Obstacle avoidance in social groups: : new insights from asynchronous models

For moving animals, the successful avoidance of hazardous obstacles is an important capability. Despite this, few models of collective motion have addressed the relationship between behavioural and social features and obstacle avoidance. We develop an asynchronous individual-based model for social movement which allows social structure within groups to be included. We assess the dynamics of group navigation and resulting collision risk in the context of information transfer through the system. In agreement with previous work, we find that group size has a nonlinear effect on collision risk. We implement examples of possible network structures to explore the impact social preferences have on collision risk. We show that any social heterogeneity induces greater obstacle avoidance with further improvements corresponding to groups containing fewer influential individuals. The model provides a platform for both further theoretical investigation and practical application. In particular, we argue that the role of social structures within bird flocks may have an important role to play in assessing the risk of collisions with wind turbines, but that new methods of data analysis are needed to identify these social structures

A model to determine the severity of a birdstrike with flocks of Canada Geese

The number of birds of a flocking species likely to be ingested into an aircraft engine in a multiple birdstrike is of profound interest to engineers when they consider birdstrike tolerance in engine design. Of even more importance than the number of birds which may enter a single engine, when power can still be supplied by the remaining engines, is the probability of more than one engine suffering an ingestion. The historical birdstrike record can provide such information but is sometimes unreliable as it may be, of necessity, based upon unreliable data; the species of the birds involved may not be accurately identified and the number of birds ingested is often impossible to verify because of the nature of the remains (Allan and Hammershock, 1994). In addition, a historical record cannot reflect current or future trends in bird populations or behaviours. Some migratory populations of the Canada Goose (Branta canadensis) are thought to be in decline, but numbers are increasing in urban areas throughout Northern America and Europe (Allan et al, 1995, Seubert 1996, USDA, 1998). These introduced, non-migratory populations have adapted very well to man-made environments such as ornamental parks and reservoirs which are often near airports. In the absence of satisfactory control techniques becoming widely used, the probability of striking a Canada Goose will rise as its numbers increase. As it is a flock-forming species the risk of a multiple ingestion becomes particularly serious

Simulating the next steps in badger control for bovine tuberculosis in England.

Industry-led culling of badgers has occurred in England to reduce the incidence of bovine tuberculosis in cattle for a number of years. Badger vaccination is also possible, and a move away from culling was "highly desirable" in a recent report to the UK government. Here we used an established simulation model to examine badger control option in a post-cull environment in England. These options included no control, various intermittent culling, badger vaccination and use of a vaccine combined with fertility control. The initial simulated cull led to a dramatic reduction in the number of infected badgers present, which increased slowly if there was no further badger management. All three approaches led to a further reduction in the number of infected badgers, with little to choose between the strategies. We do note that of the management strategies only vaccination on its own leads to a recovery of the badger population, but also an increase in the number of badgers that need to be vaccinated. We conclude that vaccination post-cull, appears to be particularly effective, compared to vaccination when the host population is at carrying capacity

The mean number of infected badgers per social group during the five years of control and five years afterwards inside the control area for simulations representing Northern Ireland.

<p>The mean number of infected badgers per social group during the five years of control and five years afterwards inside the control area for simulations representing Northern Ireland.</p

Model of Selective and Non-Selective Management of Badgers <i>(Meles meles)</i> to Control Bovine Tuberculosis in Badgers and Cattle

<div><p>Bovine tuberculosis (bTB) causes substantial economic losses to cattle farmers and taxpayers in the British Isles. Disease management in cattle is complicated by the role of the European badger (<i>Meles meles</i>) as a host of the infection. Proactive, non-selective culling of badgers can reduce the incidence of disease in cattle but may also have negative effects in the area surrounding culls that have been associated with social perturbation of badger populations. The selective removal of infected badgers would, in principle, reduce the number culled, but the effects of selective culling on social perturbation and disease outcomes are unclear. We used an established model to simulate non-selective badger culling, non-selective badger vaccination and a selective trap and vaccinate or remove (TVR) approach to badger management in two distinct areas: South West England and Northern Ireland. TVR was simulated with and without social perturbation in effect. The lower badger density in Northern Ireland caused no qualitative change in the effect of management strategies on badgers, although the absolute number of infected badgers was lower in all cases. However, probably due to differing herd density in Northern Ireland, the simulated badger management strategies caused greater variation in subsequent cattle bTB incidence. Selective culling in the model reduced the number of badgers killed by about 83% but this only led to an overall benefit for cattle TB incidence if there was no social perturbation of badgers. We conclude that the likely benefit of selective culling will be dependent on the social responses of badgers to intervention but that other population factors including badger and cattle density had little effect on the relative benefits of selective culling compared to other methods, and that this may also be the case for disease management in other wild host populations.</p></div

The mean number of infected badgers per social group during the five years of control and five years afterwards within the entire simulation area for simulations representing SW England.

<p>The mean number of infected badgers per social group during the five years of control and five years afterwards within the entire simulation area for simulations representing SW England.</p

The mean number of infected badgers per social group during the five years of control and five years afterwards inside the control area for simulations representing SW England.

<p>The mean number of infected badgers per social group during the five years of control and five years afterwards inside the control area for simulations representing SW England.</p

The mean number of infected badgers per social group during the five years of control and five years afterwards within the entire simulation area for simulations representing Northern Ireland.

<p>The mean number of infected badgers per social group during the five years of control and five years afterwards within the entire simulation area for simulations representing Northern Ireland.</p

The mean cattle herd breakdown (CHB) rate during the five years of control and five years afterwards within the entire simulation area for simulations representing SW England.

<p>The mean cattle herd breakdown (CHB) rate during the five years of control and five years afterwards within the entire simulation area for simulations representing SW England.</p

The mean cattle herd breakdown (CHB) rate during the five years of control and five years afterwards within the entire simulation area for simulations representing Northern Ireland.

<p>The mean cattle herd breakdown (CHB) rate during the five years of control and five years afterwards within the entire simulation area for simulations representing Northern Ireland.</p