title: Isotopic evidence for dietary niche overlap between barking deer and four-horned antelope in Nepal.
abstract: BACKGROUND
  Morphologically similar sympatric species may have a high degree of niche overlap. Barking deer Muntiacus vaginalis and four-horned antelope Tetracerus quadricornis are solitary ungulates of the Indian sub-continent. Limited information is available regarding their trophic ecology, particularly of the endemic four-horned antelope. We present stable carbon (δ(13)C), nitrogen (δ(15)N), and sulphur (δ(34)S) isotopic values, and nitrogen content (%N) of faeces from barking deer and four-horned antelope living in lowland Nepal to assess trophic niche differentiation of these herbivores along the browser-grazer continuum. We also describe trophic differences between those two species in ecological niches and seasonal effects on their diets.
  
  
  RESULTS
  We found that the barking deer and four-horned antelope consumed C3 plant sources exclusively. The niche partitioning in their diet was reflected by δ(34)S values. Some seasonal effects observed were: δ(13)C and δ(15)N were significantly lower in the dry season diet of four-horned antelope than that of barking deer, while δ(34)S values were significantly higher in the winter diet; monsoon diet was similar for both species. Faecal N levels for barking deer and four-horned antelope were similar throughout all the seasons, indicating that both species adapted their feeding behaviour so as to maximize protein intake, in accordance with season and environment.
  
  
  CONCLUSIONS
  Barking deer and four-horned antelope both are browsers; their dietary sources overlapped during monsoon but differed during the dry season. Conservation actions focused on resource management during the dry season to reduce food scarcity and competition over limited resources is likely to be the most effective.
authors.affiliation: Wildlife Ecology and Management, Faculty of Environment and Natural Resources, University of Freiburg, Freiburg, Germany.
authors.forename: Krishna Prasad
authors.initials: KP
authors.lastname: Pokharel
authors.affiliation: Limnological Institute, University of Konstanz, Konstanz, Germany.
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Yohannes
authors.affiliation: Limnological Institute, University of Konstanz, Konstanz, Germany.
authors.forename: Ioanna
authors.initials: I
authors.lastname: Salvarina
authors.affiliation: Wildlife Ecology and Management, Faculty of Environment and Natural Resources, University of Freiburg, Freiburg, Germany.
authors.forename: Ilse
authors.initials: I
authors.lastname: Storch
keywords: Herbivores; Niche; Resource management; Resource partitioning; Seasonal diet; Stable isotopes