Publications by authors named "Ian A Hulbert"

2 Publications

  • Page 1 of 1

The flexibility of an intermediate feeder: dietary selection by mountain hares measured using faecal n-alkanes.

Oecologia 2001 Oct 1;129(2):197-205. Epub 2001 Oct 1.

The Macaulay Land Use Research Institute, AB15 8QH, Craigiebuckler, Aberdeen, Scotland.

Herbivores with an intermediate feeding strategy either vary their diet between a grazing (bulk roughage feeders) or browsing (concentrate selectors) strategy on a seasonal basis or select a mixed diet at any one time. The underlying ecological causes of the seasonal dietary shift in a small non-ruminant intermediate feeder - the mountain or arctic hare (Lepus timidus L.) were determined. Diet composition and selection relative to availability were investigated for 41 individual free-ranging mountain hares (of which 18 female hares were radio-collared) occupying an upland mosaic landscape in north-east Scotland. Diet composition was determined using faecal n-alkane analysis. Radio-collared hares were designated as pasture, woodland or moorland hares according to the habitat that predominated their home-range. In common with previous studies, mountain hares switched from a browse-dominated diet during winter to a Gramineae-dominated diet in summer, although it was only significant for reproductively active females during the peak breeding season. Diet composition remained consistent regardless of habitat occupied. However, the diet of radio-tracked hares differed significantly from the biomass available in the individual home-ranges; Gramineae were preferentially selected over browse species throughout the year. During winter and in particular during the early breeding season, intermediate feeders, such as mountain hares, ate browse material when the availability of higher quality was restricted. The ability to browse or graze represents a flexible foraging strategy permitting survival and production through periods of changing or unpredictable forage quality and availability.
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http://dx.doi.org/10.1007/s004420100725DOI Listing
October 2001

Food competition between a large ruminant and a small hindgut fermentor: the case of the roe deer and mountain hare.

Oecologia 2001 Aug 1;128(4):499-508. Epub 2001 Aug 1.

Norwegian Institute for Nature Research, Tungasletta 2, 7005, Trondheim, Norway.

In this study, we demonstrate that the mountain hare and roe deer compete with each other. This was determined using "natural experiments" of populations found in sympatry and allopatry on the islands along the west coast of Norway. We demonstrate that both species occupy the same habitats, share the same food resources and that food availability is limited. Two browsing species as different in size as roe deer and mountain hare might be expected to partition the available vegetation (e.g. woody scrub) in terms of height above ground level. However, from the evidence collected, the feeding-height-separation hypothesis must be rejected as an explanation for ecological separation between roe deer and mountain hares because there was extensive height overlap in resource utilisation by both species and neither species changed its feeding height in response to the presence of the other. Total browse utilisation did not increase when both species were together; rather, species-specific browse utilisation declined when the other species was present. However, the foraging behaviour of each herbivore varied significantly between the allopatric and sympatric sites. When both herbivores were present, the clip diameter of shoots browsed by mountain hares declined to match those selected by roe deer, while roe deer switched from a browse-dominated diet to a diet dominated by winter-green gramineae. The change to smaller-diameter shoots likely resulted in the hare increasing its intake of digestion-inhibiting or toxic secondary metabolites, while the alternative choice of digging through the snow like roe deer to reach the winter-green gramineae is a practice considered energetically too costly for hares. On this basis, we conclude that the enforced switch to a nutritionally inferior diet by mountain hares at the sympatric sites may result in changes to growth rate and body size which consequently impact on mortality and may explain the competitive superiority of the roe deer.
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http://dx.doi.org/10.1007/s004420100683DOI Listing
August 2001