Camel spiders (Arachnida, Solifugae) are
widely distributed in desert regions of western
North America. These arachnids are voracious
predators that consume arthropods, lizards,
and even small mammals (Muma 1966a, Punzo
1998). Camel spiders are also prey for birds
and other arthropods (Polis and McCormick
1986, York et al. 2002). Though camel spiders
are likely important in desert systems as both
predators and prey, data regarding camel spider
ecology are scant, and factors regulating their
abundance are not well understood.
Camel spiders appear to prefer areas with
specific vegetation and soil characteristics, but
no generalizations about their habitat have been
identified (Brookhart 1972, Punzo 1998). In the
Chihuahuan desert of western Texas and New
Mexico, camel spiders prefer arroyos with open
sandy soils and desert grasslands (Muma 1979,
Punzo 1998). Arroyos and desert grasslands
seem to be disparate habitat types, but grass-
lands in southern New Mexico are character-
ized by open patches of bare ground similar to
arroyo sites (Duval et al. 2005).
Black-tailed prairie dogs (Cynomys ludovi-
cianus) are ecosystem engineers, organisms that
modify biotic and abiotic components of their
environments (Jones et al. 1994, 1997). Black-
tailed prairie dogs change soil processes, pro-
vide habitat for other vertebrates, and increase
arthropod diversity (Whicker and Detling 1988,
Weltzin et al. 1997, Desmond et al. 2000,
Bangert and Slobodchikoff 2006). Most impor-
tantly for ground-dwelling predators like camel
spiders, black-tailed prairie dogs increase the
percent cover of bare ground on their colonies
by decreasing vegetation height and cover and
by altering plant community structure (Agnew
et al. 1986). Considerable interest has been
given to the role of prairie dogs in grasslands,
because they have been drastically reduced
due to human activity such as shooting, poi-
soning, and introduction of plague (Stapp 1998,
Vermeire et al. 2004). Information about camel
spider presence or absence from prairie dog
colonies adds to what we know about how
prairie dogs influence arthropods at large,
especially if colonies represent favorable habi-
tat for camel spiders.
Because camel spiders occupy a middle
trophic niche in areas they inhabit, they can
influence top-down (predatory) and bottom-
up (prey) processes in desert systems. If camel
spider abundance is higher on black-tailed
prairie dog colonies compared to undisturbed
grassland, prairie dogs could indirectly alter
arthropod communities by enhancing preda-
tion pressure on the arthropods (from camel
spiders) and increasing prey availability for
organisms like burrowing owls that feed on
camel spiders. Determining the relationship
between camel spiders and black-tailed prairie
Western North American Naturalist 69(2), © 2009, pp. 272–276
CAMEL SPIDER (SOLIFUGAE) USE OF PRAIRIE DOG COLONIES
B.D. Duval1and W.G. Whitford2,3
ABSTRACT.—Solifugids (camel spiders) are widespread throughout arid regions of western North America and are
thought to be important in structuring desert arthropod communities. Despite the ubiquity of camel spiders, little is
known about their ecology. Black-tailed prairie dogs (Cynomys ludovicianus) are also widespread in western North
America and are important ecosystem engineers, but they have been reduced in extent because of human activity. Here
we report significantly greater numbers of camel spiders on black-tailed prairie dog colonies in southern New Mexico.
The difference in vegetation structure created by prairie dog activity is likely the reason for the increased prevalence of
camel spiders on colonies. Because camel spiders are important predators and prey, the observation that colonies sup-
port higher numbers of these animals provides a mechanism explaining differences in arthropod communities on and off
colonies and explaining the preferential foraging behavior of vertebrates associated with prairie dog colonies.
Key words: black-tailed prairie dogs, Chihuahuan desert, ecosystem engineering, Solifugae, grassland ecology.
1Department of Biological Sciences, Northern Arizona University, Flagstaff, AZ 86011. E-mail: firstname.lastname@example.org
2USDA–ARS Jornada Experimental Range, New Mexico State University, Box 30003, Campus Box 4901, Las Cruces, NM 88003.
3Department of Fishery and Wildlife Sciences, New Mexico State University, Las Cruces, NM 88003.
dogs will provide additional information about
the ecological role of prairie dog colonies in
grasslands and will disseminate basic ecolog-
ical information on camel spiders.
