Biology: Under
natural conditions, the period of surface activity of G. monticola
and G. sterquilinus is from 9:30 am to 1:00 pm, and from 5:00
pm to 7:00 pm, depending on atmospheric and soil temperature. No nocturnal,
surface activity was recorded. During the observations atmospheric
temperature varied between 21–40 408C in the shade. Both species
prefer open sandy or clay soils with a 20–60% vegetation cover. Glyphoderus
sterquilinus and G. monticola monticola, as do most
of the Eucraniini, specialize on dehydrated dung pellets. Specimens
were observed carrying pellets of ‘‘vizcacha’’
(Lagostomus maximus (Desmarest)), ‘‘cuis chico’’
(Microcavia australis (Geoffroy Saint-Hilaire & D’
Orbigny)), and goat. Specimens of G. sterquilinus did not
take dry horse or cow dung even when it was offered, and they were
not attracted to dung traps baited with fresh human or cow dung. When
foraging, they run on four legs, keeping their forelegs motionless
and in a horizontal position with respect to the surface. Adults run
in zig-zags or do not follow any particular direction from their burrow
(apparently searching randomly). To carry food, the beetles grasp
it with the foretibiae and run forward using only their middle and
hind legs (Fig. 2), this behavior is known only for members of the
tribe Eucraniini. It is not clear how the beetles find their way back
to the burrow. As described by Byrne et al. (2003) and Dacke and Warrant
(2002) for the South African flightless dung beetles Scarabaeus
rugosus (Hausman), S. rusticus
(Boheman), Kheper nigroaeneus (Boheman) and Pachylomerus
femoralis (Kirby) (Scarabaeinae: Scarabaeini) Glyphoderus
species must rely on cues such as the pattern of polarized light. Beetles
may use polarized light as a compass bearing that can be used to ‘‘calculate’’
the direction to the burrow. When the entrance of the burrow is reached,
the beetles enter by walking forward rather than backward. Observations
published by Zunino et al. (1989) regarding the above behavioral
character, suggested that the beetles drop the dung pellet turn back,
and enter the nest walking backward dragging the pellet. I have not
observed this for any Eucraniini species. The burrow is always previously
dug. It is variable in depth (usually between 0.25–1 m long)
and variable in slope (between 35–60 608 with respect to ground
surface). The tunnel may be straight or curved. The depth of the
burrow is apparently dictated by the level of soil moisture. Burrows
are sometimes bifurcated near the end. The beetles store the food
at the end of the burrow and no special chamber seems to be prepared
for that purpose. Usually between 3–10 dung pellets are stored,
and each pellet is carried independently. Sexual cooperation has
been observed and it follows the same behavior as that observed
for individuals. No special brood chambers were observed in burrows
constructed by pairs. During the hours where there is no surface
activity, it is common to observe the entrance of the burrow obscured
with sand or the available substrate. The behavior of G.
centralis is similar and it was described by Zunino and collaborators
in 1989.