What do European badgers (Meles meles) know about the spatial organisation of neighbouring groups?

The Distribution of Bovine Tuberculosis in Cattle Farms Is Linked to Cattle Trade and Badger-Mediated Contact Networks in South-Western France, 2007-2015

Bovine tuberculosis (bTB), mainly caused by Mycobacterium bovis, can affect domestic and wild animals as well as humans. Identifying the major transmission mechanisms in an area is necessary for disease control and management. In this study, we aimed to evaluate the involvement of different types of contact in M. bovis transmission between cattle farms of south-western France between 2007 and 2015. We analyzed an empirical contact network of cattle farms as nodes, with known infection status and molecular types (16 circulated during the study period of which 14 affected only cattle and two both badgers and cattle). Edges were based on cattle trade data (T-edges) and on spatial neighborhood relationships between farms, either direct (P-edges) or badger-mediated, when two farms neighbored the same badger home range (B-edges), or two distinct but neighboring badger home ranges (D-edges). Edge types were aggregated so that the contact network contained only unique edges labeled by one or several edge types. The association between the contact network structure and bTB infection status was assessed using a non-parametric test, each molecular type being considered a marker of an independent epidemic. Using a logistic regression model, we estimated the contribution of each edge type to the probability for an edge originating from an infected farm to end at another infected farm. A total number of 1946 cattle farms were included in the study and were linked by 54,243 edges. Within this contact network, infected farms (whatever the molecular type) always belonged to the same component, suggesting the contact network may have supported bTB spread among those farms. A significant association between the pattern of bTB-infected farms and the structure of the contact network was observed when all the molecular types were simultaneously considered. The logistic regression model showed a significant association between M. bovis infection in direct neighbors of infected farms and the connection by T-, B- and D-edges, with odds-ratios of 7.4, 1.9, and 10.4, respectively. These results indicate a multifactorial M. bovis transmission between cattle farms of the studied area, with varying implication levels of the trade, pasture and badger networks according to the molecular type.

Demographic processes drive increases in wildlife disease following population reduction

Population reduction is often used as a control strategy when managing infectious diseases in wildlife populations in order to reduce host density below a critical threshold. However, population reduction can disrupt existing social and demographic structures leading to changes in observed host behaviour that may result in enhanced disease transmission. Such effects have been observed in several disease systems, notably badgers and bovine tuberculosis. Here we characterise the fundamental properties of disease systems for which such effects undermine the disease control benefits of population reduction.

By quantifying the size of response to population reduction in terms of enhanced transmission within a generic non-spatial model, the properties of disease systems in which such effects reduce or even reverse the disease control benefits of population reduction are identified. If population reduction is not sufficiently severe, then enhanced transmission can lead to the counter intuitive perturbation effect, whereby disease levels increase or persist where they would otherwise die out. Perturbation effects are largest for systems with low levels of disease, e.g. low levels of endemicity or emerging disease.

Analysis of a stochastic spatial meta-population model of demography and disease dynamics leads to qualitatively similar conclusions. Moreover, enhanced transmission itself is found to arise as an emergent property of density dependent dispersal in such systems. This spatial analysis also shows that, below some threshold, population reduction can rapidly increase the area affected by disease, potentially expanding risks to sympatric species.

Our results suggest that the impact of population reduction on social and demographic structures is likely to undermine disease control in many systems, and in severe cases leads to the perturbation effect. Social and demographic mechanisms that enhance transmission following population reduction should therefore be routinely considered when designing control programmes.

Homing of invasive Burmese pythons in South Florida: evidence for map and compass senses in snakes

Navigational ability is a critical component of an animal's spatial ecology and may influence the invasive potential of species. Burmese pythons (Python molurus bivittatus) are apex predators invasive to South Florida. We tracked the movements of 12 adult Burmese pythons in Everglades National Park, six of which were translocated 21-36 km from their capture locations. Translocated snakes oriented movement homeward relative to the capture location, and five of six snakes returned to within 5 km of the original capture location. Translocated snakes moved straighter and faster than control snakes and displayed movement path structure indicative of oriented movement. This study provides evidence that Burmese pythons have navigational map and compass senses and has implications for predictions of spatial spread and impacts as well as our understanding of reptile cognitive abilities.

Factors shaping population density, demography and spatial organization of the Eurasian badger Meles meles in mountains – the Western Carpathians (Southern Poland) as a case study

We studied the socio-spatial ecology of the Eurasian badger (Meles meles) along the altitudinal gradient (250-1257 m a.s.l.) of the Western Carpathians (Southern Poland), 2004-2009. Family groups were small (mean 2.3 individuals) and home-ranges large (mean 5.42 km2, MCP 100%), which gave a low population density (2.2 individuals/10 km2). Badgers foraged mainly in the foothills, irrespective of the altitude at which their sett was located. They mostly searched for food in meadows, pastures and arable fields (34.4% of telemetry locations), or among shrubs (33.9%). Badgers were killed by hunters (0.37 individuals/10 km2 annually), and by wolves (0.07 individuals/10 km2). The badger population density was influenced mostly by the abundance of earthworms and hunting pressure, while the size and shape of their territories was determined by the distribution of foraging grounds.

Socio-spatial organization of Eurasian badgers (Meles meles) in a low-density population of central Europe

We studied the socio-spatial organization of Eurasian badgers (or European badgers), Meles meles (L., 1758), in a low-density population (estimate 1.8 badgers/km2) inhabiting a semi-rural area of western Switzerland. For this purpose, 8 badgers (5 males and 3 females) were caught at 5 different main setts and were radio-tracked between May 1994 and November 1996. The size of individual home ranges varied from 0.27 to 3.74 km2 (1.69 ± 1.33 km2 (mean ± SD), n = 8, 100% MCP), seemingly according to local variations in habitat productivity. Individual home ranges were spatially stable, but their size decreased significantly during winter (0.26 ± 0.42 km2, n = 7, 100% MCP). Badger social units consisted of 1–5 adults and (or) subadults (2.2 ± 1.5 animals, n = 9) and their yearly offspring. Group-range size varied from 0.57 to 3.74 km2 (2.12 ± 1.30 km2, n = 4) and seemed to be influenced by the spatial distribution pattern of food resources. Indeed, each group range encompassed approximately the same surface of agricultural land (about 0.60 km2). Territories were not well marked, some group ranges partly overlapped. Latrines, which were not numerous and principally located inside rather than along borders of group ranges, were only used irregularly or sporadically. This prompts us to encourage the reconsideration of the role of territorial behaviour in promoting group formation in Eurasian badgers.