Spalacopus

Abstract: In the coastal region of central Chile the coruro, Spalacopus cyanus, lives in large populations consisting of many small, nomadic colonies. One colony contained 15 members belonging to no less than three generations. A colony of coruros occupies a common burrow system and apparently wanders continuously in search of food. Coruros feed primarily, if not exclusively, on the tubers and underground stems of the lily, Leucoryne ixiodes. S. cyanus has a higher metabolic rate than similar-sized fossorial species of Ctenomys. In February, adult males were sexually active and two of six adult females were pregnant, each bearing three small fetuses.

Abstract: The Pliocene caviomorph rodent Actenomys has long been recognized as an early fossorial representative of the subfamily Ctenomyinae (Octodontidae), which includes one living genus, Ctenomys (tuco-tucos), and several species widely distributed in South America. To assess the degree of specialization for digging in Actenomys , we performed morphological comparisons with other octodontid genera ( Octodon , Spalacopus , and Ctenomys ) of known mode of life and behaviour. As a whole, our results indicate that, in terms of morphological specializations for digging, Actenomys occupies an intermediate position between Octodon , a generalized semi-fossorial rodent which forages above ground, and Ctenomys-Spalacopus , two highly specialized subterranean forms. The position of the deltoid process (humerus) and the length of the olecranon process (ulna)—two traits which affect the out-forces exerted by several forelimb muscles—were in Actenomys intermediate between non-subterranean and subterranean taxa. The skull, particularly the rostrum, appears to be strong, and sagittal and nuchal crests are well marked. The zygomatic arches are as flared as those of the generalized Octodon . Notably, the upper and lower incisors of Actenomys were extremely procumbent, as in many highly specialized chisel-tooth digging species. Based upon the stratigraphic and sedimentological analysis of the palaeosoils containing its fossil remains, we suggest that Actenomys lived in an environment of moderate to hig primary productivity. The texture of the palaeosoils indicate that theywere hard and highly cohesive. This situation, which contrasts with that observed in living Ctenomyinae, has relevant implications for burrowing cost. The integration of morphological and palaeoenvironmental data allowed testing of hypotheses about the palaeobiological attributes of this ancestral ctenomyine.

Abstract: Burrow systems of two coastal populations (El Alamo and Los Maitenes) of the social octodontid rodent Spalacopus cyanus were studied in central Chile. Tunnel systems were estimated to be up to 600 m long, ran at a depth of 15 cm and had a diameter of 6 cm. Tunnel openings were usually unplugged, and a minor preference toward southern and south-eastern direction of entrances was apparent. Nests, frequently found in the root system of Berberis actinacantha at a depth of 30 cm, consisted of grasses, roots and plastic bags. Nests serve for sleep, care of the pups and as latrines. Many staphylinid beetles of the genus Edrabius and other invertebrates were found in the breeding nests. Food chambers contained up to 13.2 kg of bulbs of the geophyte Dioscorea longipes collected by a single colony consisting of 26 animals (including 10 adults) and were frequently found at El Alamo. However, no bulbs were found at Los Maitenes, where the coruros forage above ground on leaves of Convolvulus arvensis within a radius of about 10 cm of the entrances. Apparently, the burrow design is also affected by food availability, soil quality, and colony size.

Abstract: The impact of the subterranean herbivorous rodent Spalacopus cyanus Molina on the herbaceous vegetation was studied by comparing biomass, species richness and species diversity at the end of the growing season in areas with and without burrows in coastal arid Chile. Total biomass was 60% higher in areas with burrows. This difference was mainly due to the large increase of Mesembryanthemum cristallinum L., a succulent prostrate annual herb. Unexpectedly, bulb biomass of geophytes, eaten by Spalacopus, did not differ between areas. However, in areas with burrows bulbs of geophytes were more numerous and smaller. It is possible that burrowing activities facilitate the occurrence of new small bulbs through seed germination. Species composition and diversity did not differ greatly between areas. Burrowing activities by Spalacopus, the life cycle of Mesembryanthemum, and climate seem to be the most important factors determining species abundance and diversity of herbs in this system.