Comparisons of digestive function between the European hare (Lepus europaeus) and the European rabbit (Oryctolagus cuniculus): Mastication, gut passage, and digestibility

Abstract

The European hare Lepus europaeus and the European rabbit Oryctolagus cuniculus are sympatric in many areas of the world. They are medium-sized herbage-feeding lagomorphs and trophic competitors. Both species feed on twigs under extreme and perhaps limiting conditions. To ascertain whether fine niche separation mechanisms occur, several comparative tests of digestive function were undertaken on samples of animals drawn from sympatric populations. The weights of the organs constituting the abdominal alimentary canal, the rates of passage and the extent of trituration of dietary markers intended to mimic twigs, and the digestibility of fibre, protein, and fat were compared. Both the stomach and the caecum of the hare were significantly smaller as a proportion of body weight, and this would result in a higher power-weight ratio. Both species rapidly passed the digestive marker, but passage was significantly faster in the hare. The rabbit chewed twig-like material with a scissor cutting and crushing action, whereas the action of the hare included a stripping action that would more efficiently access soluble carbohydrates stored in vascular rays. Both species were poor digesters of fibre, but digestibility of hemicelluloses was significantly greater in the rabbit. The faeces of both species of lagomorphs contain nutrients that can be attractive to more efficient fermenters of plant fibre, and consumption of those faeces may confound lagomorph population surveys that rely on dung counts.

Diet overlap between small ruminants and the European hare in a Mediterranean shrubland

“…The observed differences in the diet diversity indices among herbivores can be attributed to the dominance of shrubs and grasses in the diets of goats and hares respectively. The smaller number of plant species consumed by hares in relation to livestock provides further support for the hypothesis that the hare is a more specialist feeder due to its smaller mouth and overall body size [29]. Based on visual observations in the study area, it appeared that the smaller bite capacity of hares contained only one species of plant, whereas the larger bite capacity of livestock could contain a number of different plant species.…”

“…Diet overlap of all the identified plant species was estimated using the Horn overlap index R o [32]. Horn's index is considered the least biased when measuring niche overlap between herbivores using microhistological analysis of faeces to estimate diet composition [29]. Overlap coefficients higher than 0.6 are considered to represent biologically significant overlap [36,37].…”

“…Under stressful conditions, hares consume increased quantities of browse and plant biomass of very low nutritional value, such as bark, pine needles, etc. [27][28][29]. As all three of these herbivores are capable of adjusting their food intake according to availability [24,28], comparisons of their diets should be based on studies that have been conducted at the same time and site.…”

Comparative in vitro study of caecal microbial activity in brown hares and domestic rabbits which were offered the same diet

“…differ in their feeding strategy and digestive physiology. The ability to digest nitrogenous compounds is greater in rabbits than in hares (Kuijper et al 2004), and similarly, the digestibility of hemicelluloses is higher in rabbits than in hares, although both species are poor digesters of fibre (Stott 2008). In cases where only low-quality forage is available, hares maximise food processing by increasing their intake rate and decreasing the digesta retention time, while rabbits maximise digestion by increasing the mean digesta retention time (Kuijper et al 2004).…”

“…In cases where only low-quality forage is available, hares maximise food processing by increasing their intake rate and decreasing the digesta retention time, while rabbits maximise digestion by increasing the mean digesta retention time (Kuijper et al 2004). The gut passage rate has been found to be significantly faster in hares than in rabbits (Stott 2008). Another adaptive approach in leporids to cope with low-quality forage is caecotrophy, the ingestion of special soft faeces originated from caecal content.…”