Opposing effects of agricultural intensification on two ecologically similar species

•Hares were negatively associated with grazing intensity and floristic diversity.•Rabbits were positively associated with grass height and plant nutrition.•Intensification of pastures has benefited rabbits and been detrimental for hares.

Brown hares and rabbits are widely distributed in agricultural landscapes across the UK, occupy similar habitats and have considerable dietary overlap. However, as agriculture in the UK has intensified, hares have declined and become a species of conservation concern while rabbits have become an increasing pest. An intensive study of hares, rabbits and the dynamics of pastures over two grazing seasons was undertaken, in order to understand the environmental factors associated with hare and rabbit abundance at field level. Linear mixed models were used to assess the environmental variables, in terms of the structure, nutritional components and effects of livestock grazing that are associated with the abundance of the two species. The models revealed that hares were negatively associated with grazing intensity and plant diversity, whereas rabbits showed the strongest associations with nutritional content of pastures, in particular fat, nitrogen and fibre content in forage, as well as a positive association with short grass swards. The data suggest that, at the field-scale intensification of pasture use may have contributed to declines in hares and increases in rabbits.