We collected camel spiders on and off of
prairie dog colonies at the Armendaris Ranch,
about 40 km northeast of Truth or Conse-
quences, New Mexico. The ranch encompasses
approximately 146,000 ha of intact Chihuahuan
desert grassland and hosts burrograss (Sclero-
pogon brevifolius), alkali sacaton (Sporobolus
airoides), and tobosa (Hilaria mutica) grasses,
interspersed with opuntia (Opuntia spp.),
honey mesquite (Prosopis glan dulosa), and
ephedra (Ephedra torreyana) shrubs (Dick-
Peddie 1993). Black-tailed prairie dogs were
reintroduced to the Armendaris Ranch in 1994.
Prairie dogs were introduced in low-lying,
sandy-loam-soil habitats characteristic of areas
in which they historically resided (Hoogland
We collected camel spiders on 5 black-tailed
prairie dog colonies and in 5 corresponding
adjacent grassland patches (n = 5 sites per
“treatment” of colony or grassland). We installed
5 pitfalls on each colony: 1 in the center and
1 placed 100 m from the edge of colony on
each of 4 randomly generated compass bear-
ings. This was deemed a sufficient number of
traps based on experimental studies of trapping
efficiency in the Chihuahuan desert (Whitford
1975). Collections were made during four 6-
week periods between summer 2003 and sum-
mer 2004 (Greenslade 1964, Topping and Sun -
derland 1992). Pitfall traps were emptied
weekly during each 6-week sampling period.
Results are reported only for the 12 dates that
camel spiders were detected in the traps. We
considered colonies as replicate plots and report
abundances as the mean number of camel spi-
ders collected per sampling date within each
sampling season for either the colony or grass-
We measured the vegetation structure of
colonies and adjacent grassland using 100-m
transects along the pitfall grid. We estimated
percent basal cover of vegetation and bare
ground by overlaying a 0.5-m2frame with 10
×10-cm squares every 10 m along the tran-
sects (Daubenmire 1968). We randomized
height measurements within each frame by
recording the height of the first 3 plants within
the center row of the frame grid. Height and
percent cover of bare or vegetated ground are
reported as mean height in centimeters or
mean percent cover. Statistical analyses were
performed with JMP v.5.1 and SAS.
The vegetation differences between prairie
dog colonies and grassland are well docu-
mented and extreme (Fig. 1). The mean vege-
tation height on black-tailed prairie dog colonies
was significantly shorter than on adjacent
grassland patches (4.70 cm [sx
–= 0.36] vs. 9.59
–= 0.74]; Kruskal-Wallis test: χ2=
35.19, df = 1, P < 0.001). The vegetation
cover was more than 3 times greater in grass-
land than on the colony (10.66% [sx
–= 0.87] vs.
–= 0.29]; χ2= 33.07, df = 1, P <
0.001). Colonies supported a higher percent-
age of bare ground than grassland plots as well
(96.7% vs. 89.3%; one-way ANOVA: F1, 8 =
5.32, P< 0.01). Vegetation height and cover
were positively correlated (Spearman’s rank
correlation: rs= 0.71, P < 0.001).
2009] NOTES 273
Fig. 1. Prairie dog colony at the Armendaris Ranch, New Mexico: A, prairie dog colony; A-inset, camel spider; and B,
adjacent (~100 m away) grassland undisturbed by prairie dog activity.
274 WESTERN NORTH AMERICAN NATURALIST [Volume 69
Many of the camel spiders we collected were
juveniles and difficult to identify. However, we
did encounter the following species: Eremo-
bates pallipes, Eremobates similis, Eremochelis
bilobatus, and possibly Hemerotrecha fruitana.
Species were identified at the Denver Museum
of Nature and Science, Denver, Colorado.
Camel spider abundance per trap-week was
significantly higher on black-tailed prairie dog
colonies (0.47, sx
–= 0.09) than in adjacent grass-
land (0.12, sx
–= 0.02), (Wilcoxon’s rank sum: ts
= 3047.0, P < 0.001). There was a significant
seasonal effect of the abundance of camel spi-
ders, with more specimens collected in summer
2003 and summer 2004 than in winter or spring
2004 (Welch’s ANOVA: F2, 67.9 = 13.15, P<
0.001). For the summer sampling periods, sig-
nificantly more camel spiders were collected
from colonies than from grassland plots (Welch’s
ANOVA: summer 2003, F1, 20.8 = 4.36, P<
0.05; summer 2004, F1, 34.1 = 10.91, P< 0.01).
We collected no camel spiders from the grass-
land plots during the winter or spring 2004 sam-
ple periods, and the only individuals collected
for those seasons were found on prairie dog
colonies (Fig. 2). While not significant, there
was a trend for camel spider abundance to cor-
relate negatively with increased vegetation
height (Spearman’s rank correlation: rs= 0.55, P
= 0.10) and higher basal cover (lower bare
ground cover; Spearman’s rank correlation: rs=
0.40, P = 0.26).
