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JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. British Ecological Society is collaborating with JSTOR to digitize, preserve and extend access to Journal of Animal Ecology. INTRODUCTIONThis paper reports part of an investigation into the biology of the water vole, Arvicola terrestrist (Rodentia: Microtinae) in east Aberdeenshire, Scotland, carried out between October 1965 and June 1968.Water voles are microtine rodents weighing, when adult, up to 300 g. Mostly they are secretive animals moving silently, usually through thick vegetation. The preferred habitat appears to be stream banks, although examples are known of water voles living several miles from water (Gilbert White letter X to Pennant). They are strictly herbivorous, and while the main diet consists of grasses and other wild monocotyledons, herbs are sometimes eaten (Holi'sova' 1965). Perry (1943) noted that the breeding season in Britain lasts from the end of March to the latter half of September, but he found fecund animals in February. Females have a polyoestrous cycle, and the average number of embryos in utero is 5-7. There is a post-partum oestrus, and animals failing to become pregnant during it enter a lactation anoestrus. By the end of September the females have passed from a lactation anoestrus to a winter anoestrus without further ovulation. Perry found that animals born early in the season breed later that season, but that observation was not conclusively borne out by the present study. Young from early litters survive better than those from late litters, and juveniles of the year can be distinguished with certainty from adults by their weight, and by the matt quality of their pelage. First-winter and secondwinter voles can be distinguished by weight, but not with absolute certainty. Little is known about the social structure of populations, but a spatial organization is apparent, and is perhaps based on the social ranking of the members of the population. The spatial organization of the group, once established, remains constant for many months (Stoddart 1968), and there appears to be no periodic change of habitat, as occurs in the truly continential part of its distribution range (Varshavskii 1937; Zverev 1928; Myllymaiki 1959). STUDY AREAThe study area chosen for this investigation was the Sands of Forvie National Nature Reserve in east Aberdeenshire (G.R. 0227)-a little-used grouse moor of 705 ha situated on the east coast of Scotland about 20 km north of Aberdeen (Fig. 1). A small 'y'-shaped stream system on the east of the Reserve had long been known to support a population of water voles, and was chosen for study because of its relative isolation from human interference, its isolation from other areas inhabited by water voles, and its freedom from t ...

The European colonists of Tasmania named the thylacine Thylacinus cynocephalus a`marsupial wolf ' or the`Tasmanian tiger' or`hyena', in reference to its resemblance to large canids and the bold stripes on its rump. The largest marsupial carnivore in historic times, it was persecuted for alleged sheep killing and became extinct before its ecology was documented. We have reconstructed the likely prey size and the hunting and killing methods of the thylacine by comparing canine tooth strength and limb bone length ratios with those of extant marsupial and placental carnivores. The thylacine was probably a pounce± pursuit predator of fairly open habitats, which killed medium-sized prey (1±5 kg) that were small relative to its body size (15±30 kg), with a crushing, penetrating bite. The trophic niche of the thylacine was similar to that of smaller canids such as the coyote Canis latrans (rather than the wolf C. lupus), but ecomorphological convergence of the thylacine with canids was super®cial. Phylogenetic constraint has resulted in unique patterns of tooth eruption, molar tooth and jaw geometry, calcaneum architecture, and perhaps FMT/running speed relationships in the Dasyuroidea.

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