The first sign of an approaching grove-back is not just from ground-shaking tremors, but also from the appearance of more than one arrowtongue (as well as other predator species on occasion). In the distance is a faint scraping. It is a low sound, but growing against the background of slow, ground-trembling thuds.
This gigantic creature is wedge-shaped, bio-lights always aglow at night, supported on two thick, pillar-like legs. It is estimated to be at least 60 meters tall.
At times, following arrowtongues can be caught under the larger animal's skid that makes up the rear of its body. The predator will be crushed like a grape and passes over without the slightest notice from the looming giant.The enormous skid carries the rear two-thirds of its body. It is this plow-like growth that one can hear scraping from a distance. But the most remarkable aspect of this already remarkable beast is the forest of dying young plaque-bark trees growing out of its dorsal carapace. At first this was speculated that this might be some kind of protective adaptation that enables it to hide; this seems unlikely, though, given the creature's bulk. It was later learned that once the keeled grove-back reaches this size and age it has no true enemies and does not fear predation.
As a grove-back moves along, one can very clearly hear the suction of its breath as it inhales the luminous clouds of minute, airborne animals that make up its diet.
The reason for arrowtongues accompanying the grove-backs is quite simple. A predictable side effect of the travels of so large a creature as the grove-back is the flushing of enormous quantities of game. The arrowtongues opportunistically follow the huge beast, preying upon this game (even at great risk to themselves).The grove-back, for its part, placidly continues on its journey, raising and lowering its broad ax-shaped head, unaware of the dramas being played out at its feet. The creature's breath whistles out of generous gills aft of its nose. The trees on its back crack and rustle with each ponderous, lurching footfall, while the enormous skid turns the ground with a clatter of upturned boulders. The noise of the animal's passage is substantial.
A nesting grove-back will be submerged in a pit and grown over with underbrush and small trees. It looks like nothing more than a small, tree-covered hill. Based on the growth of the trees, it is estimated that the animal has been buried and immobile for at least 10 years. It turns out that the animal is hibernating. During the course of its prolonged stasis, smaller creatures (like bush jumpstars and cobalt jetdarters), as well as plants, accumulate on the behemoth's porous dorsal shell. Each day the faint life signs grow stronger. Eventually there is a 15-meter-long tunnel excavated beneath the animal. Its long ovipositor slowly squeezes eggs into a small chamber at the tunnel's end.
Five days after laying its eggs, the keeled grove-back rises shakily amidst a great cloud of debris and soil. Its stiffened legs, trembling under the immense, forgotten weight, tentatively take their first steps in more than 10 years. The tangled forest on the creature's back shakes like reeds in the wind as it moves forward.As first observed by one of the Expedition's human geologists, Dr. Brangwyn, each small young grove-back that hatches and emerges from the sandy soil, covered by sticky amniotal fluids and pinging feebly. An hour after hatching, the young, which have three functional limbs, dart off in all directions. They are fully independent and seem to delight in their speed, an ironic counterpoint to their slow-paced parent. Only later will their hind limb atrophy to be replaced by the familiar skid, as with the other keeled inhabitants of Darwin IV.
Odd twin fecal trails strewn about come from peripatetic grove-backs. These sturdy, ropey excrescences lie on the ground, on either side of a deep trench, like double weals, often a meter high and many meters long; and before becoming aware of their true origin, some Expedition members had suspected them of being an artifact, possibly of intelligent creatures. They frequently spiral into tight coils or perfect ovoids.