Data from: Sex-specific and individual preferences for hunting strategies in white sharks
Towner, Alison V. et al. (2016), Data from: Sex-specific and individual preferences for hunting strategies in white sharks, Dryad, Dataset, https://doi.org/10.5061/dryad.q90fm
Fine-scale predator movements may be driven by many factors including sex, habitat, and distribution of resources. There may also be individual preferences for certain movement strategies within a population which can be hard to quantify. Within top predators, movements are also going to be directly related to the mode of hunting; for example sit-and-wait or actively searching for prey. Although there is mounting evidence that different hunting modes can cause opposing trophic cascades, there has been little focus on the modes used by top predators, especially those in the marine environment. Adult white sharks (Carcharhodon carcharias) are well known to forage on marine mammal prey, particularly pinnipeds. Sharks primarily ambush pinnipeds on the surface but there has been less focus on the strategies they use to encounter prey. We applied mixed hidden Markov models to acoustic tracking data of white sharks in a coastal aggregation area in order to quantify changing movement states (Area Restricted Searching (ARS) vs. patrolling) and the factors that influenced them. Individuals were re-tracked over multiple days throughout a month to see if state-switching dynamics varied or if individuals preferred certain movement strategies. Sharks were more likely to use ARS movements in the morning and during periods of chumming by ecotourism operators. Furthermore, the proportion of time individuals spent in the two different states and the state-switching frequency, differed between the sexes and between individuals. Predation attempts/success on pinnipeds were observed for sharks in both ARS and patrolling movement states and within all random effects groupings. Therefore white sharks can use both a ‘sit-and-wait’ (ARS) and ‘active searching’ (patrolling) movements to ambush pinniped prey on the surface. White sharks demonstrate individual preferences for fine scale movement patterns which may be related to their use of different hunting modes. Marine top predators are generally assumed to use only one type of hunting mode, but we show that there is likely a mix within populations. As such, individual variability should be considered when modelling behavioural effects of predators on prey species.
Gansbaai South Africa