Identifying the effects of anthropogenic disturbance on the breeding behaviour of female grey seals (Halichoerus grypus), at a mainland UK colony.

Abstract

The study aimed to identify whether anthropogenic stimuli constituted a disturbance, as indicated through behavioural responses of the female grey seals (Halichoerus grypus) at Donna Nook, a mainland UK breeding colony. The colony has public access to it, and is adjacent to the Ministry of defence training range with frequent fly-overs from low flying aircraft. Data collection was non-intrusive, using in-field focal videos, proximity maps, and human activity data collection. The primary aims of the study were to identify what sources of anthropogenic disturbances, if any, effect grey seal breeding behaviour on the colony. In addition to this the study wished to observe what affect pup sex and pupping location within the colony had on breeding behaviour and individual responses to disturbance. The results of this study were in agreement with prior studies on pinniped species, indicating a very limited behavioural response of individuals to anthropogenic disturbance stimuli during the breeding season. Pedestrian disturbances had a greater impact on the behaviour of individuals than aircraft disturbances; and of all the pedestrian disturbances found at the site, photographers elicited the greatest behavioural response in individuals. Behavioural responses to disturbances were noted to be more significant over the first two minute interval after a disturbance event than over longer periods of time. In vigilance behaviours, consistent individual differences (CIDs) in an individual’s response to disturbance events were noted both across AND within disturbance contexts. Pup sex and the location of the birthing site both seemed to affect a female’s response to a disturbance event; with mothers of male pups and those females which gave birth close to the Ministry of Defence site showing significantly higher levels of vigilance behaviours after a disturbance event. Comparisons of individual responses to natural and anthropogenic disturbances revealed that individuals show a greater behavioural response to natural disturbances than those disturbances originating from a human source. The lack of behavioural responses to both natural and anthropogenic disturbance sources in the colony indicates the potential role of habituation and/or selection for behavioural types within the colony. The results of this study highlight the scope for future research into the stability of these responses to disturbance stimuli; both over numerous breeding seasons and also in periods outside of the breeding season.