Thick-tailed Three-toed Jerboa | Stylodipus telum

Tracks

The trail is clearly visible in drift sand. It consists of a series of paired hind-foot prints with no forefoot prints between them, the typical jerboa trail. Each print is a three-toed impression about two centimetres long, with the claw tips in front and the sweep of the hair brush behind. Leap length is diagnostic: much shorter than in the Great Jerboa, usually a few decimetres at an easy pace and up to about a metre in flight, whereas Allactaga in the same sand already covers eighty to a hundred and twenty-five centimetres at an easy pace. Two trails side by side in the same dune can therefore be assigned to species without seeing the animal. The second sign is the burrow system: a tunnel network up to two and a half metres long, with many entrances, each loosely closed with a plug of sand. Such a row of plugs in a dune slope, darker and looser than the surrounding sand, is the most reliable sign of occupation and much easier to find than the animal. Droppings are small, dry and elongated. Unlike many steppe rodents, the species lays up no winter store; seed chambers are absent.

Identification

A compact jerboa, about half the length of the Great Jerboa: head-body ten to thirteen centimetres and seventy to ninety grams. The upperparts are sandy brown to ochre-grey with fine dark speckling, the belly and legs pure white. The tail is characteristic: about as long as the body but distinctly thick and fleshy, ending in a poorly developed, low-contrast tuft, far less sharply black-and-white than in the Great Jerboa. The hind foot has three toes, with brushes of stiff hairs beneath. The ears are short and rounded, much shorter than the head, which separates the species at once from Allactaga. At rest the animal sits upright on hind feet and tail, with the forefeet against the chest.

Similar species

In the western part of its range the species occurs in the same sand areas as the Great Jerboa; the two can be separated even in a headlight beam. The Great Jerboa is twice as long, has erect ears nearly six centimetres long, a thin tail with a sharp black-and-white tuft and five toes. Stylodipus is smaller, has shorter ears, a thicker tail and three toes, and is tied to loose sand, whereas Allactaga prefers firmer loam and clay steppe. Further east live the very similar Stylodipus andrewsi and Stylodipus sungorus, which can be separated only on measurements, skull and range; they do not occur in the western part of the range. A gerbil in the same sands runs on four feet and has no tail tuft. In the trail the distinction from Allactaga is simple: the same bipedal series, but with much shorter leaps.

Habitat

The species is tied to loose sand: inland sand plains and shifting dunes, psammophytic steppe, wormwood and salt steppe on sandy or light clay soils, and the open patches between bushes of wormwood and saltbush. It needs open, sparsely vegetated sand in which it can dig and leap; as soon as grass or pine plantation fixes the sand, the species disappears. This type of landscape was planted on a large scale in the twentieth century to prevent sand drift.

Distribution

From southern Ukraine eastwards through southern Russia and Kazakhstan to Turkmenistan, Uzbekistan and north-western China. The western part of the range comprises the sand areas of southern Ukraine, above all the Lower Dnieper or Oleshky Sands at the mouth of the Dnieper, and the adjoining steppes of southern Russia around the Sea of Azov and the Don. The Ukrainian animals belong to the subspecies falzfeini, described in 1913 and named after Falz-Fein of Askania-Nova; this is an endemic form with a very small range that almost coincides with the Lower Dnieper Sands and the Black Sea Biosphere Reserve. GBIF holds about seventy records from this western part of the range.

• Native
• dark = core range, pale = thinly spread

Way of life

Nocturnal and solitary: the animals come above ground after sunset, forage by leaping and disappear before it gets light. Food consists of green plant parts, bulbs, roots and seeds; no store is laid up. Each animal digs its own burrow system of up to two and a half metres, with several entrances closed by day with a plug of sand, which protects against heat and predators. As in other jerboas, the winter is spent in hibernation, in the deepest chamber of the system. Females usually have two litters a year of two to four young, one in spring and one in autumn. Predators are corsac fox, steppe polecat, eagle owl and Pallid Harrier; the main cause of decline in today's landscape, however, is the loss of open sand.

Where and when to look

The Oleshky Sands and the Black Sea Biosphere Reserve lie in a war zone, are partly mined and are not accessible. In the western part of its range the species therefore cannot be visited at present. In accessible terrain the method is the same as for other jerboas: on a warm, windless summer night drive at walking pace with headlights along a sand track and watch for eyeshine and sideways leaps, and at first light search a bare dune slope for a row of closed burrow entrances and for the trail with short leaps.

Conservation status

Globally Least Concern (2017), because the Asian range is large; the assessment says little about the situation in the west of the range. The subspecies falzfeini of the Lower Dnieper Sands has one of the smallest ranges of any European mammal. It declined throughout the twentieth century as the drift sands were planted with pine on a large scale to prevent sand drift; fixed sand is unsuitable for this species. Fires in the pine plantations and the war followed. On 6 June 2023 the Kakhovka dam was blown up; the released water flooded the habitat of this subspecies, and Ukrainian ecologists pointed out immediately that this could mean the end of the population. How many animals remain is unknown, because the area is inaccessible. If the subspecies disappears, a form that occurs nowhere else disappears with it.

Scientific name

Stylodipus telum | (H. Lichtenstein, 1823)

H. Lichtenstein described the species in 1823 as Dipus, Telum; because it was later moved to another genus, the author and year stand in brackets. Stylodipus joins Greek stylos, 'pillar, style', to dipous, 'two-footed', the word behind the jerboa name Dipus; Allen gave no explanation, so what the first element is meant to say remains unclear. telum is the Latin word for 'spear, javelin', placed as a noun in apposition to the genus name; Lichtenstein gives no explanation. The specimen the first description was based on came from Kazakhstan, Kyzylorda.