Utilization of shrubs for forage and shelter by Marsh Deer (Blastocerus dichotomus) in Jataí Ecological Station, Brazil : an analysis of stable carbon isotopes and of GPS tracking data

Abstract: The South American marsh deer (Blastocerus dichotomus) is a wetland living species which is in risk of extinction in the wild. Since not much is known about its requirements concerning habitat and forage, this study aims at their choice of forage and habitat, with focus on use of shrubs available for shelter and forage. The study was performed in Jataí Ecological Station, São Paulo state, Brazil. I examined if marsh deer, like many other deer species, chose bed-sites in close proximity to large shrubs, which can provide cover from weather and predators. GPS-data from two marsh deer equipped with GPS-collars was analyzed to find the bed-sites of the deer. The bed-site coordinates were plotted on a map divided into vegetation zones with different densities of shrubs. The density and duration of bed-sites in each different vegetation zone was calculated. The results showed that the marsh deer did prefer bed-sites close to shrubs but not when shrubs become too dense. An analysis of stable carbon isotopes in hair taken from 30 marsh deer from two different populations was also performed to show the proportion between browse and grass ingested. These results estimated that only 4 - 14 % of the marsh deer's diet consists of grasses. However, it is not possible to tell from this type of analysis if the browse ingested consists of forbs or shrubs and if the marsh deer also feed on aquatic plants. No differences were seen between populations and genders.