The difference in camel spider abundance
between black-tailed prairie dog colonies and
adjacent grassland is intriguing given the lack
of knowledge of prairie dog effects on arach-
nids and the paucity of natural history and
ecological information about camel spiders.
Active, ground-dwelling arthropod predators
such as camel spiders are likely sensitive to
differences in vegetation structure, and it is
therefore intuitive that they would be captured
in higher abundance on colonies relative to
grassland patches. The increased abundance
of camel spiders on colonies adds support to
the hypotheses that camel spiders in the Chi-
huahuan desert prefer open, sandy-soil habi-
tats (Muma 1979, Punzo 1998).
That we found differences in camel spider
abundance among seasons highlights 2 impor-
tant issues. Camel spiders were collected in
every season of the study (albeit few in the win-
ter), which suggests that they might be active
for most of the year in northern Chihuahuan
desert grassland. Also, camel spiders were col-
lected in greater abundance on colonies than at
Fig. 2. Abundance of camel spiders on black-tailed prairie dog colonies (black bars) and in adjacent grassland plots
(white bars) at the Armendaris Ranch, New Mexico, during summer 2003, winter and spring 2004, and summer 2004.
Abundance is presented as mean number of camel spiders collected per sampling date per colony with one standard
error. Significantly more camel spiders were collected on colonies for the summer 2003 and summer 2004 sample
Camel Spider Abundance (mean number per colony)
Summer 2003 Winter/Spring 2004 Summer 2004
adjacent sites for every sampling period. Camel
spiders are actively foraging predators, and
while their presence on colonies does not nec-
essarily imply that they live on colonies,
their presence suggests that they are using
colonies in some capacity.
In addition to reducing vegetation cover and
increasing bare soil cover, prairie dog burrow-
ing behavior creates a network of deep burrows
not found in adjacent grassland (Hoogland
1995). Camel spiders are generally nocturnal
and require respite from extreme desert tem-
peratures but are relatively poor at creating
their own burrows (Muma 1966b). It is there-
fore possible that the observation of more camel
spiders on prairie dog colonies is related to
their use of prairie dog burrows.
Punzo (1998) has stated that a proper treat-
ment of desert arthropod community structure
should consider the influence of camel spiders
within and on these communities. Although
such an analysis is beyond the scope of this
report, our results suggest that camel spiders
use prairie dog colonies in some capacity,
likely because of decreased vegetation height
and cover, increased areas of bare ground, and
a preponderance of burrows created by prairie
dogs. As voracious predators, camel spiders
may drastically influence an arthropod com-
munity associated with the vegetation-struc-
ture differences between colonies and grass-
land. Other studies have reported lower abun-
dances of grasshoppers and harvester ants on
prairie dog colonies (O’Meilia et al. 1982,
Kretzer and Cully 2001). More-recent research
has demon strated higher abundances of grass -
hoppers and general increases in arthropod
diversity on colonies (Russell and Detling
2003, Bangert and Slobodchikoff 2006). While
beyond the purview of this report, changes
in the abundance of predators like camel spi-
ders could be responsible for those patterns.
Our data add to the growing evidence that
prairie dog colonies support different num-
bers of important arthropod taxa compared to
Furthermore, because camel spiders are prey
items for invertebrates and colony associates
like Western Burrowing Owls, prevalence of
camel spiders increases at least one prey species
on prairie dog colonies (Polis and McCormick
1986, York et al. 2002, Duval unpublished data).
By directly modifying the environment, prairie
dogs indirectly influence arthropod communities
and provide foraging resources by creating
favorable habitat patches for camel spiders
within the larger grassland mosaic.
We thank W.E. Braswell, D. Richman, and 2
anonymous reviewers for thoughtful comments
on earlier drafts of the manuscript. Jon Hernan-
dez assisted with field collections. We sincerely
thank Jack Brookhart for identifying specimens.
Research funds were provided by grants to
W.G. Whitford from the International Arid
Lands Consortium and the United States
Environmental Protection Agency’s Office of
Research and Development. We also thank the
Jornada Experimental Range, Las Cruces, New
Mexico, for support of this research.
AGNEW, W., D.W. URESK, AND R.M. HANSEN. 1986. Flora
and fauna associated with prairie dog colonies and
adjacent ungrazed mixed-grass prairie in western
South Dakota. Journal of Range Management 39:
BANGERT, R.K., AND C.N. SLOBODCHIKOFF. 2006. Prairie
dog ecosystem engineering increases arthropod beta
and gamma diversity. Journal of Arid Environments
BROOKHART, J.O. 1972. Solpugids (Arachnida) in Colorado.
