Landscape as a Shared Space for Badgers and Cattle: Insights Into Indirect Contact and Bovine Tuberculosis Transmission Risk

Abstract

Though the magnitude of effect is uncertain, badger-cattle indirect contact has been implicated in bovine tuberculosis (bTB) transmission risk to cattle despite a paucity of data on badger space use. This study tracked field use by 35 GPS-collared bTB test-negative badgers (n = 3738 locational fixes, average fixes/badger = 107) and cattle grazing regimes at 446 fields over one grazing season (May-November 2016) on 18 farms (n = 56,202 field-days). Individual badger visits spanned on average 3 farms (max. 9 farms). Badgers entered fields when occupied by grazing cattle on 20% of field-days (nights). Most individual badgers (n = 25; 71%) were recorded in the same field as cattle on multiple occasions (up to 124 field-days each). There was substantial interindividual variation, with 29% of badgers (n = 10) never co-occurring with cattle. Badger field use was positively associated with dairy (rather than beef) production (especially when grazing cattle were present) and with fodder and rough grazing fields (compared with improved pasture and 'other' cattle-related land use). Badgers were recorded in larger fields (range 0.06 to 10.9 ha) more frequently, especially when not actively grazed. They were significantly less likely to use fields with calves compared to fields containing cattle of other age groups. The presence of a badger sett in a field increased the likelihood of field use by tracked badgers. Farm management that minimises cattle-badger indirect contact in fields with setts may reduce bTB transmission risk to cattle. Delaying grazing of fodder fields after (silage) harvest until sward length has increased, restricting grazing to improved pastures, keeping calves with cows longer, or ensuring all batches of cattle have at least some calves present and not grazing fields with badger setts (or fencing around setts to prevent cattle access) may provide simple, cost-effective strategies to reduce indirect badger-cattle contact, thus potentially lowering bTB transmission risk.

Keywords: European badgers; Meles meles; cattle; grazing; indirect contact.

FIGURE 1

Temporal pattern in badger field‐days (bar chart) throughout the grazing season (May–November) showing variation in data density over the study period. With the number of badgers contributing to each day's records (line graph).

FIGURE 2

(A) Badger GPS locations (dots) with each colour representing an individual badger (n = 35) and the study fields within 18 study farms (coloured yellow) within the wider landscape for context. (B) Badger locations (red dots) within fields with cattle present and (C) fields without cattle present. NB: As the unit of variance for analysis was the field‐day (n = 56,202), cattle can be present in a field on some days and not on other days, similarly to badgers.

FIGURE 3

Relationship between field size (hectares) and badger presence where cattle are present (blue) or absent (red) with the solid lines showing the point estimates and the shaded areas indicating the 95% confidence intervals.