New arrivals: European Souslik

New Arrivals: European Souslik

European souslik, S.citellus

Some recent visitors to the zoo will have noticed that the old prairie dog enclosure now appears to be empty. More careful (and watchful) visitors, especially at quieter times, will see that we have added a new species to the collection, a group of young European souslik, Spermophilus citellus. These in many ways resemble in their behaviour the American prairie dogs, but are much smaller, about the size of a half grown guinea pig (cavy if you are an American reader). There are actually six pairs in the enclosure for now, but with luck by next year the numbers will have considerably increased.

The reason we replaced prairie dogs, which are familiar to visitors to zoos all over the world, is that sousliks are in a lot of trouble. Agricultural development, forestry, mining, and other large scale land use changes have destroyed many colonies and reduced many of the rest, while fragmenting populations into small areas of remaining habitat. For sousliks this is quite specific – they need short grass steppe with light soils suitable for excavating burrows. From these they emerge to feed on grass, seeds, flowers, arthropods and similar food resources available to a grassland rodent.

Long-Legged Buzzard, B.rufinus

Of course, animals the size of sousliks are also a major food source for predators as well. Birds of prey such as Long-Legged Buszzard Buteo rufinus especially rely heavily on them when feeding their young, as the young sousliks first emerge from the nesting burrows in late spring and early summer. Mammalian predators include Golden Jackal, Canis aureus, which is increasing its range in Europe at present. As one might expect, they are potentially quite a prolific species to keep up with this pressure, and up to 9 young have been recorded, although 4 or 5 are more usual.

European Jackal, C.aureus

There are in fact numerous species of ground squirrels, spread over both Eurasia and North America, and the group (the tribe Marmotini) which contains sousliks also includes prairie dogs, marmots, and chipmunks. All of these are mainly or entirely terrestrial, often vocal, and also have complex social structures in many cases, whereas arboreal squirrels tend to live in pairs or are entirely solitary. Recent DNA analysis of ground squirrels places the eleven or so species in Eurasia in the genus Spermophilus, while the American ground squirrels are placed in Urocitellus, Ictidomys, Ammospermophilus, and several other genera. With the much greater diversity in North America, it seems likely that ground squirrels originated there, later spreading across the Bering land bridge and diversifying in Asia, gradually spreading westwards to reach the Balkans, which is the main stronghold of S.citellus.

White-Tailed Antelope Squirrel, A. leucurus

The chief threat to survival of sousliks is agricultural development. Pasture that is left ungrazed produces grass too tall for sosuliks, which need to be able to see over short grass to detect predators, and intensive farming is also a threat. Colonies can survive in vineyards, as long as grass strips are left between the vines, but this is probably suboptimal habitat.

Thirteen-Lined Ground Squirrel, I. tridecemlineatus

To the best of my knowledge, Bristol is the first UK zoo to hold souslik. Hopefully, as our colony expands, we will be able to send starter colonies to other collections. During the winter months they hibernate, mating soon after leaving hibernation around March, so we are unlikely to see young this year. However, next year we should expect to see the expansion of our colony and hear the complex whistles they use, like their cousins the prairie dogs, to warn of approaching predators.

Woodchuck or Groundhog, M.monax

Next week, starlings at Bristol – a new series.

(images from wikipedia)