats often perceived as
‘conservation friendly’ (e.g. secondary or plantation forests)
provide low conservation value for dung beetles (Gardner
et al. in press) – a finding that increases concern over continued
primary forest loss. Since 1953, even comparatively low annual
rates of deforestation (1.4–2.0%) in Madagascar have resulted
in the apparent extinction of 43% endemic forest-dwellingspe-
cies in the tribe Helictopleurini (Coprinae) (Hanski et al., 2007).
Compounding these concerns is evidence that conservation
area networks may be insufficient to conserve dung beetle bio-
diversity. Over 23% of Costa Rica’sland surface is under conser-
vation protection (UNEP-WCMC, 2003), yet this protected area
network encompasses less than 13% of Costa Rica’s areas of
highest dung beetle species richness and endemism (Kohl-
mann et al., 2007). Over 35 years of dung beetle records from
a single Costa Rican protected area (the La Selva Biological Sta-
tion) indicate community changes over time are most affected
by the loss, rather than the gain of species, a trendthe authors
associate with the isolating effect of regional agriculture inten-
sification (Escobar et al., unpublished data).
It is in Mediterranean however, where the strongest empir-
ical evidence of dung beetle decline can be found (Lobo et al.,
2001), often associated with the replacement of extensive live-
stock grazing by intensive agriculture and afforestation, or
ivermectin use in grazing animals. Across Italy, from the first
to the last quarter of the 20th century the relative capture fre-
quency of rolling species has declined over 31%, while the
number of 30 ·30 m grid cells occupied by a rolling species de-
clined by nearly 24% (Carpaneto et al., 2007). In the Iberian
Peninsula over the same time period, the probability of finding
a roller in the decreased by 21.48% and the number of UTM
cells with rollers present declined by 20.04% (Lobo et al., 2001).
5. Conclusion
In natural systems, dung beetles appear to play an important
role in maintaining ecosystem integrity, especially through
secondary seed dispersal and nutrient cycling. With the high
sensitivity of dung beetles to many kinds of human activities
and habitat disturbance, it is imperative to understand and
protect these processes. In agricultural systems, dung beetles
play an important role in increasing primary productivity and
suppressing parasites of livestock. Improved understanding
of the linkages between dung beetle ecological functions
and ecosystem services is critical to the future management
of these services.
We suggest four future lines of dung beetle ecological
function research. First, as outlined in the above sections,
several basic gaps remain in our understanding of dung beetle
ecological processes. A focus on in situ studies that use natu-
rally assembled communities and assess specific functions in
novel geographic regions (e.g. seed dispersal in the Australian
tropics) and interactions with novel taxa (e.g. endoparasite
control in Neotropical primates) would be particularly useful
in filling in these gaps.
Second, significant trade-offs likely exist both in space and
time for dung beetle-mediated ecological functions (Rodrı´-
guez et al., 2006), with other species playing more dominant
functional roles under specific geographic areas and seasonal
conditions. Termites for example perform the majority of
waste removal in arid (Anderson et al., 1984; Herrick and
Lal, 1996; Nakamura, 1975), and seasonally arid areas (Janzen,
1983b), while earthworms play a key role in temperate regions
(Holter, 1977, 1979). Dung beetles have also been implicated in
increasing seed mortality and dispersing pathogens – ecolog-
ical functions that inherently cannot provide ecosystem ser-
vices since they are not beneficial to humans.
Third, greater emphasis on the mechanisms of function
responses to environmental change will help us to predict
the ecological implications of dung beetle biodiversity loss
(Larsen et al., 2005; Nichols et al., 2007). Understanding how
the functional consequences of species loss are buffered by
compensatory mechanisms operating at the community level
or exacerbated by non-random extinction orders will be key.
Trait-based approaches are a tangible way to determine the
ecological correlates of success (compensation) and extinc-
tion-proneness (extinction order) and directly relate those
factors to ecological function (e.g. Larsen et al., 2005; Slade
et al., 2007).
Finally, the economic value of dung beetle communities is
an important and exciting area for future study (Mertz et al.,
2007). Dung beetles and their functions are not evenly distrib-
uted across space or time, which will present challenges to
understanding the dynamics of service production, even in
those habitats where ecosystem service values can be clearly
delimited (e.g. cattle pastures) (Anduaga and Huerta, 2007).
Studies that articulate the supply and demand for dung beetle
services in a given socio-ecological context such as ecological
restoration projects and managed forests will be especially
useful (Boyd and Banzhaf, 2007).
The declining global trends in habitat and food availability
for Scarabaeine dung beetles are of great conservation con-
cern (Carpaneto et al., 2007; Nichols et al., 2007). An improved
understanding of the ecological importance of dung beetles is
one contribution to understanding the consequences of diver-
sity loss in natural and human dominated ecosystems.
Acknowledgments
We thank Andre
´s Go
´mez, Fernando Vaz-de-Mello and several
anonymous reviewers whose contributions significantly im-
proved this review. This review was fostered by the Scarabaei-
nae Research Network (Scarabnet.org), of which the authors
are members. ScarabNet and this material are based upon
work supported by the National Science Foundation under
Grant No. DEB-0043443 to S. Spector (PI), at the Center for
Biodiversity and Conservation at the American Museum of
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ARTICLE IN PRESS
Natural History. Any opinions, findings and conclusions or
recommendations expressed in this material are those of
the authors and do not necessarily reflect the views of the Na-
tional Science Foundation.
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