Southwestern Naturalist 17:31–41.
DAUBENMIRE, R.F. 1968. Plant communities: a textbook on
plant synecology. Harper and Row, New York.
DESMOND, M.J., J.A. SAVIDGE, AND K.M. ESKRIDGE. 2000.
Correlations between Burrowing Owls and black-
tailed prairie dog declines: a 7-year analysis. Journal
of Wildlife Management 64:1067–1075.
DICK-PEDDIE, W.A. 1993. New Mexico vegetation: past,
present and future. University of New Mexico Press,
DUVAL, B.D., E. JACKSON, AND W.G. WHITFORD. 2005.
Mesquite (Prosopis glandulosa) germination and sur-
vival in black-grama (Bouteloua eriopoda) grassland:
relations between microsite and heteromyid rodent
(Dipodomys spp.) impact. Journal of Arid Environ-
GREENSLADE, P.J.M. 1964. Pitfall trapping as a method for
studying populations of Carabidae (Coleoptera).
Journal of Animal Ecology 33:301–310.
HOOGLAND, J.A. 1995. The black-tailed prairie dog: social
life of a burrowing animal. University of Chicago
Press, Chicago, IL.
JONES, C.G., J.H. LAWTON, AND M. SHACHAK. 1994. Organ-
isms and ecosystem engineers. Oikos 69:373–386.
______. 1997. Positive and negative effects of organisms
as physical ecosystem engineers. Ecology 78:
KRETZER, J.E., AND J.F. CULLY. 2001. Prairie dog effects
on harvester ant species diversity and density. Jour-
nal of Range Management 54:11–14.
MUMA, M.H. 1966a. Feeding behavior of North American
Solpugida (Arachnida). Florida Entomologist 49:
2009] NOTES 275
276 WESTERN NORTH AMERICAN NATURALIST [Volume 69
______. 1966b. Burrowing habits of North American
Solpugida (Arachnida). Psyche 73:251–260.
______. 1979. Arid grassland solpugid population varia-
tions in southwestern New Mexico. Florida Ento-
O’MEILIA, M.E., F.L. KNOPF, AND J.C. LEWIS. 1982. Some
consequences of competition between prairie dogs
(Cynomys ludovicianus) and beef cattle for herbage
in Oklahoma pastures. Journal of Range Manage-
POLIS, G.A., AND S. MCCORMICK. 1986. Scorpions, spiders
and solpugids: predation and competition among
distantly related taxa. Oecologia 71:111–116.
PUNZO, F. 1998. The biology of camel spiders (Arachnida,
Solifugae). Kluwer Academic Publishers, Norwell,
MA. 312 pp.
RUSSELL, R.E., AND J.K. DETLING. 2003. Grasshoppers
(Orthoptera: Acrididae) and black-tailed prairie dogs
(Sciuridae: Cynomys ludovicianus (Ord)): associa-
tions between two rangeland herbivores. Journal of
the Kansas Entomological Society 76:578–587.
STAPP, P. 1998. A reevaluation of the role of prairie dogs in
Great Plains grasslands. Conservation Biology 12:
TOPPING, C.J., AND K.D. SUNDERLAND. 1992. Limitations
to the use of pitfall traps in ecological studies exem-
plified by a study of spiders in a field of winter
wheat. Journal of Applied Ecology 29:485–491.
VERMEIRE, L.T., R.K. HEITSCHMIDT, P.S. JOHNSON, AND B.F.
SOWELL. 2004. The prairie dog story: do we have it
right? BioScience 54:689–695.
WELTZIN, J.F., S.A. ARCHER, AND R.K. HETSCHMIDT. 1997.
Small mammal regulation of vegetation structure in
a temperate savanna. Ecology 78:751–763.
WHICKER, A.D., AND J.K. DETLING. 1988. Ecological con-
sequences of prairie dog disturbances. BioScience
WHITFORD, W.G. 1975. Jornada Validation Site Report.
US/IBP Desert Biome Research Memorandum 75-
4. Ecology Center, Utah State University, Logan.
YORK, M.W., D.K. ROSENBERG, AND K.K. STRUM. 2002.
Diet and food niche breadth of Burrowing Owls
(Athene cunicularia) in the Imperial Valley, Califor-
nia. Western North American Naturalist 62:280–287.
Received 3 October 2007
Accepted 24 September 2008